Chapter 3. Temperate Cyclones • cold air mass is one which is colder thn underlying surface.

• Cyclonic systems developing in mid & high latitude (35° & 65° Cold source regions (polar air masses) are—
latitude in both hemispheres), beyond the tropics are called Arctic Ocean – cold & moist Siberia – cold and dry
temperate cyclones. They are known as mid-latitude cyclones, Northrn Canada–cold & dry Southrn Ocean–cold & moist
extratropical cyclones, frontal cyclones or wave cyclones.
• temperate cyclone (frontal cyclogenesis) have a dynamic origin Warm Air Mass
(complex interaction of air masses under influence of Coriolis • one which is warmer thn underlying surface. Warm source
force). regions (tropical air masses) are—
Sahara Desert--warm & dry Tropical Ocean–warm & moist
Air Masses– is a large body of air having little horizontal variation
Continental Polar Air Masses (cP)--Source rgn of these air
in temp & moisture; are integral part of planetary wind system &
masses are Arctic, northern NAmerica, Eurasia & Antarctica.
are associated with wind belt; extend from surface to lower
• characterized by Dry, cold & stable conditions.
stratosphere & across thousands of km.
• weather during winter is frigid,clear & stable; in summer,
Source regions
weather is less stable with lesser prevalence of anticyclonic
• When a large parcel of air remains over a homogenous area for
winds, warmer landmasses & lesser snow.
a sufficiently longer time,it acquires characteristics of the area;
homogenous rgn can b vast ocean surface or vast plains & Maritime Polar Air Masses (mP)--source rgn of these air masses
plateaus; homogenous surfaces, over which air masses form, are are oceans bw 40° & 60° latitudes.
called source regions. • These are continental polar air masses which have moved over
• main source regions are high-pressure belts in subtropics warmer oceans, got heated up & hv collected moisture.
(giving rise to tropical air masses) & around poles ( source for • conditions over source regions are cool, moist & unstable.
polar air masses). • weather during winters is characterized by high humidity,
• Source region establishes heat & moisture equilibrium with the overcast skies & occasional fog & ppt; Summer weather is clear,
overlying air mass. When a air mass moves away from a source fair and stable.
region, upper level maintains the physical characteristics for a
longer period. This is possible bcoz air masses are stable with Continental Tropical Air Masses (cT)--source rgn include tropical
stagnant air which do not facilitate convection. Conduction and & sub-tropical desert of Sahara, W.Asia & Australia
radiation in such stagnant air is not effective. • These are dry,hot & stable & dont extend beyond source.
Conditions for formation of Air Masses • They are dry throughout the year.
• Source region should be extensive with gentle, divergent air Maritime Tropical Air Masses (mT)---source regions of include
circulation (gentle anticyclonic circulation). oceans in tropics & sub-tropics such as Mexican Gulf, Pacific &
• Areas with HP but little pressure difference or pressure Atlantic oceans.
gradient are ideal source regions. • These air masses are warm, humid and unstable.
• no major source regions in midlatitudes as these regions are • winter weather has mild temp, overcast skies with fog.
dominated by frontal cyclones and other disturbances. • summer weather is characterized by high temperatures, high
Air masses based on Source Regions—5 major source rgn humidity, cumulous clouds and convectional rainfall.
1. Warm tropical and subtropical oceans;
2. The subtropical hot deserts; Influence of Air Masses on World Weather
3. The relatively cold high latitude oceans; • properties of an air mass which influence accompanying
4. The very cold snow covered continents in high latitudes; weather are vertical temperature distribution (indicating its
5. Permanently ice-covered continent in Arctic & Antarctica stability & coldness or warmness) & the moisture content.
• air masses carry atmospheric moisture from oceans to
Accordingly, following types of airmasses are recognised: continents.
1. Maritime tropical (mT); • transport latent heat ஃ contribute to latitudinal heatbalance
2. Continental tropical (cT); • Most atmospheric disturbances like cyclones & storms
3. Maritime polar (mP); originate at contact zone bw diff air masses called as fronts.
4. Continental polar (cP); • Characteristics of air masses involved determine weather
5. Continental arctic (cA). associated with the disturbances.
first letter describes moisture properties of air mass. Fronts
• c: continental air masses (dry) • are typical features of mid-latitudes weather (30-65°N & S).
• m: maritime air masses (moist) They are uncommon (unusual) in tropical & polar regions.
second letter describes source region of air mass. • Front is a 3D boundary zone formed bw two converging air
• T: Tropical • P: Polar • A: Arctic or Antarctic masses with diff physical properties (temp,humidity, density).
• two air masses don’t merge readily due to converging atm-
• Tropical air masses are warm, & polar air masses are cold. ospheric circulation, different physical properties, relatively low
• heat transfer processes that warms or cools the air takes place diffusion coefficient & a low thermal conductivity.
slowly.
Cold Air Mass
 Front Formation– process of formation of a front is known as nces; In such situation, transition zone bw two is a steep sloped
frontogenesis (war bw two air masses), & dissipation of a front iscold front. Cold front moves up to twice as quickly as warm fronts.
known as frontolysis(one air mass win against other). Frontolysis begins when warm air mass is completely uplifted by
• Frontogenesis involve convergence of 2 distinct air masses cold air mass.
• Frontolysis involve overriding of one air mass by another. Weather along a cold front
• In northern hemisphere frontogenesis (convergence of air • weather depends on a narrow band of cloudiness & ppt (bcoz
masses) happens in anti-clockwise direction and southern slope is steep)• Severe storms can occur; in summer, thunderstorm
hemisphere, clockwise direction. This is dueto Coriolis force. common in warm sector.
• Mid-latitude cyclones (temperate cyclones or extra-tropical • In some region, tornadoes
cyclones) occur due to frontogenesis. occur in warm sector.
• Cold fronts produce sharper
General Characteristics
changes in weather (bcoz up
• temp contrast is inversely proportional to thickness of frontal
liftment of air is rapid). Temp
zone i.e, two air masses with higher temp difference dont merge
can drop > 15° in 1st hour.
readily. ஃ front is less thick when it is formed bw 2 air masses
with higher temp difference.
Cloud formation along cold
• With sudden change in temperature through a front, there is a front–approach of cold front is marked by increased wind activity
change in pressure also. in warm sector & appearance of cirrus clouds, followed by lower,
• frontal activity is associated with cloudiness & ppt because of denser altocumulus & alto–
ascent of warm air which cools down adiabatically, condenses & stratus. • At actual front,
causes rainfall; intensity of ppt depends on slope of ascent and dark nimbus & cumulonimb
amount of water vapour present in ascending air. us clouds cause heavy rain.
• Front experiences wind shift since wind motion depends on •cold front dies rapidly, but
pressure gradient and Coriolis force. weather along it is violent.
Wind Shift: A change in wind direction of 45° or more in less than
15 minutes with sustained wind speeds of 10 knots or more. Warm Front—Its a sloping
1 knot = 1.852 kmph 1 Nautical Mile = 1.852 km frontal surface along which active movt. of warm air over cold air
takes place (warm air mass is too weak to beat cold air mass).
Classification of Fronts — Based on mechanism of frontogenesis Frontolysis begins when warm air mass completely sits over the
& associated cold air mass.
weather, fronts are
of following types.

Symbols to indicate
various fronts,
frontogenesis and
frontolysis.
Weather along a warm front – As warm air moves up the slope, it
Stationary Front—Whn surface position of a front doesnt change condenses & cause ppt but, unlike cold front, temp & wind directn
(when 2 air mass are unable to push against each other; a draw), changes are gradual; causes moderate to gentle ppt over a large
a stationary front is formed; Warm or cold front stops moving area, over several hours. The passage of warm front is marked by
• wind motion on both sides of front is parallel to the front. rise in temp & pressure.
• Once this boundary resumes its forward motion, it becomes a Clouds along warm front—With the approach, hierarchy of clouds
warm front or cold front. is—cirrus, stratus & nimbus (no cumulonimbus clouds as gradient
is gentle). Cirrostratus clouds ahead of warm front create a halo
around sun & moon.
Occluded Front— Occlusion: a process by which cold front of a
rotating low-pressure system catches up warm front so that warm
air bw them is forced upwards. Such a front is formed when a cold
Weather along a stationary front— air mass overtakes a warm air mass & goes underneath it.
• Cumulonimbus clouds are formed.
• Overrunning(uplifted) of warm air along front cause frontal ppt.
• Frontal cyclones migrating along a stationary front can dump
heavy amounts of ppt, resulting in flooding along the front.

Cold Front—formed when a cold air mass replaces a warm air mass
by advancing into it or warm air mass retreats & cold air mass adva-
 front is formed as a surface of discontinuity. Such condition occur
over sub-tropical high, sub-polar low-pressure belts & along the
tropopause.
Explanation– In NH, warm air blows from south & cold air from
north of the front. When pressure drops along the front, warm
• Frontolysis begin when warm sector diminishes, & cold air mass air moves northwards, & cold air move towards south setting in
completely undertakes the warm sector on ground. motion an anticlockwise cyclonic circulation (Coriolis Force;NH).
• Thus, a long & backward swinging occluded front is formed
which could be a warm front type or cold front type occlusion.

• warm air glides ovr cold air & a sequence of clouds appear over
sky ahead of warm front & cause ppt; cold front approaches warm
air from behind & pushes warm air up. As a result, cumulus clouds
Weather along occluded front– mix of cold front type & warm develop along the cold front.
front type weather. Such fronts are common in western Europe. • This leads to well-developed extratropical cyclone, with a warm
• formation of mid-latitude cyclone involve formatn of occluded front & cold front.
front. • There are pockets of warm air wedged bw warm & cold front.
Clouds along an occluded front– A combination of clouds formed • cold front moves faster than warm front ultimately overtaking it.
at cold front & warm front. Warm front cloud & cold front clouds • wedged warm air is completely uplifted (frontolysis), & front is
are on opposite side of the occlusion. occluded & the cyclone dissipates. Thus, temperate cyclone is
intense frontogenesis involving mainly occlusion type fronts.

• Normally, individual frontal cyclones exist for 3 to 10 days moving

Stationary Front • Tie – No clear Winner in generally west to east direction. Precise movement is controlled
Cold Front • Cold Air mass is the clear winner. by orientation of polar jet stream in upper troposphere.
Warm Front • warm air mass picks up a fight but fails to
beat cold air mass. Cold Air mass is winner. Seasonal Occurrence of Temperate Cyclone–occur mostly in winter,
Occluded Front • Cold Front + Warm Front late autumn & spring; associated with rainstorms & cloudy weather.
• Double win fr cold air mass During summer, all paths of temperate cycl ones shift northward, &
Cold , Warm & Occluded front are ex of Temperature Inversion. there are only few temperate cyclones ovr sub- tropics & the warm
temperate zone, altho a high concentration of storms occurs over
Bering Strait, US & Russian Arctic & sub-Arctic zone.
Origin and Development of Temperate Cyclones
Distribution of Temperate Cyclones–
1. USA & Canada 2. belt extending from Iceland to Barents Sea &
continuing over Russia & Siberia, 3. winter storms over Baltic Sea,
4. Mediterranean basin extending up to Russia & even up to India
in winters (called western disturbances) & Antarctic frontal zone.

Characteristics of Temperate Cyclones

Size & Shape—temperate cyclones are
The isobars are not closed in a temperate Cyclones asymmetrical & shaped like an inverted ‘V’.
They stretch over 500 to 600km. They may
Polar Front Theory – Acc to this theory, warm-humid air masses spread over 2500km over NAmerica. They
from tropics meet dry-cold air masses from poles & thus a polar have a height of 8 to 11km.
Shape of a Temperate Cyclone
 Wind Velocity & Strength—wind strength is more in eastern &
southern portion, moreover NAmerica compared to Europe. Wind Wind • Much greater. • Comparatively low.
velocity increases with the approach but decreases after cyclone Velocity & • 100 – 250 kmph • Typical range: 30-150
has passed. destruction • 200–1200kmph in upper kmph.
Orientation and Movement– Polar jet stream plays a major role troposphere • Less destruction due to
in formation & hence influences the path of temperate cyclones. • Greater destructn due to winds bt more destructn
• Since these cyclones move with westerlies, they are oriented winds, storm surges & dueto flooding.
east-west. If the storm front is east-west, the centre moves torrential rains.
swiftly eastwards. If the storm front is directed northwards, the Isobars • Complete circles and the • Isobars are usually ‘V’
centre moves towards north, but after two or three days, pressure pressure gradient is steep shaped & pressure gradie
difference declines & cyclone dissipate. nt is low.
• In case storm front is directed southwards,centre moves quite Lifetime • Doesn’t last for more • Lasts for 2-3 weeks.
deep southwards-even up to Mediterranean region (sometimes than a week
causing Mediterranean cyclones or Western Disturbances Path • East–West. Turn North at • West – East (Westerlies;
Structure–north-western sector is the cold sector & north-eastern 200latitude & west at 300 Jet Streams). • Move
sector is warm sector (Bcoz cold air masses in north and warm air latitude. away from equator.
masses in south push against each other & rotate anti-clockwise in • Move away frm equator.
northern hemisphere). • movt of Cyclones in AS
& BoB is little different.
Associated Weather—approach of temperate cyclone is marked • Here, these storms are
by fall in temp, fall in the mercury level, wind shifts & halo around superimposed upon the
sun & moon, & a thin veil of cirrus clouds. monsoon circulation of
• light drizzle follows which turns into a heavy downpour. These summer months, and they
conditions change with arrival of the warm front which halts the move in northerly directn
fall in mercury level & rising temperature. with monsoon currents.
• Rain stops & clear weather prevails until cold front of anticyclo- Temperatre • temperature at centre is • All sectors of cyclone
nic character arrives which causes a fall in temp, brings cloudiness distribution almost equally distributed. have different temp
& rain with thunder. Aftr this,once again clear weather is estblshd. Calm region tropical cyclone centre is there isnt a single place
• temp cyclones experience more rainfall when there is slow movt known as eye; wind is calmwhere winds & rains are
& a marked difference in rainfall & temp bw front & rear of the at centre with no rainfall. inactive.
cyclone. Anticyclones generally accompany these cyclones. Driving derives its energy from depends on temperature,
force latent heat of condensatn, humidity and density
4. Tropical Cyclones and Temperate Cyclones ― Comparison & difference in densities of differences of air masses.
air masses doesnt contrib-
Tropical Cyclone Temperate Cyclone ute to energy of cyclone.
Origin • Thermal Origin. • Dynamic Origin: Coriolis Influence of relationship bw tropical distinct relationship with
Force, Movement of air masses. Jet streams cyclones & upper level upper level air flow (jetst
Latitude • Confined to 10-30 N • Confined to 35-65º N&S of equ
º air-flow is not very clear. ream, Rossby waves etc.)
and S of equator. ator. More pronounced in NH Clouds exhibit fewer varieties of show a variety of cloud
due to greater temp contrast. clouds – cumulonimbus, development at various
Frontal absent Cyclone formation is due to nimbostratus, etc. elevations.
system frontogenesis(occluded front) Surface anti nt associated with surface associated with anticyclo
Forman • form only on seas • Can form both on land as cyclones anticyclones & they have nes which precede & succ
with temp more than well as seas. more destructive capacity eed a cyclone; These are
26-270 C; dissipate on not very destructive.
reaching the land. Influence Both coasts affected. But Bring rains to NW India.
Season • Seasonal: Late • Irregular. But few in summers on India east coast is hot spot. ‘Western Disturbances’.
summers (Aug-Nov). & more in winters. Weather • Tough as movt can be Easy dueto general weste
Size • Ltd to small area. • They cover a larger area. Prediction erratic dueto lot of factors. rly path of cyclone, less
• size: 100–500 kms in • size: 300–2000km in diameter. variable jet stream path &
diameter. Varies with Varies region to region. simple frontal system.
strength of cyclone.
Shape • Elliptical • Inverted ‘V’ • Titbit: In certain instances, two cyclones move toward each other
Rainfall • Heavy but last few • In temperate cyclone, rainfall & revolve around one another, with the smaller & less intense one
hours. If cyclone stays is slow & continues for many moving more quickly. This phenomenon is called Fujiwhara effect.
at a place, rainfall maydays, sometimes even weeks.
continue for few days.
 5. Polar Vortex Polar Vortex and Ozone Depletion at South Pole
• PV & ozone depletion are distinct but related phenomena.
• Polar vortex (circumpolar vortex) is a polar cyclone. Arctic Ozone depletion –There is steady decline of 4% in total volume of
(polar) cyclone occur in polar rgn; can reach upto 2000km wide. ozone in Earth's stratosphere. Much larger decrease is observed
• Polar cyclones differ with others because they arenot seasonal. around Earth's polar regions. Depletion of ozone is dueto increase
They can occur at any time of the year. Polar cyclones can also in halocarbons in the atmosphere.
form quickly (sometimes less than 24 hrs), and their direction or Halogen atoms like chlorine destroy ozone – Photodissociation
movement cannot be predicted. They can last from a day up to (under influence of sunlight) of ozone-depleting substances like
several weeks. Most frequently, polar cyclones develop above halocarbon refrigerant, solvents, propellants, & foam-blowing
northern Russia & Siberia. agents (CFC, HCFC, carbon tetrachloride & trichloroethane, freons,
• polar vortex is large pocket of very cold air, typically the coldest halons) creates free chlorine atoms that destroy ozone.
air in NH, which sits over polar region during winter season.
• PV is a Cold; Circumpolar; Upper tropospheric low- pressure:
sometime extending till lower lvel of stratosphere; Large cyclonic
parcel of air (about 1000km across) (counter- clock wise in NH)
• Polar vortex is associated with jet streams (Rossby waves).
• It is formed mainly in winter & gets weaker in summer.
• It surrounds polar highs & lie within the polar front (boundary
separating the temperate and polar air masses).

Polar Vortex Cold Wave

Polar Vortex slipping into Mid-latitudes, All the terms mean
Breakdown of the polar vortex, the same ― Polar
Sudden stratospheric warming, Vortex Cold Wave
Polar vortex event.
• PV will remain in its place when westerlies along with polar jet
are strong(strong polar vortex means there is huge temp contrast But how chlorine atom reach to such high levels of atmosphere?
bw temperate & polar regions). • When the polar vortex is weak, Polar Stratospheric Clouds (PSCs)-- They are nacreous clouds that
it intrudes into mid-latitude region by buckling general wind flow extend from 12-22 km above the surface. Nacreous clouds are
pattern. This leads to significant cold outbreaks in mid-latitude rare clouds in frigid regions of lower stratosphere. They are
regions. The vortex is capable of delivering sub-zero temp to US mostly visible within two hours after sunset or before dawn. They
and Canada where is occurs the most. are bright even after sunset & before dawn bcoz at those heights
there is still sunlight. They are seen mostly during winter at high
How it slips–
latitudes. PSCs or nacreous clouds contain water, nitric acid & /or
• Polar jet traverses somewhere over 65º N and S latitudes. When
sulfuric acid. They are formed mainly during event of polar vortex
temp contrast bw polar & temperate regions is maximum, the jet
in winter; more intense at south pole. Cl-catalysed ozone depletn
is very strong, & meandering is negligible. But when temperature
is enhanced in presence of polar stratospheric clouds.PSCs convert
contrast is low, jet starts to meander (Rossby waves).
reservoir compounds into reactive free radicals (Cl & ClO) thereby
• Meandering jet creates alternating low and high-pressure cells.
significantly increasing reactive halogen radicals. The free radicals
• High-pressure cell are created below the ridges & low-pressure
accelerate depletion of ozone. Thus, polar vortex, in the form of
cells below the troughs (this is because of upper air circulations
PSCs, accelerate ozone depletion.
created by jet).
• With severe meandering, high-pressure cells push over to north
& displace the polar cyclone from its normal position i.e. cyclone
moves away from pole & slips into temperate regions.
• With strengthening of jet, high-pressure cells become weak &
retreat to its normal latitudinal position; ஃ polar cyclone moves
back to its normal position.

Ques: formation of ozone hole in Antarctic rgn has been a cause

of concern. What could be reason for ozone depletion at poles?
• Presence of prominent polar front: essential to keep polar
vortex in its place. Polar vortex gives rise to stratospheric Clouds.
• Presence of stratospheric Cloud: they hv necessary ingredients
(nitric acid and/or sulfuric acid) to amplify ozone depletion.
• Absence of polar front & stratospheric clouds: polar vortex
slips into temperate region.
• Inflow of methane: methane is not in list of ozone-depleting
substances. It doesn’t contain a halogen. But it reacts with
halogens to create reservoir compounds.
Atmospheric circulation typically found at equatorial Pacific.
• Presence of prominent tropospheric turbulence: they don’t
Thermocline: temp gradient in a body of water, separating layers
reach the stratosphere
at different temperatures.
• Increased temperature at polar region due to global warming:
doesn’t have any direct impact on ozone depletion at the poles. During El Nino year
• El Niño is occasional developmnt of warm ocean surface waters
6. El Nino along coast of Ecuador & Peru. In El Niño year, air pressure drops
• Warming & cooling of Pacific Ocean is most important in terms over large areas of central Pacific & along coast of S. America.
of general atmospheric circulation. • normal low-pressure system is replaced by a weak high in the
Normal Conditions western Pacific (southern oscillation). This change in pressure
• In a normal year, a surface low-pressure develops in region of pattern causes trade winds to be reduced ― Weak Walker Cell.
northern Australia & Indonesia and a high-pressure system over Sometimes Walker Cell might even get reversed.
coast of Peru. As a result, trade winds over Pacific Ocean move • This reduction allows equatorial counter current (west to east
strongly from east to west. current along calm doldrums) to accumulate warm ocean water
•easterly flow of trade wind carry warm surface water westward, along coastlines of Peru & Ecuador replacing the cool Peruvian
bringing convective storms (thunderstorms) to Indonesia and current.
coastal Australia.
• Along the coast of Peru, bottom cold nutrient-rich water wells
up to the surface to replace warm water that is pulled to west.

El Nino conditions: Equatorial counter current flows along calm

doldrums in west-east direction

Walker circulation (Normal Years)

• Walker circulation (Walker cell) is caused by pressure gradient
force tht results from a high pressure system over eastern Pacific
Ocean, & a low-pressure system over Indonesia. Walker cell is
indirectly related to upwelling off coasts of Peru & Ecuador. This
bring nutrient rich coldwater to surface, increasing fishing stocks.

El Nino condition: Drought in N.Australia & flood in Cen.America

• accumulation of warm water causes thermocline to drop in the

eastern part of Pacific Ocean which cuts off the upwelling of cold
deep ocean water along coast of Peru.
• develpmnt of El Niño brings drought to western Pacific, rain to
Normal Conditions: Thunderstorms in equatorial western Pacific equatorial coast of S.America, & convective storm & hurricanes
and calm conditions in equatorial eastern Pacific to central Pacific.
• El Niño normally occurs around Christmas & usually lasts for a • moderate El Nino in 2002 resulted in worst droughts in india.
few weeks to a few months. Sometimes an extremely warm • directly impacts India's agrarian economy
event can develop that lasts for much longer periods. • ultimate impact is seen in form of high inflation, & low GDP

El Nino Southern Oscillation (ENSO) Southern Oscillation Index and Indian Monsoons
• formation of El Niño (circulation of surface ocean current) is • Southern Oscillation Index (SOI) is used to measure intensity of
linked with Pacific Ocean circulation pattern known as southern Southern Oscillation. This is the difference in pressure bw Tahiti
oscillation (circulation of atmospheric pressure). in French Polynesia (Central Pacific), representing Central Pacific
• Southern Oscillation is inter-annual fluctuation of atmospheric Ocean & Port Darwin, in northern Australia representing Eastern
pressure over tropical Indo-Pacific region. El Nino & Southern Pacific Ocean. The positive & negative values of SOI, i.e. Tahiti
Oscillation coincide most of times ஃ their combination is called minus Port Darwin pressure are pointers towards good or bad
ENSO – El Nino Southern Oscillation. rainfall in India.
• In years when ENSO is strong, large-scale variations in weather Positive SOI Negative SOI
occur over world. The arid west coast of South America receives Tahiti (E.Pacific) pressure greater than that of Port Reverse
heavy rainfall, drought occurs in Australia & sometimes in India Darwin (W.Pacific)
and floods in China. Drought conditions in Eastern Pacific and good Reverse
rainfall in Western Pacific
Only ElNino = Warm water in E.Pacific + Cold water in W Pacific. Good for Indian Monsoons Reverse
Only SO = LP over E.Pacific + HP over W. Pacific
Indian Ocean Dipole effect (Not every ElNino yr is same in India)
ENSO = (Warm water in E.Pacific + LP over E.Pacific) + (Cold In recent decades, ENSO-Monsoon relationship seemed to weaken
water in W.Pacific + HP over W.Pacific). in Indian subcontinent. For e.g. 1997, strong ENSO failed to cause
drought in India. It was discovered that just like ENSO was an event
Effects of El Nino in Pacific Ocean, a similar seesaw ocean-atmosphere system in the
• warmer waters had a devastating effect on marine life existing Indian Ocean was also at play. It was discovered in 1999 & named
off the coast of Peru & Ecuador. Fish catches frm coast of South Indian Ocean Dipole (IOD).
America were lower than in normal year.
• IOD is defined by diff in sea surface temp bw two areas (or poles,
• Severe drought in Australia,Indonesia,India & southern Africa.
hence dipole)―western pole in Arabian Sea (westrn Indian Ocean)
• Heavy rains in California, Ecuador, & Gulf of Mexico.
& eastern pole in eastern Indian Ocean south of Indonesia.
• IOD starts to develop in equatorial region of Indian Ocean in April
& is best devolved in October. With a +ve IOD winds over Indian
Ocean blow from east to west (from BoB towards AS).
• results in ArabianSea (western Indian Ocean near African Coast)
being much warmer & eastern Indian Ocean around Indonesia
becoming colder and dry.
• +ve IOD–reverse happens; Indonesia much warmer and rainier.

Normal Conditions
• E.Pacific = Coast of Peru & Ecuador =Cold Ocean Water = Good
for Fishing. • W.Pacific = Indonesia & Australia == Warm Ocean
Water == Plenty of rains.

El Nino
• E.Pacific = Coast of Peru & Ecuador = Warm Ocean Water ==
Fishing industry takes a hit. • W.Pacific = Indonesia & Australia
== Cold Ocean Water == Drought.

El Nino impact on Indian Monsoons

• El Nino & Indian monsoon are inversely related; location of LP
& hence the rising limb over W.Pacific is considered to be condu
cive to good monsoon in India. • positive IOD index negated effect of ENSO, resulting in increased
Monsoon rains in several ENSO years like 1983, 1994 & 1997.
• Its shifting eastward frm its normal position, in El Nino years,
reduces monsoon in India; most prominent droughts in India hv • Similar to ENSO, atmospheric component of IOD is Equatorial
been El Nino droughts. However, not all El Nino yrs led to drought Indian Ocean Oscillation (EQUINOO: oscillation of warm water and
in India. 1997/98 was strong El Nino yr, but there was no drought atmospheric pressure bw Bay of Bengal and Arabian Sea).
(this is because of Indian Ocean Dipole – IOD).
Impact of IOD on Cyclogenesis in Northern Indian Ocean 7. Koppen’s Scheme of Classification of Climate
Positive IOD results in more cyclones than usual in Arabian Sea.
Negative IOD results in stronger than usual cyclogenesis in Bay of • empirical climate classification scheme developd by V. Koppen.
Bengal. Cyclogenesis in Arabian Sea is suppressed. • he identified close relationship bw distribution of vegetation &
climate. He selected certain values of temp & ppt & related them
El Niño Modoki to distribution of vegetation & used these fr classifying climates.
ElNiño Modoki is a coupled ocean-atmosphere phenomenon tht • recognized 5 major climatic grps; 4 based on temp & 1 on ppt.
is slightly diff from El Niño. Conventional El Niño is characterised • capital letter: A, C, D, E shows humid climate & B dry climates.
by strong anomalous warming in eastern equatorial Pacific. • climatic grps subdivided into types, designated by small letters,
• ElNiño Modoki is associated with strong anomalous warming in based on seasonality of ppt & temperature characteristics.
central tropical Pacific & cooling in eastern and western tropical • seasons of dryness are indicated by small letters: f, m, w and s.
Pacific. Such zonal gradients result in anomalou two-cell Walker f no dry season
Circulation over tropical Pacific, with a wet region in the central m monsoon climate
Pacific and dry region in the western and eastern Pacific. w winter dry season
s summer dry season
• small letter a, b, c, d refer to degree of severity of temperature.
• small letter h & k refer to tropical & mid-latitude rgn respectvly.
• B - Dry Climates subdivided using capital letters S for steppe or
semi-arid and W for deserts.

Climatic Groups According to Koppen

Climatic Group Characteristics
A – Tropical Avg temp of coldest month is 18 °C or higher
B – Dry Climates Potential evapouration exceeds precipitation
La Nina
C–Warm Temperate avg temp of coldest month of (Mid-latitude)
After El Niño event weather conditions usually return to normal.
climates years is higher than minus 3 °C but
However, in some yrs, trade winds become extremely strong, &
below 18 °C (-3 °C to 18 °C)
abnormal accumulation of cold water can occur in central and
D – Cold Snow avg temp of coldest month is minus 3 °C or
eastern Pacific. This event is called a La Niña.
Forest Climates below
E – Cold Climates Avg temperature for all months is below 10 °C
H – High Land Cold due to elevation

Climatic Types According to Koppen

Climatic Grp Type Code Characteristics
A-Tropical Tropical wet Af No dry season
Humid Tropical monsoon Am Monsoonal. Short dry seasn
Climate Tropicl wet & dry Aw Winter dry season
Effects of La Nina —
• drought over central North America. B-Dry Subtropical steppe BSh Low-latitude semiarid or dry
Climate Subtropical desert BWh Low-latitude arid or dry
• Atlantic Ocean sees very active hurricane seasons
Midlatitude steppe BSk Mid-latitude semiarid or dry
• Abnormally heavy monsoons in India & Southeast Asia,
Mid-latitude desertBWk Mid-latitude arid or dry
• Cool & wet winter in SE.Africa, wet weather in E.Australia,
C-Warm Humid subtropical Cfa No dry seasn,warm summer
• Cold winter in western Canada & north-western United States,
temperate Mediterranean Cs Dry hot summer
• Winter drought in southern United States. (Mid-latitud Marine west coast Cf No dry season, warm and
e) Climates cool summer
D-Cold Humid continental Df No dry seasn, severe winter
Snow-forest Subarctic Dw Winter dry and very severe
Climates
E-Cold Tundra ET No true summer
Climates
Polar ice cap EF Perennial ice
H-Highland Highland H Highland with snow cover
A) – Tropical Humid Climates ones practice shifting cultivation. Food is abundantly available.
• Tropical humid climates exist bw Tr of Cancer & Tr of Capricorn. 2) Commercial– In the Amazon Basin, Indian tribes collect wild
• sun overhead throughout the year & presence of ITCZ make rubber. In Congo Basin, Pygmies gather nuts. In Malaysia jungles,
climate hot & humid. Orang Asli make cane products.
• Annual range of temp is very low, & annual rainfall is high. 3) Shifting Cultivation or Slash & Burn Cultivation– followed in
• tropical group is divided into three types—-- where dense forests are common
4) Plantation Boom- With coming of Europeans, large plantations
1) Af – Tropical wet climate; estb in Java, Sumatra, Malaysia, West Africa and Central America.
2) Am – Tropical monsoon climate; The climate is very Favourable for cultivation ; most important is
3) Aw – Tropical wet and dry climate. natural rubber,cocoa, oil palm; Other crops include coconuts,
sugar, coffee (Brazil), tea, tobacco, spices, etc.
Tropical Wet Climate (Af: A – Tropical, f – no dry season)
Factors Affecting Development of Equatorial Regions
• aka Hot, Wet Equatorial Climate, Equatorial Rainforest Climate.
• Equatorial Rainforests, Equatorial Evergreen Forests, Tropical
Moist Broadleaf Forest, Lowland Equatorial Evergreen Rainforest. Equatorial climate & health– Excessive heat & high humidity
• bw 5° N & S of Equator. creates serious physical and mental handicaps. • High humidity
• greatst extent–lowlands of Amazon,Congo,Malaysia,East Indies feeds many tropical diseases such as malaria & yellow fever.
• climate dominatd by maritime tropical air mass(high humidity). • Communicable diseases are rampant as germs and bacteria are
• Temperature is uniform throughout the year. transmitted through moist air. • Insects & pests not only spread
• mean monthly temp always around 27°C with little variation. diseases but are injurious to crops.
• no winter (typical to equatorial rainforest climate). Jungle hinders development– construction of roads and railways
• Cloudiness & heavy ppt moderate the daily temperature. is a risky business as workers are exposed to wild animals, poison
• Regular land & sea breezes maintains equable climate. ous snakes, insects and most importantly tropical diseases.Once
• diurnal range of temp is small, and so is the annual range. completed, they have to be maintained at a high cost.
• Heavy thunderstorms occur almost every day in afternoons.
• Ppt heavy,well distributd all yr. Annual avg always above 150cm Rapid deterioration of tropical soil–
• In some regions, annual average may be as high as 250-300 cm. Why restoration of lost forests take decades in equatorial rgns?
• There is no month without rain (distinct dry season is absent). • fertility of topsoil in rainforest regions is very poor.
• maximum rainfall in April & Oct (shortly after equinox). • Least • Torrential downpours leach out most of the topsoil nutrients.
rainfall in June & Dec (solstice: sun is farthest from the equator). • soil deteriorates rapidly with soil erosion & soil impoverishmnt.
• double rainfall peaks coinciding with equinoxes is typical to It takes decades to replenish the soil of lost nutrients.
equatorial climates (not found in any other type of climate). • Thus, a seed doesn’t usually germinate, and even if it does, its
• High temp,abundant rain support luxuriant tropical rain forest. development is hindered due to little availability of sunlight.
• In Amazon lowlands, dense forest called selvas. • Lalang (tall grass) & thick undergrowth spring up as soon as the
• growing season all the year round; • evergreen trees yield trees are cut. They choke the restoration of forests.
tropical hardwood, e.g.mahogany, ebony, dyewoods etc. • Indonesian island of Java is an exception because of its rich
• In coastal areas & brackish swamps, mangrove forests thrive. volcanic ashes.
• Frm air, tropical rain forest appears like thick canopy of foliage,
Difficulties in livestock farming— Livestock farming is greatly
broken only where its crossed by rivers or cleared for cultivation.
handicapped by absence of meadow grass. The grass is so tall
• plants struggle upwards (most epiphytes) for sunlight resulting
and coarse that it is not nutritious; few animals like buffaloes are
in a peculiar layer arrangement. • tallest trees attain a height
kept mainly for domestic use. Their yield in milk or beef is well
close to 50 m; ground is rooted with ferns and herbaceous plants
below those of the cattle in the temperate grasslands.
which can tolerate shade. Because the trees cut out most of the
sunlight, undergrowth is not dense. Mineral resources-Gold, copper, diamonds, and other precious
metals & gemstones are found in rainforests around the world.
Ques–In spite of dense forests, countries in equatorial regions • Extracting these damages rainforest ecosystem. Examples are
are net importers of timber. Comment. gold mining in Brazilian & Peruvian Amazon, rare earth mining in
• Multiple species of trees occur in a particular area (trees do the Congo, and gold and copper mining in Indonesia and Papua
not occur in homogenous stands or pure stands) making New Guinea.
commercial exploitation a difficult task. • Some of the world’s most promising oil and gas deposits lie
• Many tropical hardwoods (very heavy) do not float readily on deep in tropical rainforests. Oil & gas development take a heavy
water, & this makes transportation an expensive matter. toll on the environment & local people ( resource curse).
• More than 70 per cent of the Peruvian Amazon is now under
Life and Economy concession for oil and gas.

1) Agriculture–forests sparsely populated. In the forests, most

primitive people live as hunter-gatherers. The more advanced
Tropical Monsoon Climate (Am: A – Tropical, m – monsoon) • Cattle, sheep rearing for domestic & commercial purposes.
• Livestock industry not as profitable as in temperate regions.
• monsoon climate is characterized by distinct wet & dry seasons Lumbering—
associated with seasonal reversal of winds. • forest yield valuable timber & prized fr their durable hardwood
• Floods in wet season and droughts in dry season are common. • Lumbering done in more accessible area; eg continental SE Asia
• three seasons namely summer, winter and rainy season. • Of tropical deciduous trees, teak(Burma leading producer 3/4th
of world’s productn), is most sought after; valuable for durability,
strength, immunity to shrinkage, fungus attack & insects.
• Teak logs are heavy, dont float readily on water. ஃ necessary to
‘poison’ the tree several years before actual felling so that it is
dry & light enough to be floated down the Chindwin & Irrawaddy
to reach sawmills at Rangoon.
• Other–Neem, Banyan, Mango, Sal, Acacia, Eucalyptus,bamboo
Agricultural Development in Monsoon Lands—
• Occur within 5° to 30° N and S of the equator. • monsoon forest cleared for agri to support very dense populat
• On-shore tropical monsoons occur in summer & off-shore dry • Farming dominant occupatn; Rice most important staple crop.
monsoon in winter; Indian sub-continent, Burma,Thailand, Laos, • Irrigation from rivers, canals, dams or wells is extensively used.
Cambodia, parts of Vietnam & south China & northern Australia. • maize,millet,sorghum,wheat,gram & beans cultivated in drier
• Monthly mean temperatures above 18 °C. or cooler areas where rice cannot be grown.
• Temp range 30-45 °C in summer. Mean summer temp is 30 °C. • Lowland cash crops—most important crop in this category is
• In winters, temp range 15-30 °C with mean temp 20-25 °C. cane sugar; 2/3rd sugar productn comes from tropical countries.
• Annual mean rainfall- 200-250 cm. Cherrapunji & Mawsynram Like India, Java, Formosa, Cuba, Jamaica, Trinidad and Barbados.
receive annual rainfall of about 1000 cm. Jute confined almost entirely to Ganges - Brahmaputra delta.
• Seasons are chief characteristics of monsoon climate. Other crops include cotton
Tropical Marine Climate– • Highland plantation crops— colonisation of tropical lands by
• Outside monsoon zone, the climate is modified by influence of Europns brought plantation agri in cooler monsoonal highlands;
on-shore trade winds all year round. This type of climate is called Coffee–originated in Ethiopia & Arabia; But Brazil accounts for
Tropical Marine Climate. Such climate has more evenly distributd almost half world’s production; mainly grown on eastern slopes
rainfall; experienced in Central America, West Indies, north-east of Brazilian plateau; also cultivated on highland slopes in Central
Australia, Philippines, part of E.Africa, Madagascar, Guinea Coast American states, India & eastern Java.
& eastern Brazil. • rainfall is both orographic & convectional Tea—originated in China; requires moderate temp (15°C), heavy
• Due to steady influence of trades, Tropical Marine Climate is rainf(150cm),well-drained highland slope; thrives well in tropical
more favourable for habitation,but it is prone to severe tropical monsoon zone(highlands); best rgn —Himalayan foothills of India
cyclones, hurricanes or typhoons. & Bangladesh, central highlands of SriLanka & western Java.
Tropical Monsoon Forests— • Shifting Cultivation—widely practised; Instead of rotating crops
• aka drought-deciduous forest; dry forest; dry-deciduous forest; in same field to preserve fertility, tribes move to new clearing
tropical deciduous forest. when their first field is exhausted. As tropical soils are rapidly
• Broad-leaved hardwood trees found; well developed in SE Asia. leached and easily exhausted, first crop may be bountiful, but
• Trees are normally deciduous, because of marked dry period, subsequent harvests deteriorate.Name of Shifting Cultivation—
during which they shed their leaves to withstand the drought.
Malaysia–Lacking Java–Humah Philippines–Caingin
• forests more open & less luxuriant than equatorial jungle, &
Burm—Taungya Sri Lanka—Chena Africa & Central America–
fewer species. Where rainfall is heavy, e.g. in southern Burma,
Thailand–Tamrai NE India—-Jhum Milpa
peninsular India, northern Australia & coastal regions with a
tropical marine climate, resultant vegetation is luxuriant.
• With decrease in rainfall in summer,forests thin out into thorny Savanna or Tropical Wet & Dry Climate (Aw: A – Tropical, w –
scrubland or savanna with scattered trees and tall grass. dry winter)
• In parts of Indian sub-continent (rain shadow regions ―regions • Savanna climate has alternate wet & dry seasons
east of Western Ghats like north Karnataka,Telangana, Vidarbha), • no distinct rainy season like in monsoon climate.
rainfall is deficient ஃ semi-desert condition are found in summer • Rains occur in warm summer months.
• Monsoonal vegetation is most varied, ranging from forests to • Floods & droughts common.
thickets, and from savanna to scrubland. • Vegetatn, wildlife & human life different frm monsoon climate.
Population and Economy in Monsoon Climate— Distribution of Savanna Climate
• Monsoon climatic regions support high population density.
• Income levels are low as most regions are still developing.
• Subsistence farming is main occupation.
• Intensive cultivation common in region with irrigation facilities.
• Shifting cultivation followed in NE India & South-East countries.
• Major crops include rice, sugar, cotton, jute, spices, etc.
• confined within tropics; best developed in Sudan ஃ its named (coffee, tea, cotton) and dairy farming.
Sudan Climate. It is a transitional type of climate found between • cattle kept by Masai are kept entirely for supply of milk. They
equatorial rainforests & hot deserts. don’t slaughter cattle for meat. Agriculture is barely practised.
• African Savanna–West African Sudan & then curves southwards • Hausa tribe of settled cultivators inhabit savanna lands of the
into East Africa & southern Africa north of Tr of Capricorn. Nigeria. They are more advanced in their civilisation. They do not
• S.American Savanna– two distinct regions namely– Llanos of practice shifting cultivation. Instead, they clear a piece of land &
Orinoco basin & Compos of Brazilian Highlands (S of equator). use it for several years.
• Australian savanna–located south of monsoon strip (northern
Australia) running from west to east north of Tropic of Capricorn. Farming–
• Indian Savanna– Northern Karnataka, Southern Maharashtra & • Droughts are long due to unreliable rainfall; Political instability
Telangana has characteristic of both semi-arid & savanna climate. hinders development of agricultural infrastructure.
• Sudan Climate, with distinct wet & dry prds, is also responsible
Savanna Climate for rapid deterioration of soil fertility.
• Rainfall–less annual rainfall. Mean annual rainfall–80 – 160 cm. • During rainy season, torrential downpours of heavy rain cause
Rain decreases with distance frm equator. In NH, rainy season leaching of nitrates, phosphates & potash.
May to Sep. In SH, rainy season from Oct to March. • During dry season, intense heating & evapouration dry up most
• Temperature–Mean annual temp greater than 18°C; monthly of the water. Many savanna areas, therefore, have poor lateritic
temp bw 20 °C & 32 °C for lowland stations. Highest temp do not soils which are incapable of supporting good crops.
coincide with prd of highest sun (eg. June in NH) but occur just
b4 onset of rainy season, i.e. April in NH & October in SH. Days Crops in Savanna
are hot & nights cold; extreme diurnal range of temp is feature of • Settlement in central Africa, northern Australia & eastern Brazil
Sudan type of climate. have shown that savannas have immense agricultural potential
• Winds—prevailing winds of region are trade winds, which bring for plantation agriculture of cotton, cane sugar, coffee, oil palm,
rain to coastal areas. They are strongest in summer (favourable groundnuts & even tropical fruits.
position of ITCZ) but dry when they reach continental interiors or • Kenya, Uganda, Tanzania & Malawi have large-scale production
western coasts. Hence, rainfall decreases from east to west). In of cotton. In West Africa, commercial cultivation of groundnuts,
West Africa, North-East Trades blow off-shore (continent to sea) oil palm & cocoa is extended into savanna lands. In cooler high–
frm Sahara Desert & reach Guinea coast as dry, dust-laden winds. lands, temperate crops are successfully raised.
reason fr alternating wet & dry seasons in Savanna type climate?
• On-shore winds in summer bring rains. Cattle rearing—
• Off-shore winds in winter keep the climate dry. • savanna is natural cattle country, & people are pastoralists. But
quality of grass doesnt support large scale ranching. Grasses here
Natural Vegetation of Savanna Climate are not like nutritious & soft grasses of temperate grasslands.
• savanna landscape has tall & coarse grass (6-12ft) & short trees • cattle varieties are also poor & yield little meat or milk.
• elephant grass attain ht of 15ft; grasslands aka bush-veld. • export of either beef or milk from tropical grasslands not done
• Grasses appear greenish & well-nourished in the rainy season.
& die down in dry season increasing the risk of forest fires. B) – Dry Climate
• trees are deciduous, shedding their leaves in cool, dry season • Grasslands & deserts are classified under B – dry climate.
to prevent transpiration, e.g. acacias. • Grasslands include subtropical savanna grasslands (BSh) and
• Trees usually have broad trunks, with water-storing devices to temperate steppe grasslands (BSk).
survive through the prolonged drought. Many trees are umbrella • Deserts 2 types: 1. hot deserts (BWh) & 2. temperate or
shaped, exposing only a narrow edge to the strong winds. mid-latitude deserts (BWk).
• As the rainfall diminishes towards deserts, savanna merges into
thorny scrub (semi-arid).
Animal Life of the Savanna
• Rich animal diversity is characteristic of savanna climate.
• zebra, antelope, deer, elephant,tiger, leopard, hyena, panther,
jaguar, jackal; reptiles & mammals like crocodiles, alligators, giant
lizards live together with rhino & hippo in rivers & marshy lakes.
• Seasonal migration of animals in search of food
• savanna is known as big game country as animals are hunted
down both legally & illegally.
Life and Economy in the Savanna Hot Desert Climate (BWh: B – Dry, W – Desert, h – low latitude)
• Masai tribes of East African plateau are pastoralists whereas • aridity of hot deserts is mainly due to effects of off-shore trade
Hausa of northern Nigeria are settled cultivators. winds; hence they are also called trade wind deserts.
• old grazing grounds of Masai tribes in Kenyan Highlands were • major hot deserts are located on western coasts of continents
taken over by white immigrant settlers for plantation agriculture bw 15° & 30°N & S. They include Sahara Desert (3.5 million sq
miles), Great Australian Desert, Arabian Desert, Iranian Desert, them while they lie dormant for years.
Thar Desert, Kalahari and Namib Deserts. • Life in Deserts—desert peopled by diff groups of inhabitants.
• In N.America, desert extends frm Mexico into US & is called by Tribe Desert Occupation
diff names, e.g. Mohave, Sonoran,Californian & Mexican Deserts. Bedouin Arabs Arabia nomadic herdsmen
• In S.America, Atacama or Peruvian Desert is driest of all deserts Tuaregs Sahara nomadic herdsmen
with less than 2 cm of rainfall annually. Gobi Mongols Gobi nomadic herdsmen
Bushmen Kalahari primitive hunters and collectors.
Mid-Latitude Desert Climate (BWk: B – Dry, W – Desert, k – high Bindibu Australia primitive hunters and collectors.
latitude)
• temperate deserts are rainless bcoz of continentality (e.g. Gobi • Settled cultivators–Modem dams constructed across Nile, e.g.
Desert) or rain-shadow effect (e.g. Patagonian Desert due to rain Aswan & Sennar Dams improved agriculture. In deserts, where
shadow effect of Andes). there are oases (depressions where underground water reaches
•many mid-latitude desert are found on plateau & are at conside surface), some form of settled life follows. Some are abnormally
rable distance frm sea. eg. Ladakh, Turkestan, Kyzyl Kum, Gobi large like Tafilalet Oasis in Morocco(5000sq miles); wall is constru
deserts & Taklimakan of Central Asia, drier portion of Great Basin cted around oasis to keep out the violent dust storms called
Desert of western US & Patagonian Deserts of Argentina etc. simooms; most important tree is date palm. Other crops– maize,
barley, wheat, cotton, cane sugar, fruits & vegetables.
Desert Climate—
• Rainfall (Both Hot & Cold deserts)--annual ppt less than 25cm. • mining settlers—Gold is mined in Great Australian Desert.
• Rain normally occurs as violent thunderstorms of convectional Kalgoorlie & Coolgardie have become large towns. In the Kalahari
type occasionally causing flash floods. Desert (thirstland), discovery of diamonds & copper has brought
• Temperature of Hot deserts—no cold season in hot deserts and many white men. In Atacama, in northern Chile, large mining
avg summer temp is high around 30°C; highest temp recorded is camps established for mining of caliche (cemented gravels) from
57.77 °C in 1922 at Al Azizia, Libya; reason fr high temp are–clear, which sodium nitrate, a valuable fertiliser, is extracted. Besides
cloudless sky, intense insolation, dry air & rapid rate of evaporatn nitrates, copper is also mined. Chuquicamata is world's largest
• Coastal deserts due to maritime influence & cooling effect of copper town. In deserts of N.America, silver is mined in Mexico,
cold currents have much lower temperatures; desert interiors, uranium in Utah & copper in Nevada. Discovery of oil, in many
experience higher summer temp & winter months are cold. parts of Saharan & Arabian Deserts, has transformed the region.
• diurnal range of temp in deserts is large. Intense insolation by
day in a rgn of dry air & no clouds causes temp to rise with sun. Steppe or Temperate Grassland Climate (BSk: B– Dry, S– Steppe,
But at night, land loses heat vry quickly by radiation & temp drop k – high latitude)
• High diurnal temp range is typical feature of hot deserts. Avg • Steppe climate aka Temperate Continental Climate.
diurnal range varies from 14 to 25 °C. • Distribution–Most temperate grasslands lie in interiors of the
• Frosts may occur at night in winter. continents in westerly wind belt. Some are formed due to rain
• Climatic Conditions in Mid-latitude deserts—These lie very far shadow effect of mountains; on leeward side desert or grassland
from the sea & sheltered by high mountains all around them. As are formed. Grasslands are treeless due to continentality and /or
a result, they are cut off from the rain-bearing winds. rain shadow effect. In Eurasia, they are called steppes; stretch
• Occasionally depressions may penetrate the Asiatic continental eastward frm shores of Black Sea to foothills of Altai Mountains.
mass & bring light rainfall in winter. Due to their coldness and
elevation, snow falls in winter.
• annual range of temp is greater than that of hot deserts.
• Continentality accounts for these extremes in temperature.
• Winters severe. When ice thaws in early summer, floods occur
• Desert Vegetation–predominant vegetation of both hot & mid-
latitude deserts is xerophytic or drought-resistant— cacti, thorny
bushes, long-rooted wiry grasses & dwarf acacias. Trees are rare
except where there is abundant groundwater to support clusters
of date palms; western coastal deserts washed by cold currents
support a thin cover of vegetation.
• Intense evapouration increases salinity of soil ஃ dissolved salts
accumulate on surface forming hard pans (Bajada, Palaya).
• Absence of moisture retards the rate of decompositn ஃ desert
soils are very deficient in humus.
• desert shrubs have long roots (in search of groundwater) & are
well spaced out to gather moisture; Plants hv few or no leaves, &
foliage is leathery, hairy or needle-shaped to reduce loss of water
through transpiration.
• seeds of grasses & herbs have thick, tough skins to protect
 • Nomadic herding in Asian Steppes–This type of migratory
animal grazing has almost disappeared from major grasslands;
herders were wandering tribes, e.g. Kirghiz, & Kazakhs; steppes
have been made into collective farms & state farms for ranching
or producing cereals.
• Extensive mechanised wheat cultivation—temperate grassland
are ideal for extensive wheat cultivation; levelness of Steppes &
other temperate grasslands all over world makes ploughing and
harvesting easy job. In Prairies, Argentinian Pampas, Ukrainian
Temperate Grassland Region
Steppes & Downs of Australia, agriculture is completely
Pustaz Hungary and surrounding regions
mechanised.
Prairies NA (bw foothill of Rockies & Grt Lakes)
• Pastoral farming– natural conditions suit animal farming. With
Pampas Argentina & Uruguay(Rain-shadow) development of refrigerated ships temperate grasslands became
Bush-veld (more tropical) Northern South Africa major pastoral regions, exporting large quantity of beef, mutton,
High Veld(more temperate) Southern South Africa wool, hides;also Milk, butter, cheese and other dairy products
Downs Australia: Murray-Darling basin
Canterbury NZ (Southern Alps rain shadow effect) Grassland Major Economic Activity
Climate Prairies • Wheat Granaries • Extensive Ranching
Pustaz • Rich black soil •Abundant wheat productn
• Temperature–Climate is continental with extremes of temp.
• Sugar from Sugar beet (Beta vulgaris roots
summers are hot & winters cold; Summers over 18-20 °C. In SH,
has high concentration of sucrose)
summers are never severe due to very narrow landmasses.
• Countries like Hungary, Ukraine, Romania
• Precipitation–avg rainfall 45 cm. But varies acc to location from
Pampas • Alfalfa: nutrient-rich grass
25 to 75cm (below 25cm is desert climate); heaviest rain in June
• Ranching, cattle rearing; Dairy products
& Jul; winter months hv 2.5cm ppt(snow), brought by Westerlies
• Extensive wheat producing region
The maritime influence in SH causes more rainfall.
• Economy depends on wheat & beef export
• Chinook (Snow eaters)--Chinook is a hot local katabatic wind
that blows down eastern slopes of Rockies in a south-westerly Downs & Canterbury • Sheep and Cattle rearing,
direction towards Prairies. It is similar to Fohn in Switzerland. • Merino sheep: wool production
It comes with the depressions in winter from the Pacific coast Veldts • Maize farms
ascending the Rockies & then descending to Prairies. It is a hot • Sheep and Cattle rearing
wind & may raise the temp by 5 °C in 20 minutes. It melts the
snow-covered pastures & benefits agriculture & animal ranching.
C – Warm Temperate (Mid-latitude) Climates
Natural Vegetation of Steppe Climate
• Grasses–Greatest diff from the tropical savanna is that steppes Mediterranean Climate (Cs: C–Warm Temperate, s–Dry summer)
are treeless, & grasses are much shorter. Grasses are tall, fresh & • aka Warm Temperate Western Margin Climate or Warm
nutritious. This is typical of grass of wheat-lands in N.America, Temperate West Coast Climate.
rich black earth or chernozem areas of Ukraine & better-watered
areas of Asiatic Steppes. Where rainfall is light or unreliable, or
soil is poor, as in the continental interiors of Asia, short steppe
type of grass prevails; grasses are not only shorter but also wiry
(lean, tough) & sparse (thinly dispersed or scattered). These
areas are less suitable for arable farming & are used for ranching.
• Trees—Poleward, increase in ppt gives rise to a transitional
zone of wooded steppes where some conifers gradually appear..
• Animals–Temperate grasslands dont hv much animal diversity.
Horses are common in Asian Steppes. • Distribution–confined to western part of continents, bw 30° &
45° N & S of equator; this type of climate is dueto shifting of wind
Economic Development of Steppes belts (westerly wind belt). Mediterranean Sea has greatest extent
• Wheat and Maize Cultivation –In recent years, grasslands have of this type of winter rain climate(winter maxima); Best-developd
been ploughed up for extensive, mechanised wheat cultivation & form of this climatic is found in central Chile.Other Mediterranean
are now the ‘granaries of world’ (Prairies); maize cultivated in the regions include---California(around SanFrancisco), SW tip of Africa
warmer & wetter areas. (around CapeTown), Southern Australia & SW Australia(Swanland)
• Ranching– tufted grasses been replaced by the more nutritious • Climate— clear skies & high temp; summers are hot and dry, &
Lucerne or alfalfa grass for cattle & sheep rearing; temperate winters are cool & wet. Mean annual ppt ranges from 35-90 cm.
grasslands are now leading ranching regions (e.g. Pampas of Temp of warmest month is ≥ 10° C. Temp of coldest month is less
Argentina). than 18° C but greater than –3° C. Climate is not extreme because
of cooling from water bodies. if grasses do survive, they are so wiry (lean, tough) & bunchy that
• dry, warm summer with off-shore trades—In summer, the belt they are not suitable for animal farming. Cattle rearing is ஃ not
of influence of Westerlies is shifted a little poleward.Rain-bearing important in Mediterranean.
winds ஃ dont to reach Mediterranean land; prevailing trade wind Agriculture in Mediterranean Climate
(tropical easterlies) are off-shore, & there is no rain. Strong winds • Orchard farming-Mediterranean land aka world’s orchard land;
from inland desert regions pose the risk of wildfires. account for 70% of world’s export of citrus fruits; olive tree most
• Rain in winter with on-shore Westerlies– Mediterranean lands typical of all Mediterranean cultivated vegetation; citrus fruits
receive most of ppt in winter when westerlies shift equatorward. such as orange, lemon, limes, citrons & grapefruit are grown; nut
• In NH, prevailing on-shore westerlies bring cyclonic rain from trees like chestnuts, walnuts, & almonds are grown; fruit trees
the Atlanticb; rain comes in heavy showers & only on a few days have long roots to draw water from depths during long summer
with bright sunny prds bw them. This is characteristic feature of drought; thick, leathery skin of citrus fruits prevents excessive
Mediterranean winter rain. transpiration; long, sunny summer enables fruits to be ripened
• Local winds of the Mediterranean Climate–Many local winds, and harvested.
hot or cold are common around Mediterranean Sea. • Crop cultivation and sheep rearing–Wheat is leading food crop.
Sirocco–hot, dry dusty wind; originates in Sahara Desert. After Barley is next most popular cereal; mountain pastures, with their
crossing Mediterranean Sea, Sirocco is cooled by the absorption cooler climate, support few sheep, goats & cattle. Transhumance
of water vapour. Its scorching heat withers vegetation and crops. is widely practised.
Bring blood rain because wind carries red dust of Sahara Desert. • Wine production–Viticulture is Mediterranean occupation.
Mistral–cold wind from the north, rushing down Rhone valley in Mediterranean regions account for 3/4th of world’s production of
violent gusts; velocity of Mistral is intensified by funnelling effect wine. 85% of grapes produced, go into wine.
in the valley bw Alps & Central Massif (Plateau in France). • Economy– net exporter of citric fruits & net importer of dairy
products. Clear summer skies & good landscapes favours tourism

Warm Temperate Eastern Margin Climate (Cfa)

• Cfa: C – warm temperate, f – no dry season, a – hot summer.
• aka Humid subtropical climate.
• found bw 20° & 35° N & S latitude (warm temperate latitudes
or subtropics; hence it is aka Humid subtropical climate); on the
east coast in both hemispheres.
Different variants of Warm Temperate Eastern Margin Climate—
a) Temperate monsoon Climate or China Type Climate,
b) Gulf Type Climate
c) Natal Type Climate.

• cold north-easterly wind along Adriatic coast is called the Bora.

• Tramontane & Gregale are cold winds of Mediterranean Sea.
• Natural Vegetation in the Mediterranean Climate—Trees with
China Type–Temperate Monsoon or China Type climate observed
small broad leaves are widely spaced & not very tall; absence of
in most part of China & southern parts of Japan.
shade is a distinct feature of Mediterranean lands. Plants are in a
• Summer–Intense heating within interiors (Tibet, desert region)
continuous struggle against heat, dry air, excessive evapouration
sets up a region of LP in summer attracting tropical Pacific air
& prolonged droughts. They are xerophytic (drought tolerant).
stream (SE Monsoon). Monsoon does not ‘burst’ suddenly, nor
• Mediterranean evergreen forests–open woodlands with ever–
‘pour’ as heavily as in India. Typhoons form in late summer, from
green oaks found; trees are stunted, with massive trunks, small
July to September.
leathery leaves & wide-spreading root system; cork oaks valued
• Winter–theres intense pressure ovr Siberia & continental polar
fr their thick barks, used fr making wine-bottle corks. In
air stream flows outwards as the NW Monsoon, bitterly cold &
Australia, eucalyptus forests replace the evergreen oak; giant
dry; Theres little rain but considerable snow on windward slopes
redwood is typical of Californian trees.
Gulf Type– Found in south-east US, bordering the Gulf of Mexico
• Evergreen coniferous trees–include pines,firs,cedars, cypresses
where continental heating in summer induces inflow of air from
which hv evergreen,needle-shaped leaves & tall, straight trunks.
cooler Atlantic Ocean. Monsoonal characteristics are less intense
• Mediterranean bushes and shrubs–most predominant type of
compared to China type. There is no complete seasonal wind
Mediterranean vegetation.
reversal. Hurricanes occur in September & October.
• Grass–Conditions in Mediterranean do not suit grass, because
Natal Type–Found in New South Wales (Australia), Natal (South
most of the rain comes in cool season when growth is slow. Even
Africa), Parana-Paraguay-Uruguay basin(S.America). Its different
from temperate monsoon or China type as it receives rainfall industry); corn’s yield is twice as much food (mainly starch) per
from on-shore Trade Winds all the year round; narrowness of the acre as wheat or other cereals. Thats why its widely cultivated in
continents & dominance of maritime influence eliminate the both warm temperate and the tropical latitudes.
monsoonal elements. South-East Trade Winds bring more even Cotton–Gulf type of climate is best for cotton growing; Its long,
distribution of rainfall throughout the year hot growing season with 200 days frost free & a moderately high
China type Temperate monsoonal temp permits crop to grow slowly & mature within 6 months. In
Gulf type Slight-monsoonal south Gulf-lands, heavy rainfall damages the lint. ஃ This area is
Natal type Non-monsoonal less suitable for cotton & is devoted to citrus fruits, cane sugar
• Climate—Characterised by a warm moist summer & cool, dry and market gardening, as in Florida; commercial cultivation of
winter (winters are also moist in Natal Type). cotton is concentrated only in Mississippi flood plains & Atlantic
• Temperature— mean monthly temp varies bw 4°C & 25°C & is coastlands; enemy of Cotton Belt is boll-weevil pest;
strongly modified by maritime influence; sometimes penetration Tobacco—native crop of America; humid atmosphere, warmth &
of cold air (Polar Vortex) from continental interior bring down well-drained soils of Gulf states, enable tobacco to b cultivated in
temp to freezing point; frost are rare,but occur in colder interior. eastern states of US. 50% tobacco comes from these states.
• Precipitation—Rainfall is more than moderate –60 to 150 cm. Crops in Southern Hemisphere–In coastlands of Natal, cane sugar
adequate for all agricultural purposes & hence supports a wide is dominant crop, followed by cotton & tobacco in interior. Maize
range of crops; very densely populated;fairly uniform distribution is extensively cultivated. In S.America where rainfall is less than
of rain throughout the year. Rain comes either from convectional 120 cm, there is grassland on which cattle & sheep are kept for
sources or as orographic rain in summer, or from depressions in meat, wool & hides; extensive natural pastures provide valuable
prolonged showers in winter. In summer, regions are under the forage for both cattle & sheep. Further north in southrn Brazil,
influence of moist, maritime airflow from the subtropical rainfall increases to more than 120cm & forest gradually replaces
anticyclonic cells. Local storms e.g. typhoons, & hurricanes occur. grass. Here occupatn is cultivation of yerba mate (Paraguay tea)
• Natural Vegetation–Supports luxuriant vegetation; lowlands & lumbering of araucaria or Parana pine. In eastern Australia,
carry both evergreen broad-leaved forests & deciduous trees; eucalyptus trees till Eastern Highlands.
On the highlands, are various species of conifers such as pines &
cypresses which are important softwoods.Perennial plant growth British Type Climate or Cool Temperate Western Margin Climate
is not checked by either a dry season or a cold season; forests of (Cf)
China & south Japan hv economic value & include oak, camphor, • Cf: C – Warm temperate, f – no dry season
South-eastern Brazil, eastern Paraguay, north-eastern Argentina • aka as North-West European Maritime Climate; cool temperate
have Parana pine, & quebracho( extremely hard wood used for western margins are under influence of Westerlies all-round the
tanning). East Australia hv Eucalyptus forest. In Natal, palm trees year. They are regions of frontal cyclonic activity (temperate cyc).
thrive. Gulf state of US hv lowland deciduous forests. typical to Britain. Also called as North-West European Maritime
Economic Development Climate due to greater oceanic influence.

Region Major Cropping Patterns

SE China • Rice, tea & mulberries (sericulture)
• Sericulture is declining
SE US • Widespread cultivatn of maize & cotton in Corn
& CottonBelts • Fruit and tobacco are also grown
Natal, S.Africa • Sugarcane
S.America • Coffee and maize and dairying
Distribution of British Type Climate—
Europe– Most pronounced in Britain. In Europe, climate extends
far inland into lowland of NW Europe (northrn & westrn France,
• Farming in monsoon China– 1/3rd of world’s rice is grown in Belgium, Netherlands, Denmark, western Norway & NW Iberia).
China. Monsoon China has all ideal conditions for padi cultivatn; North America—High Rockies prevent on-shore westerlies from
warm climate, moderately wet throughout the year, & extensive penetrating far inland. ஃ it is confined mainly to coastlands of
lowlands with fertile moisture-retentive alluvial soil, which can b British Columbia.
easily irrigated. As the flat lands are insufficient for rice cultivatn, South Hemisphere– climate experienced in southern Chile, South
farmers move up hill-slopes & grow padi on terraced uplands. Australia, Tasmania & New Zealand (rgns east of Southern Alps).
• Agriculture in Gulf states– export gave rise to corn, cotton &
tobacco. Climate—.
Corn–needs humid air, sunny summer & heavy shower; Its grown • Temperature– mean annual temp bw 5 °C & 15 °C. Summers
from Gulf coast to Mid-west south of Great Lakes, with greatest are moderately warm. Winters are abnormally mild because of
concentration in Corn Belt of Nebraska, Iowa, Indiana & Ohio. warming effect brought by warm North Atlantic Drift.Sometimes,
accounts for more than half of world’s production of corn, but unusual cold spells are caused by invasion of polar continental air
only 3% of world’s export.This is because most of the corn is used from the interiors.
for fattening animals, mostly cattle & pigs (thriving beef & pork • Precipitation–Rainfall occurs throughout the year with winter
maxima (due to frontal cyclones). Western margins have heaviest Audi, Mercedes-Benz and many other
rainfall due to westerlies. In New Zealand, western margins has world leading car manufacturers have their headquarters in
heavy orographic rainfall whereas eastern Canterbury plains Germany).
receive comparatively less rainfall due to rain-shadow effect. • Industries based on dairy products thrive in Denmark,
Canterbury Plains are east of Southern Alps Netherlands and New Zealand.
• seasons—4 distinct seasons (absent in tropics). • Tasmania is important for merino wool production. Wool
Rainforest: Only Rainy seasn; Tropical Monsoon: Summer, Winter produced here is exported to textile factories in
& Rainy; Tropical Savanna: Summer (rains) & Winter. England, Japan, China etc.
• Winter is season of cloudy skies, foggy mornings, & many rainy • Fishing is particularly important in Britain, Norway and British
days from the passing depressions. Columbia.
• Spring is the driest and the most refreshing season when Agriculture
people emerge from the depressing winter. • A large range of cereals, fruits and root crops are raised, mainly
• This is followed by the long, sunny summer. for home consumption.
• Next is the autumn with the roar of gusty winds; and the cycle • North-West Europe, which includes some of the most crowded
repeats itself. parts of the globe, has little surplus for export.
Climate Graph British Type Climate It is, in fact, a net importer of food crops, especially wheat.
Climate graph of London Market gardening
Natural Vegetation in British Type Climate • All the north-western European countries are highly
• The natural vegetation of this climatic type is deciduous forest industrialised and have high population densities.
(trees shed their leaves in the cold season). • There will normally be great demand for fresh vegetables, eggs,
• This is an adaptation for protecting themselves against the meat, milk and fruits.
winter snow and frost. • As the crops are perishable, a good network of transport is
• Shedding begins in autumn, the fall season. indispensable.
• Some of the common species include oak, elm, ash, birch, • The produce is shipped by high-speed trucks (truck farming,
beech, and poplar. which is commonly used in the United States)
• In the wetter areas grow willows (lightweight cricket bats are • In Australia, high-speed boats ply across the Bass Strait daily
made from willows. In India willows are found from Tasmania (garden state) to rush vegetables
in Kashmir). and fruits to most of the large cities in mainland Australia.
• Higher up the mountains, deciduous trees are generally Mixed farming
replaced by the conifers which can survive a higher • Arable farms are devoured by factories and wheat is now a net
altitude, a lower temperature and poorer soils. import item in Europe.
Economy in British Type Climate • Throughout north-western Europe, farmers practice both
Lumbering is quite profitable arable farming (cultivation of crops on ploughed
• Unlike the equatorial forests, the deciduous trees occur in pure land) and pastoral farming (keeping animals on grass meadows).
stands and have greater lumbering value. • Amongst the cereals, wheat is the most extensively grown,
• The open forests with sparse undergrowth mean that logging, almost entirely for home consumption.
transportation are easy and economical. • The next most important cereal raised in the mixed farm is
• The deciduous hardwoods are excellent for both fuel and barley.
industrial purposes. • The better quality barley is sold to the breweries for
• In Tasmania, the temperate eucalypts are also extensively beer-making or whisky distilling.
felled for the lumbering industry. • The most important animals kept in the mixed farm are cattle.
• Higher up the mountains, conifers (softwood) are felled and • The countries bordering the North Sea (Britain, Denmark, the
transported to paper and pulp industry. Netherlands) are some of the most advanced
• They are extensively used in cardboard making. dairying countries where cattle are kept on a scientific and
Industrialisation intensive basis.
• The regions are highly industrialized with high standard of Dairying
living. • The temperate western margin type of climate is almost ideal
• Britain, France and Germany have significant mineral resources for intensive dairying.
and are heavily industrialised. • Cheese is a specialized product of the Netherlands.
• The countries are concerned in the production of machinery, • From Denmark and New Zealand comes high-quality butter.
chemicals, textiles rather than agriculture, fishing • Milk is converted to cream (less perishable than fresh milk) and
or lumbering, though these activities are well represented in is exported to all regions across the globe.
some of the countries. • Fresh milk is converted into various forms of condensed or
• Ruhr region in Germany, Yorkshire, Manchester and Liverpool evapourated milk, and exported around the
regions in Britain are significant for wideranging world for baby-feeding, confectionery, ice-cream and chocolate
manufacturing industries. making.
• Automobile industry is the most significant (BMW, Volkswagen, Beef cattle
• Besides dairying, some cattle are kept as beef cattle.
• In Argentina or Australia, meat production is the primary fades into steppe climate.
concern. ● Stretches along continuous belt across central Canada, parts
• The high rate of beef consumption in Europe necessitates large of Scandinavian Europe & most of central & southern Russian.
imports of frozen and chilled beef. ● Summers brief & warm (20-25°C); winters long & cold (30- 40
• The pigs and poultry act as scavengers that feed on the °C below freezing).Some of lowest temp in world recorded in
left-overs from root-crops and dairy processes. Verkhoyansk (68°N) where -67°C once recorded.
• In this way, Denmark is able to export large quantities of bacon ● Annual temp range-greatest due to continentality (50- 60°C in
(cured meat from the back or sides of a pig) Siberia).
from pigs that are fed on the skimmed milk, a by-product of ● In N.America, extremes less severe, bcoz of continent’s lesser
butter-making. east-west stretch. All over Russia, nearly all rivers are frozen.
Sheep rearing ● Occasionally cold, polar local winds--'blizzards' of Canada &
• Sheep are kept both for wool and mutton. 'buran' of Eurasia blow violently.
• Britain is the home of some of the best-known sheep breeds. ● Permafrost absent as snow is poor conductor of heat, protects
• With the greater pressure exerted on land by increased ground from severe cold above. Maritime influence in
urbanisation, industrialisation and agriculture, interiors absent.Frontal disturbances might occur in winter.
sheep rearing is being pushed further and further into the ● Annual pptn 38cm-63cm- well distributed with a summer max
less-favoured areas. (convectional rains). In winter pptn is in form of snow.
• Britain was once an exporter of wool (but now it imports from ● Predominant vegetn=evergreen coniferous forest-require little
Australia). moisture. Pine, fir (douglas fir & balsam fir), spruce & larch are
• Today it exports only British pedigree animals to the newer 4 major species of conifers. Greatest single band of coniferous
sheep lands of the world (Australia). forest is Taiga (Russian word for coniferous forest) in Siberia.
• In the southern hemisphere, sheep rearing is the chief ● In Europe countries with similar type of climate & forests are
occupation of New Zealand, with its greatest concentration Sweden and Finland.
in the Canterbury Plain (the rain shadow region). ● Small amt of natural coniferous forest in Germany, Poland,
• Favourable conditions include extensive meadows, a mild Switzerland, and other parts. In N.America, belt stretches
temperate climate, well-drained level ground, scientific from Alaska across Canada into Labrador.
animal breeding, refrigeration (enables the export of chilled ● In SH coniferous forests found only on mts.uplands of S.Chile,
Canterbury lamb and Corriedale mutton New Zealand, Tasmania & SE Australia.
to every corner of the globe). ● Coniferous forests--moderate density & more uniform-- trees
Other agricultural activities straight and tall--almost all conifers evergreen--no annual
Potatoes replacement of new leaves as in deciduous trees---same leaf
• Potatoes feature prominently in the domestic economy of the remains on tree for around 5 yrs .
cool temperate regions. ● Conifers conical shape, prevent snow accumulation.
• It is the staple food in supplementing wheat or bread for Transpiration quite rapid in warm summer--leaves small, thick,
millions of people. leathery & needleshaped to check excessive transpiration.
• Potato yields far more starch than any cereals and can be ● Soils of coniferous are poor---excessively leached & acidic
cultivated over a range of climatic and soil types. ● Humus content low as evergreen leaves barely fall & rate of
Beet Sugar decomposition is slow.
• Found almost exclusively in north-western Europe (including ● Under-growth negligible bcoz of poor soil conditions.\
European Russia) and parts of U.S.A. ● Absence of direct sunlight and short duration of summer are
• The beet is crushed for sugar, and the green tops are used as other contributory factors.
animal fodder. Producing sugar from beet ● Coniferous forests found in regions with high elevation (Ex:
sugar started during the Napoleonic Wars when military forests just below snowline in Himalayas)-on very steep slopes
blockades caused a scarcity of sugar. where soils immature/ non-existent, even conifer can't survive
(Ex: Southern slopes of Greater Himalayas).
D – Cold Snow-forest Climates ● Eco Development--Only small fraction of coniferous forests in
Canada, Russia etc. exploited. Agriculture is most unlikely as
Taiga or Boreal Climate few crops can survive in sub-Arctic climates.
● Trapping----fur-bearing animals are trapped in northerly
● (Dfc: f – no dry season, c – cold summer) lands of Canada and Eurasia.
● Siberian Climate or Cool Temperate Continental Climate or ● • Wherever the cold is severe, the quality and thickness of
Continental Sub-Polar Climate the fur increases.
● just below Arctic circle ― 50° to 70° N • In Canada trappers and hunters, armed with automatic rifles,
● found only in NH due to great east-west extent. reside in log cabins in the midst of the coniferous
● absent in SH bcoz of narrowness of landmasses & strong forests to track down these animals.
oceanic influence in high latitudes. • Muskrat, ermine, mink, and silver fox are the most important
● On poleward side, merges into Arctic tundra; equatorward it fur-bearing animals.
• To ensure a more regular supply of furs, many fur farms have
been established in Canada and Siberia. the Arctic Ocean which is frozen for threequarters
Lumbering of the year, and there are few saw-mills there.
• This is the most important occupation of the Siberian type of • However, with the use of the Northern Sea Route, which links
climate. Murmansk and Vladivostok via the Arctic
• The vast reserves of softwood coniferous forests provide the Ocean, development is increasing.
basis for the lumbering industry. Cheap electricity
• The world’s greatest softwood producers are Russia, U.S.A., • Cheap hydro-electricity for driving the saw-mills is harnessed in
Canada and the Fennoscandian countries the mountainous uplands of North America
(Finland, Norway and Sweden). and Europe and has greatly assisted the lumbering industry.
• Contract labourers called lumberjacks used to temporarily Laurentian Climate or Cool Temperate Eastern Marine Climate
move to the forest regions to fell the trees. Now (Dfc)
felling is done by machines. • Dfb: f – no dry season, b – warm summer.
• Rivers for transportation: The softwood logs easily float on • It is an intermediate type of climate between the British Type
rivers. Hence rivers are used to transport logs Climate (moderate) and the Taiga Type
to the sawmills located down the stream. Climate (extreme).
• Sawmilling: Logs are processed in sawmills into timber, • It has features of both the maritime and the continental
plywood, and other constructional woods. climates.
• Paper and pulp industry: Timber is pulped by both chemical Distribution of Laurentian Climate
and mechanical means to make wood pulp. • Laurentian type of climate is found only in two regions and that
Wood pulp is the raw material for paper-making and newsprint. too only in the northern hemisphere.
U.S.A. is the leader. • North-eastern North America, including eastern Canada,
• But in the field of newsprint, Canada accounts for almost half north-east U.S.A., and Newfoundland. This may
of the world’s total annual production. be referred to as the North American region.
• As a fuel: Very little softwood is burnt as fuel as its industrial • Eastern coastlands of Asia, including eastern Siberia, North
uses are far more significant. China, Manchuria, Korea and northern Japan.
• As an industrial raw material: In Sweden, matches form a major Absent in Southern Hemisphere
export item. • In the southern hemisphere only a small section of continents
• From the by-products of the timber, many chemically extends south of 40° S latitude.
processed articles are derived such as rayon turpentine, • Some of these small sections come under the rain-shadow
varnishes, paints, dyes, liquid resins, wood-alcohols, disinfectants region of Andes (Patagonia).
and cosmetics. • So, these regions are subjected to aridity rather than
Factors that favour lumbering in Taiga climate continentality.
Softwood trees • In other regions, the oceanic influence is so profound that
• The coniferous forest belts of Eurasia and North America are neither the continental nor the eastern margin
the richest sources of softwood. type of climate exists.
Demand Climate
• Softwood is used in construction, furniture, matches, paper Temperature
and pulp, rayon and chemical industry. • Characterized by cold, dry winters and warm, wet summers.
Limited species • Winter temperatures is below freezing-point and snow fall is
• The conifers are limited in species. Pine, spruce and fir in the quite natural.
northern forests and larch in the warmer • Summers are as warm as the tropics (~25 °C).
south are the most important. Precipitation
Pure stands • Rainfall occurs throughout the year with summer maxima
• Unlike rainforests, they occur in homogeneous groups (pure (easterly winds from the oceans bring rains).
stands). • Annual rainfall ranges from 75 to 150 cm (two-thirds of rainfall
• This saves time, costs and enhances the commercial value of occurs in the summer).
the felled timber. • Dry westerlies that blow from continental interiors dominate
• Lumbering is normally carried out in the winter when the sap winters.
ceases to flow (sap stays in the ground, and The North American region
the wood is lighter). • In summer, prolonged heat waves cause discomfort.
Cheap means of transportation • In winter, the temperature drops below freezing and snowfall
• The snow-covered ground makes logging and haulage occurs.
(commercial transport) a relatively easy job. • Precipitation occurs all-round the year due to the influence of
• The logs are dragged to the rivers and float to the saw-mills warm Gulf Stream (increases the moisture
downstream when the rivers thaw in spring. of easterly winds in summer) and the Great Lakes (westerlies,
• It is quite easy in Canada, Norway and Sweden as the rivers are temperate cyclones in winter).
not frozen for a greater part of the year. • The warm Gulf Stream increases the moisture of easterly
• But in Russian taiga, most of Siberian rivers drain poleward into winds.
• Convergence of the warm Gulf Stream and the cold Labrador are most common.
Current near Newfoundland produces dense • They have been extensively felled for the extraction of
mist and fog and gives rise to much precipitation. temperate hardwood.
• It is said that Newfoundland experiences more drizzles than • In Manchuria, Korea and Japan, the forests have made way for
any other part of the world. the agriculture.
Cold and warm ocean current mixing zone off Newfoundland Economic Development
The Asiatic region • Lumbering, timber, paper and pulp industries are the most
• Rainfall distribution of the Asiatic region is far less uniform important economic undertakings.
when compared to North American Region. • Agriculture is less important because of long and severe
• Winters are cold and very dry while summers are very warm winters.
and exceptionally wet. • In the North American region, farmers are engaged in dairy
• The rainfall regime resembles the tropical monsoon type in farming.
India. • The Annapolis Valley in Nova Scotia is the world’s most
• Intense heating in interior of China in summer creates a region renowned region for apples.
of low-pressure, and moisture-laden winds • Fishing is, however, the most outstanding economic activity.
from the Pacific Ocean and the Sea of Japan blow in as the Fishing off Newfoundland
South-East Monsoon. • Regions around the Grand Banks of Newfoundland are the
• Thus, the Laurentian type of climate in China is often described world’s largest fishing grounds.
as the Cool Temperate Monsoon Climate. • Mixing of warm Gulf Stream and cold Labrador currents make
• It has a very long, cold winter, and a large annual range of the region the most productive fishing
temperature. ground on earth.
• Much of the winter precipitation in northern China, Korea and • The gently sloping continental shelves stretch for over 200
Hokkaido, Japan, is in the form of snow. miles south-east of Newfoundland, and off the
Japan coasts of the Maritime Provinces and New England. Hence
• The climate of Japan is modified by the meeting of warm and microscopic plankton are abundant.
cold ocean currents. Fish feed on minute marine organisms called plankton. Plankton
• It receives adequate rainfall from both the South-East is abundantly available in shallow waters
Monsoon in summer and the North-West Monsoon (continental shelves) where they have access to both sunlight as
in winter (western coasts of Japan) well as nutrients. Also, cold and
• The warm Kuroshio makes the climate of Japan less extreme. warm water mixing creates upwelling of cold nutrient-rich water
• The meeting zone between warm Kuroshio from south and to the surface.
cold Oyashio from the north produce fog and • Fish of all types and sizes feed and breed here and support a
mist, making north Japan a second Newfoundland. thriving fishing industry.
• Fishing replaces agriculture as the main occupation in many of • In Newfoundland, fishing industry employs almost the entire
the indented coastlands. population.
Cold and warm ocean current mixing zone off Japan • Further inland, in lakes and rivers (St. Lawrence and the Great
Climate Graph Lakes), freshwater fish like salmon are caught.
Climate graph of places with Laurentian climate • All the fishing activities are carried out by highly mechanised
Natural Vegetation trawlers which can store fish in refrigerated
• The predominant vegetation is cool temperate forest. chambers for months.
• The heavy rainfall, the warm summers and the damp air from • St. John’s, chief port of Newfoundland is the headquarters of
fogs, all favour the growth of trees. the Grand Banks fishing industries.
• Forest tend to be coniferous north of the 50° N latitude. • All processing activities like cutting, cleaning, packing for
• In the Asiatic region (eastern Siberia and Korea), the coniferous disposal are done at the ports itself.
forests are a continuation of the great coniferous • Along with Canada and U.S.A., countries like Norway, France,
belt of the taiga. Britain, Portugal, Denmark, Russia and Japan,
Lumbering also send fishing fleets to the Grand Banks.
• From Laurentian Climate regions, both temperate hardwood • Over-fishing is a growing problem.
and temperate softwood are obtained. Fishing off Japan
• Much of the coniferous forests of fir, spruce and larch are • North-west Pacific surrounding the islands of Japan is another
exploited to a great extent. very important fishing grounds of the world.
• Conifers are present in pure stands with only a handful of • Majority of the people in the region depend on fishing for
species. survival.
• Eastern Canada is the heart of the Canadian timber and wood • Hakodate and Kushiro are large fishing ports with complete
pulp industry (St. Lawrence River helps in refrigeration facilities.
export). • Japan accounts for a sixth of the world’s total annual fish
• South of latitude 50° N., the coniferous forests give way to caught.
deciduous forests. Oak, beech, maple and birch • The Japanese fishing trawlers venture far and wide into the
Arctic, Antarctic and the Atlantic waters. • The tundra climate is characterized by a very low mean annual
• Large whaling fleets with processing plants venture into distant temperature.
regions as far as Arctic and Antarctic (Japan • In mid-winter temperatures are as low as 40 – 50 °C below
is criticized for its whaling operations). freezing. Summers are relatively warmer.
• The Japanese make use of fish wastes, fish meal and seaweeds • Normally not more than four months have temperatures above
as fertilizers in their farms. freezing-point.
• Japan is one of the few countries that has taken to seaweed • Within the Arctic and Antarctic Circles, there are weeks of
cultivation (India is taking baby steps). continuous darkness (earth’s tilted axis and revolution
• Coastal farms that are submerged in water grow weeds for sale around the sun).
as fertilizers, chemical ingredient and food. • The ground remains solidly frozen and is inaccessible to plants.
• Another aspect of Japanese fishing is pearl culture. Pearls are • Frost occurs at any time and blizzards, reaching a velocity of
harvested from pearl oysters. 130 miles an hour is not infrequent.
• As natural pearls are difficult to obtain, the Japanese have Precipitation
begun to harvest cultured pearls. • Precipitation is mainly in the form of snow and sleet.
Why is fishing the dominant occupation of Japan? • Convectional rainfall is generally absent.
• The mountainous nature of Japan and parts of mainland Natural Vegetation
eastern Asia support little agricultural activity (80 • There are no trees in the tundra.
per cent land in Japan is classified as ‘non-agricultural’. Around • Lowest form of vegetation like mosses, lichens etc. are found
50% of the total land is covered by forests). here and there.
• Japan is not well endowed with natural resources. Hence • Climatic conditions along the coastal lowlands are a little
fishing forms a dominant aspect of the economy. favourable.
• The scarcity of meat (there is little pasture in Japan for • Coastal lowlands support hardy grasses and reindeer moss
livestock farming of any kind) popularised fish as the which provide the only pasturage for reindeers.
principal item of diet and the chief protein food of the Japanese • In the brief summer, berry-bearing bushes and Arctic flowers
and the Chinese as well. bloom.
• There exists a great demand for fish and fish products in the • In the summer, birds migrate north to prey on the numerous
nearby countries where fishing industry is under- insects which emerge when the snow thaws.
developed. • Mammals like the wolves, foxes, musk-ox, Arctic hare and
• Japan has huge stakes in international fishing enterprises and lemmings also live in tundra regions.
her advanced fishing techniques give her an • Penguins live only in Antarctic regions.
edge over competitors. Human Activities
• Advanced financial services, encouraging government policy, • Human activities of the tundra are largely confined to the
advanced technology at hand, skilled workforce coast.
with decades of experience in fishing and the only available • People live a semi-nomadic life.
natural resource to exploit, make Japan a • In Greenland, northern Canada and Alaska live the Eskimos.
leader in fishing industry. • During winter they live in compact igloos.
Geographical advantage • Their food is derived from fish, seals, walruses and polar bears.
• The continental shelves around the islands of Japan are rich in • Nowadays rifles instead of traditional harpoons are used to
plankton, due to the meeting of the warm Kuroshio and the cold track down animals.
Oyashio currents and provide excellent breeding grounds for all Recent Development of the Arctic Region
kinds of fish. • New settlements have sprung up because of the discovery of
•indented coastline of Japan provides sheltered fishing ports, minerals.
calm waters & safe landing places, ideal for the fishing industry. • Gold is mined in Alaska, petroleum in the Kenai Peninsula,
E – Cold Climates Alaska; and copper at the Rankin Inlet, Canada.
Tundra Climate or Polar Climate or Arctic Climate • With the declining reserves of iron ore around the Great Lakes,
Distribution of Tundra Climate iron ore deposits in Labrador are gaining
Distribution importance. New railway lines have been constructed to bring
• Found in regions north of the Arctic Circle and south of the ores to the St. Lawrence River.
Antarctic Circle. • Rich deposits of iron ores at Kiruna and Gallivare helped
• The ice-caps are confined to highlands and high latitude Sweden enjoy a prosperous export trade in iron
regions of Greenland and Antarctica. and steel and other metallurgical products.
• In the southern hemisphere, Antarctica is the greatest single • New ports on the Arctic seaboard of Eurasia has made it
stretch of ice-cap (10,000 feet thick). possible to ship timber and fur from Siberia. Modern
• The lowlands – coastal strip of Greenland, the barren grounds ice-breakers makes the frozen seas navigable.
of northern Canada and Alaska and the Arctic
seaboard of Eurasia, have tundra climate.
Climate
Temperature