Climate

Climate is a composed term which has different features and factors to describe it as an
integrated unit. It is accompanied by number of elements like temperature, humidity, air
pressure and amount of precipitation over the land. These factors are controlling factors
and known as factors of climate.

Definition
According to the early Greek astronomers “The climate is the study of condition of the
atmosphere over a definite time and under definite conditions.”
According to F.J. Monkhouse “climate help to determine food, clothing, housing, and
general modes of life.”

Difference between Weather and Climate

Goh says about the difference between weather and climate:

“The term weather should not be confused with climate though they are closely related to
each other. In the same country even small or large, the weather phenomenon can change
tremendously. It may be sunny in one area and raining dogs and cats in the few
kilometers away area”.

When we talk about climate we are referring to the average atmospheric conditions of a
certain area over a considerable time. This involves systematic observations, recording of
different parameters like pressure, winds, cloud cover, sun shine and humidity.

The importance of weather and climate

The exquisite influence of climate can be seen visually over man’s activities he performs
in daily life. Forces of natures has altered the extent of food we eat, the clothes we wear
and the things we perform to sustain is all controlled by nature. The elements of Weather
and climate Rainfall, pressure winds, temperature are important because of their far-
reaching global influences.

Rainfall
Rainfall includes other forms of precipitation like snow hail, mist, dew, ice is always
measured by an instrument called rain gauge. The total amount obtained from the daily
averages of rain taking place over 35 years will be taken into consideration and develop a
map having place with same rain amount called isohyet.

Pressure
Air exert no of gases in it, so it also possesses pressure. The instrument measures this
pressure is called Barometer. The barometer is sensitive to gravitational force so at
different latitudes its amount of measurement will be different.
Temperature
Temperature is a very important element of climate. The instrument used for measuring
temperature is thermometer. Which is a narrow glass tube filled with mercury or alcohol.
To obtain Centigrade temperature = (F -32)/ 1.8
To obtain Fahrenheit temperature = (1.8 x 20 c) +32

Humidity
Humidity is the measure of dampness in the air which varies greatly from place to place
at variant time of the days, the actual amount of humidity present in the air is called
absolute humidity whereas the ratio between total amount of humidity and the actual
amount an air passage can hold is called relative humidity.

3.1 Climate of Pakistan

Pakistan is located at the side out of the tropics where the sun slant to much especially
summers in Pakistan. Therefore, it records for higher time periods for summer season
rather than of winter. Air in Pakistan is mainly heated up by terrestrial radiations.

The oceans have moderate influence on temperature. water has a tendency of holding the
temperature for a longer period if time as it holds the energy present in temperature for a
longer time span therefore the moderate effect of water is observed in maritime.

Pakistan can be divided into following temperature regions:

1) Warm Summers and mild winters
2) Hot summers and mild winters
3) Warm summers and cool winters
4) Warm to cool summer and cold winters

3.1.1 Warm Summers and Mild winters

In Pakistan summer temperature remain between 21 to 31 o C and temperatures in winter
between 10 to 20o C.

Region:
The following region is present in Narrow coastal belt. Where temperature shows a
general tendency of warm summers and mild winters due to maritime effect in the area.

Regions categorization based on temperature

HOT 32o Cor more (90o F or
more)
WARM 21 o to 31o C (70- 89 o F)
MILD 10 o to 20 o C (50 – 69 o F)
COOL 0 o to 9 o c (32-49 o F)
COLD Below 0 o C (Below 32 o F)
3.1.2 Hot Summers and Mild Winters
The temperature of the hottest month is 32 0c or more and winters temperature is between
10 to 200 c.

Region:
This area is extended over the extensive areas of Indus plain from north to the southern
side and western side of Baluchistan.

3.1.3 Warm Summers and Cool Winters

In this region the temperature of the summer season is about 21 to 31 0 C. and the coolest
month is ranging between 0 to 9 0C.

Region:
This warm summer and cool winters are mostly experiences in the western highlands of
Pakistan.

3.1.4 Warm to Cold Summer and Cool to Cold Winters

Summer temperatures are extremely low ranging between 0 to 20 C and winters
temperatures are below freezing that is 0 to 1 0 C.

Region:
The region accompanied with such extremes of temperature lies in the northern
mountainous areas of the region.

Major Temperature Regions of Pakistan (January)

Major Temperature Regions of Pakistan (June)

Temperature Regions of Pakistan

3.2 Air Pressure and Winds in Pakistan
Air pressure distribution in Pakistan exhibits a marked contrast in summers and winters.
In summer air pressure remains extremely low while in winters it is high, as a result the
pattern of prevailing winds also changes tremendously.

Summers:
In summers air pressure remains low throughout Pakistan. It begins to decrease in April
and continues to fall till July. After July, it tends to increase but continues to relatively
low up till September.

The NE and SE trade winds roaming from the southern hemisphere to the equator. The
area under it is called ITCZ (Inter tropical Convergence Zone).

The Intense low pressure brings no of climatic changes over the area:
1) The Equatorial low-pressure belt becomes very weak.
2) The ITCZ moves northward and lies over Northern part of South of Asia.
3) The North east trade winds disappear
4) The south Eats trade winds of Southern hemisphere no longer stop at the Equator.
They cross the Equator and proceed to low pressure belt over Pakistan. Hence
deflected on the right side becoming south westerlies in summer. These south
westerlies are Monsoon winds which is a low-pressure system over Indian Ocean.
Thus, the Monsoon winds can be classified as seasonal winds over the South of
Asian region.

Winters:
By the month of September, the low-pressure system during the summer is about to
diminish and gets weak, the air pressure begins to rise with the highest pressure being
reached in January from 1014 mb to 1016 mb.

In the system of winds circulation, two major events take place

a) An Intense high-pressure belt developed over central Asia from where cold winds
are generated below and in all directions of Himalayas. Some cold wind system
also enters to Baluchistan from Afghanistan.
b) The other Major event is the wind circulation which effects the low-pressure
system in Pakistan. And entered by mid latitudes which can cause cyclonic
activities often.

3.3 Rainfall
Monsoon:
Pakistan receives the tail of monsoon winds which enters the country after India. They
usually reach in early July and somewhat end to start of September. Most of the rain fall
take place during July to September is the result of Monsoon.

Since it enters from the east, the main winds enter in Punjab, with the secondaries
entering from southern Punjab. The hills and mountains record for 500 millimeters of
rain.

From Sargodha to south wards the rain are 250 mm or less. The highest rain during
monsoon season is recorded at Murree (813mm) and the lowest in Naukandi (2.5mm).

Rainfall by western disturbance

The western disturbance enters Pakistan from the west after Passing through Iran and
Afghanistan. They carry most of the moisture on the long board journey so only bring
little rain to Pakistan. Despite the fact western part receive more rainfall because of
western depression from other sources. Sindh is the driest part of the country. Rainfall
recorded in this region is about less than 25 mm.