NCE 424
HYDROLOGY
PART 2:
METEOROLOGY
DELIVERED BY:
ENGR. HADJI PEEJAY ARANDA
FACULTY – CIVIL ENGINEERING DEPARTMENT
UNIVERSITY OF THE EAST - CALOOCAN
WHAT IS
METEOROLOGY
●
Meteorology is the study of the gaseous envelop in the
planet. This gaseous envelop is called atmosphere and
there are 5 layers that are known as follows:
– Troposphere
– Stratosphere
– Mesosphere
– Ionosphere or Thermosphere
– Exosphere
LAYERS OF
ATMOSPHERE
ATMOSPHERIC
PARAMETERS
●
Part of the water cycle occurs at the troposphere and
stratosphere. The movement of air in there part of the
atmosphere must be understood as well
●
It is also important to know some of the parameters
that is important to both hydrology and meteorology.
These are as follows:
– Lapse rate
– Atmospheric pressure
●
Lapse rate ( φ )is the rate of temperature decrease in
the atmosphere as the elevation increases
●
In fluid mechanics, lapse rate is computed to be
0.0065K/m
ATMOSPHERIC
PARAMETERS
●
The atmospheric pressure is computed using the
equation:
g
T
P 2=P 1
( )
T1
2 αR
P 2=ρ RT
●
Another important parameter to be learned is
saturation vapor pressure es which is computed using
the following formula
17.27 T
237.3+T
e s =611 e
where es is in N/m2 and T is in Celsius
ATMOSPHERIC
PARAMETERS
●
Another way to compute for the saturation vapor
pressure is from this empirical equations
e s =0.0446−0.0064|1.8 T +48|+33.864(0.00738 T +0.8072)8
es is in millibars
T is in 0C
this equation is valid for the temperature range of
-550C to 550C
PRECIPITABLE WATER
●
The amount of moisture present in a column of air
from the ground to the upper atmosphere is called
precipitable water PW
●
The empirical formula for computing the precipitable
water is
P W =(h2−h1 )H ave ρave
Where:
PW = Precipitable water (kg)
h2 ,h1 = elevation difference
(m)
ρ = density of air (kg/m3)
ATMOSPHERIC
PARAMETERS
● The term Hav refers to the specific humidity which is
the mass of water vapor over unit mass of moist air
and it is computed to be
0.622 e
H AV =
P
Where:
e = Vapor Pressure
P = atmospheric pressure
EXAMPLE
Calculate the mass of precipitable water between 0
and 1km above the surface of the earth assuming the
atmosphere is saturated. Surface air pressure is taken
to be 100.7kPa and the temperature is 320C
EXAMPLE
SOLUTIONS
LATENT HEAT
●
Another meteorological property to analyze is called
latent heat. This is the amount of heat needed to
convert 1g of water to vapor without any change in
temperature
LH=597.3−0.564T
Where:
LH = Latent Heat g/cal
T = Temperature 0C
This equation is good up to 400C
HUMIDITY
●
Humidity generally indicates the amount of moisture
present in the atmosphere
●
Absolute humidity is the mass of water vapor present
at air and it is expressed in g/m3.
●
Since atmosphere is mostly unsaturated, humidity is
best expressed in terms of relative humidity the
empirical formula of which is
e
RH=100
es
Where
RH is relative humidity (%)
e is vapor pressure
es is saturation vapor pressure
HUMIDITY
●
Humidity is also computed using this empirical
equation
8
RH=100
[ 112−0.1 T +T D
112+0.9T ]
Where:
RH is relative humidity
T is air temperature
TD is dew point temperature
HUMIDITY
●
Dew point temperature is the temp. which the air
cannot “hold” the water vapor that is mixed in the air.
This means that some of the water vapor will condense
into liquid. It usually lower than or equal to the air
temperature
●
A dew point temperature of 600F (160C) or lower is
generally considered to be comfortable.
●
A relative humidity of 100% means that the air temp.
T is equal to the dew point temperature TD
EXAMPLE
Calculate the relative humidity and the latent heat
given the following:
T = 330C
TD = 180C
EXAMPLE
SOLUTIONS
TYPES OF CLOUDS
●
Another aspect of meteorology that will be considered
is the type of clouds. The following general types of
clouds are:
– Cirrus (Ci)
– Cirrostratus (Cs)
– Cirrocumulus (Cc)
TYPES OF CLOUDS
●
Another aspect of meteorology that will be considered
is the type of clouds. The following general types of
clouds are:
– Altostratus (As)
– Altocumulus (Ac)
– Stratus (St)
TYPES OF CLOUDS
●
Another aspect of meteorology that will be considered
is the type of clouds. The following general types of
clouds are:
– Stratocumulus (Sc)
– Nimbostratus (Ns)
– Cumulus (Cu)
TYPES OF CLOUDS
●
Another aspect of meteorology that will be considered
is the type of clouds. The following general types of
clouds are:
– Cumulonimbus (Cb)
●
Clouds are formed when condensing water vapor
freezes to form ice crystals. These ice crystals are so
small and light that it can be carried up by
prevailing winds and causing it to merge with
other ice crystals until it becomes too heavy and
will fall as precipitation
TYPES OF CLOUDS
●
If the atmospheric temperature is very low, the ice
crystals will retain its shape and form and falls as
SNOW
TYPES OF CLOUDS
●
If the atmospheric temperature is above freezing, the
crystals will melt and fall down as RAIN
TYPES OF CLOUDS
●
If the wind speed in the area is very strong as seen by
along cold/warm fronts, the ice crystals will be tossed
up and down the atmosphere and will consolidate into
large chunks of ice called HAIL
