Specific humidity Assignment PDF

Geography Lab: Humidity
SECTION A
1) Specific humidity is given by E=RH×Es
100
Where Estands for specific humidity (the real quantity of water present in the air),
RH is the relative humidity in g/Kg, Es is the saturation water vapor of the air in
millibars.
We get saturation water vapor by Es=6.11×10×(7.5×Tc
237.7+Tc )
Where , Es is the saturation water vapor of the air in millibars, Tc is the given
temperature in degrees celcius.
Es=6.11×10×(7.5×30
237.7+30)=1.9279mb
From there we can now the saturation water vapor of the air is used to compute the
specific humidity (the actual amount of water vapor present in the air). This results into
the following:
E=RH×Es
100
E=(75×1.9279mb
100 )=1.4459g/Kg
2) Dew point temperature is given by Tdc=−430.22+237.7×ln ⁡(E)
−ln⁡(E)+19.08
Where Tdc is the dew point temperature in degrees celcius (°C), ln ⁡(E) is the natural
logarithm of the specific humidity (the actual amount of water vapor present in the air)
Tdc=−430.22+237.7×0.3687
−0.3687+19.08 =−18.3087°C

3) Relative humidity can be found from E=RH×Es
100
Where Eis the specific humidity (the actual amount of water vapor present in the air),
RH is the relative humidity in g/Kg, Es is the saturation water vapor of the air in
millibars.
Dew point temperature is given by Tdc=−430.22+237.7×ln ⁡(E)
−ln⁡(E)+19.08
Where Tdc is the dew point temperature in degrees celcius (°C), ln ⁡(E) is the natural
logarithm of the specific humidity (the actual amount of water vapor present in the air)
This implies that −430.22+237.7×ln(E)=0
237.7×ln(E)=430.22
ln(E)=430.22
237.7 =1.8099
E=e1.8099=6.1098
Saturation vapor pressure (Es) is given from (1) as
Es=6.11×10×(7.5×Tc
237.7+Tc )
Where , Es is the saturation water in the air in millibars, Tc is the given temperature in
degrees celcius.
We are givenTc=20°C. Inserting this into the formula results into:
Es=6.11×10×(7.5×20
237.7+20)=0.9639mb
Therefore relative humidity can be computed as:
Therefore relative humidity
RH=100×E
Es
RH=100×E
Es
=100×6.1098
0.9639 =633.8624%

Where Eis the specific humidity (real quantity of water present in air),
RH stands for relative humidity in g/Kg, Es is the saturation water vapor of the air in
millibars.
4) Filling the table
SAMPLE TEMPERATURE (°C) RELATIVE
HUMIDITY
ACTUAL SPECIFIC
HUMIDITY (g/Kg)
DEW
POINT (°C)
RANK
A 15 90% 24.4811 20.7731 1
B 22 60% 23.2919 19.9652 2
C 26 40% 18.0728 15.9264 4
D 30 45% 23.1093 19.8375 3
E 35 30% 17.6444 15.5509 5
This table has been filled by use of the following formulas
Dew point temperature is given by Tdc=−430.22+237.7×ln ⁡(E)
−ln⁡(E)+19.08
Where Tdc is dew point temperature in degrees celcius (°C), ln ⁡(E) is natural logarithm
of the specific humidity ( genuine quantity of water vapor existent in air).
Relative humidity can be found from E=RH×Es
100
Where Eis the specific humidity (the actual amount of water vapor present in the air),
RH stands for relative humidity in g/Kg, Es is the saturation water moisture of air in
millibars .
TABLE 1.
Temp( ̊C) -40 -
30
-20 -
10
0 5 10 1
5
20 25 30 35 40
Humidity 0.1 0.3 0.75 2 3. 5 7 1 14 20 26 35 47