This document discusses key concepts relating to atmospheric temperature and humidity. It explains that the minimum daily temperature occurs at night when outgoing longwave radiation from the Earth is strongest, while the maximum occurs during the day when incoming shortwave radiation peaks. It also describes how net radiation determines if a surface warms or cools, and why there is a lag between peak incoming solar radiation and peak temperature. Additionally, it defines concepts like dew point, relative humidity, and saturation vapor pressure, and how these relate to the air's capacity to hold water vapor at different temperatures. Graphs and equations are provided showing relationships between temperature, vapor pressure, and humidity.

1. 1

2. 2

3. Q: When is the minimum
temperature during a day?
Q: When is the maximum
temperature during a day?
Outgoing LW radiation
emitted by the earth should
be similar to the daily
temperature, why?
because Stefan-Boltzmann law
E=sT4

4. Q: Why there is a lag between maximum
incoming SR and temperature?
Q: What determines temperature
variations?
Net radiation  Net R
Net R=Incoming SW- Outgoing LW
if Net R >0, surface is warming
if Net R <0, surface is cooling
Why
lag?

5. Pressure = Force per unit area

6. the weight of the column of air
will be about 14.7 lbs.
Hence, the pressure at sea level
is = force/area = 14.7 lbs/inch2
Sea-level pressure is also given in other units:
14.7 lbs/inch2 =1013.25 millibars (mb)

7. Air pressure = total air weight per unit area
of the atmospheric column above z
Lecture 1 - 7

8. Dalton's law
p  p H 2 O  p C O 2  p N 2  ...
p  total pressure of the gas m ixture
p H 2 O  partial pressure of w ater vapor (H 2 O )
p C O 2  partial pressure of carbon dioxide (C O 2 )
p N 2  partial pressure of nitrogen (N 2 )
Total pressure exerted by a gaseous mixture is
equal to the sum of the partial pressures of
each individual component in a gas mixture

9. For example
Gas 1
P1
Gas 2
P2
Gas 3
P3
Gas mixture
P
=
Per unit area
Per unit area
Per unit area
P = P1 + P2 +P3
Per unit area

10. Example
 Given a parcel of air comprised of only nitrogen, oxygen, and water vapor
PTotal = PN2+ PO2 + PH2O
1000 mb = 780 mb + 210 mb + 10 mb

11. No water condensation
No weather
Under what conditions does
condensation occur?
Temperature
= Dew point temperature
Relative humidity = 100%
Fig. 11-9, p. 306

12. Relative
Humidity

13. NYC daily Weather
Temperature
dew point temperature
Relative humidity
Wind
Rain

14. 
Temperature = 43oF
Dew point = 31oF
Relative humidity

15. How much water
vapor can be held in
the air?
What determines
the capacity?

16. Vapor Pressure
p H 2O
Saturation Vapor
Pressure P*H2O
Total weight of water vapor per unit area
Vapor pressure PH2O (mb)
120
T=30°C
110
100
90
80
70
60
50
Dry Air
40
30
20
Water
10
0
0
10
20
30
Temperature (oC)
40
50
PH 2 O  0

17. Vapor Pressure
p H 2O
Saturation Vapor
Pressure P*H2O
Total weight of water vapor per unit area
Vapor pressure (mb)
120
T=30°C
110
100
90
H2O
vapor
80
70
Moist Air
60
50
40
30
PH 2 O  0
20
10
evaporation
Water
0
0
10
20
30
Temperature (oC)
40
50

18. *
H 2o
Saturation Vapor Pressure
P
Total weight of water vapor per unit area
T=30 oC
Vapor pressure (mb)
120
Saturation: balance between the
number of water molecules entering
and leaving the water surface.
110
100
90
80
17.27 T
70
PH 2 O (T )  0.6108 e T  273.3
*
60
=
50
40
30
*
H 2O
P
20
10
0
0
10
20
30
Temperature (oC)
40
50

19. Saturation vapor pressure (mb)
Temperature determines
the capacity of holding water vapor in the air
120
110
100
90
80
70
60
50
40
30
20
10
0
*
H 2O
P
This curve indicates how
much water vapor can be
held in the air at a given
temperature
17.27 T
PH 2 O (T )  0.6108 e T  273.3
*
T=44 oC
T=10 oC
T=30 oC
0
10
20
30
40
Temperature (oC)
50

20. Atlantic and eastern Pacific: hurricane
Western Pacific: typhoon
Indian Ocean & Australia: tropical cyclone
20

21. Relative Humidity
PH 2 O
RH 
*
H 2O
 100%
P
Total weight of water vapor per unit area
Saturation vapor pressure (mb)
120
*
H 2O
P
Saturation: balance between the
number of water molecules entering
and leaving the water surface.
110
100
90
T=30 oC
80
70
60
50
=
*
H 2O
P
40
30
20
PH 2 O
10
0
0
10
20
30
Temperature (oC)
40
50

22. *
H 2o
Saturation Vapor Pressure
P
Total weight of water vapor per unit area
Saturation vapor pressure (mb)
120
*
H 2O
Saturation: balance between the
number of water molecules entering
and leaving the water surface.
110
100
90
P
Air isT=30 oC to
cooled
oC
T=20
80
70
PH 2 O
RH 
60
*
H 2O
 100%
=
P
50
40
30
*
H 2O
P
20
10
0
0
10
20
30
Temperature (oC)
Dew point
40
50

23. Dew point temperature
Temperature to which a given parcel
of air must be cooled for water vapor
to condense into water.

24. Saturation vapor pressure (mb)
110
RH 
100
PH 2 O
*
H 2O
*
H 2O
P
120
 100%
P
90
80
Tdew Dew point
70
60
3
H 2O
P
50
40
2
H 2O
P
30
20
1
H 2O
10
P
0
0
10
o
10 C
20
30
40
o
o
34 C
26 C
50

25. NYC daily Weather
Temperature indicates
the capacity of holding
water vapor in the air


Dew point temperature
indicates how much
water vapor is in the air
Relative humidity

26. Saturation vapor pressure (mb)
120
110
100
90
80
70
60
50
40
30
20
10
0
This curve indicates how much water
vapor can be held in the air at a given
temperature
e s (T )
 17.625T 
e s (T )  6.1 exp 

 T  243.04 
T=44 oC
T=10 oC
T=30 oC
0
10
20
30
Temperature (oC)
40
50