1. Atmospheric Relationships
Created By:
Mr. Kreeger

2. Homework and Page References
HW #1- Explain why the maximum temperature in any given day occurs after 12pm and why the minimum temperature occurs after midnight-(1 paragraph)
HW #2-Do problems 12,13,14 and 15 on page 490 of text
HW #2- Using your reference tables find the Dewpoint and relative humidity given the following.
WB=22C, DB=10C
WB=13C, DB=8C
WB=20C, 18C
What do you notice when the about the relative humidity when the temp and dewpoint are close to one another what do you notice when they are further from each other. Draw a graph dipicting this relationship

3. Table of Contents Temperature Variations Moisture Variations
How is temperature affected
How the atmosphere receives its energy
Factors that affect temperature
Latitude
Altitude
Closeness to water
Moisture Variations
Relative Humidity
How to determine dewpoint temperature
How to determine relative humidity using chart
Pressure Variations

4. 1. Temperature Variations
All weather is driven unequal heating of the Earth’s surface. (Remember Specific Heat)
Heat Energy is responsible for changes in atm variables

5. 1a. How temperature is affected
Temp- Affected by intensity and duration of insolation (Incoming solar radiation)
Daily and seasonal changes of temp occur b/c amount of incoming solar radiation and outgoing re-radiation is different

7. 1b. How the atmosphere receives its energy
Recieves energy by:
Conduction
Direct Absorption and insolation when light passes through atm.
Reradiation from earths surface Related to amount of H2O vapor and CO2 in atm.
Condensation (latent heat) and Sublimation
Isolines connect equal lines of temp isotherms

8. 1c. Factors that affect temperature
Latitude-Higher latitude lower intensity of solar radiation. (why??)
Altitude-higher altitude lower temp. (Why??)
Closeness to H20- Coastal regions have cooler summer temps and warmer winter temps (Why???)
b/c water heats up and cools slower than land.

9. 2. Moisture Variations
Moisture content changes all the time, water can be found in all three phases in atm.
Ability to hold moisture is directly related to temp. (warm air- more moisture, cold air-less moisture)

11. 2. Moisture Variations Cont..
When air holds all the water it can at a given temp saturated (not usually the case)
To obtain saturation, more water must be added without changing temp or air must be cooled to dewpoint temp. ( The temp at which condensation occurs), holding all moisture it can at given temp
Amount of H2O vapor actually present is called absolute humidity ( Greater absolute humidity greater dewpoint temp)

12. 3. Relative Humidity
Comparison between the amount of moisture in the air with the amount moisture the air can hold at a given temp.
Ex. If air holding half as much moisture as it could be at a given temp RH=50%
If temp rises and moisture content stays the same RH decreases.
If temp falls and the moisture content stays the same RH increases.

13. 3. Relative Humidity Cont
RH=(water vapor content/water vapor capacity)x100
Temperature (°C)
Saturation mixing ratio (gm/kg)

14. Comparison: Phoenix Arizona N. Minnesota T = 25°C T = -10°C RH = 20%
Which air contains more water vapor?
Temperature (°C)
Saturation mixing ratio (gm/kg)

15. 4. How to determine Dewpoint Temperature
Use of a sling pyschrometer
Has two thermometers( 1 wet bulb, 1 dry bulb)
Wet bulb- water evaporates quickly-lower temp
Dry bulb-measures air temp
Can use a dew point temp chart

16. Dew point Temp chart

17. 4a. Steps in determining dewpoint temp
Assume DB=10C, WB=6C, diff=4C
Locate dry bulb temp (y axis of chart)
Locate diff between WB and DB temp (X axis of chart)
Find point where horizontal line from DB reading meets vertical line from diff between WB and DB. That is your dewpoint temp

18. 5. Determining Relative Humidity with Chart
Steps are the same as determining as finding dewpoint only diff is you are using a different chart

19. Chart for Relative Humidity

20. Try These… 57% 17 °C 86% 4 °C 57% 4 °C 91% 16 °C 100% 14 °C 45% -9 °C
Dry Bulb
Wet Bulb
R Humidity
DPT
26°C
20 °C
6 °C
5 °C
12 °C
8 °C
18 °C
17 °C
14 °C
0 °C
-3 °C
57%
17 °C
86%
4 °C
57%
4 °C
91%
16 °C
100%
14 °C
45%
-9 °C

21. More Difficult... 82% 18 °C -.5 °C 45.5% 100% 17 °C 20% -17 °C 69%
Dry Bulb
Wet Bulb
R Humidity
DPT
21°C
19°C
11°C
6 °C
17 °C
17°C
2°C
-3 °C
9°C
6.5 °C
70°F
60 °F
82%
18 °C
-.5 °C
45.5%
100%
17 °C
20%
-17 °C
69%
3.5 °C
15 °C
21 °C
52%
11 °C(50 °F)

22. Try These -14C -16C 24C 10C 12C 67% 11C 6C 16C 71% 8C DB WB Dewpoint
Difference
Dewpoint RH
-14C
-16C
24C
10C
12C
67%
11C 6C
16C
71% 8C

23. Determining Cloud Base Altitude
Must know both the Dry Bulb Temperature (DB) and the Dewpoint Temperature (DP)
Follow the dashed line up the chart this represents the dewpoint and find where it intersects the Solid line which is the dry bulb temperature.

25. 6. Pressure Variations
Force of weight pushing down on a unit area of a surface is called air pressure or atm pressure.
Use a barometer to measure air pressure-tube filed with Hg when air pressure outside rises, increase pressure at base tube rises, avg sea level pressure =30.0 in of Hg mb.
Use ESRT to convert between millibars and inches of Hg

27. Try these !!!!
Millibars
Inches of Hg
1025.0
29.25
977.0
30.31
1013.2

28. 6. Pressure Variations
On weather maps isolines called isobars connect = lines of air pressure –show pressure patterns over large areas, pressure interval =4mb
Ranges from 960mb to 1050mb

29. Changes in Air Pressure
Temperature- warm air is lighter than cold air!
Humidity- humid (moist) air is lighter than dry air!! Water vapor (H2O) weighs less than the N and O gases that it pushed out
Winds are caused by the unequal heating of the atmosphere (remember that temperature causes changes in air pressure)