I. Relative Humidity
1.
For a volume of air starting at the equator, sketch the path it takes as it circulates in a
Hadley Cell. Let’s assume that the air starts out both very warm (say, 28° C), and nearly saturated (containing 21 g water per kg air), and cools to 1° C as it rises above the equator.
On the plot above, show the temperature and water content of air as it travels through the
Hadley Cell. Label points on the plot corresponding to (A) base of the cell at the equator;
(B) top of the cell at the equator; and (C) base of the cell (sea level) after descending at
~30 degrees N or S latitude.
What is the beginning relative humidity of the air? What is its relative humidity as it reaches the top of the Hadley Cell? How about just after it has descended to the bottom of the Hadley Cell at point (C)?

II. The Western U.S. and California Example: Does orographic precipitation really happen?
1.
Using the data table (last page), plot a topographic profile across California:
4000
3500
3000
2500
2000
WEST
1500
1000
500
0
123 122.5
122 121.5
121
Longitude
120.5
2.
Plot the average annual precipitation along the same profile here:
EAST
120 119.5
70
60
50
40
30
20
10
0
123
WEST
122.5
122 121.5
121
Longitude
120.5
120
EAST
119.5

3.
Discuss the patterns of precipitation from West to East. Are the data consistent with your expectations based on the orographic effect?
Why are some locations at very high elevation relatively dry (e.g., Carson City or Topaz
Lake), whereas some locations at relatively low elevation are moderately wet (e.g.
Sabastopol)?
4.
On the map of the Western US on the following page:
A) Sketch the major mountain chains (Sierra Nevada, Rockies, Coast Ranges, etc…).
B) Indicate areas that you expect to have low, moderate, and high annual precipitation. Think about both the orographic effect and global atmospheric circulation patterns.

Location
Auburn
Big Canyon
Blue Canyon
Calaveras
Calistoga
Carson City (NV)
Davis
Echo Summit
Grizzly Flats
Napa
Placerville
Point Reyes
Sacramento
Sebastopol
Sonoma
Topaz Lake
Truckee
Volcanoville
Longitude
121.06
120.90
120.20
120.31
122.58
119.76
121.76
120.03
120.51
122.30
120.73
123.80
121.50
122.81
122.46
119.55
120.15
120.78 elevation (m)
387
259
1609
1430
112
1417
18
2240
1177
18
839
9
5
20
29
1537
1834
927
precipitation (in/yr)
38.5
32.8
67.7
54.5
37.4
11.2
17.3
50.8
48.9
24.1
39.9
25.5
17.4
31.6
29.5
8.4
32.1
45.9