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Weather and Climate 101
Due: 12 October 2006
Fall Semester
Name: _____________________
Businger/Xie
Homework Assignment #2
1. Clouds in the atmosphere are classified by the level in which they occur.
a. Name two examples each of low, middle and high clouds.
b. What are the height ranges of each of the levels in part a) above.
c. Name a cloud that spans all three levels.
3. Describe the following clouds:
a. stratus:
b. virga:
c. mountain wave or lenticular cloud:
4. Describe the difference between an environmental lapse rate and an adiabatic lapse rate?
5. An air parcel that continues to move in the direction that it is vertically displaced in is said to be __________ .
6. An air parcel that returns to its original level after being vertically displaced is said to be _________ .
7. The magnitude of the moist adiabatic lapse rate is (less than, greater than) [circle one] the dry adiabatic lapse
rate due to the effect of _______ .
8. Given the dry and moist adiabatic lapse rates in the figure on the right, draw a line that represents a
conditionally unstable lapse rate.
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9. a) An air parcel that is saturated (100% relative humidity) is lifted from sea level to the top of a mountain pass
at 2 km elevation. If its temperature was 15˚ C at sea level, its new temperature at the pass will be
___________ ? (Show your work below)
b) If the air parcel in part a) descended the far side of the pass back to a sea level elevation, its final
temperature will be _____________? Use your answer to a) as the starting point, and assume the
descending parcel is dry because the excess cloud water has rained out. (Show your work below).
10. Outline the steps in the “Warm Cloud Process.”
11. Outline the steps in the “Cold Cloud Process.”
12. What is the difference between freezing rain and sleet?
13. There are usually large spaces of blue sky between cumulus clouds? Explain why this is so, and why
cumulus clouds are frequently observed during the afternoon.
14. What is the primary difference between a cloud droplet and a raindrop? Why do typical cloud droplets (say
of a size of 20 m) seldom reach the ground as rain?
15. Why is it that the Coriolis force and the centrifugal force cannot cause motion in air that is at rest?
16. Why will Denver, Colorado, always have a lower station pressure than Chicago, Illinois?
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17. What is the name of the force that initially sets the air in motion and, hence, causes the wind to blow?
18. Explain why, on a map, closely spaced isobars indicate strong winds, and widely spaced isobars indicate
weak winds?
19. Why do upper-level winds in the middle latitudes of both hemispheres generally blow from west to east?
20. Describe how the wind blows around high-pressure and low-pressure centers aloft and near the surface in
the Northern Hemisphere? Analyze the force balance involved. How about the Southern Hemisphere?
21. If the clouds overhead are moving from north to south, would the upper-level center of low pressure be to
the east or west of you?
22. Why are the surface winds that blow over the ocean closer to being geostrophic than those that blow over
the land?
23. Why does a sea breeze blow from sea to land and a land breeze from land to sea?
24. Which wind will produce clouds: a valley breeze or a mountain breeze? Why?
25. Explain why Chinook winds are warm and dry.
26. Describe how the winds along the west coast of North America produce upwelling.
27. What are the major signatures of an El Niño event in the eastern and central Pacific?
28. How do these changes in the ocean and atmosphere interact and amplify each other (the Bjerknes
feedback)?
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29. a. Using the diagram below draw and label the major features of the general circulation of the Earth's
atmosphere. Include arrows for winds, locate highs (H) and lows (L), Hadley cell, trade winds, westerlies,
easterlies, ITCZ, and polar front.
b. Using your sketch of the general circulation above, give the predominant surface-wind direction
expected at each location.
i) Boston, Mass. (43˚ N) Westerly
ii) Honolulu, Hawaii (20˚ N) NE
30. Sketch a weather map for the central Pacific below for a typical tradewind day in Hawaii. Include the
location of the equator, 30° north latitude, the Big Island, the ITCZ, a few representative isobars and label
the typical locations of centers of high (H) and low (L) pressure. (Refer to #29 for guidance).