Quiz
#3 Study Guide Pt. 3
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Chap. 7 (pps 189-202) ***
Formation of precipitation.
Approximate sizes of cloud condensation
nuclei, cloud droplets, and raindrops. It is relatively easy to form
cloud droplets (condensation); what about precipitation? Which of
the two processes below is the most important precipitation producing
process in the US?
Collision coalescence process.
Produces rain in warm clouds (clouds in the tropics which contain water
droplets only). Falling droplets collide (why?) and stick together.
Effects of cloud thickness and updraft speed on raindrop size. Which
cloud type produces the largest raindrops and the heaviest
precipitation? About how large can raindrops get (why don't they get
any larger)?
Ice crystal process.
Structure of a cold cloud. What are
supercooled water droplets? Where are they found in cold clouds?
Are there more water droplets or ice crystals in the mixed phase
region in a cold cloud? Are ice crystal nuclei abundant or scarce in
the atmosphere? Where does precipitation begin to form in a cold
cloud? Why are ice crystals able to grow while supercooled water
droplets do not? Riming (accretion). Graupel. Can the ice crystal
process produce rain or just frozen forms of precipitation?
Types of precipitation.
Rain, virga, snow (snowflakes), drizzle,
fall streaks, sleet (ice pellets), hail, freezing rain, graupel
("soft hail" or snow pellets). What type of cloud and special cloud
characteristics are needed for hail formation (see Fig. 7-14 on p.
199)?
Radar (time permitting).
Microwave
radiation is reflected by the precipitation size particles in a cloud;
ordinary radar locates the precipitation and provides an estimate of
its intensity. Doppler radar measures the shift in the frequency
of the reflected signal and can measure the speed of precipitation
particle motion toward or away from the radar antenna.
Sample Questions from the Fall 2000 Quiz
Packet Quiz
#4:
6, 9, 12, 13, 15 Final Exam: 9, 40