Ch. 15,
p. 438, #10-15, 17, 24
10. Why
does air cool when it rises through the atmosphere?
A. As air rises, it expands because air pressure
decreases with an increase in altitude. When air expands, it cools
adiabatically.
11. Explain the difference between environmental lapse rate and adiabatic
cooling.
A. The environmental lapse rate refers to the
temperature drop with increasing altitude in the troposphere; that is the
temperature of the environment at different altitudes. It implies
no air movement. Adiabatic cooling is associated only with ascending
air, which cools by expansion.
12. If unsaturated air at 23oC were to rise, what would
its temperature be at 500 meters? If the dew point temperature at the
condensation level were 13oC, at what altitude would clouds begin
to form?
A. 18oC (because of the dry adiabatic
rate); 1000 meters.
13. Why does the adiabatic rate of cooling change when condensation
begins? Why is the wet adiabatic rate not a constant figure?
A. When condensation occurs, latent heat is released
by the vapor/water droplets into the surrounding air. This heats up
the surrounding air, countering some of the cooling defined by the dry adiabatic
rate. The wet adiabatic rate depends on the quantity of vapor in the
air.
14. The contents of an aerosol can are under very high pressure.
When you push the nozzle on such a can, the spray feels cold. Explain.
A. When you push the nozzle on the aerosol can,
pressure in the can decreases as the contents begins to escape the can. The
drop in pressure results in adiabatic cooling.
15. How do orographic lifting and frontal wedging act to force air
to rise?
A. In orographic lifting, a mountain side serves
as a barrier to cause air to ramp up. In frontal wedging, a cold mass
of air acts as a barrier forcing warmer air to ramp up and rise.
17. How does stable air differ from unstable air? Describe
the general nature of the clouds and precipitation expected with each.
A. Stable air resists upward movement, whereas
unstable air does not. Clouds formed when stable air is forced to rise
are generally thin and precipitation, if any, is moderate or light. Conversely,
when unstable air rises, clouds are often towering and precipitation can be
heavy.
24. List five types of fog and discuss the details of their formation.
A. advection fog - forms when moist air moves
over a cool surface.
radiation fog - forms on cool, clear calm nights when radiation cooling
is sufficient to bring air below its dew point.
upslope fog - forms by adiabatic cooling of air as it moves up a slope.
steam fog - forms when cool air overlies a relatively warm water surface.
Often there is sufficient evaporatio from the warm water to create saturation
and fog.
frontal fog - forms when rain evaporates as it falls
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