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sleuth9216's avatar

How does the high/low temperatures, the barometric pressure, and the relative humidity influence what kinds of clouds are out?

Asked by sleuth9216 (231points) April 22nd, 2008

and no, i couldn’t find it on google

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robmandu's avatar


The formation of clouds is an application of the First Law of Thermodynamics. According to the First Law, a change in the internal energy of a system can be due to the addition (or loss) of heat or to the work done on (or by) the system. In the atmosphere system, the change of internal energy is measured as a change in temperature and the work done is manifested as a change in pressure. Because air is a relatively poor conductor of heat energy, the assumption is made that the parcel of air upon which work is being done is insulated from the surrounding environment. This is the adiabatic assumption. For a rising air parcel, the change in internal energy is therefore due entirely to pressure work with no addition or loss of heat to the surrounding environment. A simple relationship for temperature change for a rising parcel of air can then be determined. This change of temperature with height is the dry adiabatic lapse rate of -9.8oC per kilometer.

Air is, of course, not entirely dry and always contains some water vapor which can condense as the air parcel rises and cools. Condensation creates clouds and affects the temperature and vertical motion of the parcel. During condensation, heat is released (latent heat of condensation). This addition of heat to the system violates the adiabatic assumption. The rate of cooling of an ascending air parcel undergoing condensation is, therefore, less than for dry air. The lapse rate for air under these conditions is the moist adiabatic lapse rate and is approximately -5oC per kilometer.

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