Summary

In this module, we discussed the dry and moist adiabatic lapse rates. Parcels cool rapidly when they ascend and warm rapidly when they descend. An ascending air parcel that's saturated with water vapor does not cool so rapidly because the process of condensation releases latent heat.

The specific temperatures experienced by a dry, moist, or semi-moist air parcel on the way up or on the way down can be determined by the use of sounding diagrams. A sounding diagram includes a grid of temperature and pressure, and also contains lines which show the rate at which dry or moist air parcels would cool or warm. A fifth set of lines depicts saturation mixing ratio and shows at what point an ascending air parcel with a given water vapor mixing ratio would reach saturation.

Sounding diagrams can be used to understand a variety of processes. We looked at two here: estimation of the height of cloud base, and the principles behind the chinook wind. In a later module, a continuation of this one, we shall look at atmospheric soundings and learn how to forecast thunderstorms.

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