Summary

This module discussed the interpretation of rawinsonde data on sounding diagrams. Layers of clouds and fog can be identified as locations in which the temperature is nearly as cold as the dew point. The diurnal heating and cooling of the ground produces changes in the temperature of the lowest part of the atmosphere, with an inversion typically forming at night and a dry adiabatic layer typically forming during the day.

Both dry and moist parcel stability were discussed. A particular layer of the atmosphere is said to be stable if an air parcel, when lifted, becomes colder than its surroundings and is accelerated back downward. Layers of dry parcel instabiity correspond to superadiabatic lapse rates on the sounding diagram. To diagnose moist stability, unless the entire air mass is already saturated, it is necessary to actually estimate the temperature of a lifted parcel at various levels and compare it with the environmental temperature. If the parcel is warmer than the environment, convection is possible. The degree of instability can be quantified using stability indices such as the lifted index and CAPE. Other characteristics of the convection can also be determined from the parcel and environmental temperatures.

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