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The type and size of precipitation leaving the cloud base depends on the conditions within the cloud, but the precipitation that actually reaches the ground is modified by conditions in the air layer between the cloud and the ground. In general, the temperature structure determines whether the precipitation will arrive as frozen or as liquid water, while the humidity of the layer determines the amount of evaporation that will occur and hence the ultimate size of the precipitation particles. In both cases the fall velocity will dictate the time over which the processes can act and hence how completely they will be.
The intensity and duration of precipitation is determined largely by the type of cloud system involved. This in turn is intimately connected with the cloud formation processes considered (i.e. Coalescence model and Bergeron-Findeisen model). In general cumulus vertical motions give large drops and intense precipitation for a short period. Usually their influence is restricted to a fairly small geographical area. Stratus and altostratus, in contrast involve more persistent and less vigorous vertical motions over a much wider area. Hence prolonged, steadier and usually less intense precipitation results. The
difference in intensity decreases as the duration increases. World rainfall statistics suggest that intensity is approximately proportional to the inverse square root of the duration, but that there are many regional variations. Types of precipitation include convectional, orographic and frontal.
francis1897 answered the question on October 5, 2022 at 05:27