CLOUD CLASSIFICATION ACCORDING TO THE PHASE STRUCTURE. THE CLOUD PHASE INDEX

I. P. Mazin

The modern classification of clouds according to their phase structure (liquid, ice, and mixed clouds) is discussed and it is shown that this classification is not informative. It is suggested that cloud phase structure be described by the cloud phase index (CPI)n of different orders n. The index (CPI)n measures a relative contribution of ice particles to microphysical properties of clouds: the cloud particle concentration (n = 1, zero order index), the phase relaxation time (n = 2, first-order index), the optical properties (n = 2, second-order index), and the total water content (n = 3, third-order index). The index changes within a cloud at negative temperature between 0 and 1 and may be used locally or for the whole cloud. The cloud phase indices can be useful in field and numerical experiments when studying cloud phase structure and its variations in space and time.