Premium
Entrainment in cumulus clouds. I: Thermodynamics and buoyancy
Author(s) -
Telford James W.,
Chai Steven K.
Publication year - 1993
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711951202
Subject(s) - buoyancy , cloud base , entrainment (biomusicology) , liquid water content , environmental science , atmospheric sciences , potential temperature , meteorology , cloud top , cloud physics , convection , cloud height , mechanics , thermodynamics , geology , physics , cloud computing , cloud cover , satellite , astronomy , computer science , rhythm , acoustics , operating system
Conclusions drawn from thermodynamic composition diagrams are examined in terms of their applicability in real conditions. Displays show the temperature and wet‐bulb temperature of samples calculated at 1000 mb. Additional lines show total mixing ratio and saturation pressure. A point giving the composition where there is a minimum of liquid water in cloud can be taken as a saturation pressure point. Such a point can be selected with a PC ‘mouse’ on the monitor display of the thermodynamic diagram, whereupon the program draws the associated constant virtual‐temperature (density and buoyancy) or the constant temperature line. Buoyancy can then be used to eliminate some sources of outside air as possible components for in‐cloud mixtures. Similarly, constant temperature lines associated with constant‐altitude‐aircraft cloud measurements provide an estimate of the composition which would remain after precipitation removed the condensed water and ice. Examination of Cooperative Convective Precipitation Experiment data show that many cloud compositions consist of cloud‐base air mixed with air remaining from previous clouds. Sometimes this air is from clouds which have precipitated, even though the sampled cloud is not precipitating. Similarly, balloon soundings in clear air may show parcels containing most patches from previous clouds. Such soundings, not representing air near the cloud under study, cannot be used to give unambiguous information about the level of mixing. Studies based on balloon soundings often suggest that the entrained air originates from above the level where the cloud is sampled, but several claim otherwise. The moist air may be important in radiation studies.