6/11/2023 0 Comments Precipitate definitionWhat causes these physically unreasonable precipitation efficiencies? How should precipitation efficiency be defined and calculated properly? These are the key questions we want to address in this paper. For example, both LSPE and CMPE could be greater than 100% and LSPE could be negative (e.g., Fig. The CMPE, on the other hand, is examined mainly in cloud modeling studies, because the vapor condensation and deposition rates can be produced during the model integration.ĭespite these efforts, precipitation efficiency remains to be defined properly and to be calculated accurately. Precipitation efficiency can also be defined as the ratio of the surface rain rate to the sum of vapor condensation and deposition rates, or cloud microphysics precipitation efficiency (CMPE e.g., Weisman and Klemp 1982 Lipps and Hemler 1986 Ferrier et al. The LSPE has been used mostly in observational studies, since the vapor convergence and surface evaporation can be calculated from the sounding and field experiment data. Precipitation efficiency can be defined as the ratio of the surface rain rate to the sum of vapor convergence and surface evaporation rates, or large-scale precipitation efficiency (LSPE e.g., Auer and Marwitz 1968 Heymsfield and Schotz 1985 Chong and Hauser 1989 Doswell et al. The dependence of precipitation efficiency on environmental warming is a key issue for the climate change study.īecause of its fundamental importance, the precipitation efficiency of convective storms has been estimated in many studies in the past five decades ( Braham 1952). This implies that in a warmer climate, there may be more warm rain at the expense of less cloud water available for mid- and high-level clouds. 1988) and found that there is a substantial increase in precipitation efficiency of light warm rain as the sea surface temperature (SST) increases, but precipitation efficiency of heavy rain associated with deep convection is independent of sea surface temperature. For example, Lau and Wu (2003) analyzed satellite data from the Tropical Rainfall Measuring Mission (TRMM Simpson et al. In addition to the weather-scale topics, precipitation efficiency is also an important parameter for cloud–climate feedback processes. (1996) proposed an ingredient approach to forecasting the potential for heavy rainfall and flash floods using the precipitation efficiency as an essential conversion rate. For example, precipitation efficiency is a key parameter in the closure assumptions in some cumulus parameterization schemes ( Kuo 1965, 1974 Fritsch and Chappell 1980 Kain and Fritsch 1993 Grell 1993). This quantity is a crucial factor in a number of research topics. Therefore, precipitation efficiency is defined to evaluate how efficiently the convective system produces precipitation. However, due to reevaporation of rain and local atmospheric moistening, not all condensation or moisture fluxes are used to produce precipitation. So precipitation can be simply assumed to be proportional to the condensation rate (microphysical view) or the moisture flux in the convective systems (large-scale view). But the occurrence of precipitation is associated with environmental dynamics and thermodynamics of weather and climate events. Precipitation is directly produced by cloud microphysics processes at convective temporal and spatial scales.
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