The initiation and intensity of warm rain are processes dominated by the evolution of cloud droplet spectra.To treat the cloud condensation process properly is a fundamental step for the simulation of warm rain format...The initiation and intensity of warm rain are processes dominated by the evolution of cloud droplet spectra.To treat the cloud condensation process properly is a fundamental step for the simulation of warm rain formation.Double-moment bulk schemes with a limited number of prognostic variables cannot simulate the evolution of droplet spectra properly.A triple-moment bulk scheme,however,should overcome the problem of spurious cloud droplet spectrum broadening induced by double-moment schemes.To compare the effects of a newly developed triplemoment scheme with double-moment schemes on warm rain formation,the authors conducted WRF-LES numerical simulations to investigate the impacts of the two types of condensation scheme on rain initiation and intensity.In the early stage of raindrop formation,the simulation with the triple-moment scheme delays the raindrop initiation and produces droplet spectra with smaller average radii than those with the double-moment scheme.In the developing stage,the triple-moment scheme reduces the raindrop water content at the precipitation center.However,the further triple-moment scheme for raindrop is needed to simulate the development of warm rain accurately.展开更多
The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, obs...The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, observations have revealed that the use of such methods is not applicable for all actual cases. In this study, formulas were derived based on cloud microphysics and the properties of gamma function to solve the average cloud droplet radius and the cloud droplet spectral shape parameter. The gamma distribution shape parameter, relative dispersion, and cloud droplet spectral distribution can be derived through solving the droplet spectral shape parameter equation using the average droplet radius, volume radius, and their ratio, thereby deriving an analytic solution. We further examined the equation for the droplet spectral shape parameter using the observational droplet spectral data, and results revealed the feasibility of the method. In addition, when the method was applied to the two-parameter cloud microphysical scheme of the Weather Research and Forecast(WRF) model to further examine its feasibility, the modeling results showed that it improved precipitation simulation performance, thereby indicating that it can be utilized in two-parameter cloud microphysical schemes.展开更多
基金supported by the National Basic Research Program of China(973 Program)[Grant 2014CB441403]the National Natural Science Foundation of China [Grants41275147]+1 种基金the National Key Research and Development Program of China [2016YFC0209000]Ningxia scientific supporting program [Grants 2015KJHM31]
文摘The initiation and intensity of warm rain are processes dominated by the evolution of cloud droplet spectra.To treat the cloud condensation process properly is a fundamental step for the simulation of warm rain formation.Double-moment bulk schemes with a limited number of prognostic variables cannot simulate the evolution of droplet spectra properly.A triple-moment bulk scheme,however,should overcome the problem of spurious cloud droplet spectrum broadening induced by double-moment schemes.To compare the effects of a newly developed triplemoment scheme with double-moment schemes on warm rain formation,the authors conducted WRF-LES numerical simulations to investigate the impacts of the two types of condensation scheme on rain initiation and intensity.In the early stage of raindrop formation,the simulation with the triple-moment scheme delays the raindrop initiation and produces droplet spectra with smaller average radii than those with the double-moment scheme.In the developing stage,the triple-moment scheme reduces the raindrop water content at the precipitation center.However,the further triple-moment scheme for raindrop is needed to simulate the development of warm rain accurately.
基金supported by National Basic Research Program of China(Grant No.2011CB403406)
文摘The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, observations have revealed that the use of such methods is not applicable for all actual cases. In this study, formulas were derived based on cloud microphysics and the properties of gamma function to solve the average cloud droplet radius and the cloud droplet spectral shape parameter. The gamma distribution shape parameter, relative dispersion, and cloud droplet spectral distribution can be derived through solving the droplet spectral shape parameter equation using the average droplet radius, volume radius, and their ratio, thereby deriving an analytic solution. We further examined the equation for the droplet spectral shape parameter using the observational droplet spectral data, and results revealed the feasibility of the method. In addition, when the method was applied to the two-parameter cloud microphysical scheme of the Weather Research and Forecast(WRF) model to further examine its feasibility, the modeling results showed that it improved precipitation simulation performance, thereby indicating that it can be utilized in two-parameter cloud microphysical schemes.
