Simulation results of the WDM6 scheme and the Thompson scheme,both of which are commonly-used double-moment bulkmicrophysics schemes,are compared within theWeather Research and Forecasting model.The purpose of the com...Simulation results of the WDM6 scheme and the Thompson scheme,both of which are commonly-used double-moment bulkmicrophysics schemes,are compared within theWeather Research and Forecasting model.The purpose of the comparison is to study the difference in the aspects of the warm-rain hydrometeor number concentrations,the droplet size distributions,and the budgets of the rain mixing ratio and number concentration.It is found that the WDM6 scheme overestimates the ratio and the amount of large precipitation,and underestimates those of small precipitation,compared to the Thompson scheme.The cloud number concentration(CNC)predicted in the WDM6 scheme is one to three orders ofmagnitude smaller than that of the Thompson scheme,which is set to the specific valueof CNC.The cloud droplet spectra of the WDM6 scheme are broader.The WDM6 scheme produces a larger rain number concentration and smaller mass mean diameter of raindrops under the influence of both warm and cold rain processes—specifically,autoconversion and melting of snow and graupel.The WDM6 scheme produces a larger autoconversion rate and smaller total melting rate of snow and graupel than the Thompson scheme in the rain mixing ratio budget.The sign of the difference in the rain-cloud collection varieswith region,and the rain-cloud collection process together with evaporation of rain have a major influence on the sign of the surface precipitation difference between the two schemes.展开更多
From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectra...From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectral dispersion of cloud droplet size distributions. The further investigation indicates that the threshold value is an increasing function of spectral dispersion and cloud droplet number concentration. These results may improve our understanding of the cloud-precipitation interaction and the aerosol indirect effect.展开更多
基金sponsored by the National Natural Science Foundation of China [grant number 41530427]
文摘Simulation results of the WDM6 scheme and the Thompson scheme,both of which are commonly-used double-moment bulkmicrophysics schemes,are compared within theWeather Research and Forecasting model.The purpose of the comparison is to study the difference in the aspects of the warm-rain hydrometeor number concentrations,the droplet size distributions,and the budgets of the rain mixing ratio and number concentration.It is found that the WDM6 scheme overestimates the ratio and the amount of large precipitation,and underestimates those of small precipitation,compared to the Thompson scheme.The cloud number concentration(CNC)predicted in the WDM6 scheme is one to three orders ofmagnitude smaller than that of the Thompson scheme,which is set to the specific valueof CNC.The cloud droplet spectra of the WDM6 scheme are broader.The WDM6 scheme produces a larger rain number concentration and smaller mass mean diameter of raindrops under the influence of both warm and cold rain processes—specifically,autoconversion and melting of snow and graupel.The WDM6 scheme produces a larger autoconversion rate and smaller total melting rate of snow and graupel than the Thompson scheme in the rain mixing ratio budget.The sign of the difference in the rain-cloud collection varieswith region,and the rain-cloud collection process together with evaporation of rain have a major influence on the sign of the surface precipitation difference between the two schemes.
基金Project supported by the Special Foundation for China Nonprofit Industry (Grant No. GYHY200706036)the National Excellent Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 40825008)the National Basic Research Program of China (Grant No. 2010CB833406)
文摘From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectral dispersion of cloud droplet size distributions. The further investigation indicates that the threshold value is an increasing function of spectral dispersion and cloud droplet number concentration. These results may improve our understanding of the cloud-precipitation interaction and the aerosol indirect effect.
