The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parame...The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parameter in the commonly used bulk double-moment schemes, the cloud droplet spectra cannot reasonably be described during the condensation process. Therefore, a newly-developed triple-parameter condensation scheme with the shape parameter diagnosed through the number concentration, cloud water content, and reflectivity factor of cloud droplets can be applied to improve the evolution of the cloud droplet spectrum. The simulation with the new parameterization scheme was compared to those with a high-resolution Lagrangian bin scheme, the double-moment schemes in a parcel model, and the observation in a 1.5D Eulerian model that consists of two cylinders. The new scheme with the shape parameter varying with time and space can accurately simulate the evolution of the cloud droplet spectrum. Furthermore, the volume-mean radius and cloud water content simulated with the new scheme match the Lagrangian analytical solutions well, and the errors are steady, within approximately 0.2%.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
为了定量评估对数正态谱分布假设对水云光学厚度(COT)与有效粒子半径(Re)反演的影响,利用欧洲中期数值天气预报中心建立的RTTOV(Radiative Transfer for TIROS Operational Vertical Sounder)模式,对比模拟了基于对数正态谱和修正Gamma...为了定量评估对数正态谱分布假设对水云光学厚度(COT)与有效粒子半径(Re)反演的影响,利用欧洲中期数值天气预报中心建立的RTTOV(Radiative Transfer for TIROS Operational Vertical Sounder)模式,对比模拟了基于对数正态谱和修正Gamma谱两种云滴谱分布下FY-4A/AGRI(Advanced Geosynchronous Radiation Imager)的第2、5通道液态水云的反射率,分析了这两个谱分布假设条件下水云反射率随COT以及Re的变化特征。在此基础上,建立了两种谱分布条件下的COT和Re查算表,并基于2020年夏季的一个初生对流云个例,定量分析了云滴谱分布类型对云参数反演结果的影响。结果表明,在第2通道,两个云滴谱类型假设下计算的反射率仅有0.1%~2%的差异,但在第5通道,采用修正Gamma云滴谱计算的反射率比采用对数正态云滴谱计算的反射率低10%~20%。反演结果表明,采用对数正态云滴谱反演的有效粒子半径Re比采用修正Gamma云滴谱反演的Re整体偏大,前者反演的Re集中在15~35μm,而后者反演的Re集中在10~30μm。采用两种云滴谱反演的COT的空间一致性良好,相差-2%~5%。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41275147 and 41875173)the STS Program of Inner Mongolia Meteorological Service, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences and Institute of Atmospheric Physics, Chinese Academy of Sciences (Grant No. 2021CG0047)
文摘The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parameter in the commonly used bulk double-moment schemes, the cloud droplet spectra cannot reasonably be described during the condensation process. Therefore, a newly-developed triple-parameter condensation scheme with the shape parameter diagnosed through the number concentration, cloud water content, and reflectivity factor of cloud droplets can be applied to improve the evolution of the cloud droplet spectrum. The simulation with the new parameterization scheme was compared to those with a high-resolution Lagrangian bin scheme, the double-moment schemes in a parcel model, and the observation in a 1.5D Eulerian model that consists of two cylinders. The new scheme with the shape parameter varying with time and space can accurately simulate the evolution of the cloud droplet spectrum. Furthermore, the volume-mean radius and cloud water content simulated with the new scheme match the Lagrangian analytical solutions well, and the errors are steady, within approximately 0.2%.
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.
文摘利用长春2007年5月16日的一次层状云降水过程的飞机观测资料,并结合天气图、卫星云图及雷达回波等资料,综合分析了此次降水过程中粒子浓度、粒子谱、雷达垂直累积液态水(vertical integrated liquidwater,VIL)、微波辐射计积分液态水(liquid water content,LWC)以及地面雨强特征。研究表明,层状云微结构在水平方向上的起伏较大,出现两次典型的含水量跃变:第1次液态水跃变主要是因为粒子浓度增加;第2次液态水跃变是因为粒子浓度和粒子谱共同作用的结果;雷达VIL值和地面雨强两者呈正相关。
文摘为了定量评估对数正态谱分布假设对水云光学厚度(COT)与有效粒子半径(Re)反演的影响,利用欧洲中期数值天气预报中心建立的RTTOV(Radiative Transfer for TIROS Operational Vertical Sounder)模式,对比模拟了基于对数正态谱和修正Gamma谱两种云滴谱分布下FY-4A/AGRI(Advanced Geosynchronous Radiation Imager)的第2、5通道液态水云的反射率,分析了这两个谱分布假设条件下水云反射率随COT以及Re的变化特征。在此基础上,建立了两种谱分布条件下的COT和Re查算表,并基于2020年夏季的一个初生对流云个例,定量分析了云滴谱分布类型对云参数反演结果的影响。结果表明,在第2通道,两个云滴谱类型假设下计算的反射率仅有0.1%~2%的差异,但在第5通道,采用修正Gamma云滴谱计算的反射率比采用对数正态云滴谱计算的反射率低10%~20%。反演结果表明,采用对数正态云滴谱反演的有效粒子半径Re比采用修正Gamma云滴谱反演的Re整体偏大,前者反演的Re集中在15~35μm,而后者反演的Re集中在10~30μm。采用两种云滴谱反演的COT的空间一致性良好,相差-2%~5%。
