不同形状冰晶权重假定对冰云光学和辐射特性的影响

摘要

在BCC_RAD辐射传输模式和包含多形状冰晶粒子的冰云光学性质参数化方案的基础上,详细分析了不同冰晶粒子权重选取对冰云光学和辐射特性的影响.结果显示,不同形状冰晶粒子权重的选取对长波带平均消光系数、单次散射比、不对称因子和短波带平均不对称因子均有较大的影响.冰晶粒子权重选取对长波辐射通量有很大影响:对长波向下辐射通量,权重选择不同可在云底处造成高达10.50 W/m2的差别;对长波向上辐射通量,权重选择不同可在云顶处造成高达15.05 W/m2的差别.冰晶粒子权重选择对短波辐射通量也存在较大影响:对短波向下辐射通量,权重选择不同可在云底处造成高达12.48 W/m2的差别;对短波向上辐射通量,权重选择不同可在云顶处造成高达10.23 W/m2的差别.冰晶粒子权重选择对长波加热率影响较大,在云顶处和云底处分别可达1.31和-2.06 K/d.研究表明,不同形状冰晶粒子权重的选取对冰云光学性质和辐射计算均有较大的影响,在长波区间尤其明显.%Based on the BCC_RAD (Beijing Climate Center radiative transfer model) and a multi-shape ice cloud radiative parameterization scheme,the effects of different ice crystal weight assumptions on ice cloud optical properties and radiation are discussed in detail.The results show that the influences of the ice crystal weight assumption chosen on the ice cloud longwave band-averaged volume extinction coefficient,the single scatter albedo and the asymmetry factor are obvious.The ice crystal weight assumption has a significant influence on longwave radiative flux.For the longwave downward radiative flux,the assumption can cause up to 10.50 W/m2 of the flux difference at the cloud base.For the shortwave upward radiative flux,the assumption can cause up to 15.05 W/m2 of the flux difference at the cloud top.The ice crystal weight assumption also has a significant influence on the shortwave radiative flux.For the shortwave downward radiative flux,the assumption can cause up to 12.48 W/m2 of the flux difference at the cloud base.For the shortwave upward radiative flux,the assumption can cause up to 10.23 W/m2 of the flux difference at the cloud top.The assumption also has a great effect on longwave heating rate,which could be 1.31 K/d at the cloud top and-2.06 K/d at the cloud base.In summary,the weight assumption has an important influence on ice cloud optical properties and radiation calculations,particularly in the longwave region.