长波辐射对大气变化的敏感性和在WRF模式中的应用检验

用RRTM长波辐射 (LWR)参数化方案测试了LWR对大气变化的敏感性。结果表明 :高云对向外长波辐射(OLR)、30 0和 5 0 0hPa净LWR通量的减弱作用较中、低云大 ;低云对 85 0hPa和地表净LWR通量的减弱作用较中、高云大。在云层中 ,LWR冷却率受云影响最大 ;在云层下方 ,云对LWR的影响迅速减小 ;而在云层上方 ,冷却率几乎不受云的影响。当水汽含量减少或增加时 ,地表向下LWR受到相应减弱或增强 ,而净LWR则在一定程度上受到相应增强或减弱 ,并且越接近地面 ,受到水汽变化的影响就越大。O3 对LWR的影响相对云和水汽来说是比较小的。文中介绍了在WRF模式中应用RRTM方案预报LWR不同季节的 2个个例 ,给出了应用NCEP/AVN分析资料预报和验证中国范围 2d之内LWR通量的模拟结果。试验表明 ,OLR和 5 0 0hPa净LWR通量与高度形势场有较好的对应关系 ,而地表净LWR很大程度上还受到地形的影响。

THE SENSITIVITY OF LONG WAVE RADIATION TO ATMOSPHERIC CHANGES AND THE SIMULATING IN THE WATHER RESEARCH AND FORECAST(WRF) MODEL

The tests on sensitivity of long wave radiation (LWR) to atmospheric changes using RRTM radiative parameterization have been made. The result shows that the reduction effect of high cloud on the OLR,300 and 500 hPa surface net long wave (LW) flux is larger than middle and low cloud. The reduction effect of low cloud on the 850 hPa and the surface net LW flux is larger than middle and high cloud. The effect of clouds on LWR cooling rate is the largest in the presence of clouds, and rapidly decreases under the cloud levels, and is not influenced above the cloud levels. Downward LW fluxes at ground surface would decrease or increase, but net LW fluxes would reverse with the decrease or increase of water vapor content, also the closer to the ground surface, the larger the effect of water vapor changes on LWR. The effect of ozone on LWR is smaller relative to cloud and water vapor.This paper discusses two cases in different season of applying RRTM scheme to forecast LWR in WRF model and gives the results of forecasting and verifying all over China in the two days using the NCEP/AVN analysis data. The results show that OLR and 500 hPa surface net LW flux is very correlative to geopotential height field,but net LW flux at ground surface is also influenced by topography to a large extent. In addition, the errors of LWR increase with forecast time, but they possess the character of diurnal and seasonal variation, the forecast errors of net LW fluxes at ground surface are a bit smaller in the nighttime than in the daytime, and the forecast error growth of LWR with forecast time is larger in summer and autumn than in winter.