RTTOV和CRTM对“罗莎”台风卫星微波观测的模拟研究与比较

Simulative study of satellite microwave observations for Typhoon Luosha using RTTOV and CRTM and the comparison

中文关键词:  快速辐射传输模式，RTTOV， CRTM，卫星微波观测，云雨条件

英文关键词:Rapid radiative transfer model, RTTOV, CRTM, Satellite microwave observation, Cloud and precipitation conditions

中文摘要:

      快速辐射传输模式中水成物辐射效应的考虑对卫星观测模拟具有重要的影响。利用区域中尺度数值模式WRF预报输出水成物含量和温湿廓线等参数，使用欧洲中期数值天气预报中心和美国卫星资料同化联合中心发展建立的快速辐射传输模式RTTOV和CRTM，结合雅可比模式计算得到的响应函数，分析了各种水成物辐射效应对AMSUA/B卫星微波观测各通道亮温模拟的影响，并比较了RTTOV和CRTM结果间的异同。结果表明，RTTOV和CRTM两个快速辐射传输模式计算得到的水成物响应函数和水成物辐射效应对模拟亮温影响特征基本一致，但量级上存在差异。雅可比表征的水成物响应函数和水成物本身的分布层次对应关系良好，云水和雨水的响应函数主要分布在中下层，冰水和雪则分布在中上层。相对于RTTOV，CRTM计算得到的水成物响应函数要大一些。对AMSUA，云水和雨水的辐射效应对通道模拟亮温主要以增温为主，尤其是在低频的窗区通道，冰晶和雪则体现散射效应为主的降温作用。对AMSUB，水成物辐射效应的考虑使得模拟亮温降低，尤其是通道2降温幅度最大。CRTM计算出的水成物辐射效应带来的模拟亮温变化幅度大于RTTOV。目前，CRTM除了考虑云、雨、冰和雪4种水成物外，还考虑霰和雹的辐射效应，对水成物辐射效应的考虑比RTTOV更完善一些。

英文摘要:

      The inclusion of the radiative effect of hydrometeor in the rapid radiative transfer model has important effect on the simulation of satellite observations. In this paper, with the hydrometeor amounts from the WRF forecast as an input, both the rapid radiative transfer models RTTOV and CRTM, together with their Jacobian models, are utilized to investigate the radiative effect of the hydrometeors on the simulation of the AMSUA/B microwave satellite observations. The results are also compared between the different models. It is shown that the characteristics of the response function and the influence on the simulation of satellite brightness temperature of hydrometeor are almost the same for RTTOV and CRTM. The response function of hydrometeor obtained from Jacobin models corresponds well with the distribution of hydrometeor. The response function of cloud and rain water concentrates on the low and middle levels and that of ice and snow locates on the middle and high levels. The magnitude from CRTM is larger than that from RTTOV. For AMSUA, the radiative effect of cloud and rain water increases the simulated brightness temperature, especially on those window channels with low frequency. The ice and snow show an effect of lowering temperature as compared with the satellite observation. For AMSUB, hydrometeor mainly decreases the simulated brightness temperature, especially on the channel 2. The result of CRTM is also larger than that of RTTOV. At present, only cloud, rain, ice and snow are taken into account by RTTOV. The considersion of radiative effect of hydrometeor by CRTM is more perfect than that of RTTOV since graupel and hail are included as well with it.