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

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.