Abstract:
Radiative characteristics of convective precipitating cloud can be used for the classification of convective/stratiform precipitation and for the algorithm to retrieval the rain rate from brightness temperature observed by satellite remote sensors. The typical convective cloud system in Yichang area on 9 July 2003 is simulated with MM5 model and its upwelling radiative brightness temperature is simulated with Monte-Carlo 3D microwave radiative transfer model. The columnar precipitation simulated by MM5 model shows consilient with that observed by rain gauges. As for the cloud microphysical particles, it is found that except for the cloud ice, the contents of the cloud water, precipitable water and precipitable ice particles from the MM5 are nearly equivalent to that retrieved from TMI data. The simulated Tb85V from M-C model also indicates similar distribution with the observed by TMI. Tb85 is sensitive primarily to the precipitated ice and snow content in clouds. The weak correction between Tb85 and the surface rain rate is found. Given the rain rate less than about 5 mm per hour in this case, Tb19 rises since the rain rate increases. However it descends with the rain rate increasing while the rain rate is over 5 mm per hour. Because of the notable intercorrelation between Tb19 and graupel content, it can be regarded as the indicator of surface rain rate in the strong convective center, at least as the estimator of columnar precipitated water content at upper layers. The feeble correlation between Tb85 and graupel columnar content happens because the upwelling Tb85 is synthetically affected by the various hydrometers such as the emission from cloud water and the scattering from ice particles, in addition the shift caused by oblique FOV. Tb37 has obvious correlation with the surface rain rate when it is less than 20 mm per hour and is saturated when the rain rate is over 20 mm per hour. Cloud water and precipitated rain in the convective cloud play roles on Tb37. The Tb at each channel shows the synthetical results of tilted cloud cell or oblique FOV. The higher frequency, the lower Tb values show and the more replacement happens due to the oblique FOV. Tb85 observed at 52.8° angle is even 15 K less than that received at zenith, and the shift can reach 25 km as well as the title cloud cell.