FY-2C静止气象卫星资料对不透明云云顶气压的反演研究

A STUDY OF CLOUD TOP PRESSURE FOR THE OPAQUE CLOUDS RETRIEVAL FROM GEO-STATIONARY SATELLITE FY-2C

采用红外窗区通道法尝试对FY-2C静止气象卫星图像上的不透明云的云顶气压进行反演,并结合MODIS反演产品和CloudSat/CPR雷达探测产品对反演结果进行对比分析。结果表明:(1)对于厚实密蔽的云层,不透明云云顶气压的反演结果与MODIS反演结果一致性较好,特别是对于发展较强的对流云和厚实密蔽的多层云,易满足云层比辐射率近似为1的条件,可近似看作黑体;(2)对于单层云和光学厚度不够厚的云层,反演结果更接近辐射中心,尤其是对于锋面云带暖水云上空覆盖卷云的情况,由于FY-2C对于薄卷云的检测不如MODIS细致,导致反演结果与MODIS和CloudSat存在一定偏差。

An algorithm was used to retrieve the cloud top pressure（CTP） of opaque clouds from the imagery of the geo-stationary satellite FY-2C, and the IR Window（IRW） technique was applied to determine the pixel CTP of the opaque clouds together with NCEP atmospheric profiles. The results were compared with the MODIS/MOD06 CTP products and the CloudSat/CPR CTP estimated from radar reflectivity as a nearest neighbor path along the CloudSat ground track. The results show that the IRW technique works reliably with opaque clouds and IRW brightness temperatures can be compared to temperature profiles to infer the level of best agreement that is taken to be the level of the cloud. The comparisons demonstrate close agreement between FY-2C, MODIS and CPR at the optically thick clouds, especially for the deep convective clouds and the multi-layered clouds where the emissivity is approximately equal to 1.0 as blackbody. The differences in FY-2C, MODIS and CPR retrievals lie in the regions with transmissive clouds above lower opaque clouds where the CTP results from IRW technique demonstrate the pressure of the ＂radiative center＂ of the clouds, rather than the true cloud top pressure.