FY-3气象卫星中分辨率光谱成像仪和扫描辐射计11μm红外窗区通道的比较

在中国新一代气象卫星风云三号搭载的遥感器中,不同遥感器设有相近的通道.针对扫描辐射计(VIRR)第四通道(波段范围10.3~11.3μm)和中分辨率光谱成像仪(MERSI)第五通道(中心波长11.25μm),应用精确的逐线辐射传输模式(LBLRTM)模拟计算了红外波段8~14μm大气顶向外出射的光谱辐射率,大气廓线采用ECMWF再分析产生的具有代表性的全球52条大气廓线数据集.结合上述两个通道的光谱响应函数,计算了卫星接收到的大气顶出射辐射,从理论上分析了两个通道观测亮温之间的关系.应用2008年9月青海湖辐射校正场FY-3实际观测数据,检验了两个通道的关系.比较结果表明:LBLRTM模拟计算得到的MERSI和VIRR两个红外窗区通道的亮温有较好的一致性和线性关系,MERSI稍低于VIRR,偏差随温度的升高而线性增加.实际观测数据受诸多因素的影响,通道对比结果与理论模拟有一定的差异,VIRR观测亮温低于MERSI.结合MODIS的观测数据,分别与两个通道的观测结果进行了对比,确认了VIRR可能较低地估计了温度,MERSI与MODIS的符合程度在温度探测的绝对精度范围之内.该研究结果有助于评价MERSI和VIRR两个红外相似通道观测结果的异同性.

COMPARISON OF INFRARED 11μm WINDOW CHANNELS FOR MEDIUM RESOLUTION SPECTRAL IMAGER AND VISIBLE AND INFRARED RADIOMETER ON FY-3 METEOROLOGY SATELLITE

The different remote sensors on China new generation meteorology satellite FY-3 have similar thermal infrared channels. For the visible and infrared radiometer (VIRR) infrared 4-channel and medium resolution spectral imager(MER- SI) infrared 5-channel, the line-by-line radiative transfer model (LBLRTM), in which the atmospheric profiles adopt glob- al 52 atmospheric profiles generated by ECMWF, was performed to calculate the spectral radiance emitted from the earth-at- mosphere between 8μm and 14μm. The radiance received by the satellite was computed combined with the spectral re- sponse functions of channels and then the theoretical relationship of the brightness temperatures for the two channels was an- alyzed. The FY-3 actual observation data at QingHai Lake in September 2008 was used to examine the relationship. The comparison of the results indicates that the brightness temperatures for both channels calculated by LBLRTM agree each other well, but the temperature obtained from MERSI is lower than that from VIRR. The temperature difference between the two channels increases with the increase of temperature. Because FY-3 actual observations are affected by many factors, VIRR temperature is lower than MERSI, which is different from the theoretical result of the model. The matched MODIS data is used to compare with MERSI and VIRR. It is concluded that VIRR might underestimate the temperature. The deviation of MODIS and MERSI temperaturesis within the absolute accuracy of the temperature measurements. The results described here should be valuable for assessing the similarities and differences for the two similar infrared channels of MERSI and VIRR.