摘要:通过446183条全球晴空大气廓线的红外辐射传输模拟和统计回归，建立了由Himawari08成像仪通道遥测数据估算晴空地表上行、下行长波辐射通量的反演模式，模式应用于成像仪观测资料，处理出晴空地表上行、下行长波辐射通量实时产品，2016年2~6月的产品精度验证试验结果为：与相同时刻的AQUA卫星CERES仪器同类产品相比，地表上行通量均方根误差Re=7.9 W/m2，相关系数R=0.9399，地表下行通量Re=14.5 W/m2，R=0.9586；与由中国地面气象站地面气温和相对湿度观测经Brunt、Brutsaert经验公式计算的实时地表下行长波辐射通量相比，Re=15.34 W/m2，R=0.8786；与用陆表温度计算的地表上行长波辐射通量相比，Re=12.6 W/m2，R=0.9977。研究了2016年2、6月的晴空地表长波辐射产品，发现陆地晴空上、下行通量有着与太阳加热地表增温相应的明显日变化特征，峰值出现在12：00（当地时间，下同）至14：00，低谷出现在04：00至07：00，下行通量与上行通量几乎同步变化或约有延时，陆地上2个通量归一化的日变化指数类似一个半正弦曲线，而海面长波辐射通量则没有明显的日变化规律。
关键词:地表上行长波辐射/
地表下行长波辐射/
辐射传输模拟/
日变化
Abstract:Based on infrared radiative transfer simulation of 446183 global atmospheric profiles and statistical regression analysis, two retrieval models relating the clear-sky surface downward and upwelling longwave radiation fluxes with the channel observations of Himawari08 satellite are established. By applying the models to the observation data of Himawari08, the two flux products from February 2016 have been processed. Several experiments are conducted to validate the processed products, and results show that the RMSE (Root Mean Squared Error) is 7.9 W/m2 and the correlation coefficient R is 0.9399 when comparing the surface upwelling longwave flux product with that of AQUA/CERES; the RMSE is 14.5 W/m2 and R is 0.9586 when comparing the surface downward longwave flux product with that of AQUA/CERES; the RMSE is 15.34 W/m2 when the satellite estimated downward fluxes are compared with the empirically calculated fluxes by Brunt equation and ground air temperature and humidity observations collected at 2260 Chinese ground meteorological stations; the RMSE is 12.6 W/m2 when comparing the upwelling flux product with the flux derived from land surface temperature product of Himawari08. Two months' products in February 2016 and June 2016 are selected to study the diurnal variation of the two fluxes. The results indicate that the diurnal cycles of the two fluxes are highly associated with the solar heating surface over land with the maxima appearing from 1200 LST to 1400 LST and the minima at around 0400 LST to 0700 LST in winter and summer. The diurnal variation of downward flux is either in the same phase with that of upward flux over most land, or one hour later in some locations. The variation patterns of both flux cycles can be approximated with a half-sine curve and two lines. But over ocean there are no distinct diurnal variation characters.
Key words:Surface upward longwave radiation/
Surface downward longwave radiation/
Radiative transfer simulation/
Diurnal variation
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