边界层温度廓线遥感反演的本地化改进研究

An improvement of localization in the retrieval algorithm of temperature profile within boundary layer

中文关键词:  荒漠戈壁, 大气边界层, 温度廓线, 统计和物理算法, 气溶胶, 地表温度

英文关键词:Boundary layer, Temperature profile, Statistical and physical algorithm, Aerosol, Surface temperature

中文摘要:

      采用MODIS资料和美国发展的MODIS大气温、湿度廓线统计反演算法，估算大气温度、湿度廓线作为初始场，应用101层快速透过率模式（PFAAST）估算了大气透过率，并采用Newton非线性迭代算法反演中国西北荒漠戈壁地区大气温度廓线。结果表明：该方法对边界层高度及以上部分的大气温度反演得比较好，误差基本都在2 K范围内，边界层范围内的温度反演误差较大，反演误差与气溶胶光学厚度增量和地表温度估算误差呈显著正相关关系，与大气水汽混合比的关系较差。文中从敏感性试验和理论分析角度阐述了地表温度和气溶胶光学厚度估算误差对大气温度反演误差的影响，发现不同光谱波段的地表温度权重均随地表温度的增加有不同程度增加，地表温度反演误差增加将增加地表温度权重，提高地表温度估算误差有助于提高地表温度权重的精度；荒漠戈壁地区大气边界层中气溶胶浓度较高，光学厚度较大，使边界层大气透过率降低，进而降低卫星红外遥感波段的地表温度权重和空气温度权重。由于该模式没有很好地考虑边界层中沙尘气溶胶的影响，使卫星反演的大气透过率偏高，以至于高估地表温度权重和大气温度权重，使得反演的表面温度和空气温度偏低。该研究结合太阳光度计获得的光学厚度资料，采用统计方法对气溶胶效应引起的大气透过率误差和表面温度估算误差进行校正，并对物理算法进行本地化改进，实现了边界层温度廓线的反演。

英文摘要:

      Using the statistical synthetic regression algorithm by the USA, the temperature and moisture profile of the atmosphere is retrieved based on the MODIS data, which, as an initial condition, is then employed for estimating the atmosphere transmittance through Pressure-Layer Fast Algorithm for Atmospheric Transmittances(PFAAST), and thus the atmosphere temperature is retrieved via the nonlinear physical retrieval algorithm. The results show that the atmospheric temperature error is within 2 K at and above the top of boundary layer with a larger error within boundary layer, that is positively correlated with the aerosol optical depth (AOD) increment as well as the estimated error of surface temperature, but with poor correlation with atmospheric moisture mixing ratio. On the basis of the radiative transfer theory and sensible experiments, the effect of AOD and surface temperature on retrieval error is analyzed with the result that the surface temperature weighting to different spectral band is enhanced with increasing surface retrieval error, suggesting that a reasonable surface temperature precision is helpful for improving surface temperature weighting. Aerosol concentration is high within the boundary layer over the desert and the Gobi region in the northwestern China, which reduces the atmospheric transmittance therein. Besides, the surface temperature weighting and air temperature weighting to infrared band should be decreased in case the infrared remote sensing data are used. In view of that the sand aerosol effect within boundary layer is omitted, the atmosphere transmittance retrieved is overestimated and thus the surface temperature weighting and air temperature weighting are overestimated as well, causing that the air temperature retrieved is underestimated. According to the observed aerosol optical depth from sunphotometer, an improvement in the AOD effect and thus the surface temperature is obtained resulting from improved temperature profile that is able to reflect the real atmosphere structure within boundary layer.