分裂窗辐射量线形组合反演陆面温度的影响因子分析

ANALYSIS ON INFLUENCING FACTORS OF LAND SURFACE TEMPERATURE RETRIEVED BY USING SPLIT WINDOW ALGORITHM WITH LINEAR COMBINATION OF TWO CHANNELS' RADIANCE

大气特性与地物发射率是影响陆温反演精度的主要因素,不同的分裂窗表达式用于陆温反演存在不同的反演结果,其中两通道辐射量线形组合形式的分裂窗算法受大气影响最小,反演温度的误差也最小.其反演温度的误差与大气透过率和大气向上辐射无关,但与地物的发射率、大气向下辐射相关.分裂窗表达式B(λ,′Ts°)=a.I(λ1)+b.I(λ2)+c中的反演系数a、b与大气向上辐射无关,但分别与通道1、通道2的大气透过率成反比.当定标点发射率不完全一致时,二者还与大气向下辐射相关;相反,如果定标点发射率完全一致,二者与大气向下辐射无关.使用辐射量线性组合的分裂窗形式反演陆温时,当大气向下辐射与地物的P lanck辐射越相近,误差越小.

Characteristics of atmosphere and emissivities are the major influencing factors in land surface temperature retrieval. Different split window expressions can result in different retrievals of land surface temperature. Among them, the split window algorithm with linear combination of two channels＇ radiance has the least atmospheric influence. Retrieved temperature errors are correlated with emissivities and downwelling atmospheric radiance, not correlated with transmittance and upwelling atmospheric radiance. Retrieved coefficients （ a and b） of split window method （B（ λ＇, Ts＇ ） = a ·I（λ1 ） ＋ b·I（λ2 ） ＋ c ） have not relations with upwelling atmospheric radiance, but have inverse ratio with transmittance of two channels, respectively. When the land surfaces for calibration have different emissivities, the retrieved coefficients a and b have relations with downwelling atmospheric radiance, however, if the land surfaces for calibration have the same emissivities, the retrieved coefficients a and b will bear no relation to downwelling atmospheric radiance. When the downwelling atmospheric radiance is more approach to Planck radiance of land surface, the error of this method will be more trivial.