大气逆辐射对草地下垫面地表温度的影响研究

根据SKYNET合肥站三年期间无云晴天4～50 μm波段地表向上长波辐射Rlu和大气逆辐射Rld的观测资料,定量分析了大气逆辐射对草地下垫面地表温度的影响.结果表明:大气逆辐射对地表温度日平均值的影响程度在夏季最大、秋季次之、冬季最小,当地表比辐射率ε=0.98时,地表视温度与地表温度日平均差值全年在0.96～4.41 K之间,7、8月份在1.3 K以上;任何季节.大气逆辐射对地表温度日分布的影响幅值均在夜间大、白天小、中午前后最小,冬季影响最为显著,地表视温度与地表温度的差值T*-Ts均具有"V"型日分布特征;长波辐射比Rld/Rlu越大,大气逆辐射对地表温度的影响程度越大,得出了T*-Ts与长波辐射比以及地表比辐射率之间的定量统计关系.

Effect of Downwelling Atmospheric Radiation on Grass Land Surface Temperature

The effect of downwelling atmospheric radiation(Rld) on grass land surface temperature(Ts) is analyzed based on the three-year observations of upwelling surface long-wave radiation(Rlu) and Rld in 4～50 μm band on clear days at SKYNET Hefei site. Results indicate that the effect of Rld on mean daily Ts are stronger in summer than in fall and the weakest in winter. The mean daily difference between apparent surface. temperature T* and Ts ranges from 0.96 K to 1.41 K through all year, with value larger than 1.3 K in July and August provided that land surface emissivity ε equals to 0.98. The effect of Rld on diurnal variation of Ts is weakest at noon, greatest at night with the diurnal distribution of T*－Ts showing“V”shape for each season and the effect is most remarkable in winter. The larger the ratio Rld/Rlu, the greater the effect of Rld on Ts and the quantitative statistical relationship between the ratio Rld/Rlu, surface emissivity ε and T*－Ts are obtained under different seasonal conditions.