青藏高原东侧MODIS地表温度产品验证

Validation of MODIS Land Surface Temperature Products in East of the Qinghai-Xizang Plateau

利用青藏高原东侧理塘大气边界层观测站的热红外测温仪和长波辐射表的实测数据,分析了实测地表温度Ts的精度及其影响因子,对MODIS地表温度(LST)产品进行了评估。结果表明,与用红外测温仪测量的地表辐射温度Tr相比,考虑了地表辐射率和大气下行辐射后的地表温度Ts_R偏低,差值随着地表发射率递减,随着长波净辐射递增,白天偏低可达1.9 K,夜间偏低可达1.1 K。当地表温度<285 K时,Ts_R与用长波辐射估算的地表温度Ts_L之间的差值集中在2.5 K以内;而当地表温度>285 K时,偏差可达10 K。地表发射率的误差≤0.01时,地表温度计算误差≤0.5 K。Tr、Ts_R和Ts_L与LST之间都存在显著正相关,其中Ts_L与LST的相关系数最大。夜间的相关系数大于白天;Terra卫星的相关系数(尤其是白天)大于Aqua卫星。基于LST的Ts_L回归模型估算标准误差为4.4904 K,达到99%的置信水平。

In order to validate the Moderate Resolution Imaging Spectroradiometer( MODIS) Land Surface Temperature( LST) products in the east of the Qinghai- Xizang plateau,the ground observation data of Litang Atmospheric Boundary Layer Observation Station are used. The accuracy of the ground- based surface temperature and its influencing factors are also analyzed. The results showthat the surface radiometric temperatures( Tr)measured by the thermal infrared thermometer are lower up to 1. 9 K during daytime and 1. 1 K during nighttime than the surface temperatures( Ts_R) in account of the surface emissivity and atmospheric downward radiation.The deviations decrease with surface emissivity and increase with net long- wave radiation. The absolute errors between Ts_Rand the surface temperature estimated using long- wave radiations( Ts_L) concentrate in less than2. 5 K when Ts_Lare lower than 285 K,but reach up to10 K when Ts_Lare higher than 285 K. If the surface emissivity error is less than 0. 01,the surface temperature calculation error is less than 0. 5 K. Tr,Ts_Rand Ts_Lare significantly positively correlated with LST and the correlation coefficients between Ts_Land LST are biggest. The coefficients are larger during nighttime than daytime,while are larger for Terra than Aqua,particularly during daytime. The regression model of Ts_Lbased on the LST has a standard error of 4. 4904 K and passes the 99%confidence level.