祁连山草地MODIS LST产品真实性检验

Validation of MODIS land surface temperature products in grasslands of Qilian Mountain

利用祁连山自动站实测地表温度数据,对中分辨率成像光谱仪(moderate-resolution imaging spectroradiometer,MODIS)地表温度(land surface temperature,LST)日产品(MOD/MYD11A1)进行真实性检验和对比分析,评价不同下垫面上MODIS LST标准产品的空间适应性,订正由地表类型变化而引起MODIS LST产品的误差。结果表明,在祁连山西段海拔相对较低的荒漠草地上,MOD11A1 LST产品与实测地表温度数据具有较高的空间一致性,平均误差和均方根误差较低,分别为1.62和3.88℃;在祁连山海拔相对较高的东段山地草甸和中段高寒草地上,MYD11A1 LST产品精度较高,平均误差为2.02和3.72℃,均方根误差为5.12和6.92℃。在祁连山地区,MODIS LST产品精度不仅受地表类型的影响,同时还受植被覆盖度和海拔高度的影响。在海拔相对较高的祁连山东段山地草甸和中段高寒草地区,由于地表升温速度慢,植被盖度较高,MOD11A1 LST产品的精度较低,且高估了该地区的实际地表温度,均方根误差在5.12℃以上。通过误差订正可有效提高MODIS LST产品在祁连山山地草甸、高寒草地和荒漠草地上的精度,均方根误差分别降低了1.29、2.66和0.91℃。

Land surface temperature(LST)values measured at automatic weather stations in Qilian Mountain in China,were adopted to perform validation tests and comparative analysis of daily moderate resolution imaging spectroradiometer(MODIS)LST products(MOD/MYD11A1).The aim of the study was to assess the space adaptability of standard MODIS LST products on different underlying surfaces and to correct the error detected in these products due to changes in land surface types.The results indicated that in desert grasslands with low altitudes in the western section of Qilian Mountain,MOD11A1 LST products showed higher space consistency and adaptability,with respect to the measured LST.The average error and root mean square error(RMSE)were 1.62℃and 3.88℃,respectively.On the mountain grassland in the eastern section and alpine grassland in the middle section of Qilian Mountain,which had higher altitudes,MYD11A1 LST products showed higher accuracy;average errors were 2.02℃and 3.72℃,respectively,while the RMSEs were 5.12℃and 6.92℃,respectively.In addition to the effect of land surface types,the accuracy of MODIS LST products is also influenced by vegetation cover and altitude,as seen in the Qilian Mountain.On the mountain grassland in the eastern section and alpine grassland in the middle section of Qilian Mountain,which have higher altitudes,MOD11A1 LST products showed less accuracy due to the slow rate of temperature rise and high vegetation coverage,which resulted in an overestimation of the actual LST in these areas,with an error of over 5.12℃.With the help of error correction,the accuracies of MODIS LST products when used on mountain,alpine,and desert grasslands of the Qilian Mountain were effectively improved,as the RMSEs of the products were reduced by 1.29,2.66,and 0.91℃,respectively.