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

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.