Scale Mismatch Between In Situ and Remote Sensing Observations of Land Surface Temperature: Implications for the Validation of Remote Sensing LST Products

The validation of remote sensing land surface temperature (LST) products is vital for their broad application. Conventional validation methods use ground-based measurements to evaluate the LSTs retrieved from remote sensing data. However, it is difficult to directly validate low or medium spatial resolution LST products because of the scale mismatch between in situ and remote sensing observations. In this letter, we compare two ground-based in situ observations with Moderate Resolution Imaging Spectroradiometer (MODIS) 1-km-resolution LST products (MOD11A1). We focus on the differences in scale between the ground-based measurements and the MODIS observations. A comparison of the results obtained during the daytime with those obtained at night indicates that stronger heterogeneity leads to a greater scale-mismatch effect. Because the LST heterogeneity influences the mismatch effect, semivariance is employed to analyze the heterogeneity of the MODIS 1-km mixed-pixel data using the LSTs retrieved from the high-resolution Thermal Airborne Spectrographic Imager and the Advance Spaceborne Thermal Emission and Reflection Radiometer data.