Normalization of the temporal effect on the MODIS land surface temperature product using random forest regression

摘要

Information about land surface temperature (LST) acquired from remote sensing satellite observations is very important to monitor surface energy and water exchange processes at the land-atmosphere interface. However, the wide-view of the popularly used polar-orbiting satellites (Terra and Aqua) face the challenge from the temporal effect on their LST products induced by the big temporal differences along the scan line. To generate a time-consistent LST product, a practical normalization method is proposed in this study based on random forest regression for LST observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on-board Terra satellite. A linking model is constructed to express LST as a function of various surface variables including vegetation indices, leaf area index, surface albedo, water index, solar radiation factor, and surface elevation. Under the assumption that the temporal effect is induced primarily by the differences in incident solar radiation, the temporal effect normalization is conducted by deriving a temporally consistent solar radiation factor which is used to drive the linking model and obtain the normalized LST. The proposed method is applied to the central Iberian Peninsula on the day of year 170 and 181, 2015. Results show that the areas with positive complement in solar radiation factor generally exhibit a positive increase in LST. An obvious improvement can be observed in the spatial pattern of the normalized LST data with the disappearance of the temperature boundary due to the big difference of satellite observation time. The Meteosat Second Generation (MSG) LST data which have the observations at the same local solar time is used for quantitative validation. The evaluation shows that the normalized LST data is more coincident with the MSG LST data than the original MODIS LST data, with significant improvements in the root mean squared deviation and bias with the MSG LST data (1.23 K and 1.66 K, respectively). Unlike previous normalization methods, the proposed method is conducted based on only satellite observations without other ancillary data. Therefore, the method demonstrates good potential for normalizing the temporal effect of the wide-view polar-orbiting satellite observations.