Temporal and spatial changes in estimated near-surface air temperature lapse rates on Tibetan Plateau

Abstract

Lapse rate (LR) of near-surface (2 m) air temperature is essential for determining spatially distributed and gridded air temperature interpolated from in situ observational sites. However, due to the limitation of sparse observational networks, high-resolution LRs are not usually available on regional scales, especially in mountainous regions. The purpose of this study is to estimate LRs for the entire Tibetan Plateau (TP) using observed air temperature and moderate-resolution imaging spectroradiometer (MODIS) night-time land surface temperatures (LSTs) and to analyse the spatio-temporal changes of the estimated LRs. First, diurnal cycles of LRs derived from in situ observations in three subregions of the TP were analysed, which shows that the LRs in the western and northeastern regions were shallow in the cold season and steep in the warm season, whereas the southeastern region exhibited a different pattern. Further comparisons revealed that the LRs for night-time air temperatures better represented the LRs for daily mean air temperatures than the daytime ones, and the night-time MODIS LSTs correlated well with the night-time air temperatures, especially for the MODIS Terra data sets. Therefore, the night-time MODIS LSTs from the Terra data sets were used to estimate high-resolution (10 km) LRs for the daily mean temperatures over the entire TP. Estimated LRs over most areas of the TP were shallower than the commonly used environmental LR (−6.5 K/km). The LRs in the southeastern region were steeper than those in the northeastern region, while steeper LR values occurred in the northwestern region with lower temperatures and less humidity.