Spatial and temporal patterns of land surface temperature in the Mekong Basin

Abstract

The surface energy budget is strongly influenced by incoming and outgoing radiation, which in turn mainly determines the Land Surface Temperature (LST). If regular measurements of LST are available on a broad spatial scale, they can be used as a measure for climate variability and change. In this research, a 13 year time series of the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor was used to analyze spatial LST patterns of the Mekong Basin (MB) along with the temporal evolution of the variable in the area. The MODIS LST data used had a temporal granularity of 8 days. In general, LST proved to be strongly dependent on the topography. The topographic height explained 42% of daytime LST in summer. In winter and generally in the night-time scenes, the topographic heights could explain 89-97% of the spatial LST patterns. For further analysis, the area of interest (MB) was divided into six physiographic homogenous regions. Mean temperature and annual maximum and minimum values of LST were calculated for the regions. As expected, low temperatures together with large day-night magnitudes were predominantly found in the high-lying Tibetan Plateau. The southern regions in contrary show high mean temperatures along with low day-night magnitudes. In almost all regions, a weak year-to-year variability of LST (regional 8-day daytime/night time deviations lower than 4°C/6°C) was recorded. Only the regional 8-day daytime/night time deviations of the Tibetan Plateau reach 6°C and 18°C. Land use is besides the topography also a strong driver in explaining LST patterns. This fact is shown on the example of forested parts in Cambodia, which underwent deforestation during the study period, leading to substantially increasing LST.