Using Multi-Years MODIS LST Data to Monitor the Ground Surface Freezing and Thawing Conditions on the Qinghai-Tibet Plateau

摘要

As the influence of global warming, it is important to assess the freezing and thawing conditions of the ground surface to fully understand the impacts of frozen ground on the surface and subsurface hydrology, the surface energy and moisture balance, ecosystem conservation, and engineering constructions on the Qinghai-Tibet Plateau (QTP). However, assessing the changes of ground surface freezing and thawing conditions on the QTP still remains a challenge owing to the sparseness and discontinuity of remote sensing and ground observations. The ground surface thawing index can be used to predict changes of the thermal regime of permafrost and can be good indicators of climate change in the QTP, which is of great importance for a variety of engineering applications. In this study, we firstly used the harmonic analysis of time series (HANTS) algorithm to fill in the Land Surface Temperatures (LST) data gaps of the Moderate Resolution Imaging Spectroradiometer (MODIS) observation data caused by the cloud contamination. Then we used the MODIS LST data to estimate the daily ground surface temperatures (GST) by a multiple linear regression model on the QTP. Finally, we calibrated the model by the ground temperature observations at a selection of meteorological stations. The precisely estimation of the multi-years thawing index within 2003-2012 is calculated to monitor the ground surface freezing and thawing conditions change on QTP.