Evaluation of spatial-temporal dynamics in surface water temperature of Qinghai Lake from 2001 to 2010 by using MODIS data

Lake surface water temperature (SWT) is an important indicator of lake state relative to its water chemistry and aquatic ecosystem, in addition to being an important regional climate indicator. However, few literatures involving spatial-temporal changes of lake SWT in the Qinghai-Tibet Plateau, including Qinghai Lake, are available. Our objective is to study the spatial-temporal changes in SWT of Qinghai Lake from 2001 to 2010, using Moderate-resolution Imaging Spectroradiometer (MODIS) data. Based on each pixel, we calculated the temporal SWT variations and long-term trends, compared the spatial patterns of annual average SWT in different years, and mapped and analyzed the seasonal cycles of the spatial patterns of SWT. The results revealed that the differences between the average daily SWT and air temperature during the temperature decreasing phase were relatively larger than those during the temperature increasing phase. The increasing rate of the annual average SWT during the study period was about 0.01A degrees C/a, followed by an increasing rate of about 0.05A degrees C/a in annual average air temperature. The annual average SWT from 2001 to 2010 showed similar spatial patterns, while the SWT spatial changes from January to December demonstrated an interesting seasonal reversion pattern. The high-temperature area transformed stepwise from the south to the north regions and then back to the south region from January to December, whereas the low-temperature area demonstrated a reversed annual cyclical trace. The spatial-temporal patterns of SWTs were shaped by the topography of the lake basin and the distribution of drainages.