Impacts Of Land Use Cover Change (LUCC) On Land Surface Temperature (LST) Based On MODIS Datasets

By using MODIS (MODerate-resolution Imaging Spectroradiometer) datasets during2001-2012on Land Surface Temperatures (LSTs) and WRF (Weather Research and Forecasting) model, impacts due to Three Gorges Project on LSTs and influences of urbanization on LSTs in Yangtze River delta are analyzed to study the extreme cases on Land Use Cover Change (LUCC). Spatial characteristics of daytime and nighttime LSTs, and impacts of water body on LSTs, and potential spatial zones of influences due to Three Gorges Project in LSTs are analyzed both in winter and summer. Also spatial characteristics in four seasons, and evolution of the Urban Heat Island (UHI) and influences of Yangtze River delta urbanization in major cities on LSTs are analyzed. The main conclusions are as follows:(1) There are some spatial differences for daytime and nighttime LSTs and DTRs (Diurnal Temperature Range) during winter and summer. After removing impacts of climate background, some discrepancies exist in magnitudes and changes signs of the LSTs/DTRs temporal trends. In summary, all these noted that it is very important and necessary for investing climatic effects of Three Gorges Project to fully consider the impacts of topography and climate background. Removing the impacts of climate background and then separating the topographical effects through subtracting the variables after impounding (2003-2012) from ones before impounding (2001-2002), are proposed and utilized in the present paper. Results show that, relative to the period before impounding, winter LSTs after impounding obviously increase, and the intensity and range of nighttime are stronger than daytime, summer LSTs decrease, the intensity of nighttime is weaker than daytime, respectively, and the corresponding DTRs during both winter and summer decrease. With increments in distances from the water body, additionally, the climatic effects of reservoir get weaker. The potential spatial zones of influences induced by Three Gorges Project are limited to the distances0-8km from the water body.(2) WRF model could reappear distribution characteristics of the LSTs reasonably. Consistent with the results of the MODIS data, topography plays an important role to the distribution of LSTs change in the study area, but the simulated results are higher than observation especially on the Yangtze River. After impounding, winter LSTs increase, the intensity of nighttime is weaker than daytime, and summer LSTs decrease, but both winter and summer range have small amplitude just in water body and the surrounding region. Overall, the potential spatial zones of influences are consistent with MODIS observations limited to the distances0-8km from the water body.(3) At all seasons there are some spatial differences for daytime and nighttime LSTs and DTRs, fully considering the impacts of topography and different types of land surface is very important and necessary for analyzing climatic effects of urbanization in Yangtze River delta. The UHI effect observed is most significant in summer, weaker in spring, not significant in autumn and winter. The total proportion and intensity of UHI were increasing during2001-2012, finally, arranged in "Z" distribution. Major cities in Yangtze River Delta has smaller warming trend at daytime than nighttime in spring, cooling trend is larger at daytime than nighttime in summer and winter, autumn has a cooling trend at daytime and warming trend at nighttime. After removing impacts of climate background, there is a cooling trend at daytime and warming trend at nighttime in spring and autumn, cooling trend is larger at daytime than nighttime in summer and winter. DTRs are decreasing in four seasons, it means that the most important effect of urbanization is to make diurnal temperature range decrease on LST.