Exploring Typical Lake Water Surface Temperature Changes Across Xinjiang During 2000-2017

Since the 1980 s,the issues regarding global environmental change,including the core of global climate change,has attracted large-scale attention from all over the world.It has been identified that a sensitive indicator of global change depicts that lake changes in arid areas are susceptive records of climate and environmental changes.The arid zones of Northwest China's fragile ecology could respond to regional environmental changes.Therefore,this paper analyzes the lakes which comprise of more than 10 km2,from 2000 to 2017,in order to derive the dynamic changing trend of30 typical lake water surface temperatures during the daytime and nighttime across Xinjiang,by utilizing the MODIS 6 km resolution land surface temperature synthetic data(MOD11B3).This paper employs the measured data from an automatic weather station located on the east bank of Lake Sayram,in order to verify the lake water surface temperature data.It has been identified that the measured data displayed a highly significant correlation with the lake water surface temperature data.Thus,it can be proved that the data extracted from MODIS possesses high reliability.From a general standpoint,the distribution pattern of lake water surface temperature in Xinjiang is roughly similar to the temperature of closed-basin lakes,which is higher than that of closed-mountain lakes.The surface temperature of lakes on the edge of the Junggar Basin,along with the surrounding lakes of the Tarim Basin,are higher than that of the surrounding mountain lakes.The distribution of lakes in the Karakun Mountains,which has an average annual temperature between the range of-10 ? to-5 ?,depict a sparse trend in the east and west,while remaining denser in the middle.Also,it can be noticed that the range of-15 ° C to-10 ° C indicate a trend of being denser in the east and west,while being sparse in the middle.In addition,the average annual temperature difference between day and night in southern Xinjiang is universally higher than that of northern regions,which may be due to the difference in climate and the elevation of lakes.Under the background of the air temperature change rate of 0.016±0.028 ?/yr in Xinjiang,the temperature changes from the 30 typical lakes in Xinjiang generally show the same trend with the average change rate of daytime being 0.005±0.04?/yr(R=0.045),along with the average change rate of nighttime being 0.076±0.026 ?/yr(R=0.659**).The spatial distribution pattern of lake water surface temperature change rate during the night time depicts an obvious regularity: the existence of the highest warming rate of lake water surface temperature in the middle of the Kunlun Mountains,which showed a sign of warming trend gradually decreasing from the middle to the east and west,even getting cold.In addition,the analysis of 10 alpine lakes reveals a huge temperature difference between day and night(8.71 ?-28.32 ?).There are two types of affecting factors included in this paper,which have been listed to analyze the distribution pattern of lake water surface temperature: climate and elevation.There is a significant correlation between lake water surface temperature and the local climate factors(air temperature and precipitation).Among the 9 lakes close to the observation station,4 of them have the same trend as the observation station.It can also be seen that the change rates of all the lakes are faster than the local air temperature change rate.In terms of elevation,the changing trend of the lake water surface temperature,during both the daytime and night time,shows a good coordination with the overall elevation and the low elevation respectively.The average lake water surface temperature during the night time shows a better correlation with the altitude,than during the daytime.By analyzing these similar trends of lake water surface temperature and climate change in Xinjiang,we can deduce that the impact of climate change on lakes is far more evident.The lake water surface temperature change is affected by both natural factors and human factors,and the different elements of these two factors could also correspond to each other.Any change in element may lead to various consequences of moving the whole body.Therefore,one of the important tasks of future research should be dedicated to explore the internal relations comprehensively and meticulously between the influencing elements of lakes.