| Changes in precipitation and evaporation caused by global warming are strongly changing the water cycle process in arid areas.Evapotranspiration(ET)process is a water cycle process accompanied by energy exchange.Clarifying regional evapotranspiration changes plays a positive role in regional climate change and scientific management of water resources and ecological environment protection The surface evaporation is an important means of maintaining the surface water balance,is also a main way of water consumption in the earth system,for lack of water resources arid areas,clear regional surface evaporation is advantageous to the limited water resources reasonable allocation and regional coordinated development of social economy at present,in this research for a variety of surface cover types The applicability of remote sensing evapotranspiration inversion in such a comprehensive region needs to be further verified.Therefore,this paper chose the Northern Slope of Tianshan Mountain as the research area and applied MODIS remote sensing image data to calculate land surface albedo,land surface temperature,land surface ratio emissivity and vegetation coverage NDVI,combined with elevation data and meteorological data,uses SEBS model to quickly calculate monthly evapotranspiration of vegetation growing season in different years in the study area,so as to deeply study the spatio-temporal variation characteristics of surface EVapotranspiration on the Northern Slope of Tianshan Mountain in Xinjiang Based on the analysis of evapotranspiration change trend and land cover data,evapotranspiration changes under different land use types were analyzed.Based on the analysis of correlation between evapotranspiration and major meteorological factors,the following conclusions were drawn:(1)From the spatio-temporal variation characteristics of evapotranspiration in a year,evapotranspiration changes greatly with seasons and underlying surface characteristics.There are great differences in evapotranspiration values in April and May,and the difference is not obvious in June,which is concentrated between 5 and 6mm.In July 2000,2015,the average daily ET was higher,and in August,the average daily ET decreased rapidly,basically falling below 4.6mm,in September,between2.5-4mm,and in October,the average daily ET decreased rapidly again,and was between 1-2 mm in all years The spatial variation of ET in the north slope of Tianshan Mountain was correlated with the spatial variation of vegetation index.The maximum value of ET in each month was mainly distributed in the forestland in the north of Tianshan Mountain The concentrated growth area of grassland is distributed in bands along the mountain range,followed by the cultivated land distribution area,which has a large ET value and changes significantly with the season.The desert distribution area has the smallest ET value in each month of the whole region,and the difference of ET in each month is small.(2)From the characteristics of interannual spatio-temporal variation of EVapotranspiration,ET in the study area showed a slight upward trend in general from 2000 to 2020,with little fluctuation in each year.The average ET value in each year was affected by the maximum ET value,and the trend of change was consistent with that of the maximum ET value and the average ET value,with the increase rate of 3.76 mm·(10a)-1?2.28mm·(10a)-1respectively The annual ET spatial distribution on the Northern Slope of The Tianshan Mountains can be roughly divided into five types.The 0-400 mm distribution area accounts for a small proportion of the study area,mainly concentrated in the area with serious desertification and desertification,400-600 Mm was mainly distributed in the desert area north of the oasis agricultural area,and the distribution area was large.The distribution area of 600-800 mm was mainly distributed in the oasis agricultural area,and 80-1000 mm was distributed in the oasis agricultural area and the mountainous grassland growing area,1000 The distribution area above mm is mainly the woodland growth area,the distribution area is small,mainly distributed along the Tianshan Mountain range in the north slope mountainous area.(3)From the perspective of the inter-annual spatial variation trend of EVapotranspiration,most regions showed an upward trend,and the most significant upward trend was 0.35-0.91 in the border area of Qitai County and Mulei Kazakh Autonomous County.The areas with more significant downward trend were mainly distributed in the west of Wusu City,and the significant upward and downward trends were-0.35--0.1 in other regions.(4)According to the inter-annual characteristics of evapotranspiration under different land cover types,the land cover types on the Northern Slope of Tianshan Mountains can be roughly divided into six types:cultivated land,forest land,grassland,water area,building land and unused land.The grassland area is the largest,and the rest are unused cultivated land,forest land in descending order For building land,evapotranspiration increased in all land use types except unused land.The proportion of EVapotranspiration in grassland was the largest,and the proportion of ET in building land and water area was the smallest.(5)From the factors influencing evapotranspiration,the spatio-temporal variation of ET on the Northern Slope of the Tianshan Mountains is directly influenced by the land use type of the underlying surface.In terms of the influence of meteorological factors,except for the average temperature in 2000 and 2020,all other meteorological factors have a decreasing trend opposite to the variation trend of ET,with the average temperature rising at a rate of 0.076?per year and ET at a rate of 0.019mm·a-1 per year As the velocity increases,it can be seen that the variation trend of average temperature and ET is consistent,and the correlation between average temperature and air pressure and ET is significant,which has a great influence on ET. |
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