Estimation Of Daily Evapotranspiration From Remote Sensing In Northern Slope Of Tianshan And Its Influencing Factors

Biosphere evapotranspiration in the earth's atmosphere and hydrosphere plays an important role,on the one hand,the land surface evaporation is one of the land surface process in the atmosphere interaction of the key process,the understanding and study of global climate change,the importance of evaporation of information has been paid more attention to,on the other hand,in the case of global water resources the increasingly shortage,for reasonable utilization and allocation of water resources,to more in-depth understanding of different vegetation coverage and land utilization situation of water consumption conditions,especially in hydrology and agriculture,soil evaporation and vegetation transpiration is a necessary prerequisite for the accurate calculation of basin water balance research and estimation of crop yield,this is real important for agricultural production practice.Based on the multi-source remote sensing data(Landsat8,GF-1),the SEBS model was used to calculate the single day evapotranspiration in Hutubi in 12 months in 2015.In this paper,the temporal and spatial distribution of evapotranspiration in the Hutubi river basin is analyzed,and the inversion accuracy is verified by using the penman's formula,the results of the micro Lysimeter and the evaporating dish.The factors such as air pressure,temperature,humidity,wind speed and normalized vegetation index were selected to analyze the relationship between these factors and evapotranspiration.The main results are as follows:(1)From the perspective of time,the single day evapotranspiration in Hutubi River Basin in 2015 showed obvious seasonal variation.The summer evapotranspiration is the highest and the lowest in winter.During the month of 2015,the annual variation of single day evapotranspiration in Hutubi River Basin showed an upward trend from month to month,and 1~8 month showed a downward trend in8~12.One day in May,a slight decrease in the amount of evapotranspiration,which has a certain relationship with the weather and other weather factors.In August 18,2015,the daily evapotranspiration of Hutubi County reached the maximum value in a year,the average daily evapotranspiration was 3.387 mm.In February 23,2015,thedaily evapotranspiration was the smallest,and the average daily evapotranspiration was 1.042 mm.From the overall situation in 2015,the study area in 2015 single day evapotranspiration in 7,8 larger in the month of two,in the month of December,in the year of January,in the month of the year of the month of the year of three.In July2015,the standard deviation of the single day evapotranspiration in Hutubi was 0.252,which showed that the dispersion degree of the evapotranspiration data in the year of July was small and relatively stable.In June 2015,the standard deviation of the single day evaporation in Hutubi was the largest,which was 0.359,which indicated that the data of evaporation in the year of June was large and the data were unstable.For the Hutubi River Basin in 2015,the fitting polynomial equation of single day evapotranspiration is: y = 0.0035x`4-0.0939x3 + 0.7603x`2-1.8245 x + 2.2949,R`2 is0.8522.(2)From space,the territory of Hutubi County terrain can be roughly divided into three parts: the southern mountains and hills,with an average altitude of 2400meters;the central alluvial plain,at an altitude of 460 to 700 meters;the northern desert,at an elevation of 360-460 meters.Hutubi County,low-lying South High North,from southeast to northwest tilt.Evapotranspiration in Hutubi county has obvious regional characteristics.The evapotranspiration of forest land,farmland and river is the highest,and the vegetation coverage is higher.The evapotranspiration in desert Gobi region is very low.It can be seen that evapotranspiration is basically the spatial trend of evapotranspiration in the northern part of Hutubi desert in the central plain of Hutubi province in southern Hutubi.(3)As can be seen from the above table,the SEBS model is used to estimate the evapotranspiration of Landsat8 and GF-1 by remote sensing,and the variation trend of evapotranspiration estimated by the two different data sources is basically the same.The evapotranspiration values estimated from the GF-1 data are closer to the reference values than the Landsat8 estimated evapotranspiration.The results show that the high spatial resolution image is more accurate than the ground resolution image.The Penman formula is close to the field experimental data,which shows that the Penman formula has certain reference value.(4)The amount of information in order to overcome the shortcomings of the single sensor remote sensing remote sensing inversion to overcome the shortcomings,the inversion accuracy can not meet the requirements of the shortcomings,through the multi satellite multi-source remote sensing data(Landsat8,GF-1,DEM)composed of multi angle remote sensing data,remote sensing comprehensive quantitative retrieval of key surface parameters.Overall,with GF-1 as the source data to estimate the evapotranspiration values than the Landsat8 estimated evapotranspiration is closer to the reference value,it can improve the application of multi-source remote sensing evapotranspiration quantitative remote sensing inversion precision,accuracy of evapotranspiration plays a role.(5)For the whole Hutubi River Basin,the temperature,wind speed,sunshine hours,NDVI and evapotranspiration are positively proportional to the relationship between pressure and evapotranspiration.At the 0.01 level,temperature,sunshine hours and NDVI were significantly positively correlated.At the 0.05 level,there was a significant negative correlation between air pressure and evapotranspiration.(6)Sunshine hours have the most significant influence on the actual evapotranspiration.Secondly,the higher the temperature,the more the net solar radiation is converted to the part of the energy that is used for evapotranspiration,and the temperature has a second significant influence on the evapotranspiration value.The more vegetation,the greater the vegetation water demand,when the plant transpiration and soil evaporation will increase,thereby affecting the evapotranspiration.Therefore,the third environmental factors affecting evapotranspiration is the normalized difference vegetation index.To sum up,the environmental factors that affect the single day evapotranspiration in Hutubi in the top three are: sunshine hours,temperature,NDVI,followed by air pressure and wind speed.There was a significant negative correlation between air pressure and evapotranspiration.