Study On Drought Monitoring In Sichuan Province Based On Improved Linear Dual Source Remote Sensing Evapotranspiration Model

Evapotranspiration(ET)which consists of plant transpiration and soil evaporation is important components of water vapor transmission and transfer.It is also an important descriptive parameter of surface drought information.In recent decades,with the rapid development of economic situation,global warming and population growing,drought happened in many areas.Evapotranspiration has greatly changed.In recent years,there has been a large area of drought in Sichuan Province,which has a serious impact on the national economy and agricultural development.Therefore,the correct inversion of surface evapotranspiration is of great significance in analyzing and utilizing water resources and improving the monitoring level of agricultural drought and hydrological drought.Especially in terms of improving agricultural production management and global climate change.Firstly,the meteorological station data and remote sensing data are collected,and the data are processed.Secondly,a modified mixed linear dual source remote sensing evapotranspiration model is got.The surface evapotranspiration of Sichuan Province is obtained by using this model.The accuracy of the model is verified and evaluated by the actual evapotranspiration product.Thirdly,We study the occurrence and evolution of drought in Sichuan Province based on the evapotranspiration drought index(EDI).Then,the characteristics of evapotranspiration and drought variation in Sichuan Province in the past 15 years are analyzed.Finally,the surface evapotranspiration system of Sichuan Province is constructed to provide service to the demand users and management departments.The main research contents and achievements of this paper include the following aspects:1)By analyzing the existing evapotranspiration model,we modify the hybrid linear dual source remote sensing evapotranspiration model and use it to fit actual evapotranspiration in recent 15 years of Sichuan Province.Sichuan Province's actual variation trend of evapotranspiration is decreasing from 2001 to 2015,and themaximum value of actual evapotranspiration is in the summer,followed by autumn,spring and winter.The actual evapotranspiration in the east Sichuan Basin and Panzhihua in south Sichuan is higher than that in western Sichuan and north Sichuan.2)The paper use the Hargreaves formula to estimate the potential evapotranspiration(PET),and use the average temperature,the highest temperature and the lowest temperature data of Sichuan Province in recent 15 years.We analyze the time and space distribution characteristics of potential evapotranspiration,found that the value of potential evapotranspiration fluctuates is not obviously in every season.The spring,summer,autumn and winter is stable during 2001 to 2015.By season analysis,potential evapotranspiration is maximum in summer,followed by autumn,spring and winter minimum.In terms of spatial distribution,spring,autumn and winter showed a decreasing trend from south to north of Sichuan,while summer showed a law of differentiation from east to west of Sichuan.3)We obtain actual ET and PET obtained by inversion and calculation,using them to calculate EDI.The results showed that the EDI value showed a downward trend in the last 15 years,but the EDI value in this year was larger than 0.5 in each month.Comparing the EDI value in the year,the maximum value usually appeared in spring and winter,which indicated that the continuous drought of winter and spring was easy to occur in the study area.In recent years,the drought cycle is shorten and drought affected areas continue to increase.Through the GIS platform,we understand the variation of drought in each city state of Sichuan Province.That could provide some ideas for drought disaster prevention.There is an obvious increasing trend of drought degree and drought range from east or southeast to west and northwest.4)Based on Internet+ and WebGIS technology to achieve the Sichuan province evapotranspiration information network publishing.In the management efficiency,interoperability and timelinessthe,the system has a great breakthrough compared with the traditional management.It is mainly reflected in the visualization of the surface evapotranspiration information in Sichuan province.To some extent,the visualization of surface evapotranspiration information in Sichuan Province has been realized.In addition,This system is almost no requirements for the client,user-friendly operation.The system uses ESRI ArcGIS Server as development platform,combined with JavaScript and HTML language to realize the visual display of Sichuan province information system.In addition to the conventional map operation function,the system also has a print a map and data download function.Users can quickly and easily understand the changes of evapotranspiration in Sichuan Province,to provideservices for the majority of users and management departments.