بررسي پتانسيل داده هاي ماهواره اي به منظور برآورد تبخير و تعرق در مناطق نيمه خشك

چكيده انگليسي :

Evaluating The Potential of Remote Sensing Data to Estimate Evapotranspiration in Semi Arid Regions Nahid Moshtagh Email address n moshtagh1984@yahoo com Date Of Submission February 13 2012 Department of Natural Resources Isfahan University of Technology 84156 Iran Degree M Sc Language Farsi Dr Saeed Soltani Email ssoltani@cc iut ac ir Dr Reza Jafari Email jafari@cc iut ac irAbstract The shortage of water resources in our country has become a major challenge in recent years andevapotranspiration ET is major water losses in agriculture land use So sustainable and optimum waterresources management and plant water requirement require the accurate estimation of ET Estimation ofET from remote sensing data is more appropriate than field methods because spatial and temporalcoverage of this method is very extend and time and cost are optimized Studies have shown that thesurface energy balance algorithm Sebal is one of the most appropriate methods in of ET estimation This algorithm used the surface temperature albedo vegetation indices and their inter relationship forcalculating surface flux in different types of ground cover Therefore the aim of this study was to estimateactual ET with above algorithm in Damaneh region of Isfahan province using Landsat TM 6 1 2009 data For accurate estimation of ET the TM image was corrected for geometric and radiometric errors Surfacetemperature is a key element in Sebal algorithm Thus two well known methods were used to mapsurface temperature in the study area In the first method the sensor temperature converted to actual landsurface temperature LST by calculating the spectral radiance of band 6 and from NDVI index and thenusing of Planck s law mapping LST was achieved Results showed that bare ground had maximumtemperature and dense vegetation cover had minimum temperature 328 and 291 k respectively Thesecond method in addition to above parameters in calculation of surface temperature other parameterssuch as atmospheric water vapor content was also considered atmospheric water vapor was extractedfrom band 2 17 18 and 19 of MODIS image that was acquired at the same time with TM image usingband ratio technique In this method also the minimum and maximum temperature were obtained in cropland and bare soils pixels with 291 8 and 330 K respectively The both methods results were comparedwith observation data according to the results the first method had higher accuracy than second method To estimate ET using Sebal algorithm all input parameters of Sebal including surfacetemperature obtained from first method surface albedo vegetation indices surface emissivity incoming and outgoing short and long radiation soil heat flux sensible heat flux evaporative fractionwere calculated using available equations and then daily ET was calculated in millimeters per day According to extracted ET map of the study area ET rates range from 0 0002 to 7 203 ET mm day Finally to assess the accuracy of mapping ET Potential evapotranspiration of the region was calculatedusing FAO Penman Manthis technique and its actual evapotranspiration map was produced cropcoefficient resulting from NDVI that extracted from TM image reflective bands Results showed thatthere was a high relationship between ET resulted from Sebal and the FAO Penman Manthistechniques r2 0 97 P 01 In general it can be said that the estimation of ET in broad agricultural landsfrom remote sensing data is more applicable and can be used as a useful tool for determining plant waterrequirements and management of water resources Key words ET TM MODIS LST SEBAL FAO Penman Manthis

مشتاق، ناهيد

بررسي پتانسيل داده هاي ماهواره اي به منظور برآورد تبخير و تعرق در مناطق نيمه خشك

TM , MoDis , دماي سطحي زمين , الگوريتم سيال , فائو , پنمن , مانتيث