Estimation of Regional Reference Evapotranspiration from Land Surface Temperature and Co-Kriging Method at Tehran Province, Iran

Evapotranspiration is the main factor of water cycle in nature and having the information of the amount of that is necessary to soil and water study. Estimation of this amount by using available equations indicates only the amount of evapotranspiration at the stations. Whereas in order to expansion water resources for irrigation and drainage, regional scale studied are required which geostatistical tools are used for achieving that. In this study reference evapotranspiration at 31 meteorology stations in Tehran province with Hargreaves-Samani method in January (wet) and July (dry) were estimated. To supply reference evapotranspiration maps in province that capable to be used at regional study, Co-Kriging was used. Land surface temperature was covariate in this method and has been determined by using image of NOAA14–16 at (1999–2003) and spilit window algorithms. Estimated temperature of images was compared with the temperature of 5cm depth of soil and Mean Absolute Error (MAE) was criterion for algorithms evaluation. Then land surface temperatures were determined from the network with 9200 x 7500m distance at area and were used for covariate of co-Kriging method and the maps of monthly reference evapotranspiration were drawn.