Calculation of Real Evapotranspiration by the Application of Metric Method on Landsat-8 Data

Abstract

In geological remote sensing approaches for estimating evapotranspiration, METRIC method is among the most modern and precise approaches that many positive experiments have been reported regarding its applicability. In this study, the value of actual evapotranspiration (ET) occurred in Marvdasht farmlands, Fars province, Iran, was calculated instantaneously (hourly) and daily (24 hours), at 24 April 2017 using METRIC method and Lansat-8 data. In order to accuracy assessment of the results, estimated values were compared to the values calculated with Penman Monteith method in places that covers by alfafa crop. Our observations showed that ET values obtained via METRIC model on average, have 0.51mm difference in estimations, comparing to the Penman Manteith method.

Seasonal variation of surface energy balance over Mubi northeastern Nigeria during 2000-2020

“…Solar radiation (short and longwave radiation) are input energies to the surface energy balance. These energies, directly or indirectly, are the results of nuclear interactions occurring on the solar surface and is equal to the total available energy for the occurrence of the Earth's surface and atmospheric processes [4,5]. Basically, solar radiation has two acting parts: one is incoming (downward Rs↓) radiation on Earth's surface that depends on the atmospheric transitivity, solar constant, solar altitude, and incidence angle, and another part are outgoing (upward Rs↑) that is reflected back to space due to the combined effect of surface, clouds, aerosol, gases, etc [1].…”

“…Where, 𝜌𝑎𝑖𝑟 is the air density in kg/m 3 , Cp is the specific heat of air at constant pressure, which is equal to 1000 (J/kgK), dT is the indicator of temperature difference in Kelvin between two elevations near surfaces of z1 and z2, and 𝑟𝑎ℎ is the aerodynamic resistance (m/s) available for the heat transfer between z1 and z2, which are considered 0.1 and 2 meters [4,26,27]. Aerodynamic resistance is affected by the surface roughness and is determined by vegetation height and structure, wind speed, and atmospheric stability [6].…”