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A meteorological‐based crop coefficient model for estimation of daily evapotranspiration
Author(s) -
Varmaghani Arman,
Eichinger William E.,
Prueger John H.
Publication year - 2021
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.14025
Subject(s) - evapotranspiration , crop coefficient , mean squared error , environmental science , eddy covariance , relative humidity , precipitation , linear regression , vegetation (pathology) , coefficient of determination , atmospheric sciences , hydrology (agriculture) , meteorology , mathematics , statistics , geography , ecosystem , ecology , geology , biology , medicine , geotechnical engineering , pathology
Estimation of daily evapotranspiration (ET) over cloudy regions highly desires models which rely on meteorological data only. Notwithstanding, the conventional crop coefficient ( K c ) method requires detailed knowledge of geo/biophysical properties of the coupled land‐vegetation system, precipitation, and soil moisture. Six Eddy Covariance (EC) towers in Iowa, California and New Hampshire of the USA (covering corn, soybeans, prairie, and deciduous forest) were selected. Investigation on 6 years (2007–2012) 15‐min micrometeorological records of these sites revealed that there is an indubitable strong interaction between relative humidity (RH), reference ET (ET o ), and actual ET at different timescales. This allowed to bypass the need for the non‐meteorological inputs and express K c as a second‐order polynomial function of RH and ET o , the ambient regression evapotranspiration model (AREM). The coefficients of the empirical function are crop‐specific and may require calibration over different soil types. The mean absolute percentage error (MAPE) of the regression against daily EC observations was 17% during the growing season, and 32% throughout the year with root mean square error (RMSE) of 0.74 mm day −1 and coefficient of determination of 0.71. The model was fully operational (MAPE of 34% and RMSE of 0.82 mm day −1 ) over the four Iowan sites based on inputs from local weather stations and NLDAS‐2 forcing data of NASA. AREM was capable of capturing the dynamics of ET at 15‐min and daily timescales irrespective of varying complexities associated with biophysical, geophysical and climatological states.