Hydrological models require accurate precipitation and air temperature inputs in order to adequately depict water fluxes and storages across Arctic regions. Biases such as gauge undercatch, as well as uncertainties in numerical weather prediction reanalysis data that propagate through water budget models, limit the ability to accurately model the terrestrial arctic water cycle. A hydrological m...

A brief history of development of the 1985 Hargreaves equation and its comparison to evapotranspiration ~ET! predicted by the Food and Agricultural Organization of the United Nations ~FAO! Penman-Monteith method are described to provide background and information helpful in selecting an appropriate reference ET equation under various data situations. Early efforts in irrigation water requiremen...

Estimated daily reference crop evapotranspiration (ETo) is normally used to determine the water requirement of crops using the crop factor method. Many ETo estimation methods have been developed for different types of climatic data, and the accuracy of these methods varies with climatic conditions. In this study, pair−wise comparisons were made between daily ETo estimated from eight different E...

The recommended Penman±Monteith reference crop evapotranspiration (ET0) with derived crop coef®cients (Kc) from the phenomenological stages of Acala cotton is used to estimate the crop water requirements (CWRs) of Acala cotton in the Gezira area of Sudan. The published basal crop factors of Acala cotton were used with Penman±Monteith equation as well to estimate ET. The results were compared wi...

Evapotranspiration (ET) is one of the major components of hydrologic cycle. Accurate estimation of this parameter is essential for studies such as water balance, irrigation system design and management, and water resources management. Generally we used climate data for calculating evapotranspiration from indirect methods. This study investigates the utility of artificial neural networks (ANNs) ...

The Penman-Monteith equation is useful for computing evaporation rates of uniform surfaces, such as dense vegetation or bare soil. This equation becomes less useful for evaluation of evaporation rates at the regional scale, where surfaces are generally characterized by a patchy combination of vegetation and soil. This is particularly true in the arid and semi-arid regions of the world. The appr...

Daily evapotranspiration (ET) rates are needed for irrigation scheduling. Owing to the difficulty of obtaining accurate field measurements, ET rates are commonly estimated from weather parameters. A few empirical or semi–empirical methods have been developed for assessing daily reference crop ET, which is converted to actual crop ET using crop coefficients. The FAO Penman–Monteith method, which...

The proposed method for calculation of potential evapotranspiration is Penman-Monteith FAO method, but there are other methods that require less meteorological data but estimates close to the FAO Penman-Monteith method in different climatic conditions.  Performance evaluation of these methods on the same basis is prerequisite for selecting an alternative approach in accordance with available da...

The impact ofmodel structure andparameterization on the estimation of evaporation is investigated across a range of Penman–Monteith type models. To examine the role of model structure on flux retrievals, three different retrieval schemes are compared. The schemes include a traditional single-source Penman– Monteith model (Monteith, 1965), a two-layer model based on Shuttleworth and Wallace (198...