A method and system for calculating evapotranspiration based on soil heat flux

Abstract

The invention discloses a method and system for calculating evapotranspiration based on soil heat flux, and belongs to the technical field of hydrological information forecasting. Including: obtaining the soil heat flux, surface temperature and surface air specific humidity of the target area through direct measurement by instruments or indirect calculation based on soil temperature and humidity parameters; The surface air specific humidity is input into the maximum entropy-increased evapotranspiration model, and the latent heat flux is obtained by simultaneous solution; based on the unit conversion, the latent heat flux is converted into the evapotranspiration of the target area. The invention uses the soil heat flux to measure and calculate the evapotranspiration value. By obtaining the soil heat flux instead of the net radiation item as the input of the maximum entropy increase evapotranspiration model, it avoids the dependence on the observation of radiation energy, and overcomes the difficulty of obtaining the net radiation variable, which is difficult to measure. The disadvantages of high cost and unclear error make the calculation of evapotranspiration simple and reliable.

Description

technical field [0001] The invention belongs to the technical field of hydrological information forecasting, and more specifically relates to a method and system for calculating evapotranspiration based on soil heat flux. Background technique [0002] Evapotranspiration characterizes the process of water emission from soil, vegetation, etc. to the atmosphere driven by solar radiation, and has been extensively studied in many aspects such as hydrology, agriculture, and ecology. At present, evapotranspiration simulation based on physical process is mainly based on discrete gradient method and Penman formula method. Although the discrete gradient method model has the advantages of simplicity and intuition, the simulation of evapotranspiration is not constrained by energy conservation and requires a large number of input parameters (gradient variables, wind speed, roughness, etc.), and the uncertainty of the model is relatively large. The Penman formula rule satisfies the energ...

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Problems solved by technology

However, this method relies on accurate observation of solar radiation or surface net radiation, and radiation observation instruments have large errors, especially the acquisition of net radiation variables is difficult and has large errors

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