Measuring and calculating method and system for deducing evapotranspiration based on soil heat flux

Abstract

The invention discloses a measuring and calculating method and system for deducing evapotranspiration based on soil heat flux and belongs to the technical field of hydrological information forecasting. The method comprises the steps that: the soil heat flux, the surface temperature and the surface air specific humidity of the ground surface of a target area are obtained through direct instrument measurement or indirect calculation based on soil temperature and humidity parameters; the soil heat flux, the ground surface temperature and the ground surface air specific humidity of the ground surface of the target area areinputted into a maximum entropy increase evapotranspiration model, and simultaneous solving is performed to obtain latent heat flux; and the latent heat flux is converted into evapotranspiration of the target area based on unit conversion. According to the method, the evapotranspiration value is calculated by adopting the soil heat flux, and the obtained soil heat flux replaces a net radiation item to serve as the input of the maximum entropy increase evapotranspiration model, so that the dependence on radiation energy observation is avoided, the defects of high net radiation variable obtaining difficulty, high measurement cost, unclear error and the like are overcome, and the evapotranspiration calculation is simple, convenient 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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