Method for obtaining field evapotranspiration of field scale

Abstract

The invention discloses a method for obtaining field evapotranspiration of field scale, comprising the following steps: S1. space registration is carried out to thermal infrared remote sensing data of original spatial resolution and visible light remote sensing data of the original spatial resolution; S2. sub-pixel temperature is calculated by utilizing the thermal infrared remote sensing data and the visible light remote sensing data whichare treated with space registration; S3. field parameters including albedo, specific emittance and vegetation coverage are calculated by utilizing the visible light remote sensing data of the original spatial resolution; S4. the field net radiation flux is calculated according to the albedo, the specific emittance and the sub-pixel temperature; S5. soilheat flux is calculated by utilizing the field net radiation flux and the vegetation coverage; and S6. the field sensible heat flux H is calculated, and the field evapotranspiration of the field scale can be calculated according to the field sensible heat flux, the field net radiation flux, the soil heat flux and field energy equilibrium equation. By adopting the method in the invention, the field evapotranspiration of the field scale can be obtained.

Description

technical field [0001] The invention relates to the technical field of hydrometeorology, in particular to a method for obtaining field-scale farmland evapotranspiration. Background technique [0002] Farmland evapotranspiration is the sum of crop transpiration and soil evaporation between trees. It is the main expenditure item of farmland water balance, an important basis for planning water storage and water supply, designing drought prevention and drought resistance measures, and an important factor for identifying crop water supply conditions. index. However, due to the spatial heterogeneity of farmland, traditional atmospheric or hydrological observation methods can only obtain the evapotranspiration at a single point, and cannot obtain the spatially continuous evapotranspiration distribution. Compared with the above-mentioned traditional observation methods, remote sensing has advantages such as dynamics and large-scale coverage. Using remote sensing to monitor evapotra...

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Problems solved by technology

Medium and high-resolution remote sensing data are suitable for small-scale research in the field, and can better reflect the flux differences between different crops, but their time resolution is too low (about half a month), and when there are cloudy and rainy days It takes more than one month to obtain a remote sensing image, and the cost of obtaining images is high, so it is difficult to obtain time series data, which is not enough to reflect the trend of evapotranspiration in the crop growing season

Low- and medium-resolution remote sensing data have good regional and timeliness, and can cover a large area of ​​the earth's surface in a short period of time, which is very important for drought monitoring and climate change research. Due to the calculation error caused by the mixed pixels caused by the low spatial resolution and the non-uniformity of the ground surface, it faces serious scale problems in practical applications.

[0003] The existing thermal infrared remote sensing data that can be used for evapotranspiration estimation has low spatial resolution (high temporal resolution), and there are a large number of mixed pixels, which makes it impossible to obtain field-scale (hectare-level) farmland evapotranspiration

At present, it is difficult to calculate field-scale farmland evapotranspiration using thermal infrared remote sensing data: (1) Due to the low spatial resolution of existing thermal infrared remote sensing data, it is impossible to obtain the size of field-scale (ha-level) farmland evapotranspiration; (2) lack of A method of combining low spatial resolution thermal infrared remote sensing data with visible light remote sensing data for sub-pixel temperature calculation; (3) lack of algorithms for calculating farmland evapotranspiration based on remote sensing data

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