A method and system for partitioning components of evapotranspiration based on dual-source Bowen ratio

Abstract

The application provides a method for dividing surface evapotranspiration components based on dual-source Penman-Monteith, which comprises the following steps: step 1, collecting meteorological data; step 2, constructing function expressions of ecosystem Penman-Monteith, vegetation canopy Penman-Monteith and soil layer Penman-Monteith based on the collected meteorological data; step 3, substituting the Penman-Monteith expressions in step 2 into energy balance equation and water vapor balance equation to deduce plant transpiration and soil evaporation division factors; and step 4, calculating plant transpiration and soil evaporation according to the division factors. The application can accurately divide the ecosystem evapotranspiration into plant transpiration and soil evaporation by only using conventional meteorological data driving. The application can provide a theoretical basis for ecosystem evapotranspiration component simulation, technical support for improving the calculation efficiency of existing global models in the process of ecosystem evapotranspiration component simulation, and a scientific basis for ecological hydrology research.

Description

Technical Field

[0001] This invention belongs to the technical field of eco-hydrology, and specifically relates to a method and system for segmenting surface evapotranspiration components based on dual-source wave ratio. Background Technology

[0002] Ecosystem evapotranspiration (ET) is a core component of the terrestrial water cycle and energy exchange, involving the integrated processes of vegetation photosynthetic transpiration and surface evaporation, and characterizing the productivity and water consumption composition of an ecosystem. The classification of evapotranspiration components—namely, plant transpiration and surface evaporation—is crucial for understanding ecohydrological processes, optimizing water resource management, and improving the accuracy of land surface models. The development of global models and datasets has driven the need for simplified models for calculating evapotranspiration and its components. While some simplified evapotranspiration estimation models exist, traditional evapotranspiration segmentation models often require numerous and difficult-to-obtain input parameters, posing significant difficulties and challenges to the research and data application of terrestrial ecosystem evapotranspiration components. Therefore, a simple and accurate model for segmenting evapotranspiration is urgently needed. Summary of the Invention

[0003] This invention proposes a method for segmenting evapotranspiration in terrestrial ecosystems into plant transpiration and surface evaporation. Based on the theoretical framework of energy and water vapor balance of the entire ecosystem, vegetation canopy, and soil layer, and using conventional meteorological variables, this invention proposes calculation formulas for the ecosystem Bowen ratio, vegetation canopy Bowen ratio, and soil Bowen ratio. Furthermore, based on the overall ecosystem energy balance and water vapor balance frameworks, it derives and establishes quantitative relationships between the aforementioned three Bowen ratios and the segmentation factors for plant transpiration and soil evaporation in the ecosystem. Given the evapotranspiration of the ecosystem, using these segmentation factors to segment evapotranspiration yields the plant transpiration and soil evaporation of the ecosystem.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A method for segmenting surface evapotranspiration components based on dual-source BRV ratio includes the following steps:

[0006] Step 1. Collect meteorological data;

[0007] Step 2. Based on the collected meteorological data, construct functional expressions for the ecosystem Bovn ratio, vegetation canopy Bovn ratio, and soil layer Bovn ratio, respectively;

[0008] Step 3. Substitute the Bowen ratio expression from Step 2 into the energy balance equation and the water vapor balance equation to derive the plant transpiration and soil evaporation dividing factors.

[0009] Step 4. Calculate plant transpiration and soil evaporation based on the segmentation factors.

[0010] Furthermore, the meteorological data in step 1 includes air temperature Ta, relative humidity RH, wind speed u, solar radiation Rn, and saturated vapor pressure difference VPD.

[0011] Furthermore, the functional expressions for the ecosystem Bovn ratio, vegetation canopy Bovn ratio, and soil Bovn ratio in step 2 are as follows:

[0012]

[0013]

[0014]

[0015] in, , , These are the total latent heat flux of the ecosystem, the latent heat flux of vegetation canopy transpiration, and the latent heat flux of soil evaporation, respectively. , , These are the ecosystem Bwen ratio, the vegetation canopy Bwen ratio, and the soil Bwen ratio, respectively. Hs , Hsc and Hss These are the sensible heat fluxes of the ecosystem, the vegetation canopy, and the soil layer, respectively. , , , , These are the empirical coefficients of the ecosystem Bowen ratio. , , , , These are the empirical coefficients of the vegetation canopy Bowen ratio. , , , , These are the empirical coefficients of the soil layer Bowen ratio. 、 、 These are the functional expressions for the ecosystem Bwen ratio, the vegetation canopy Bwen ratio, and the soil Bwen ratio, respectively.

[0016] Furthermore, in step 2, through actual measurement... , , Calibration to determine coefficients - , - , - .

[0017] Furthermore, the plant transpiration and soil evaporation dividing factors in step 3 are:

[0018]

[0019] in, It is a dividing factor between plant transpiration and soil evaporation.

[0020] Furthermore, the ecosystem is Boweni function expression The input variables are air temperature Ta and air relative humidity RH.

[0021] Furthermore, the ecosystem is Boweni function expression The input variables are wind speed u and saturated vapor pressure difference VPD.

[0022] Furthermore, the ecosystem is Boweni function expression The input variables are air temperature Ta and solar radiation Rn.

[0023] Furthermore, the plant's transpiration rate is:

[0024] Soil evaporation is: .

[0025] On the other hand, the present invention provides a system for segmenting surface evapotranspiration components based on dual-source Bowman ratio, comprising:

[0026] Data collection module: It is used to collect meteorological data;

[0027] Bowen ratio function construction module: It is used to construct function expressions for ecosystem Bowen ratio, vegetation canopy Bowen ratio and soil layer Bowen ratio based on collected meteorological data;

[0028] Segmentation factor derivation module: It is used to substitute the Bowen ratio expression into the energy balance equation and water vapor balance equation to derive the segmentation factor of plant transpiration and soil evaporation.

[0029] Plant transpiration and soil evaporation acquisition module: It is used to calculate plant transpiration and soil evaporation based on the segmentation factor.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention, based on energy balance and water vapor balance theories and combined with ecohydrological research, fully considers the urgent need of current scientific research and production units for simplified evapotranspiration segmentation methods for ecosystems, and creatively proposes a simplified evapotranspiration segmentation method for ecosystems. This model only requires conventional meteorological data (such as air temperature, saturated vapor pressure difference, wind speed, net radiation, and air pressure) to accurately divide ecosystem evapotranspiration into plant transpiration and soil evaporation. This invention provides a theoretical basis for simulating ecosystem evapotranspiration components, provides technical support for improving the computational efficiency of existing global models in simulating ecosystem evapotranspiration components, and provides a scientific basis for ecohydrological research. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a comparison chart of plant transpiration in an ecosystem calculated using the method of this invention and the measured values.

[0034] Figure 2 This is a comparison chart of soil evaporation in an ecosystem calculated using the method of this invention and the measured values. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] Example 1

[0037] The invention will now be further described with reference to the accompanying drawings.

[0038] A method based on dual-source Bowen ratio to segment surface evapotranspiration components was used, with conventional meteorological input variables as the driving force, to estimate plant transpiration and soil evaporation in the ecosystem.

[0039] It includes the following steps:

[0040] 1) Collect meteorological data, including air temperature Ta, relative humidity RH, wind speed u, solar radiation Rn, and saturated vapor pressure difference VPD;

[0041] Table 1 shows some of the data collected in Example 1 of this study.

[0042] Table 1

[0043]

[0044] 2) Construct the system β and vegetation canopy β respectively. Compared with soil layer Bowen The function expression;

[0045] By definition, the ecosystem Bovn ratio is: (1)

[0046] The vegetation canopy Bovn ratio is: (2)

[0047] The soil layer wave ratio is (3)

[0048] Accordingly, the formulas for solving the functions corresponding to each Bowen ratio are constructed as follows:

[0049] (4)

[0050] (5)

[0051] (6)

[0052] Wherein, Hs, Hsc, and Hss are the sensible heat fluxes of the ecosystem, vegetation canopy, and soil layer, respectively; relevant constant parameters can be obtained through measured λET, λT, and λE calibration.

[0053] Derivation of the relationship between the plant transpiration and soil evaporation segmentation factor R and the ecosystem Bowen ratio β and the vegetation canopy Bowen ratio. Compared with soil layer Bowen Link model;

[0054] By definition, the dividing factor between plant transpiration and soil evaporation.

[0055] (7)

[0056] According to the principle of energy balance

[0057] (8)

[0058] According to the principle of water vapor balance

[0059] (9)

[0060] Derivation and construction of the relationship equation

[0061] (10)

[0062] (11)

[0063] Therefore, the plant transpiration and soil evaporation partitioning factor R is obtained, and given the ecosystem λET is determined, it can be calculated. and To achieve the objective of this invention.

[0064] (12)

[0065] (13)

[0066] The data collected in steps 1) and 2) are processed by substituting the meteorological data observations and the observations of total ecosystem evapotranspiration λET, plant transpiration λT, and soil evaporation λE into and combining them with formulas (4), (5), (6) and (11), (12), (13) to calibrate the constant parameters appearing in formulas (4), (5), and (6), which are as follows:

[0067] a1=0.006,a2=-0.26.a3=0.0008,a4=-0.06.a5=0.127,

[0068] b1 = 5 × 10 -7 , b2=0.0012,b3=2.04,b4=2.51,b5=3.27,

[0069] c1=0.0005,c2=-0.0689,c3=-0.00024,c4=0.054,c5=1.72;

[0070] The expressions for each Bowen ratio are as follows:

[0071]

[0072] Simultaneously, plant transpiration λT and soil evaporation λE were calculated and obtained.

[0073] The plant transpiration λT and soil evaporation λE calculated by this method are compared with the measured values ​​to analyze and evaluate the calculation results of this method. Figure 1 and Figure 2 As shown.

[0074] Figure 1 A comparison was made between the vegetation transpiration latent heat flux calculated using this invention and the measured transpiration latent heat flux. The results showed a high degree of agreement, with a slope of 0.97, a coefficient of determination of 0.93, and a root mean square error of only 16.13 W / m². -2This indicates that the method can accurately calculate the latent heat flux of vegetation transpiration.

[0075] Figure 2 A comparison was made between the soil evaporative latent heat flux calculated using this invention and the measured soil evaporative latent heat flux. The results showed a high degree of agreement, with a slope of 0.91, a coefficient of determination of 0.67, and a root mean square error of only 8.14 W / m². -2 This indicates that the method can accurately calculate the latent heat flux of soil evaporation.

[0076] Example 2

[0077] This embodiment provides a system for segmenting surface evapotranspiration components based on dual-source Bowman ratio, including:

[0078] Data collection module: It is used to collect meteorological data;

[0079] Bowen ratio function construction module: It is used to construct function expressions for ecosystem Bowen ratio, vegetation canopy Bowen ratio and soil layer Bowen ratio based on collected meteorological data;

[0080] Segmentation factor derivation module: It is used to substitute the Bowen ratio expression into the energy balance equation and water vapor balance equation to derive the segmentation factor of plant transpiration and soil evaporation.

[0081] Plant transpiration and soil evaporation acquisition module: It is used to calculate plant transpiration and soil evaporation based on the segmentation factor.

[0082] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0083] It should be understood that the above description of the preferred embodiments is quite detailed, but this should not be construed as limiting the scope of protection of this invention. It is neither necessary nor possible to exhaustively describe all possible implementations. Those skilled in the art, guided by this invention, can make substitutions or modifications without departing from the scope of the claims, all of which fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for segmenting surface evapotranspiration components based on dual-source BRV ratio, characterized in that, Includes the following steps: Step 1. Collect meteorological data, including air temperature Ta, relative humidity RH, wind speed u, solar radiation Rn, and saturated vapor pressure difference VPD. Step 2. Based on the collected meteorological data, construct functional expressions for the ecosystem BRVEN ratio, vegetation canopy BRVEN ratio, and soil BRVEN ratio, respectively; the functional expressions for the ecosystem BRVEN ratio, vegetation canopy BRVEN ratio, and soil BRVEN ratio are as follows: in, , , These are the total latent heat flux of the ecosystem, the latent heat flux of vegetation canopy transpiration, and the latent heat flux of soil evaporation, respectively. , , These are the ecosystem Bwen ratio, the vegetation canopy Bwen ratio, and the soil Bwen ratio, respectively. Hs , Hsc and Hss These are the sensible heat fluxes of the ecosystem, the vegetation canopy, and the soil layer, respectively. , , , , These are the empirical coefficients of the ecosystem Bowen ratio. , , , , These are the empirical coefficients of the vegetation canopy Bowen ratio. , , , , These are the empirical coefficients of the soil layer Bowen ratio. 、 、 These are the functional expressions for the ecosystem Bwen ratio, the vegetation canopy Bwen ratio, and the soil Bwen ratio, respectively. Step 3. Substitute the Bowen ratio expression from Step 2 into the energy balance equation and the water vapor balance equation to derive the plant transpiration and soil evaporation dividing factors. Step 4. Calculate plant transpiration and soil evaporation based on the segmentation factors.

2. The method for segmenting surface evapotranspiration components based on dual-source BORINCO ratio according to claim 1, characterized in that, Step 2, through actual measurement , , Calibration to determine coefficients - , - , - .

3. The method for segmenting surface evapotranspiration components based on dual-source BOWN ratio according to claim 2, characterized in that, The plant transpiration and soil evaporation dividing factor in step 3 is: in, It is a dividing factor between plant transpiration and soil evaporation.

4. The method for segmenting surface evapotranspiration components based on dual-source BORINCO ratio according to claim 1, characterized in that, The ecosystem Bövenby function expression The input variables are air temperature Ta and air relative humidity RH.

5. The method for segmenting surface evapotranspiration components based on dual-source BORINCO ratio according to claim 1, characterized in that, The ecosystem Bövenby function expression The input variables are wind speed u and saturated vapor pressure difference VPD.

6. The method for segmenting surface evapotranspiration components based on dual-source BOWN ratio according to claim 1, characterized in that, The ecosystem Bövenby function expression The input variables are air temperature Ta and solar radiation Rn.

7. The method for segmenting surface evapotranspiration components based on dual-source BOWN ratio according to claim 3, characterized in that, The plant's transpiration rate is: Soil evaporation is: .

8. A system for segmenting surface evapotranspiration components based on dual-source BOWN ratio, characterized in that, include: Data collection module: It is used to collect meteorological data; Bowen ratio function construction module: It is used to construct function expressions for ecosystem Bowen ratio, vegetation canopy Bowen ratio and soil layer Bowen ratio based on collected meteorological data; Segmentation factor derivation module: It is used to substitute the Bowen ratio expression into the energy balance equation and water vapor balance equation to derive the segmentation factors of plant transpiration and soil evaporation. Plant transpiration and soil evaporation acquisition module: It is used to calculate plant transpiration and soil evaporation based on the segmentation factor; The system for segmenting surface evapotranspiration based on dual-source BRV ratio is used to perform the steps in the method for segmenting surface evapotranspiration based on dual-source BRV ratio as described in any one of claims 1-7.

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