A coupling modeling method of a row-sowing aquatic vegetation canopy radiation model and an atmospheric radiation transfer model

Abstract

The application relates to a coupling modeling method of a row-sowing aquatic vegetation canopy radiation model and an atmospheric radiation transmission model, which comprises the following steps: the row-sowing aquatic vegetation canopy is regarded as a regular rectangular box for reflectivity modeling; a brightness-spectrum-humidity model considering soil properties and humidity is adopted for the bottom soil spectrum; in view of the problems of high calculation cost and direction loss in the coupling process of the canopy radiation model and the atmospheric radiation model, a simplified atmospheric radiation transmission model is adopted, and each parameter of the radiation transmission matrix is calculated by ignoring the gas transmission characteristics; the coupling is carried out by using the superposition method, and the canopy reflectivity in different observation directions at the top of the atmosphere is calculated. The application describes the energy transmission process of the interaction between the surface radiation and the atmospheric layer, the coupling method of the model can provide a simple, fast and integrated reversible radiation transmission model, the model can simulate the anisotropy of the surface radiation, and the analysis capability of a remote sensing satellite for the surface radiation can be improved.

Description

Technical Field

[0001] This invention relates to a coupled modeling method for a row-seeded aquatic vegetation canopy radiation model and an atmospheric radiation transfer model, belonging to the field of optical remote sensing, and is of great significance in wetland ecological research and quantitative monitoring of crops. Background Technology

[0002] Rice has a typical row-sown planting structure. Currently, relatively complete rice radiation modeling methods have two areas for improvement: first, they do not consider the differences in spectral reflectance of different underlying soil surfaces; second, they have not yet integrated atmospheric transfer models to extend the model to satellite optical remote sensing. Soil, as the underlying layer of the radiation transfer model, has a significant impact on the overall spectral reflectance. Furthermore, traditional atmospheric correction methods have strict parameter requirements and treat the ground as a Lambertian surface, failing to consider the anisotropy of rice canopy reflectance. Therefore, studying the spectral variations of the underlying soil with latitude and humidity is beneficial for improving the accuracy of overall reflectance simulation. At the same time, appropriately simplifying the atmospheric correction model helps to maintain the anisotropy of rice canopy reflectance and enhance the model's practical value.

[0003] This invention couples a brightness-spectrum-humidity model, simplifies the atmospheric radiative transfer model, and extends the radiative transfer model of row-sown aquatic vegetation to the soil and atmospheric layers. This model can efficiently and accurately simulate the canopy and top-layer atmospheric reflectance of rice under different underlying surfaces, and can simulate realistic rice spectral reflectance data, which is of great significance and application value for remote sensing monitoring and inversion of rice. Summary of the Invention

[0004] A coupled modeling method for a row-seeded aquatic vegetation canopy radiation model and an atmospheric radiative transfer model includes the following steps:

[0005] (1) The soil-rice-atmosphere structure is decomposed into a three-layer model, and the soil moisture spectral reflectance, the rice canopy reflectance and the atmospheric top reflectance are calculated respectively.

[0006] (2) The spectral reflectance of the subsurface soil under different humidity conditions in different regions of different dimensions was calculated using the brightness-spectrum-humidity model;

[0007] (3) Input the spectrum calculated by the soil model into the bottom layer of the rice radiation model to calculate the canopy reflectance of the rice.

[0008] (4) The rice canopy reflectance was input into a simplified atmospheric correction model using the four-flow radiative transfer model, and the atmospheric top reflectance of rice was calculated based on relevant parameters.

[0009] (5) In step (1), for ease of calculation, the entire scene is divided into three components, namely: the surface soil layer, the middle row-sown aquatic vegetation layer and the top atmosphere layer; the surface soil layer is located at the starting point of the four-flow radiative transfer equation, and its spectral properties largely determine the overall reflectance of the row-sown aquatic vegetation scene, and its reflectance characteristics mainly depend on the local soil properties and soil moisture; the middle row-sown aquatic vegetation layer obtains the overall reflectance by assuming the row-sown structure of the row-sown aquatic vegetation and calculating different components in the field of view, while its bottom reflectance input depends on the soil reflectance, and the canopy reflectance is obtained by inputting the relevant parameters of the row-sown aquatic vegetation; the canopy reflectance of the row-sown aquatic vegetation is input into the simplified atmospheric correction model, and various atmospheric parameters are input to calculate the radiative transfer matrix to ensure the non-Lambertianity of the surface reflectance.

[0010] (6) The specific calculation process of step (2) is as follows:

[0011] Step 1: Using three fundamental spectra extracted from the global spectral library, namely global spectral vectors (GSVs), simulate the reflectance of dry soil surfaces:

[0012]

[0013] Where a1, a2, and a3 are fitting coefficients, and G1, G2, and G3 are global spectral vectors; although GSV can reasonably fit any given dry soil reflectance spectrum, these coefficients are directly related to the reflectance spectrum but not directly related to the soil composition.

[0014] Step 2: Assuming that soil brightness only affects the "intensity" of soil reflectance, while the "shape" of soil reflectance depends on other factors such as roughness, organic matter content, and mineralogical composition, we separate the soil brightness effect from the spectral shape effect through intensity-shape transformation:

[0015]

[0016] In the formula, B represents soil luminance, which determines the intensity of soil reflectivity. and Related to other soil properties; this intensity shape transformation is similar to transforming Cartesian coordinates to spherical coordinates; therefore, angles and Similar to latitude and longitude on Earth;

[0017] Step 3: Use a water film coating method to maintain the consistency of the radiative transfer model: the coupling achieved through radiative transfer is similar to the coupling of soil, vegetation, and atmosphere; wet soil is considered as a system consisting of a dry soil layer covered by a thin layer of water; in this method, the reflectivity of wet soil formed by the combination of dry soil and water film includes the contributions of the following factors: 1) the first interaction of the water film on the surface of soil particles, i.e., Fresnel reflection. 2) Reflections from the background, including multiple reflections between soil and water layers:

[0018]

[0019] in Indicates the reflectance of moist soil. This represents the probability of the water film distribution. These represent the Fresnel reflectance from one medium to another, with "1" and "2" referring to air and water, respectively. Indicates the water absorption coefficient. Indicates the optical thickness of the water film. This indicates the background reflectance.

[0020] Assuming the water film on the ground is non-uniform, and since surface reflection is not affected by film thickness, only the transmission loss caused by water absorption is corrected. Therefore, the dry soil area percentage is P (k = 0), and the soil reflectance is obtained by combining these assumptions. for:

[0021]

[0022] Where μ is equal to the expected value of the water film thickness, The data represents the reflectance of dry soil and is given as a function of soil moisture:

[0023]

[0024] In the formula, The soil moisture volume percentage is used as input to the brightness-spectrum-humidity model. Soil moisture capacity is an indicator of soil's ability to retain water, expressed as a percentage.

[0025] (7) The calculation process of step (3) is as follows:

[0026] Step 1: The radiative transfer equation for a single dielectric layer can be expressed as:

[0027]

[0028] in, This represents the radiation from the sun that reaches the bottom of the medium layer. This represents the scattered light incident on the bottom of the medium. This represents the upward scattered radiation from the top of the dielectric layer. This indicates direct radiation observed from the top of the medium layer. This represents the solar incident radiation at the top of the dielectric layer. This represents the incident radiation scattered from the top of the dielectric layer. This represents the upward scattered radiation from the bottom of the dielectric layer. The direct radiation in the observation direction is represented by the coefficients in the layer scattering matrix, which are divided into the reflection factor ρ and the transmission factor τ. The double subscripts indicate the types of incident and outgoing radiation respectively: s represents direct solar radiation Es, d represents diffuse radiation E– or E+, and o represents radiation Eo in the observation direction.

[0029] Step 2: Divide the matrix into blocks according to the direction of light transmission and the position of the dielectric layer, and we can obtain:

[0030]

[0031] In the annotation, d represents downward radiation, u represents upward radiation, R represents the reflectance factor submatrix, T represents the transmission factor submatrix, t represents the top of the layer, and b represents the bottom of the layer. The third step: using the radiative transfer relationship between the media, the reflectance of the vegetation canopy can be calculated.

[0032] (8) The calculation process of step (4) is as follows:

[0033] Step 1: Calculate the simplified 6S model; this model requires 7 input parameters, namely the geometric parameters of the sun and the observatory, specifically including the solar zenith angle. Observing the zenith angle and relative azimuth Aerosol optical thickness (AOT) at 550 nm 550 Ozone content (UO3), water vapor content (UH2O), and atmospheric pressure (Pa); by simplifying the process variables in the following formula: , S and This reduces the complexity and computation time of atmospheric radiative transfer models.

[0034]

[0035] It is the TOA reflectance in the direction of observation. It is bidirectional transmission of gas. is atmospheric reflectance, and S is atmospheric spherical albedo. and It is the total atmospheric albedo in the solar and observation directions, excluding the effects of gas absorption;

[0036] Step 2: Calculate the surface reflectivity of the third layer, i.e., the atmosphere. :

[0037]

[0038] Expanding, we get:

[0039]

[0040] In the formula, TOA represents the top of the atmosphere, s and o have the same meaning as above, indicating the direction of radiation, and 1, 2, and 3 represent the soil layer, aquatic vegetation layer, and atmosphere, respectively. Ignoring gas transport for now, we get:

[0041]

[0042] in It is the total optical thickness of the atmosphere, which is the sum of the optical thickness of aerosols and molecules; It represents the transmittance in the direction of sunlight. The transmittance represents the direction of observation, with the number in parentheses indicating the medium layer. Therefore, the scattering transmittance, neglecting the effects of gas transmission, is as follows:

[0043]

[0044] in These represent the transmittance from solar incident light to scattered light and from sky scattered light to scattered light, respectively. and The total transmittance represents the total transmittance of the sun and the direction of observation, respectively. Subtracting the direct or scattered components from each component yields the other component.

[0045] Therefore, the reflectivity of TOA in the observation direction can be calculated. for:

[0046]

[0047] The advantages of this invention compared to existing technologies are as follows: In the field of vegetation remote sensing, current models describing the reflectance spectral characteristics of row-sown aquatic vegetation against a water background do not consider the influence of soil and atmosphere. This invention extends the model for row-sown aquatic vegetation by incorporating the influence of soil reflectance spectral variations and couples a simplified atmospheric correction model while maintaining the anisotropy of rice canopy radiation. This invention is significantly innovative and provides a more efficient and accurate new approach for the precise monitoring of row-sown aquatic vegetation and its application in large-scale satellite remote sensing. Attached Figure Description

[0048] Figure 1 This is a diagram showing the relationship between solar radiation and various layers of the soil-rice-atmosphere system. Figure 2The technical process of this invention is as follows: Figure 3 The simulated reflectance spectrum varies with the leaf area index. Detailed Implementation

[0049] To better illustrate the coupled modeling method of the row-seeded aquatic vegetation canopy radiation model and the atmospheric radiative transfer model involved in this invention, the model of this invention was tested and analyzed, and good results were achieved. The specific implementation method is as follows:

[0050] (1) The soil-rice-atmosphere structure is decomposed into a three-layer model, and the soil moisture spectral reflectance, the rice canopy reflectance and the atmospheric top reflectance are calculated respectively.

[0051] (2) The spectral reflectance of the subsurface soil under different humidity conditions in different regions of different dimensions was calculated using the brightness-spectrum-humidity model;

[0052] (3) Input the spectrum calculated by the soil model into the bottom layer of the rice radiation model to calculate the canopy reflectance of the rice.

[0053] (4) The rice canopy reflectance was input into a simplified atmospheric correction model using the four-flow radiative transfer model, and the atmospheric top reflectance of rice was calculated based on relevant parameters.

[0054] The coupled modeling method of the geometric optical-radiative transfer model of row-sown aquatic vegetation canopy reflectance and the rice crop growth model of this invention helps to explore the relationship between the canopy reflectance spectrum of aquatic vegetation, the spectrum of the underlying soil, and atmospheric transmission more deeply and scientifically. At the same time, this invention can solve the problem that existing models, due to neglecting the spectral differences of the soil under aquatic vegetation and the influence of the Lambertian surface assumption on atmospheric transmission, lead to discrepancies between simulated and measured values. It also provides an effective particle filtering method. This invention will provide a more efficient and accurate new approach for the monitoring, yield estimation, early warning, protection, and inversion of biophysical parameters of aquatic vegetation, and has important significance and application value for remote sensing monitoring and inversion of rice.

[0055] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A coupled modeling method for a row-seeded aquatic vegetation canopy radiation model and an atmospheric radiative transfer model, characterized in that... Includes the following steps: (1) The soil-row-sown aquatic vegetation-atmosphere structure was decomposed into a three-layer model to simulate the spectral reflectance of soil, the reflectance of the row-sown aquatic vegetation canopy and the satellite-observed reflectance of the top layer of the atmosphere, respectively. (2) A brightness-spectrum-humidity model was used for the bottom soil to simulate the spectral reflectance of soil under different humidity conditions in different latitude regions. The specific implementation process is as follows: Step 1: Using three fundamental spectra extracted from the global spectral library, namely global spectral vectors (GSVs), simulate the reflectance of dry soil surfaces: Where a1, a2, and a3 are fitting coefficients, and G1, G2, and G3 are global spectral vectors; although GSV can reasonably fit any given dry soil reflectance spectrum, these coefficients are directly related to the reflectance spectrum but not directly related to the soil composition. Step 2: Assuming that soil brightness only affects the "intensity" of soil reflectance, while the "shape" of soil reflectance depends on other factors, namely roughness, organic matter content, and mineralogical composition, we separate the soil brightness effect from the spectral shape effect through intensity-shape transformation: In the formula, B represents soil luminance, which determines the intensity of soil reflectivity; angle and Related to other soil properties; this intensity shape transformation is similar to transforming Cartesian coordinates to spherical coordinates; therefore, angles and Similar to latitude and longitude on Earth; Step 3: Use a water film coating method to maintain the consistency of the radiative transfer model: the coupling achieved through radiative transfer is similar to the coupling between soil, vegetation, and atmosphere; wet soil is considered as a system consisting of a dry soil layer covered by a thin layer of water; the reflectivity of wet soil formed by the combination of dry soil and water film includes the contributions of the following factors: 1) the first interaction of the water film on the surface of soil particles, i.e., Fresnel reflection. 2) Reflections from the background, including multiple reflections between soil and water layers: in Indicates the reflectance of moist soil. This represents the probability of the water film distribution. These represent the Fresnel reflectance from one medium to another, with "1" and "2" referring to air and water, respectively. Indicates the water absorption coefficient. Indicates the optical thickness of the water film. Indicates background reflectance; Assuming the water film on the ground is non-uniform, and since the surface reflection effect is not affected by the film thickness, only the transmission loss caused by water absorption is corrected; therefore, the dry area ratio of the soil is P (k = 0), and the soil reflectance is obtained by combining these factors. for: Where μ is equal to the expected value of the water film thickness, The data represents the reflectance of dry soil and is given as a function of soil moisture: In the formula, The soil moisture volume percentage is used as input to the brightness-spectrum-humidity model. Soil moisture capacity is an indicator of soil's water retention capacity, expressed as a percentage. (3) Input the spectrum calculated by the soil spectral reflectance model into the bottom layer of the row-sown aquatic vegetation radiation model to calculate the canopy reflectance of the row-sown aquatic vegetation. (4) The reflectance of the canopy of row-sown aquatic vegetation was input into the simplified atmospheric radiative transfer model using the four-flow radiative transfer model, and the atmospheric top reflectance of the row-sown aquatic vegetation was calculated based on the relevant parameters.

2. The coupled modeling method for a row-seeded aquatic vegetation canopy radiation model and an atmospheric radiation transfer model according to claim 1, characterized in that: The step (1) described "decompose the soil-row-aquatic vegetation-atmosphere structure into a three-layer model and calculate the soil spectral reflectance, the canopy reflectance of the row-aquatic vegetation and the top atmospheric reflectance respectively"; For ease of calculation, the entire scene is divided into three components: the bottom surface soil layer, the middle row-sown aquatic vegetation layer, and the top atmosphere layer. The surface soil layer is located at the starting point of the four-flow radiative transfer equation. Its spectral properties largely determine the overall reflectance of the row-sown aquatic vegetation scene, and its reflectance characteristics mainly depend on local soil properties and soil moisture. The middle row-sown aquatic vegetation layer calculates the overall reflectance of different components within the field of view by assuming the row-sown structure of the aquatic vegetation. Meanwhile, the reflectance of its bottom layer depends on the soil reflectance. The canopy reflectance is obtained by inputting relevant parameters of the row-sown aquatic vegetation. The canopy reflectance of the row-sown aquatic vegetation is input into a simplified atmospheric radiative transfer model, and various atmospheric parameters are input to calculate the radiative transfer matrix to ensure the non-Lambertianity of the surface reflectance.

3. The coupled modeling method for a row-seeded aquatic vegetation canopy radiation model and an atmospheric radiation transfer model according to claim 1, characterized in that: The calculation process for "inputting the spectrum calculated by the soil model into the bottom layer of the row-sown aquatic vegetation radiation model to calculate the canopy reflectance of the row-sown aquatic vegetation" in step (3) is as follows: Step 1: The radiative transfer equation for a single dielectric layer can be expressed as: in, This represents the solar radiation incident on the bottom of the dielectric layer. This represents the scattered light incident on the bottom of the medium. This represents the upward scattered radiation from the top of the dielectric layer. This indicates direct radiation observed from the top of the medium layer. This represents the solar incident radiation at the top of the dielectric layer. This represents the incident radiation scattered from the top of the dielectric layer. This represents the upward scattered radiation from the bottom of the dielectric layer. The direct radiation in the observation direction is represented by the layer scattering matrix, where the coefficients are divided into the reflection factor ρ and the transmission factor τ. The double subscripts indicate the types of incident and outgoing radiation, respectively: s represents the direct solar radiation E. s d represents diffuse radiation E – or E + o represents the radiation E in the direction of observation. o ; Step 2: Divide the matrix into blocks according to the direction of light transmission and the position of the dielectric layer, and we can obtain: In the annotation, d represents downward radiation, u represents upward radiation; R represents the reflectance factor submatrix, T represents the transmission factor submatrix, t represents the top of the layer, and b represents the bottom of the layer; the third step is to calculate the reflectance of the vegetation canopy by using the radiative transfer relationship between the media.

4. The coupled modeling method of a row-seeded aquatic vegetation canopy radiation model and an atmospheric radiation transfer model according to claim 3, characterized in that: The calculation process for "using the four-stream radiative transfer model to input the canopy reflectance of row-sown aquatic vegetation into a simplified atmospheric correction model, and calculating the atmospheric top-layer reflectance of row-sown aquatic vegetation based on relevant parameters" in step (4) is as follows: Step 1: Calculate the simplified atmospheric radiative transfer model; this model requires seven input parameters, namely the geometric parameters of the sun and the observation instrument, specifically including the solar zenith angle. Observing the zenith angle and relative azimuth Aerosol optical thickness (AOT) at 550 nm 550 Ozone content (UO3), water vapor content (UH2O), and atmospheric pressure (Pa); by simplifying the process variables in the following formula: , S and This reduces the complexity and computation time of atmospheric radiative transfer models. It is the TOA reflectance in the direction of observation. It is bidirectional transmission of gas. is atmospheric reflectance, and S is atmospheric spherical albedo. and These are the total atmospheric albedo at the solar incidence and the observation direction, respectively; Step 2: Calculate the surface reflectance of the third layer, i.e., the atmosphere. : Expanding, we get: In the formula, TOA represents the top of the atmosphere, and 1, 2, and 3 in parentheses represent the soil layer, aquatic vegetation layer, and atmosphere, respectively. Ignoring gas transport for now, we get: in It is the total optical thickness of the atmosphere, which is the sum of the optical thickness of aerosols and molecules; It represents the transmittance in the direction of sunlight. The transmittance represents the direction of observation, with the number in parentheses indicating the medium layer. Therefore, the scattered transmittance, neglecting the effects of gas transmission, is as follows: in and These represent the transmittance from direct sunlight to scattered light and from sky to scattered light, respectively. Therefore, the reflectivity of TOA in the observation direction can be calculated. for:

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