A method for retrieving aerosol parameters using atmospheric synchronous correction

Abstract

The present invention discloses an atmospheric synchronous correction aerosol parameter inversion method, comprising the following steps: photographing at least two pairs of aerosol inversion intensity and polarization channel radiance data from a satellite platform atmospheric synchronous correction instrument; converting the aerosol inversion intensity and polarization radiance data under clear sky conditions into apparent reflectance data according to a reflectance calculation formula; constructing a lookup table based on a 6SV radiation transmission model; calculating the surface reflectance and polarization reflectance under different aerosol models and different aerosol optical thickness conditions according to a formula; for each aerosol model, using the intensity surface reflection a priori model and constructing a first cost function, and making the cost function equal to 0 through aerosol optical thickness interpolation; using the surface polarization reflection a priori model and constructing a second cost function, when the aerosol model is minimized, it is the final inversion result. The present invention can not only improve the inversion accuracy of atmospheric synchronous correction aerosol parameters, but also improve the atmospheric correction accuracy of the load to be corrected.

Description

Technical Field

[0001] The invention relates to the field of satellite remote sensing quantitative inversion, and in particular to an atmospheric synchronous correction aerosol parameter inversion method. Background Art

[0002] On the one hand, atmospheric aerosols will cause remote sensing images to be blurred, affecting the qualitative use of data; on the other hand, they will change the spectral characteristics of objects in remote sensing images, affecting the quantitative use of data. Therefore, in order to better utilize satellite remote sensing images, atmospheric correction is required. The onboard atmospheric synchronous polarimeter can obtain intensity and polarization signals at the same time, and is designed to invert high-precision aerosol parameters for the main payload atmospheric correction.

[0003] At present, the traditional methods of aerosol inversion based on satellite-borne polarization sensors mainly include two technical solutions. One is to invert aerosol parameters based on intensity data alone. The main inversion algorithms include those based on the relationship between surface reflectivity between bands and the surface library method. For example, the dark target method (DT) uses the shortwave infrared band to estimate the surface reflectivity in the visible light band, and the deep blue algorithm (DB) uses the minimum reflectivity technology to build a surface reflectivity library in different bands; the other is to invert aerosol parameters based on polarization data alone. The main inversion algorithms include those based on the relationship between surface polarization reflectivity between bands and the surface polarization reflectivity model (BPDF) method. For example, the spectrally invariant characteristic algorithm of surface polarization reflectivity (SNOSPR) estimates the surface polarization reflectivity by using the characteristic that the red and near-infrared surface polarization reflectivity basically does not change with the band. The official POLDER fine mode aerosol inversion algorithm estimates the surface polarization surface reflectivity based on the BPDF model. However, there are the following problems when using intensity or polarization data alone: ​​first, the intensity signal is greatly affected by the surface, especially in bright surface areas; second, the polarization signal is greatly affected by the aerosol model. For example, within the scattering angle range of 80°-120°, it is generally only sensitive to fine-mode aerosols. Therefore, using intensity or polarization signals alone to invert aerosol parameters will result in large errors under certain conditions. Summary of the invention

[0004] The object of the present invention is to provide an atmospheric synchronous correction aerosol parameter inversion method to solve the above-mentioned problems existing in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An atmospheric synchronous correction aerosol parameter inversion method comprises the following steps:

[0007] S100, capture at least two pairs of aerosol inversion intensity and polarization channel radiance data from the atmospheric synchronous correction instrument on the satellite platform, and obtain the solar zenith angle, solar azimuth angle, observation zenith angle, observation azimuth angle, longitude and latitude information;

[0008] S200, converting the aerosol inversion intensity and the polarized radiance data under clear sky conditions into apparent reflectivity data respectively according to a reflectivity calculation formula;

[0009] S300, constructing a lookup table based on the 6SV radiation transfer model, wherein the lookup table contains atmospheric parameters under different solar zenith angles, observation zenith angles, relative azimuth angles, different aerosol models, and different aerosol optical thicknesses. ;

[0010] S400, based on the information of the solar zenith angle, the solar azimuth angle, the observation zenith angle and the observation azimuth angle, interpolate different aerosol models under the observation angle from the lookup table, and the atmospheric parameters under different aerosol models are: ;

[0011] S500, calculate the surface reflectivity under different aerosol models and different aerosol optical thickness according to the formula and polarization reflectivity ;

[0012] S600, constructing a priori surface model for aerosol inversion intensity and polarization channel based on prior knowledge of surface reflectivity , using the intensity of the surface reflectance to test the model first and Constructing the first cost function;

[0013] S700, for each aerosol model, the cost function is interpolated by aerosol optical thickness If it is equal to 0, the aerosol optical thickness is the final aerosol optical thickness result corresponding to the aerosol model;

[0014] S800, calculating the corresponding aerosol model and aerosol optical thickness according to the formula in step S500 , using the ground surface polarization reflectance prior model and Constructing a second cost function;

[0015] S900, when the aerosol model makes the second cost function When it is the minimum, the aerosol model and the corresponding aerosol optical thickness are the final inverted aerosol parameter results.

[0016] In some specific embodiments,

[0017] The reflectivity calculation formula in step S200 is: ;

[0018] In the formula, represents the apparent reflectance, subscript I Represents intensity data, P represents polarization data, represents the radiance, represents the distance between the Earth and the Sun, represents the solar irradiance at the top of the atmosphere, Represents the solar zenith angle.

[0019] In some specific embodiments,

[0020] The solar zenith angle has a value range of: 0°-84°;

[0021] The observation zenith angle value range is: 0°-84°;

[0022] The relative azimuth angle ranges from 0° to 180°.

[0023] In some specific embodiments,

[0024] The calculation formula of step S500 is: .

[0025] In some specific embodiments,

[0026] The first cost function formula is: .

[0027] In some specific embodiments,

[0028] The second cost function formula is: .

[0029] The beneficial effects of the present invention are as follows: the present invention discloses a method for inverting atmospheric synchronous correction aerosol parameters. The present invention effectively and simultaneously combines intensity and polarization data, that is, determines the aerosol optical thickness through intensity data, and determines the optimal aerosol model through polarization data, and finally inverts the aerosol parameters. The present invention has the following inventive effects: (1) a new method for inverting atmospheric synchronous correction aerosol parameters by combining intensity and polarization data is proposed; (2) the new method can improve the inversion accuracy of atmospheric synchronous correction aerosol parameters; (3) the aerosol parameters inverted by the new method can improve the atmospheric correction accuracy of the load to be corrected. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of an atmospheric synchronous correction aerosol parameter inversion method of the present invention;

[0031] Figure 2 It is a technical flow chart of another embodiment of an atmospheric synchronous correction aerosol parameter inversion method of the present invention;

[0032] Figure 3This is a comparison diagram of the results of the present invention and the foundation site. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Reference Figure 1 , Figure 2 and Figure 3 The method for retrieving atmospheric synchronous correction aerosol parameters shown in the figure comprises the following steps:

[0035] S100, capture at least two pairs of aerosol inversion intensity and polarization channel radiance data from the atmospheric synchronous correction instrument on the satellite platform, and obtain the solar zenith angle, solar azimuth angle, observation zenith angle, observation azimuth angle, longitude and latitude information;

[0036] S200, converting the aerosol inversion intensity and the polarized radiance data under clear sky conditions into apparent reflectivity data respectively according to a reflectivity calculation formula;

[0037] S300, constructing a lookup table based on the 6SV radiation transfer model, wherein the lookup table contains atmospheric parameters under different solar zenith angles, observation zenith angles, relative azimuth angles, different aerosol models, and different aerosol optical thicknesses. ;

[0038] S400, based on the information of the solar zenith angle, the solar azimuth angle, the observation zenith angle and the observation azimuth angle, interpolate different aerosol models under the observation angle from the lookup table, and the atmospheric parameters under different aerosol models are: ;

[0039] S500, calculate the surface reflectivity under different aerosol models and different aerosol optical thickness according to the formula and polarization reflectivity ;

[0040] S600, constructing a priori surface model for aerosol inversion intensity and polarization channel based on prior knowledge of surface reflectivity , using the intensity of the surface reflectance to test the model first and Constructing the first cost function;

[0041] S700, for each aerosol model, the cost function is interpolated by aerosol optical thickness If it is equal to 0, the aerosol optical thickness is the final aerosol optical thickness result corresponding to the aerosol model;

[0042] S800, calculating the corresponding aerosol model and aerosol optical thickness according to the formula in step S500 , using the ground surface polarization reflectance prior model and Constructing a second cost function;

[0043] S900, when the aerosol model makes the second cost function When it is the minimum, the aerosol model and the corresponding aerosol optical thickness are the final inverted aerosol parameter results.

[0044] In some specific embodiments,

[0045] The reflectivity calculation formula in step S200 is: ;

[0046] In the formula, represents the apparent reflectance, subscript I Represents intensity data, P represents polarization data, represents the radiance, represents the distance between the Earth and the Sun, represents the solar irradiance at the top of the atmosphere, Represents the solar zenith angle.

[0047] It should be noted here that the reflectivity calculation formula can also be expressed by the following formula: In the formula, represents the atmospheric radiation, are respectively expressed as the downward and upward atmospheric transmittance, is the atmospheric albedo, is the surface (polarization) reflectivity. Example

[0048] This method is applied to the atmospheric synchronous correction instrument SMAC remote sensing data. The specific implementation plan is as follows:

[0049] 1) For SMAC data, the data used in the present invention include intensity observation data at 490 and 670 nm, polarization data at 670, 870, 1610 and 2250 nm, as well as solar zenith angle, observation zenith angle, relative azimuth angle data, and longitude and latitude information;

[0050] 2) According to formula (1), the intensity and polarized radiance data under clear sky conditions are converted into apparent reflectance data respectively;

[0051]

[0052] In the formula, represents the apparent reflectance, subscriptI Represents intensity data, P represents polarization data, represents the radiance, represents the distance between the Earth and the Sun, represents the solar irradiance at the top of the atmosphere, Represents the solar zenith angle.

[0053] 3) The apparent reflectance data at 490 and 670 nm and the apparent polarized reflectance at 670, 870, 1610 and 2250 nm are calculated from step 2). At the same time, the apparent reflectance can be expressed by formula (2):

[0054]

[0055] In the formula, represents the atmospheric radiation, They are respectively expressed as downward and upward atmospheric transmittance, S is the atmospheric albedo, is the surface (polarization) reflectivity.

[0056] 4) Based on the 6SV radiation transfer model, a lookup table is constructed, which contains atmospheric parameters under different solar zenith angles (0°-84°), observation zenith angles (0°-84°), relative azimuth angles (0°-180°), different aerosol models, and different aerosol optical depths (AOD). .

[0057] ;

[0058] 4) Based on the solar zenith angle, observation zenith angle, and relative azimuth information, the atmospheric parameters under different bands, different aerosol models, and different AOD conditions at the observation angle are interpolated from the lookup table. .

[0059] 5) Calculate the surface reflectance at 490 and 670 nm under different aerosol models and different AOD conditions according to formula (3):

[0060] ;

[0061] 6) Constructing a priori surface model of aerosol inversion intensity channel based on prior knowledge of surface reflectivity ; Use the intensity of surface reflection to test the model first and Construct the cost function 1, as shown in formula (4): ;

[0062] 7) For each aerosol model, the cost function is interpolated by AOD When the AOD is equal to 0, the AOD is the final AOD result corresponding to the aerosol model.

[0063] 8) Calculate the corresponding AOD for each band, each aerosol model and Using the ground surface polarization reflectance prior model Construct cost function 2, as shown in formula (5):

[0064] 9) When the aerosol model uses the cost function When it is the minimum, the aerosol model and the corresponding AOD are the final inverted aerosol parameter results.

[0065] In some specific embodiments,

[0066] The solar zenith angle has a value range of: 0°-84°;

[0067] The observation zenith angle value range is: 0°-84°;

[0068] The relative azimuth angle ranges from 0° to 180°.

[0069] In some specific embodiments,

[0070] The calculation formula of step S500 is: .

[0071] In some specific embodiments,

[0072] The first cost function formula is: .

[0073] In some specific embodiments,

[0074] The second cost function formula is: .

[0075] The beneficial effects of the present invention are as follows: the present invention discloses a method for inverting atmospheric synchronous correction aerosol parameters. The present invention effectively and simultaneously combines intensity and polarization data, that is, determines the aerosol optical thickness through intensity data, and determines the optimal aerosol model through polarization data, and finally inverts the aerosol parameters. The present invention has the following inventive effects: (1) a new method for inverting atmospheric synchronous correction aerosol parameters by combining intensity and polarization data is proposed; (2) the new method can improve the inversion accuracy of atmospheric synchronous correction aerosol parameters; (3) the aerosol parameters inverted by the new method can improve the atmospheric correction accuracy of the load to be corrected.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A method for inverting atmospheric synchronous correction aerosol parameters, characterized in that: The following steps are involved: S100, capture at least two pairs of aerosol inversion intensity and polarization channel radiance data from the atmospheric synchronous correction instrument on the satellite platform, and obtain the solar zenith angle, solar azimuth angle, observation zenith angle, observation azimuth angle, longitude and latitude information; S200, converting the aerosol inversion intensity and the polarized radiance data under clear sky conditions into apparent reflectivity data respectively according to a reflectivity calculation formula; S300, constructing a lookup table based on the 6SV radiation transfer model, wherein the lookup table contains atmospheric parameters under different solar zenith angles, observation zenith angles, relative azimuth angles, different aerosol models, and different aerosol optical thicknesses: atmospheric path radiation Downward atmospheric transmittance T ↓ , upward atmospheric transmittance T ↑ , atmospheric albedo S; S400, interpolating different aerosol models based on the solar zenith angle, the solar azimuth angle, the observation zenith angle and the observation azimuth angle from the lookup table, the atmospheric parameters under different aerosol models are: atmospheric path radiation Downward atmospheric transmittance T ↓ ', upward atmospheric transmittance T ↑ ', atmospheric albedo S'; S500, calculate the surface reflectivity under different aerosol models and different aerosol optical thickness according to the formula and polarization reflectivity S600, constructing a priori surface model for aerosol inversion intensity and polarization channel based on prior knowledge of surface reflectivity Using Intensity Surface Reflectance to Predict Models and Constructing a first cost function; S700: for each aerosol model, make the first cost function CF1 equal to 0 by interpolating the aerosol optical thickness, where the aerosol optical thickness is the final aerosol optical thickness result corresponding to the aerosol model; S800, calculating the corresponding aerosol model and aerosol optical thickness according to the formula in step S500 Using the ground surface polarization reflectance prior model and Constructing a second cost function; S900, when the aerosol model minimizes the second cost function CF2, the aerosol model and the corresponding aerosol optical thickness are the final inverted aerosol parameter results; The reflectivity calculation formula in step S200 is: In the formula, represents apparent reflectance, the subscript I represents intensity data, P represents polarization data, L represents radiance, d represents the distance between the sun and the earth, ESUN represents the solar irradiance at the top of the atmosphere, and θ s represents the solar zenith angle; The calculation formula of step S500 is: The first cost function formula is: The second cost function formula is:

2. The atmospheric synchronous correction aerosol parameter inversion method according to claim 1, characterized in that: The solar zenith angle has a value range of: 0°-84°; The observation zenith angle value range is: 0°-84°; The relative azimuth angle ranges from 0° to 180°.

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