Atmospheric high-resolution radiation transfer calculation method for greenhouse gas

Abstract

The invention discloses an atmospheric high-resolution radiation transfer calculation method for greenhouse gases, which is used for simultaneously calculating absorption of molecules and scattering action and earth surface reflection of particulate matters with high spectral resolution, and comprises the following steps: acquiring atmospheric state parameters; doppler broadening, collision broadening and comprehensive broadening under the combined action of the Doppler broadening and the collision broadening are calculated, and the absorption coefficient of atmospheric molecules, the total optical thickness of the atmospheric molecules and light intensity attenuation caused by the absorption action are calculated; the scattering coefficient and the extinction coefficient of the particulate matter are calculated; integrating the land reflectance and the ocean reflectance to obtain global surface reflectance; the absorption of atmospheric molecules in the radiation transmission process and the attenuation of cloud and aerosol in the radiation transmission process are simulated, and the atmospheric roof radiance is obtained by combining the global surface reflectance simulation. Compared with an existing atmospheric radiation transmission model, the method has the advantages of high accuracy, high resolution and the like, is suitable for multiple scenes, and lays a foundation for satellite load forward modeling and inversion algorithm development.

Description

Technical Field

[0001] The invention belongs to the technical field of atmospheric environment remote sensing monitoring, and in particular relates to an atmospheric high-resolution radiation transmission calculation method for greenhouse gases. Background Art

[0002] With the increase of global industrialization and energy consumption, the concentration of typical greenhouse gases such as carbon dioxide and methane in the earth's atmosphere continues to rise, leading to global climate change and environmental problems. Greenhouse gas emissions have led to the continuous aggravation of climate and environmental problems. However, there are still great deficiencies in the understanding of greenhouse gases and their source and sink spatial and temporal distribution, which prevents the construction of carbon-climate interaction models and accurate prediction of climate change. Therefore, high-precision and high-accuracy greenhouse gas monitoring has great scientific significance for the study of climate change and the global carbon cycle. In addition, high-quality greenhouse gas observation data can be further processed through inversion models to obtain near-surface carbon fluxes and anthropogenic carbon emissions, which can provide high-quality data and theoretical basis for global carbon inventory, government departments to formulate climate mitigation policies, and carbon neutrality and carbon peak path planning, which has great social value.

[0003] Therefore, in order to better understand and monitor the carbon cycle process in the atmosphere, scientists have developed atmospheric carbon monitoring satellites. The satellite payload system is novel and complex, and it is urgent to carry out full-link simulation of the satellite payload before hardware development to conduct error analysis and parameter scheme demonstration.

[0004] The radiation transmission process of sunlight or laser in the atmosphere is an important part of the full-link simulation. The transmission process of sunlight or laser in the earth-atmosphere is the process of interaction with atmospheric molecules and aerosols. In this process, sunlight or laser will be affected by the absorption and scattering of atmospheric molecules and aerosols, resulting in energy changes and conversions. This process causes the radiation spectrum received by the satellite spectrometer to be enhanced and weakened to varying degrees. The radiation transmission process mainly includes the absorption of molecules, the scattering of particulate matter (clouds and aerosols), and the reflection of the ground. The existing atmospheric radiation transmission models can be divided into three types according to the spectral resolution: low-resolution model (>5cm); -1 ), medium resolution model (1cm -1 ~5cm -1 ) and high-resolution models (<1cm -1 ). The biggest difference between atmospheric radiation transfer models lies in the method of solving the radiation transfer equation. Different radiation transfer models have different spectral resolutions. The scope of application of atmospheric radiation transfer models is mainly constrained by spectral resolution.

[0005] The existing atmospheric radiation transfer model cannot meet the full-link simulation requirements of satellite payloads. The existing low- and medium-resolution atmospheric radiation transfer models take into account both molecular absorption and aerosol scattering, while the high-resolution radiation transfer model only takes into account molecular absorption. For satellite payload radiation transfer simulation, molecular absorption and aerosol scattering need to be considered simultaneously. In addition, taking the integral path differential absorption lidar as an example, its line width is 50MHz, corresponding to the required spectral resolution of 0.017cm. -1 Therefore, from the perspective of spectral resolution, only high spectral resolution models can meet the simulation requirements of integral path differential absorption lidar.

[0006] The Chinese patent application with publication number CN119000616A is aimed at the Fengyun satellite spectral imager, and has developed a Fengyun satellite spectral imager atmospheric correction method, device, medium and product based on the 6S radiation transfer model. The 6S radiation transfer model and the spectral response function of MERSI are used to generate target coefficients; a lookup table is constructed; an interpolation algorithm is applied to obtain matching data values ​​of the second parameter corresponding to each pixel in the target MERSI observation data; the target coefficient of each pixel in the target MERSI observation data is determined from the lookup table; the 6S radiation transfer model is applied to obtain the corrected reflectivity of each pixel; according to the corrected reflectivity of each pixel, the visible light channel true color quick view is corrected to obtain a corrected true color composite image, which can perform atmospheric correction on the MERSI wide-area global image.

[0007] Among the current existing technologies, 6S and others take into account the radiation transmission of molecular absorption and aerosol scattering at the same time, but the spectral resolution of the model is low, which makes it difficult to meet the high spectral resolution simulation requirements of satellite passive payloads. Therefore, it is necessary to model the top of the atmosphere radiation transmission simulation calculation of greenhouse gas passive payloads in order to evaluate the performance of greenhouse gas passive payloads. Summary of the invention

[0008] In view of the above, the purpose of the present invention is to provide a high-resolution atmospheric radiation transfer calculation method for greenhouse gases, which simultaneously calculates the absorption of molecules and the scattering effect of particulate matter and surface reflection with high spectral resolution, simulates the radiation brightness at the top of the atmosphere, and achieves high-accuracy and high-resolution calculations. It is suitable for multiple scenarios and can be used to carry out target gas radiation transfer simulation in different scenarios, laying the foundation for satellite payload forward simulation and inversion algorithm development.

[0009] In order to achieve the above-mentioned invention object, the technical solution provided by the present invention is as follows:

[0010] An embodiment of the present invention provides a method for calculating atmospheric high-resolution radiation transfer for greenhouse gases, comprising the following steps:

[0011] Get atmospheric state parameters;

[0012] Calculate the Doppler broadening caused by the Doppler frequency shift produced by the motion of molecules in the atmosphere, and calculate the collision broadening caused by the collision of molecules, atoms and ions in the atmosphere;

[0013] Calculate the comprehensive broadening of the atmospheric molecular spectral lines under the combined effects of Doppler broadening and collision broadening, and calculate the absorption coefficient of atmospheric molecules, the total optical thickness of atmospheric molecules, and the light intensity attenuation caused by absorption based on the comprehensive broadening;

[0014] Calculate the optical characteristic parameters of particles including scattering coefficient and extinction coefficient according to Mie scattering theory;

[0015] The global surface reflectivity is obtained by combining the land reflectivity and the ocean reflectivity;

[0016] The absorption of atmospheric molecules during radiation transmission and the attenuation of clouds and aerosols during radiation transmission are simulated, and the radiation brightness of the top of the atmosphere is obtained by combining the global surface reflectivity simulation.

[0017] Specifically, the obtaining of atmospheric state parameters includes:

[0018] Obtain atmospheric state parameters including basic information of atmospheric temperature, humidity, pressure profile and atmospheric molecular concentration profile in the ECMWF ERA5 meteorological reanalysis data;

[0019] The distribution information of cloud-aerosol parameter profiles in the atmosphere measured by the CALIPSO satellite is obtained as the atmospheric state parameters. The distribution information of cloud-aerosol parameter profiles includes the types of clouds and aerosols, extinction coefficient profiles, and layered optical depth.

[0020] Specifically, the calculation of the Doppler broadening caused by the Doppler frequency shift generated by the motion of molecules in the atmosphere includes:

[0021] Considering the spectral line broadening caused by the Doppler effect generated by molecular motion, that is, Doppler broadening, the line function is a Gaussian line shape. The half-height and half-width calculation formula of the Doppler broadened spectral line at a specific temperature T is:

[0022]

[0023] Among them, α D (T) represents the half-width at half-height of the Doppler broadened spectrum, v ij represents the wave number of the spectral line transition in vacuum, i represents the isotope number of the gas molecule, j represents the discrete characteristic spectrum wave number of the gas molecule, c represents the speed of light in vacuum, M represents the mass of a single molecule, and N A represents Avogadro's constant, k represents Boltzmann's constant;

[0024] The Gaussian line function of Doppler broadening is:

[0025]

[0026] Among them, f G (v,v ij ,p,T) represents Doppler broadening, and v represents the wave number at any position.

[0027] Specifically, the calculation of collision broadening caused by collisions between molecules, atoms and ions includes:

[0028] Considering the irregular phase mutations of radiation wave trains caused by collisions between molecules, atoms and ions in the atmosphere, that is, collision broadening, the linear function is the Lorentzian line type. The half-height and half-width calculation formula of the collision broadening spectrum line at a specific temperature T and pressure p is:

[0029]

[0030] where γ(p,T) is the half-width at half-height of the collision-broadened spectrum, and T ref Indicates the reference temperature, n air represents the temperature coefficient of the half-width function of air broadening, γ air represents the half-height and half-width of the air broadening under standard atmosphere, γ self represents the half-height and half-width of the self-broadening, p self Represents the partial pressure of gas molecules in the atmosphere, p ref Indicates reference standard atmospheric pressure;

[0031] The Lorentzian line function of collision broadening is:

[0032]

[0033] Among them, f D (v,v ij ,p,T) represents collision broadening, δ(p ref ) represents the frequency deviation under reference standard atmospheric pressure.

[0034] Specifically, the calculation of the comprehensive broadening of the atmospheric molecular spectral lines under the combined effects of Doppler broadening and collision broadening includes:

[0035] The calculation formula for the comprehensive broadening of atmospheric molecular spectral lines is:

[0036]

[0037] Among them, f(v,v ij ,p,T) represents the comprehensive broadening of the atmospheric molecular spectral lines, f G (v,v ij,p,T) represents Doppler broadening, f D (v,v ij ,p,T) represents collision broadening, Represents a Voigt convolution operation.

[0038] Specifically, the calculation of the absorption coefficient of the atmospheric molecules, the total optical thickness of the atmospheric molecules, and the light intensity attenuation caused by the absorption effect based on the comprehensive broadening includes:

[0039] The calculation formula for the absorption coefficient of atmospheric molecules is:

[0040] k ij (v,p,T)=S ij (T)f(v,v ij ,p,T)

[0041] Among them, k ij (v,p,T) represents the absorption coefficient of atmospheric molecules, f(v,v ij ,p,T) represents comprehensive widening, S ij (T) represents the spectral line intensity of the high-resolution atmospheric molecular absorption spectrum database;

[0042] The calculation formula for the total optical depth of atmospheric molecules is:

[0043]

[0044] Among them, τ ij (v,r) represents the total optical thickness of atmospheric molecules at wave number v and height r, X gas (r) represents the number density of atmospheric molecules at a specified location, k ij (v,r) represents the atmospheric molecular absorption coefficient, and its value is affected by the wave number v and the height r. grad and r TOA Represent the height of the earth's surface and the top of the atmosphere respectively;

[0045] The calculation formula for light intensity attenuation caused by absorption is:

[0046] I(v)=I0exp(-τ)

[0047] Among them, I(v) represents the attenuation of light intensity at wave number v, I0 represents the incident light intensity of sunlight, and τ represents the optical thickness of the molecule.

[0048] Specifically, the optical characteristic parameters of particles including scattering coefficient and extinction coefficient calculated according to Mie scattering theory include:

[0049] According to the Mie scattering theory, the scattering coefficient and extinction coefficient of particles are used to describe the interaction between particles and sunlight. The calculation formula is:

[0050]

[0051] Among them, α represents the extinction coefficient, β represents the scattering coefficient, N0 represents the aerosol particle number density, r m represents the median radius of the aerosol number concentration spectrum distribution, σ represents r m The standard deviation, Q ext Represents the extinction efficiency factor of a single particle, Q back represents the backscattering efficiency factor of a single particle, r represents the particle radius, r max Indicates the maximum radius of the particle, r min Indicates the minimum radius of the particle.

[0052] Specifically, the global surface reflectivity is obtained by integrating the land reflectivity and the ocean reflectivity, including:

[0053] The land reflectivity is obtained through the MODIS MCD43C4 dataset;

[0054] The ocean reflectivity is measured based on the scattering contribution of Fresnel reflection and ocean white caps, and the calculation formula is:

[0055] R sea =(1-W)R s +WR f

[0056] Among them, R sea represents the ocean reflectivity, R s represents the Fresnel reflectivity of the sea surface, R f represents the ocean white cap reflectivity, and W represents the coverage of the ocean white cap.

[0057] Specifically, the simulation of the absorption of atmospheric molecules during the radiation transmission process and the attenuation of clouds and aerosols during the radiation transmission process includes:

[0058] The line-by-line integrated radiative transfer model LBLRTM is used to simulate the absorption of atmospheric molecules in the process of radiative transfer, and the discrete ordinate radiative transfer model DISORT is used to simulate the attenuation of clouds and aerosols in the process of radiative transfer.

[0059] Specifically, the radiance of the top of the atmosphere obtained by combining the global surface reflectivity simulation includes:

[0060] By coupling the radiation transfer model LBLRTM and the radiation transfer model DISORT, the absorption and scattering of molecules and particles in the radiation transfer process are accurately simulated, and the radiation brightness of the top of the atmosphere is obtained by combining the global surface reflectivity simulation.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] (1) The high-resolution atmospheric radiation transfer calculation method for greenhouse gases provided by the present invention can simultaneously perform molecular absorption and particle scattering with high spectral resolution, thus making up for the shortcomings of existing atmospheric radiation transfer models.

[0063] (2) The high-resolution atmospheric radiation transfer calculation method for greenhouse gases provided by the present invention can be used to simulate the top-of-atmosphere radiance (given spectrum or continuous spectrum) under various scenarios such as different surface states, different observation geometries, and different atmospheric conditions under the sun, and is applicable to a variety of scenarios.

[0064] (3) Compared with the existing atmospheric radiation transfer models, the method of the present invention has the advantages of high accuracy and high resolution, and is suitable for multiple scenarios, thus laying a foundation for satellite payload forward simulation and inversion algorithm development. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0066] Figure 1 It is a flow chart of a method for calculating atmospheric high-resolution radiation transmission of greenhouse gases provided by an embodiment of the present invention;

[0067] Figure 2 It is a schematic diagram of a process for simultaneously performing molecular absorption and particle scattering simulation provided by an embodiment of the present invention;

[0068] Figure 3 It is the calculation result of the top-of-atmosphere radiance in the shortwave infrared band provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0069] 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 and embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0070] The inventive concept of the present invention is: in order to address the problem that the atmospheric radiation transfer model in the prior art cannot simultaneously simulate molecular absorption and particle scattering with high spectral resolution, the embodiment of the present invention provides an atmospheric high-resolution radiation transfer calculation method for greenhouse gases, which simulates the radiation brightness of the top of the atmosphere by performing computational modeling on the molecular absorption, the scattering effect of particulate matter, and the surface reflection at high spectral resolution, thereby achieving high-accuracy and high-resolution calculations.

[0071] Figure 1 FIG. 1 is a flow chart of a method for calculating atmospheric high-resolution radiation transmission of greenhouse gases provided by an embodiment of the present invention. Figure 1 As shown, the embodiment provides a method for calculating atmospheric high-resolution radiation transfer for greenhouse gases, comprising the following steps:

[0072] S1, obtain atmospheric state parameters.

[0073] Obtain atmospheric state parameters including basic information of atmospheric temperature, humidity, pressure profile and atmospheric molecular concentration profile in the ECMWF ERA5 data set of meteorological reanalysis data. The data set covers the reproduction of past atmospheric states using ground-based, airborne and satellite-based meteorological observation data, numerical models and data assimilation technology, thereby obtaining long-series historical weather data with rich atmospheric elements and uniform temporal and spatial resolution.

[0074] Another important atmospheric state parameter is the distribution of clouds and aerosols. The distribution information of cloud-aerosol parameter profiles in the atmosphere measured by the CALIPSO satellite is obtained with a horizontal spatial resolution of 5km. The distribution information of cloud-aerosol parameter profiles includes the types of clouds and aerosols, extinction coefficient profiles, and layered optical thickness. In the actual atmospheric environment, clouds and aerosols often coexist at the same time, so the radiation transfer calculation also needs to consider the extinction of clouds and aerosols at the same time.

[0075] S2, calculates the Doppler broadening caused by the Doppler frequency shift produced by the motion of molecules in the atmosphere, and calculates the collision broadening caused by the collisions between molecules, atoms and ions in the atmosphere.

[0076] The absorption spectrum of atmospheric molecules is not truly monochromatic light, but actually has a certain line width, so the broadening amplitude needs to be determined. Collision broadening is proportional to the atmospheric pressure, so it mainly occurs at low altitudes, while Doppler broadening is dominant at high altitudes. Figure 2 shown.

[0077] S2.1, considering the spectral line broadening caused by the Doppler effect of molecular motion, i.e. Doppler broadening, the line function is a Gaussian line shape. The half-height and half-width calculation formula of the Doppler broadened spectral line at a specific temperature T is:

[0078]

[0079] Among them, α D (T) represents the half-width at half-height of the Doppler broadened spectrum, v ij It represents the wave number of the spectral line transition in vacuum, i represents the isotope number of the gas molecule, and j represents the discrete characteristic spectral wave number of the gas molecule, the unit is cm -1 , c represents the speed of light in vacuum, M represents the mass of a single molecule, N A Avogadro's constant is 6.02214129×10 23 mol -1 , k represents the Boltzmann constant 1.380649×10 -16 erg K -1 .

[0080] The Gaussian line function of Doppler broadening is:

[0081]

[0082] Among them, f G (v,v ij ,p,T) represents Doppler broadening, and v represents the wave number at any position.

[0083] S2.2, considering the irregular phase mutations of radiation wave trains caused by collisions between molecules, atoms and ions in the atmosphere, that is, collision broadening, the linear function of which is the Lorentzian line type. The half-height and half-width calculation formula of the collision broadening spectrum line at a specific temperature T and pressure p is:

[0084]

[0085] where γ(p,T) is the half-width at half-height of the collision-broadened spectrum, and T ref Indicates the reference temperature 296K, n air represents the temperature coefficient of the half-width function of air broadening, γ air It represents the half-height and half-width of the air broadening under standard atmosphere (temperature 296K, pressure 1 standard atmosphere), γ self represents the half-height and half-width of the self-broadening, p self Represents the partial pressure of gas molecules in the atmosphere, p ref Indicates reference standard atmospheric pressure (1atm).

[0086] The Lorentzian line function of collision broadening is:

[0087]

[0088] Among them, f D (v,v ij,p,T) represents collision broadening, δ(p ref ) represents the frequency deviation under reference standard atmospheric pressure.

[0089] S3, calculates the comprehensive broadening of the atmospheric molecular spectral lines under the combined effects of Doppler broadening and collision broadening, and calculates the absorption coefficient of the atmospheric molecules, the total optical thickness of the atmospheric molecules, and the light intensity attenuation caused by absorption based on the comprehensive broadening.

[0090] In the actual atmosphere, the broadening of the absorption lines of greenhouse gases is often caused by the combined effects of Doppler broadening and collision broadening. In the embodiment, Voigt convolution is used to describe the combined broadening of the molecular lines by the two.

[0091] S3.1, the comprehensive broadening of atmospheric molecular spectral lines is expressed as the Voigt convolution of Gaussian and Lorentzian line shapes, and the calculation formula is:

[0092]

[0093] Among them, f(v,v ij ,p,T) represents the comprehensive broadening of the atmospheric molecular spectral lines, f G (v,v ij ,p,T) represents Doppler broadening, f D (v,v ij ,p,T) represents collision broadening, Represents a Voigt convolution operation.

[0094] S3.2, after obtaining the comprehensive broadened absorption line type of atmospheric molecules, the absorption coefficient of atmospheric molecules can be obtained by combining the spectral line intensity in the high-resolution atmospheric molecular absorption spectrum database (HITRAN2020). The calculation formula is:

[0095] k ij (v,p,T)=S ij (T)f(v,v ij ,p,T)

[0096] Among them, k ij (v,p,T) represents the absorption coefficient of atmospheric molecules, f(v,v ij ,p,T) represents comprehensive widening, S ij (T) represents the spectral line intensity of the high-resolution atmospheric molecular absorption spectrum database.

[0097] S3.3, the absorption coefficient characterizes the absorption capacity of a single atmospheric molecule for solar radiation. Combined with the number density of air molecules, the total optical thickness of atmospheric molecules in the sunlight transmission path can be calculated. The calculation formula for the total optical thickness of atmospheric molecules is:

[0098]

[0099] Among them, τ ij (v,r) represents the total optical thickness of atmospheric molecules at wave number v and height r, X gas (r) represents the number density of atmospheric molecules at a specified location, k ij (v,r) represents the atmospheric molecular absorption coefficient, and its value is affected by the wave number v and the height r. grad and r TOA Represent the height of the earth's surface and the top of the atmosphere respectively.

[0100] S3.4, optical thickness, as a dimensionless unit, is a key parameter that describes the absorption strength of specific atmospheric molecules for solar radiation. Based on the Beer-Lambert law, the attenuation of light intensity due to absorption after light passes through a specific substance is:

[0101] I(v)=I0exp(-τ)

[0102] Among them, I(v) represents the attenuation of light intensity at wave number v, I0 represents the incident light intensity of sunlight, and τ represents the optical thickness of the molecule, which can be calculated by the formula.

[0103] S4, calculating the optical characteristic parameters of the particles including the scattering coefficient and the extinction coefficient according to the Mie scattering theory.

[0104] The scattering effect of atmospheric particles refers to the phenomenon that various solid and liquid particles in the atmosphere interact with light and change its propagation state. The process of particle scattering simulation is as follows: Figure 2 shown.

[0105] According to Mie scattering theory, the interaction between particles and sunlight can be described by the optical characteristic parameters of particles (such as scattering coefficient and extinction coefficient). First, calculate the Mie scattering coefficient a n and b n :

[0106]

[0107] Where x represents the scale parameter, r represents the particle radius, m represents the complex refractive index of the particle, the superscript ' represents the derivative, ψ n (x) and ξ n (x) represents the Riccati-Bessel function, which is calculated iteratively by the following formula:

[0108]

[0109] ξ n (x) = ψ n (x)-iχ n (x)

[0110] Here, n represents the number of iterations.

[0111] In the actual calculation process, there will be problems such as slow iteration convergence and long operation time. Therefore, the logarithmic derivative D is used. n (x) Calculate the Mie scattering coefficient:

[0112]

[0113] D n The recursive relation of (x) is:

[0114]

[0115] Based on this, the extinction efficiency factor and backscattering efficiency factor of a single particle can be calculated:

[0116]

[0117] Among them, Q ext Represents the extinction efficiency factor of a single particle, Q back Represents the backscattering efficiency factor of a single particulate matter particle.

[0118] Substituting the calculated extinction and scattering efficiency factors into the following formula, the extinction coefficient and scattering coefficient of the particles can be obtained. The calculation formula is:

[0119]

[0120] Among them, α represents the extinction coefficient, β represents the scattering coefficient, N0 represents the aerosol particle number density, r m represents the median radius of the aerosol number concentration spectrum distribution, σ represents r m The standard deviation of r represents the particle radius, r max Indicates the maximum radius of the particle, r min Indicates the minimum radius of the particle.

[0121] The calculated single particle extinction coefficient and scattering coefficient are then substituted into the particle cluster to obtain the optical properties of the particle scene.

[0122] S5, the global surface reflectivity is obtained by integrating the land reflectivity and the ocean reflectivity.

[0123] S5.1, obtain land reflectance using the MODIS MCD43C4 dataset. This dataset provides 0.05 oAnd two spatial resolutions of 500m, and a temporal resolution of 16 days. MCD43C4 covers seven bands of MODIS, so the MODIS MCD43C4 data product is directly selected as the surface reflectivity input of the radiation transfer model in the embodiment. However, it should be noted that the MODIS satellite surface reflectivity data product only includes the land part, and the surface reflectivity of the water part needs to be simulated based on the Fresnel reflection law combined with the ocean reflectivity model.

[0124] S5.2, Ocean reflection is mainly composed of Fresnel reflection (reflection at the air-water interface), followed by scattering contribution from ocean white caps (including ocean foam and sea bubbles). Therefore, the reflectivity of the ocean surface is calculated as follows, using the formula:

[0125] R sea =(1-W)R s +WR f

[0126] Among them, R sea represents the ocean reflectivity, R s represents the Fresnel reflectivity of the sea surface, R f represents the ocean white cap reflectivity, and W represents the coverage of the ocean white cap.

[0127] The Fresnel reflection of the ocean surface can be calculated by the following formula:

[0128]

[0129] Where ρ is the Fresnel reflection coefficient, Ω is the solid angle of the backscattering pattern, and Ω L Denotes the solid angle of the Lambertian scattering pattern. In the zenith mode, Ω L =π. Therefore, the ocean backscatter solid angle can be written as Ω = 4π < S 2 >, in the formula <S 2 > represents the variance of ocean wave slope, which characterizes the roughness of the ocean surface. The roughness of the ocean surface is mainly constrained by the wind speed on the ocean surface. The relationship between the roughness of the ocean surface and the wind speed in the sea surface reflection model can be calculated by the formula:

[0130] <S 2 >=0.003+5.12×10 -3 U 12.4

[0131] Among them, U 12.4 Indicates the wind speed at 12.4m above the sea surface. In addition, it can also be based on the wind speed U at 10m above the sea surface. 10 Quantify the roughness of the ocean surface, the calculation formula is as follows,

[0132]

[0133] Wind speed is the main factor affecting the slope and age of waves, and its direction and amplitude determine the size of the sea surface reflectivity. Generally speaking, the greater the sea surface wind speed, the higher the roughness of the sea surface and the lower the sea surface reflectivity; but too high wind speed can also cause the waves to break, which in turn causes an increase in ocean white cap scattering and thus increases the sea surface reflectivity.

[0134] In the zenith observation mode, the ocean white cap coverage is set to 0.02 and the ocean white cap reflectivity is set to 0.08 in the embodiment. The U10 data in ECMWF ERA5 is used as the simulation input to calculate the global sea surface reflectivity, and the global surface reflectivity in the zenith observation mode can be obtained by combining the land surface reflectivity of MODIS.

[0135] S6 simulates the absorption of atmospheric molecules during radiation transmission and the attenuation of clouds and aerosols during radiation transmission, and combines the global surface reflectivity simulation to obtain the top of the atmosphere radiation brightness.

[0136] The core of the atmospheric radiation transfer model lies in the solution of the radiation transfer equation. The radiation transfer equation describes the equation of the transmission process of radiation emitted by sunlight or laser in the atmosphere. There are many methods to solve the radiation transfer equation. In the embodiment, the line-by-line integrated radiation transfer model LBLRTM is used to simulate the absorption of sunlight by atmospheric molecules, and the discrete ordinate radiation transfer model DISORT is used to simulate the attenuation of sunlight by clouds and aerosols, wherein the atmospheric molecular absorption spectrum database adopts the HITRAN 2020 version.

[0137] LBLRTM is an atmospheric radiation transfer model with high spectral resolution based on the line-by-line integration method, which can calculate the atmospheric emissivity and transmittance. The calculation of this model relies on a high spectral resolution absorption spectrum database as input, so the HITRAN 2020 version is used in the embodiment to simulate and calculate the absorption spectrum characteristics of atmospheric molecules. However, LBLRTM can only calculate the absorption of molecules and cannot simulate the scattering process of particulate matter. Therefore, the DISORT model is used to make up for this defect. The DISORT radiation transfer model is a computational model for simulating atmospheric and surface radiation transfer. It is mainly used to study the optical properties and transport processes of atmospheric components, as well as to simulate and predict the radiation field and spectral characteristics of the earth's surface. The main features of the DISORT model include accurate modeling of the multi-spectral radiation characteristics of atmospheric components, the ability to simulate the radiation field distribution under different spectral ranges and detection angles, and high accuracy and flexibility. By coupling the two radiation transfer models, the absorption and scattering effects of molecules and particulate matter in the radiation transmission process can be accurately simulated, and the top of the atmosphere radiation brightness can be obtained by combining the global surface reflectivity simulation. The calculation results of the top of the atmosphere radiance in the short-wave infrared band are as follows: Figure 3 shown.

[0138] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-resolution atmospheric radiation transfer calculation method for greenhouse gases, characterized in that: The following steps are involved: Get atmospheric state parameters; Calculate the Doppler broadening caused by the Doppler frequency shift produced by the motion of molecules in the atmosphere, and calculate the collision broadening caused by the collision of molecules, atoms and ions in the atmosphere; Calculate the comprehensive broadening of the atmospheric molecular spectral lines under the combined effects of Doppler broadening and collision broadening, and calculate the absorption coefficient of atmospheric molecules, the total optical thickness of atmospheric molecules, and the light intensity attenuation caused by absorption based on the comprehensive broadening; Calculate the optical characteristic parameters of particles including scattering coefficient and extinction coefficient according to Mie scattering theory; The global surface reflectivity is obtained by combining the land reflectivity and the ocean reflectivity; The absorption of atmospheric molecules during radiation transmission and the attenuation of clouds and aerosols during radiation transmission are simulated, and the radiation brightness of the top of the atmosphere is obtained by combining the global surface reflectivity simulation.

2. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 1 is characterized in that: The obtaining of atmospheric state parameters comprises: Obtain atmospheric state parameters including basic information of atmospheric temperature, humidity, pressure profile and atmospheric molecular concentration profile in the ECMWF ERA5 meteorological reanalysis data; The distribution information of cloud-aerosol parameter profiles in the atmosphere measured by the CALIPSO satellite is obtained as the atmospheric state parameters. The distribution information of cloud-aerosol parameter profiles includes the types of clouds and aerosols, extinction coefficient profiles, and layered optical depth.

3. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 1 is characterized in that: The calculation of Doppler broadening caused by Doppler frequency shift generated by molecular motion in the atmosphere comprises: Considering the spectral line broadening caused by the Doppler effect generated by molecular motion, that is, Doppler broadening, the line function is a Gaussian line shape. The half-height and half-width calculation formula of the Doppler broadened spectral line at a specific temperature T is: Among them, α D (T) represents the half-width at half-height of the Doppler broadened spectrum, v ij represents the wave number of the spectral line transition in vacuum, i represents the isotope number of the gas molecule, j represents the discrete characteristic spectrum wave number of the gas molecule, c represents the speed of light in vacuum, M represents the mass of a single molecule, and N A represents Avogadro's constant, k represents Boltzmann's constant; The Gaussian line function of Doppler broadening is: Among them, f G (v,v ij ,p,T) represents Doppler broadening, and v represents the wave number at any position.

4. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 3 is characterized in that: The calculation of collision broadening caused by collisions between molecules, atoms and ions includes: Considering the irregular phase mutations of radiation wave trains caused by collisions between molecules, atoms and ions in the atmosphere, that is, collision broadening, the linear function is the Lorentzian line type. The half-height and half-width calculation formula of the collision broadening spectrum line at a specific temperature T and pressure p is: where γ(p,T) is the half-width at half-height of the collision-broadened spectrum, and T ref Indicates the reference temperature, n air represents the temperature coefficient of the half-width function of air broadening, γ air represents the half-height and half-width of the air broadening under standard atmosphere, γ self represents the half-height and half-width of the self-broadening, p self Represents the partial pressure of gas molecules in the atmosphere, p ref Indicates reference standard atmospheric pressure; The Lorentzian line function of collision broadening is: Among them, f D (v,v ij ,p,T) represents collision broadening, δ(p ref ) represents the frequency deviation under reference standard atmospheric pressure.

5. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 4 is characterized in that: The calculation of the comprehensive broadening of the atmospheric molecular spectral lines under the combined effects of Doppler broadening and collision broadening comprises: The calculation formula for the comprehensive broadening of atmospheric molecular spectral lines is: Among them, f(v,v ij ,p,T) represents the comprehensive broadening of the atmospheric molecular spectral lines, f G (v,v ij ,p,T) represents Doppler broadening, f D (v,v ij ,p,T) represents collision broadening, Represents a Voigt convolution operation.

6. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 5, characterized in that: The calculation of the absorption coefficient of the atmospheric molecules, the total optical thickness of the atmospheric molecules, and the light intensity attenuation caused by the absorption effect based on the comprehensive broadening includes: The calculation formula for the absorption coefficient of atmospheric molecules is: k ij (v,p,T)=S ij (T)f(v,v ij ,p,T) Among them, k ij (v,p,T) represents the absorption coefficient of atmospheric molecules, f(v,v ij ,p,T) represents comprehensive widening, S ij (T) represents the spectral line intensity of the high-resolution atmospheric molecular absorption spectrum database; The calculation formula for the total optical depth of atmospheric molecules is: Among them, τ ij (v,r) represents the total optical thickness of atmospheric molecules at wave number v and height r, X gas (r) represents the number density of atmospheric molecules at a specified location, k ij (v,r) represents the atmospheric molecular absorption coefficient, and its value is affected by the wave number v and the height r. grad and r TOA Represent the height of the earth's surface and the top of the atmosphere respectively; The calculation formula for the light intensity attenuation caused by absorption is: I(v)=I0exp(-τ) Among them, I(v) represents the attenuation of light intensity at wave number v, I0 represents the incident light intensity of sunlight, and τ represents the optical thickness of the molecule.

7. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 1, characterized in that: The optical characteristic parameters of the particles including the scattering coefficient and the extinction coefficient are calculated according to the Mie scattering theory, including: According to the Mie scattering theory, the scattering coefficient and extinction coefficient of particles are used to describe the interaction between particles and sunlight. The calculation formula is: Among them, α represents the extinction coefficient, β represents the scattering coefficient, N0 represents the aerosol particle number density, r m represents the median radius of the aerosol number concentration spectrum distribution, σ represents r m The standard deviation, Q ext Represents the extinction efficiency factor of a single particle, Q back represents the backscattering efficiency factor of a single particle, r represents the particle radius, r max Indicates the maximum radius of the particle, r min Indicates the minimum radius of the particle.

8. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 1, characterized in that: The global surface reflectivity is obtained by integrating the land reflectivity and the ocean reflectivity, including: The land reflectivity is obtained through the MODIS MCD43C4 dataset; The ocean reflectivity is measured based on the scattering contribution of Fresnel reflection and ocean white caps, and the calculation formula is: R sea =(1-W)R s +WR f Among them, R sea represents the ocean reflectivity, R s represents the Fresnel reflectivity of the sea surface, R f represents the ocean white cap reflectivity, and W represents the coverage of the ocean white cap.

9. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 1, characterized in that: The simulation of the absorption of atmospheric molecules during the radiation transmission process and the attenuation of clouds and aerosols during the radiation transmission process includes: The line-by-line integrated radiative transfer model LBLRTM is used to simulate the absorption of atmospheric molecules in the process of radiative transfer, and the discrete ordinate radiative transfer model DISORT is used to simulate the attenuation of clouds and aerosols in the process of radiative transfer.

10. The atmospheric high-resolution radiation transfer calculation method for greenhouse gases according to claim 9, characterized in that: The radiance of the top of the atmosphere obtained by combining the global surface reflectivity simulation includes: By coupling the radiation transfer model LBLRTM and the radiation transfer model DISORT, the absorption and scattering of molecules and particles in the radiation transfer process are accurately simulated, and the radiation brightness of the top of the atmosphere is obtained by combining the global surface reflectivity simulation.

Images