Method and system for rapid simulation of near-space microwave detection instrument channels

Abstract

The present invention discloses a method and system for rapidly simulating channels of near-space microwave detection instruments. The method comprises the following steps: S1, based on the theory of oxygen absorption spectrum, calculating the relative intensity and line shape of oxygen absorption lines in the atmosphere of near-space after being affected by the Zeeman splitting effect; S2, constructing the complex propagation matrix of the i-th layer according to the relative intensity and line shape of the oxygen absorption lines in the i-th layer of the atmosphere of near-space; S3, based on the i-th layer complex propagation matrix and the theory of near-space microwave radiation transmission, calculating the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument using a line-by-line integration model; S4, based on the calculated single-layer transmittance matrix, parameterizing the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect separately.

Description

Technical Field

[0001] The present invention relates to the technical field of passive microwave sensors, and in particular to a method and system for quickly simulating channels of near-space microwave detection instruments. Background Art

[0002] The goal of developing a forward radiative transfer model (RTM) for passive microwave sensors is to mathematically describe the radiative transfer from the Earth's surface through the atmosphere to the sensor receiver. The accuracy of the model depends on how well the surface, atmosphere, and sensor submodels represent the relevant physical processes, as well as on mathematical approximations used to reduce the computational burden. RTMs are widely used in numerical weather prediction models, meteorological parameter inversion, and instrument design.

[0003] Because oxygen absorption lines split under the influence of the Earth's magnetic field, this phenomenon directly affects oxygen absorption characteristics above 40 km and cannot be ignored. Failure to account for the Zeeman splitting effect in radiative transfer models will result in significant simulation errors. To accurately describe the propagation of radiation in polarizable absorbing media, a coherence matrix-based transmission equation is required to describe the interaction between radiation and the medium. Specifically, by defining the power coherence matrix and the brightness temperature matrix, vector radiative transfer equations for the emitting and absorbing media are derived. The general solution of the corresponding brightness temperature matrix is ​​then found, ultimately establishing a radiative transfer equation in coherence matrix form that includes a phase term and expresses polarization information. This method enables the development of a line-by-line integral model for near-space microwave radiative transmission. This line-by-line atmospheric radiative transfer model accurately calculates the absorption, emission, and scattering of radiation in the atmosphere for a given sensor configuration, providing a basis for determining satellite orbit altitude, observation angle, and operating spectrum. Based on this existing model, the frequencies of oxygen fine structure lines can be simulated, the atmospheric altitude range over which oxygen lines can be detected under different frequency perturbations can be analyzed, and the influence of the Earth's magnetic field on oxygen absorption lines can be studied. However, the calculation speed of this model is very slow, and it is difficult to use it directly in numerical forecasting applications, which greatly reduces the application efficiency.

[0004] Forward radiative transfer models (FRTs) simulate the brightness temperature of specific instrument channels and are essential components of numerical weather prediction (NWP) assimilation or inversion systems. Fast radiative transfer models can significantly improve the computational efficiency of satellite radiation. Accurate FRTs are key technologies for satellite data assimilation in NWP and are also effective tools for satellite data inversion and sensor calibration and validation. Fast models require the ability to quickly and accurately calculate atmospheric gas absorption. A common approach is to derive the parametric relationship between transmittance and pressure, temperature, and water vapor mixing ratio. Due to the presence of the Earth's magnetic field, microwave sounding channels capable of detecting above 40 km are severely affected by Zeeman splitting, resulting in partially polarized energy received by the channels and a strong dependence on the magnetic field strength and the angle between the Earth's magnetic field and the direction of electromagnetic wave propagation. However, current domestic FRT models do not account for the Zeeman splitting effect and cannot accurately simulate high-altitude instrument detection channels, nor can they incorporate observational information into assimilation systems. Summary of the Invention

[0005] The object of the present invention is to provide a method and system for quickly simulating channels of near-space microwave detection instruments, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides a method for rapidly simulating a channel of a near-space microwave detection instrument, comprising the following steps:

[0007] S1. Based on the theory of oxygen absorption spectrum, calculate the relative intensity and line shape of oxygen absorption lines in the atmosphere of near space after being affected by the Zeeman splitting effect;

[0008] S2. Constructing a complex propagation matrix for layer i based on the relative intensity and line shape of the oxygen absorption line in layer i of the atmosphere where the near space is located, where layer i is any one of n uniform layers into which the atmosphere where the near space is located is vertically divided, and i is a positive integer less than n. The complex propagation matrix for layer i is used to describe the propagation characteristics of the oxygen absorption line in layer i after being affected by the Zeeman splitting effect;

[0009] S3. Based on the complex propagation matrix of the i-th layer and the near-space microwave radiation transmission theory, the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument is calculated using the line-by-line integration model;

[0010] S4. Based on the calculated single-layer transmittance matrix, for the channel affected by the Zeeman splitting effect, the average transmittance within its frequency band is parameterized separately.

[0011] In a preferred embodiment, in step S2, the complex propagation matrix of the i-th layer is represented as G i , G i Use plural expressions:

[0012] (1);

[0013] Where Q is the attenuation matrix and B is the phase matrix.

[0014] In a preferred embodiment, in step S3, based on the complex propagation matrix of the i-th layer and the near-space microwave radiation transmission theory, a line-by-line integral model is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, including:

[0015] The complex propagation matrix G of the i-th layer i , converted into an exponential matrix E i :

[0016] (2);

[0017] Set the cumulative matrix of the nth layer of the top atmosphere to the unit matrix I, and calculate the cumulative matrix P layer by layer from the nth layer of the top atmosphere i , where P i-1 = P i E i , the unit matrix I is used to represent the transmission effect without atmospheric influence, and the cumulative matrix P i It represents the total transmission effect of microwave signal from layer i to layer n of the top atmosphere;

[0018] The cumulative matrix P for the i-th layer i Perform conjugate transpose operation to obtain the conjugate transpose matrix P i + , and the single layer transmittance matrix γ of the i-th layer in any channel of the microwave detection instrument ch :

[0019] (3).

[0020] In a preferred embodiment, in step S4, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, including:

[0021] According to the single layer transmittance matrix γ of the i-th layer in any channel of the microwave detection instrument ch , determine the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i :

[0022] (4);

[0023] where ω is the zenith angle.

[0024] In a preferred embodiment, in step S4, based on the calculated single-layer transmittance matrix, for the channel affected by the Zeeman splitting effect, the average transmittance within its frequency band is parameterized separately, further comprising:

[0025] According to the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i The specific diagonal elements τ i , construct the prediction factor, and solve the coefficient corresponding to the prediction factor in the rapid radiation transfer model according to formula (5):

[0026] (5);

[0027] Among them, C i,0 is the preset coefficient of the microwave detection instrument in the i-th layer in any channel. The number of prediction factors is m. X i,j is the jth predictor, C i,j is the coefficient corresponding to the j-th predictor, which is selected based on any channel.

[0028] In a preferred embodiment, in step S4, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, and it also includes: constructing a fast radiation transmission model based on the Zeeman splitting effect according to the prediction factor and the coefficient corresponding to the prediction factor, and using the fast radiation transmission model to calculate the average brightness temperature of the microwave detection instrument in any channel.

[0029] In a preferred embodiment, the fast radiative transfer model is used to calculate the average brightness temperature of any channel of the microwave detection instrument, including:

[0030] S41. Based on the prediction factors and their corresponding coefficients, determine the total channel transmittance γ from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle using formula (6): ch,i :

[0031] (6);

[0032] Among them, k ranges from 1 to i, and ω is the zenith angle;

[0033] S42, according to the total channel transmittance from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle, the formula Determine the weighted contribution factor of each layer to brightness temperature;

[0034] S43. Determine the contribution value of each layer to the brightness temperature of the satellite microwave sounding instrument based on the weighted contribution factor of each layer to the brightness temperature and the average atmospheric temperature of each layer;

[0035] S44. Superimpose the contribution values ​​of each layer to the brightness temperature of the microwave detection instrument channel to obtain the average brightness temperature of the microwave detection instrument in any channel:

[0036] (7);

[0037] Where n is the total number of atmospheric layers, T i is the atmospheric temperature of the ith layer.

[0038] The present invention also provides a system for rapid simulation of channels of near-space microwave detection instruments, the system comprising:

[0039] An acquisition module is used to calculate the relative intensity and line shape of oxygen absorption lines in the atmosphere of near space after being affected by the Zeeman splitting effect based on oxygen absorption spectrum theory;

[0040] A complex propagation matrix construction module is used to construct the i-th layer complex propagation matrix based on the relative intensity and line shape of the i-th layer of oxygen absorption line in the atmospheric layer where the near space is located, wherein the i-th layer is any one of n uniform layers into which the atmospheric layer where the near space is located is divided vertically, and i is a positive integer less than n. The i-th layer complex propagation matrix is ​​used to describe the propagation characteristics of the i-th layer oxygen absorption line after being affected by the Zeeman splitting effect;

[0041] Single-layer transmittance matrix calculation module, which is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument using a line-by-line integration model based on the i-th layer complex propagation matrix and near-space microwave radiation transmission theory;

[0042] A model building module is used to parameterize the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect based on the calculated single-layer transmittance matrix.

[0043] In a preferred embodiment, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, including:

[0044] According to the single layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument is determined. i :

[0045] (4);

[0046] Where ω is the zenith angle;

[0047] According to the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i The specific diagonal elements τ i, construct the prediction factor, and solve the coefficient corresponding to the prediction factor in the rapid radiation transfer model according to formula (5):

[0048] (5);

[0049] Among them, the number of predictors is m, X i,j is the jth predictor, C i,j is the coefficient corresponding to the jth predictor, and the predictor is selected based on any channel;

[0050] According to the prediction factors and their corresponding coefficients, a fast radiation transfer model based on the Zeeman splitting effect is constructed, and the average brightness temperature of the microwave detection instrument in any channel is calculated using the fast radiation transfer model.

[0051] In a preferred embodiment, the fast radiative transfer model is used to calculate the average brightness temperature of any channel of the microwave detection instrument, including:

[0052] According to the prediction factors and their corresponding coefficients, the total channel transmittance γ from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle is determined by formula (6): ch,i :

[0053] (6);

[0054] Among them, k ranges from 1 to i, and ω is the zenith angle;

[0055] According to the total channel transmittance from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle, the formula Determine the weighted contribution factor of each layer to brightness temperature;

[0056] Determine the contribution value of each layer to the brightness temperature of the satellite microwave sounding instrument based on the weighted contribution factor of each layer to the brightness temperature and the average atmospheric temperature of each layer;

[0057] The contribution of each layer to the brightness temperature of the microwave sounding instrument channel is superimposed to obtain the average brightness temperature of the microwave sounding instrument in any channel:

[0058] (7);

[0059] Where n is the total number of atmospheric layers, T i is the atmospheric temperature of the ith layer.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] The present invention realizes the ability to simulate the Zeeman splitting effect of the fast radiation transfer model by combining the theoretical basis of the line-by-line integration model and the model structure of the fast radiation transfer model, solves the key technical problems that the line-by-line integration model cannot simulate quickly and the fast model cannot simulate accurately, and realizes the accurate and fast simulation of the channel of the near-space microwave detection instrument, making important contributions to the fields of numerical weather forecasting, atmospheric parameter inversion and high-altitude atmospheric detection instrument design. The present invention can achieve significant improvements in both accuracy and speed. Compared with ordinary fast models, the present invention can simulate the Zeeman splitting effect, and the simulation results are comparable to the accuracy of the line-by-line integration model; compared with the line-by-line integration model, the simulation time of the global ascending and descending orbit of each channel of this model can be reduced from 8 hours to 1.5 hours, and the simulation speed is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 A flow chart of a method for rapid channel simulation of near-space microwave detection instruments provided by an embodiment of the present invention;

[0063] Figure 2 Schematic diagram of the oxygen absorption coefficient distribution in the frequency range of 50-70 GHz provided by an embodiment of the present invention;

[0064] Figure 3 Schematic diagram of the Zeeman splitting frequency shift and relative intensity of the 5+ oxygen absorption line provided in an embodiment of the present invention;

[0065] Figure 4 The relative intensities of the sub-lines after Zeeman splitting of the 15+ oxygen line provided in the embodiment of the present invention;

[0066] Figure 5 The relative intensities of the sub-lines after Zeeman splitting of the 17+ oxygen line provided in the embodiment of the present invention;

[0067] Figure 6 The standard atmospheric profile temperature provided by the embodiment of the present invention;

[0068] Figure 7 The spectral response function of SSMIS channel 19 of the DMSP-F17 satellite provided in an embodiment of the present invention;

[0069] Figure 8 An atmospheric profile set for calculating SSMIS channel transmittance provided by an embodiment of the present invention;

[0070] Figure 9 The probability density distribution of SSMIS channels 19-22 of the DMSP-F17 satellite with and without the Zeeman splitting effect provided in an embodiment of the present invention;

[0071] Figure 10A comparison chart of simulation results and observation values ​​with and without the Zeeman splitting effect provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0072] The technical solutions in the embodiments of the present invention are described clearly and completely below. The embodiments of the present invention and all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0073] Example 1

[0074] like Figures 1 to 10 As shown, the method for rapid simulation of a near-space microwave detection instrument channel in this embodiment includes the following steps:

[0075] Step S1: Based on the oxygen absorption spectrum theory, the relative intensity and line shape of the oxygen absorption line in the atmosphere of near space (around 50-70 GHz) affected by the Zeeman splitting effect are calculated.

[0076] It should be noted that near space refers to the area between 20 and 100 kilometers above the ground, usually between the mesosphere and thermosphere of the atmosphere. This area belongs to the upper layer of the atmosphere and has different physical properties and environmental conditions from the lower atmosphere. Figure 2 As mentioned above, oxygen molecules produce strong microwave absorption in the 50-70 GHz frequency band due to molecular energy level transitions, forming a series of characteristic absorption peaks. The labeled 7+, 9+, 11-, 13-, etc. correspond to absorption peaks of different frequencies. The "absorption peaks" formed by oxygen molecules in near space can be understood by reference. When an external magnetic field intervenes (such as the Zeeman splitting effect), the energy level of oxygen molecules is split into multiple sub-energy levels under the action of the magnetic field. At this time, the original single "absorption peak" corresponds to the transition between different sub-energy levels, and is split into multiple fine spectral lines, such as Figure 3 As shown in the figure, under a magnetic field of 0.31 Gauss, the 5+ line splits into components such as σ⁻, π, and σ⁺, presenting multiple thin lines with frequency offsets (like the teeth of a comb).

[0077] Step S2, construct the i-th layer complex propagation matrix according to the relative intensity and line shape of the i-th layer oxygen absorption line of the atmospheric layer where the near space is located. The i-th layer is any one of the n uniform layers into which the atmospheric layer where the near space is located is divided along the vertical direction (z direction), and i is a positive integer less than n. The area where the near space is located (20-100 kilometers high) is evenly divided into n layers along the vertical direction, that is, it is assumed that the atmosphere is composed of n highly consistent isothermal and isobaric layers, and the medium characteristics in each layer are uniform. The i-th layer complex propagation matrix is ​​used to describe the propagation characteristics of the i-th layer oxygen absorption line after being affected by the Zeeman splitting effect. The i-th layer complex propagation matrix is ​​the complex propagation matrix in the z direction. The following describes in detail how to construct the i-th layer complex propagation matrix:

[0078] Under the influence of an external magnetic field, the Zeeman splitting effect causes the energy levels to split, and the emitted radiation originates from the atomic magnetic dipole. The magnitude and direction of the magnetic dipole moment can be represented by the quantum mechanical matrix elements μ(N, M, ΔJ, ΔM), which represent the transition strength when transitioning from one quantum state to another.

[0079] Where N represents the principal quantum number of the atom. The magnetic quantum number M describes the quantum number of the component of the electron's orbital angular momentum (or total angular momentum) in the direction of the magnetic field. Its value is related to the angular momentum quantum number J (total angular momentum quantum number), typically M = −J, −J + 1, …, 0, …, J − 1, J, reflecting the spatial orientation of the atomic state in the magnetic field. ΔM represents the difference between the final magnetic quantum number M′ and the initial magnetic quantum number M during an atomic transition, that is, ΔM = M′ − M. It determines the type of transition and is directly related to the polarization characteristics of the emitted light: ΔM = 0 corresponds to a π-component transition, resulting in the emission of light that is mostly linearly polarized (i.e., polarized perpendicular to the magnetic field). ΔM = ±1 corresponds to a σ-component transition, resulting in the emission of light that may be linearly polarized (when observed transversely) or circularly polarized (when observed longitudinally). In the Zeeman splitting effect, atomic energy levels are split by an external magnetic field, and ΔM constrains the selection rules for the transition. Only transitions satisfying ΔM = 0, ±1 are allowed to occur. Transitions with different ΔM produce spectral components of different polarizations and frequencies, making them a key parameter for analyzing atomic radiation behavior and spectral splitting in magnetic fields. ΔJ represents the change in the total angular momentum quantum number, describing the change in the atomic total angular momentum J before and after the transition.

[0080] In the direction specified by the polar angle, the Zeeman splitting component and The emitted radiation intensity matrices are:

[0081] ;

[0082] .

[0083] Among them, σ and π are the identifiers that distinguish different transitions (with different ΔM) and their polarization characteristics in the Zeeman splitting effect, I σ± represents the radiation intensity of the σ component (ΔM=±1), I π Represents the radiation intensity of the π component (ΔM=0).

[0084] Transition matrix under different polarizations The expression of is different, the linear polarization is:

[0085] ;

[0086] ;

[0087] Under left-hand or right-hand circular polarization conditions:

[0088] ;

[0089] ;

[0090] Here, θ is the angle between the magnetic field direction and the propagation direction.

[0091] Based on this, the complex propagation matrix of the i-th layer is expressed as G i , G i Use plural expressions:

[0092] (1);

[0093] Where Q is the attenuation matrix and B is the phase matrix.

[0094] In step S3, based on the complex propagation matrix of the i-th layer and the near-space radiation transmission theory, a line-by-line integral model is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, including:

[0095] The complex propagation matrix G of the i-th layer i , converted into an exponential matrix E i :

[0096] (2);

[0097] In actual situations, without neglecting the phase, the vector radiation transfer equation for radiation propagating along the z direction can be written as:

[0098] T B (z) = E i (T B (0)-T i )E i + + T i;

[0099] T i is the atmospheric temperature of the i-th layer, T B is the brightness temperature matrix, E i + It's E i The conjugate transposed matrix of E in formula (7) i Diagonalizing the matrix yields:

[0100] ;

[0101] in, , ;

[0102] The eigenvalues ​​of the complex propagation matrix are:

[0103] , ,and ,

[0104] In order to maintain the consistency of polarization, the sign of Δ should be chosen so that its real part is consistent with (G 22 -G 11 ) has the same sign as the real part. Under circular polarization conditions, G 12 =G 21 .

[0105] When solving for radiation, the atmosphere is assumed to be a highly consistent isothermal and isobaric layer. The brightness temperature matrix at the top of the atmosphere is the sum of the contributions of each layer. The brightness temperature matrix at the nth layer is:

[0106] (8);

[0107] Among them, T i is the atmospheric temperature of the i-th layer, and the cumulative matrix of the n-th layer of the top atmosphere is set to the unit matrix I, P n =I, starting from the top nth layer of the atmosphere, calculate the cumulative matrix P layer by layer i , where P i-1 = P i E i , the unit matrix I is used to represent the transmission effect without atmospheric influence, and the cumulative matrix P i represents the total transmission effect of a microwave signal from layer i to layer n of the top atmosphere. Using radiative transfer theory including a phase term, a brightness temperature matrix is ​​calculated, whose diagonal elements correspond to the brightness temperatures of satellite radiometer channels with right-handed (vertical) and left-handed (horizontal) circular polarization (linear polarization), respectively.

[0108] The cumulative matrix P for the i-th layer i Perform conjugate transpose operation to obtain the conjugate transpose matrix P i+ , and the single layer transmittance matrix γ of the i-th layer in any channel of the microwave detection instrument ch :

[0109] (3).

[0110] In step S4, based on the calculated single-layer transmittance matrix, for the channel affected by the Zeeman splitting effect (detection altitude above 40 km), the average transmittance within its frequency band is parameterized separately, including:

[0111] According to the single layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument is determined. i :

[0112] (4);

[0113] where ω is the zenith angle.

[0114] According to the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i The specific diagonal elements τ i , construct the prediction factor, and solve the coefficient corresponding to the prediction factor in the rapid radiation transfer model according to formula (5):

[0115] (5);

[0116] Among them, C i,0 is the preset coefficient of the microwave detection instrument in the i-th layer in any channel. The number of prediction factors is m. X i,j is the jth predictor, C i,j is the coefficient corresponding to the jth predictor, which is selected based on any channel.

[0117] According to the prediction factors and their corresponding coefficients, a fast radiation transfer model based on the Zeeman splitting effect is constructed, and the average brightness temperature of the microwave detection instrument in any channel is calculated using the fast radiation transfer model.

[0118] The fast radiative transfer model is used to calculate the average brightness temperature of any channel of the microwave sounding instrument, including:

[0119] Step S41: Based on the prediction factors and the coefficients corresponding to the prediction factors, the total channel transmittance γ from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle is determined by formula (6): ch,i :

[0120] (6);

[0121] Among them, k ranges from 1 to i, and ω is the zenith angle;

[0122] Step S42: According to the total channel transmittance from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle, the formula γ ch,i-1 -γ ch,i Determine the weighted contribution factor of each layer to brightness temperature;

[0123] Step S43: determining the contribution value of each layer to the brightness temperature of the satellite microwave sounding instrument based on the weighted contribution factor of each layer to the brightness temperature and the average atmospheric temperature of each layer;

[0124] Step S44: superimpose the contribution values ​​of each layer to the brightness temperature of the microwave detection instrument channel to obtain the average brightness temperature of the microwave detection instrument in any channel:

[0125] (7);

[0126] Where n is the total number of atmospheric layers, T i is the atmospheric temperature of the ith layer.

[0127] In addition, the above-mentioned microwave detection instrument can also be described as a satellite-borne microwave vertical sounding instrument, which has the same meaning.

[0128] Example 2

[0129] The present invention also provides a system for rapid simulation of near-space microwave detection instrument channels, including: an acquisition module 501, a complex propagation matrix construction module 502, a single-layer transmittance calculation module 503 and a model construction module 504.

[0130] The acquisition module 501 is used to calculate the relative intensity and line shape of the oxygen absorption line in the atmosphere of the near space after being affected by the Zeeman splitting effect based on the near space microwave radiation transmission theory.

[0131] The complex propagation matrix construction module 502 is used to construct the i-th layer complex propagation matrix based on the relative intensity and line shape of the i-th layer oxygen absorption line of the atmospheric layer where the near space is located, wherein the i-th layer is any one of the n uniform layers into which the atmospheric layer where the near space is located is divided vertically, i is a positive integer less than n, and the i-th layer complex propagation matrix is ​​used to describe the propagation characteristics of the i-th layer oxygen absorption line after being affected by the Zeeman splitting effect.

[0132] The single-layer transmittance calculation module 503 is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument using a line-by-line integration model based on the i-th layer complex propagation matrix and near-space radiation transmission theory;

[0133] The model building module 504 is used to parameterize the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect based on the calculated single-layer transmittance matrix.

[0134] Furthermore, in a preferred embodiment, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, including:

[0135] According to the single layer transmittance matrix of the microwave detection instrument in any channel, the optical thickness τ of the i-th layer in any channel is determined. i :

[0136] (4);

[0137] Where ω is the zenith angle;

[0138] According to the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i The specific diagonal elements τ i , construct the prediction factor, and solve the coefficient corresponding to the prediction factor in the rapid radiation transfer model according to formula (5):

[0139] (5);

[0140] Among them, C i,0 is the preset coefficient of the microwave detection instrument in the i-th layer in any channel. The number of prediction factors is m. X i,j is the jth predictor, C i,j is the coefficient corresponding to the jth predictor, and the predictor is selected based on any channel;

[0141] According to the prediction factors and their corresponding coefficients, a fast radiation transfer model based on the Zeeman splitting effect is constructed, and the average brightness temperature of the microwave detection instrument in any channel is calculated using the fast radiation transfer model.

[0142] Furthermore, the fast radiation transfer model is used to calculate the average brightness temperature of the microwave sounding instrument in any channel, including:

[0143] According to the prediction factors and their corresponding coefficients, the total channel transmittance γ from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle is determined by formula (6): ch,i :

[0144] (6);

[0145] Among them, k ranges from 1 to i, and ω is the zenith angle;

[0146] According to the total channel transmittance from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle, the formula Determine the weighted contribution factor of each layer to brightness temperature;

[0147] Determine the contribution value of each layer to the brightness temperature of the satellite microwave sounding instrument based on the weighted contribution factor of each layer to the brightness temperature and the average atmospheric temperature of each layer;

[0148] The contribution of each layer to the brightness temperature of the microwave sounding instrument channel is superimposed to obtain the average brightness temperature of the microwave sounding instrument in any channel:

[0149] (7);

[0150] Where n is the total number of atmospheric layers, T i is the atmospheric temperature of the ith layer.

[0151] Example 3

[0152] The following describes the method for rapid simulation of near-space microwave detection instrument channels using the DMSP-F17 satellite SSMIS channel 19 as an example (the central detection frequency of SSMIS channel 19 is 63.283248 GHz).

[0153] Step S1: Based on the oxygen absorption spectrum theory, the relative intensity and line shape of the oxygen absorption line in the atmosphere of near space (around 50-70 GHz) affected by the Zeeman splitting effect are calculated.

[0154] By inputting the center frequency of channel 19 and atmospheric parameters (temperature, pressure), the corresponding oxygen absorption line (15+ and 17+) frequencies (62.9980 GHz and 63.5685 GHz) can be located by frequency. The Zeeman splitting line intensity and frequency distribution of the 15+ and 17+ oxygen lines under given geomagnetic field and atmospheric conditions (geomagnetic field strength Be = 0.5 Gauss; atmospheric temperature Ta = 300 K; atmospheric pressure P = 1 hPa) are shown as follows: Figure 4 and Figure 5 shown.

[0155] Step S2: constructing the i-th layer complex propagation matrix according to the relative intensity and line shape of the i-th layer oxygen absorption line of the atmospheric layer where the near space is located.

[0156] Based on the relative intensities and absorption line shapes at specific frequencies, the propagation matrix G can be calculated in complex form: iAssuming the center frequency is 62.9980-0.004 GHz (the SSMIS channel consists of two passbands, each of which can detect within a certain frequency range, the range is determined by the bandwidth. In other words, the parameters of multiple fine frequencies within a specific channel of the sensor can be calculated. This example only gives the calculation result of one frequency), Be=0.5 Gauss; CBTH=cos(135°). The atmospheric parameters are Figure 6 The standard atmospheric profile data is shown. The corresponding π component propagation matrix when the current center frequency is shifted by 0.1 MHz is:

[0157] -3.558766467027890E-021 + i-6.801726282895659E-012,

[0158] -3.598358045331063E-021 + i-6.856653699677251E-012;

[0159] The resulting propagation matrix of the σ+ component is:

[0160] -3.558766467027890E-021 + i-6.801726282895659E-012,

[0161] -3.598358045331063E-021 + i-6.856653699677251E-012;

[0162] The σ-component propagation matrix results as:

[0163] -3.558766467027890E-021 + i-6.801726282895659E-012,

[0164] -3.598358045331063E-021 + i-6.856653699677251E-012;

[0165] In step S3, based on the complex propagation matrix of the i-th layer and the near-space radiation transmission theory, a line-by-line integration model is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument.

[0166] This step mainly uses the line-by-line integration model to calculate the channel transmittance corresponding to multiple sets of atmospheric profiles and geomagnetic field parameters. Taking the DMSP-F17 satellite SSMIS channel 19 as an example, the monochromatic transmittance of the SSMIS channel 19 frequency can be calculated based on the line-by-line integration model. The calculated monochromatic transmittance is convolved with the spectral response function to obtain the corresponding channel (total) transmittance. The spectral response function of SSMIS channel 19 is given by Figure 7 Given; among them, 7 (a) and 7 (b) are the spectral response functions corresponding to the two passbands in SSMIS channel 19, respectively. The distribution of the passband spectral response function in the channel can reflect the passband shape characteristics and is used to calculate the channel transmittance.

[0167] enter Figure 8 Multiple sets of atmospheric profiles in Figure 8 The number and height of the profiles in the left and right columns differ. The left column has low profile heights (to 0.01 hPa) and is used for training low-altitude channels, with a large number of profiles. The right column has high profile heights (to above 0.001 hPa) and is used for training upper-atmosphere channels, such as SSMIS channels 19 and 20. The corresponding Earth magnetic field intensity Be, the cosine value CBTH of the angle between the Earth's magnetic field and the wave propagation direction, and the angle corresponding to the cosine value CBTH in Table 1 can be used to calculate the channel transmittance corresponding to SSMIS channel 19.

[0168] Table 1 Geomagnetic field parameters used to calculate SSMIS channel transmittance

[0169]

[0170] Table 2 Input data of each atmospheric layer of SSMIS channel 19 at a zenith angle of 51°

[0171]

[0172] Table 2 shows the input data for each of the 105 atmospheric layers at a zenith angle of 51° for SSMIS channel 19. The first column shows altitude (km); the second column shows pressure (hPa); the third column shows temperature (K); and the fourth column shows water vapor (ppmv). Table 3 shows the optical depths of various atmospheric layers for Be = 0.2 Gauss and CBTH = -1, used to calculate the single-layer transmittance matrix.

[0173] Table 3 Optical depths of different atmospheric layers corresponding to SSMIS channel 19 at Be = 0.5 Gauss and CBTH = -1

[0174]

[0175] Step S4: Based on the calculated single-layer transmittance matrix, for the channel affected by the Zeeman splitting effect, parameterize the average transmittance within its frequency band separately.

[0176] Perform regression calculation on the single-layer transmittance matrix calculated in step S3 to solve the coefficients corresponding to the prediction factors in the rapid radiation transfer model and generate an nc or bin coefficient file.

[0177] Therefore, the present invention can achieve significant improvements in both accuracy and speed. First, compared with the ordinary fast model, this model can simulate the Zeeman splitting effect, and the simulation results are comparable to the accuracy of the line-by-line integration model; second, compared with the line-by-line integration model, this model reduces the simulation time of the global ascending and descending orbit of each channel, and the simulation speed is significantly improved. For specific results comparison, please refer to Figure 9 and Figure 10 .

[0178] Figure 9 The probability density function of the brightness temperature deviation (observed brightness temperature - simulated brightness temperature, OB) of the SSMIS upper atmosphere sounding channel is shown, where Figure 9 (a), (b), (c), and (d) show the probability density distributions of the OB for SSMIS channels 19, 20, 21, and 22, respectively. The blue color represents the result without considering the Zeeman effect, while the red color represents the result with the Zeeman effect. Figure 9 shows that accounting for the Zeeman splitting effect in the rapid radiative transfer model significantly reduces the simulated brightness temperature deviations of the SSMIS channels. The average OB value for channel 19 decreases from 2.63 K to 1.74 K, for channel 20 from 9.27 K to 4.03 K, and for channel 21 from 3.33 K to 1.43 K. While channel 22 is less affected by Zeeman splitting, its average OB value still decreases by 0.42 K. Overall, after implementing the Zeeman module in the rapid radiative transfer model, the OB values ​​of the SSMIS upper atmosphere sounding channels conform more closely to a normal distribution.

[0179] Figure 10 It is the scatter statistical result of the rapid radiation simulation brightness temperature of DMSP-F17 SSMIS Channel 19 and Channel 20 from April 22 to 30, 2023 and the observation data. Figure 10 (a) and (c) are the scatter plots of brightness temperature observations and simulations of SSMIS channel 19 and channel 20 without considering the Zeeman splitting effect. Figure 10 (b) and (d) show the observed and simulated brightness temperature scatter plots for SSMIS Channel 19 and Channel 20, respectively, taking into account the Zeeman splitting effect. It can be seen that the root mean square error (RMSE) for Channel 19 decreases from 3.252 K to 2.677 K, while that for Channel 20 decreases from 11.909 K to 5.055 K. Including the Zeeman splitting effect in the rapid radiative transfer model significantly improves model accuracy.

[0180] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for rapid simulation of a near-space microwave detection instrument channel, characterized by: The steps include: S1. Based on the theory of oxygen absorption spectrum, calculate the relative intensity and line shape of oxygen absorption lines in the atmosphere of near space after being affected by the Zeeman splitting effect; S2. Constructing a complex propagation matrix for the i-th layer based on the relative intensity and line shape of the oxygen absorption line in the i-th layer of the atmosphere where the near space is located, wherein the i-th layer is any one of n uniform layers into which the atmosphere where the near space is located is vertically divided, and i is a positive integer less than n. The complex propagation matrix for the i-th layer is used to describe the propagation characteristics of the oxygen absorption line in the i-th layer after being affected by the Zeeman splitting effect; S3. Based on the complex propagation matrix of the i-th layer and the near-space microwave radiation transmission theory, the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument is calculated using the line-by-line integration model; S4. Based on the calculated single-layer transmittance matrix, for the channel affected by the Zeeman splitting effect, the average transmittance within its frequency band is parameterized separately; In step S2, the complex propagation matrix of layer i is represented as G i , G i Use plural expressions: （1）； Where Q is the attenuation matrix and B is the phase matrix; In step S3, based on the complex propagation matrix of the i-th layer and the near-space microwave radiation transmission theory, a line-by-line integral model is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, including: The complex propagation matrix G of the i-th layer i , converted into an exponential matrix E i : （2）； Set the cumulative matrix of the nth layer of the top atmosphere to the unit matrix I, and calculate the cumulative matrix P layer by layer from the nth layer of the top atmosphere i , where P i-1 = P i E i , the unit matrix I is used to represent the transmission effect without atmospheric influence, and the cumulative matrix P i It represents the total transmission effect of microwave signal from layer i to layer n of the top atmosphere; The cumulative matrix P for the i-th layer i Perform conjugate transpose operation to obtain the conjugate transpose matrix P i + , and the single layer transmittance matrix γ of the i-th layer in any channel of the microwave detection instrument ch : （3）。 2. The method for rapid simulation of a near-space microwave detection instrument channel according to claim 1, characterized in that: In step S4, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, including: According to the single layer transmittance matrix γ of the i-th layer in any channel of the microwave detection instrument ch , determine the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i : （4）； where ω is the zenith angle.

3. The method for rapid simulation of a near-space microwave detection instrument channel according to claim 2, characterized in that: In step S4, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, which also includes: According to the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i The specific diagonal elements τ i , construct the prediction factor, and solve the coefficient corresponding to the prediction factor in the rapid radiation transfer model according to formula (5): （5）； Among them, c i,0 is the preset coefficient of the microwave detection instrument in the i-th layer in any channel. The number of prediction factors is m. X i,j is the jth predictor in the i-th layer, C i,j is the coefficient corresponding to the j-th predictor in the i-th layer, and the predictor is selected based on any channel.

4. The method for rapid simulation of a near-space microwave detection instrument channel according to claim 3, characterized in that: In step S4, based on the calculated single-layer transmittance matrix, the average transmittance within the frequency band of the channel affected by the Zeeman splitting effect is parameterized separately, which also includes: constructing a fast radiation transmission model based on the Zeeman splitting effect according to the prediction factor and the coefficient corresponding to the prediction factor, and using the fast radiation transmission model to calculate the average brightness temperature of the microwave detection instrument in any channel.

5. The method for rapid simulation of a near-space microwave detection instrument channel according to claim 4, characterized in that: The fast radiative transfer model is used to calculate the average brightness temperature of any channel of the microwave sounding instrument, including: S41. Based on the prediction factors and their corresponding coefficients, determine the total channel transmittance γ from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle using formula (6): ch,i : （6）； Among them, k ranges from 1 to i, and ω is the zenith angle; S42, according to the total channel transmittance from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle, the formula Determine the weighted contribution factor of each layer to brightness temperature; S43. Determine the contribution value of each layer to the brightness temperature of the satellite microwave sounding instrument based on the weighted contribution factor of each layer to the brightness temperature and the average atmospheric temperature of each layer; S44. Superimpose the contribution values ​​of each layer to the brightness temperature of the microwave detection instrument channel to obtain the average brightness temperature of the microwave detection instrument in any channel: （7）； Where n is the total number of atmospheric layers, T i is the atmospheric temperature of the ith layer.

6. A system for rapid simulation of near-space microwave detection instrument channels, characterized by: The system comprises: An acquisition module is used to calculate the relative intensity and line shape of oxygen absorption lines in the atmosphere of near space after being affected by the Zeeman splitting effect based on oxygen absorption spectrum theory; A complex propagation matrix construction module, which is used to construct an i-th layer complex propagation matrix based on the relative intensity and line shape of the i-th layer of oxygen absorption line in the atmospheric layer where the adjacent space is located, wherein the i-th layer is any one of n uniform layers into which the atmospheric layer where the adjacent space is located is vertically divided, i is a positive integer less than n, and the i-th layer complex propagation matrix is ​​used to describe the propagation characteristics of the i-th layer oxygen absorption line after being affected by the Zeeman splitting effect; Single-layer transmittance matrix calculation module, which is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument using a line-by-line integration model based on the i-th layer complex propagation matrix and near-space microwave radiation transmission theory; A model building module for parameterizing the average transmittance within a frequency band for channels affected by the Zeeman splitting effect based on the calculated single-layer transmittance matrix; In step S2, the complex propagation matrix of layer i is represented as G i , G i Use plural expressions: （1）； Where Q is the attenuation matrix and B is the phase matrix; In step S3, based on the complex propagation matrix of the i-th layer and the near-space microwave radiation transmission theory, a line-by-line integral model is used to calculate the single-layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, including: The complex propagation matrix G of the i-th layer i , converted into an exponential matrix E i : （2）； Set the cumulative matrix of the nth layer of the top atmosphere to the unit matrix I, and calculate the cumulative matrix P layer by layer from the nth layer of the top atmosphere i , where P i-1 = P i E i , the unit matrix I is used to represent the transmission effect without atmospheric influence, and the cumulative matrix P i It represents the total transmission effect of microwave signal from layer i to layer n of the top atmosphere; The cumulative matrix P for the i-th layer i Perform conjugate transpose operation to obtain the conjugate transpose matrix P i + , and the single layer transmittance matrix γ of the i-th layer in any channel of the microwave detection instrument ch : （3）。 7. The system for rapid channel simulation of near-space microwave detection instruments according to claim 6, characterized in that: Based on the calculated single-layer transmittance matrix, for the channel affected by the Zeeman splitting effect, the average transmittance within its frequency band is parameterized separately, including: According to the single layer transmittance matrix of the i-th layer in any channel of the microwave detection instrument, the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument is determined. i : （4）； Where ω is the zenith angle; According to the optical thickness matrix τ of the i-th layer in any channel of the microwave detection instrument i The specific diagonal elements τ i , construct the prediction factor, and solve the coefficient corresponding to the prediction factor in the rapid radiation transfer model according to formula (5): （5）； Among them, the number of predictors is m, X i,j is the jth predictor, C i,j is the coefficient corresponding to the jth predictor, and the predictor is selected based on any channel; According to the prediction factors and their corresponding coefficients, a fast radiation transfer model based on the Zeeman splitting effect is constructed, and the average brightness temperature of the microwave detection instrument in any channel is calculated using the fast radiation transfer model.

8. The system for rapid channel simulation of near-space microwave detection instruments according to claim 7, characterized in that: The fast radiative transfer model is used to calculate the average brightness temperature of any channel of the microwave sounding instrument, including: According to the prediction factors and their corresponding coefficients, the total channel transmittance γ from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle is determined by formula (6): ch,i : （6）； Among them, k ranges from 1 to i, and ω is the zenith angle; According to the total channel transmittance from the i-th layer to the top of the atmosphere in any channel of the microwave detection instrument at any zenith angle, the formula γ ch,i-1 -γ ch,i Determine the weighted contribution factor of each layer to brightness temperature; Determine the contribution value of each layer to the brightness temperature of the satellite microwave sounding instrument based on the weighted contribution factor of each layer to the brightness temperature and the average atmospheric temperature of each layer; The contribution of each layer to the brightness temperature of the microwave sounding instrument channel is superimposed to obtain the average brightness temperature of the microwave sounding instrument in any channel: （7）； Where n is the total number of atmospheric layers, T i is the atmospheric temperature of the ith layer.

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