Rainy day troposphere refractive index profile inversion method based on buoy platform

Abstract

The invention discloses a rainy day troposphere refractive index profile inversion method based on a buoy platform, and relates to the technical field of marine atmosphere exploration, and the method comprises the steps: obtaining a priori knowledge base based on sounding data statistical learning, setting a threshold value, and searching and constructing an initial parameter profile in the priori knowledge base; decomposing the population into a plurality of sub-populations, distributing each sub-population to different CPU / GPU nodes, and calculating a target function for each individual; obtaining sea surface temperature and sea surface humidity from the buoy platform as boundary constraint conditions, performing inversion by using a multi-target genetic immune algorithm, and obtaining an inversion result when a target function value is less than or equal to a threshold value; and calculating an atmospheric refractive index profile based on an inversion result. According to the method, attitude shaking of the offshore floating platform is considered and corrected; the accuracy of inversion of the troposphere refractive index profile in rainy days is effectively improved, the offshore troposphere refractive index profile is detected in real time, and the calculation efficiency is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of marine atmospheric sounding, in particular to a method for retrieving the tropospheric refractive index profile on rainy days based on a buoy platform. Background Art

[0002] The tropospheric refractive index is a core parameter for evaluating the propagation of space radio waves and plays a key role in fields such as aviation navigation, space vehicle tracking and control, over-the-horizon propagation, radar blind area detection, and satellite remote sensing calibration. The abnormal tropospheric refractive index over the sea, which causes electromagnetic signal loss of lock, transmission delay, and even changes in the signal propagation path (atmospheric duct propagation), has always been a major safety hazard for maritime activities. In areas where ships enter and leave ports or where the navigation density is high, signal loss of lock easily causes chaos in the navigation order; signal transmission delay poses difficulties for the maritime tracking and control of spacecraft; changes in the signal propagation path expand the radar detection blind area and pose a serious threat to maritime safety activities. At the same time, the abnormal tropospheric refractive index over the sea can also increase the errors in radar ranging, angle measurement, and speed measurement, enhance radar clutter, and have a greater impact on radio communication.

[0003] The phenomenon of abnormal tropospheric refractive index over the sea occurs frequently, especially the interference of precipitation under rainy conditions. Raindrops themselves change the electromagnetic wave propagation path, resulting in the need to additionally consider the correction of the liquid water path (LWP) for the inversion of the refractive index profile. The existing methods for retrieving the tropospheric refractive index over the sea have low accuracy and low computational efficiency for rainy day inversion results and cannot meet the real-time requirements for computational speed in engineering applications. Summary of the Invention

[0004] In order to overcome the above problems existing in the prior art, the present invention proposes a method for retrieving the tropospheric refractive index profile on rainy days based on a buoy platform.

[0005] The technical solution adopted by the present invention to solve its technical problems is: A method for retrieving the tropospheric refractive index profile on rainy days based on a buoy platform, comprising the following steps: Step 1, constructing a temperature and humidity stratification knowledge base Q using the archived data of the nearshore sounding station, and setting a threshold group , searching in the knowledge base, randomly selecting m groups in Q, and using the pressure-height empirical formula to calculate the pressure profile with the sea surface pressure obtained from the buoy platform as the initial value to obtain m groups ; Step 2, calculating the zenith angle, constructing m groups , decomposing the population m into s subpopulations, and distributing each subpopulation to different CPU / GPU nodes, and calculating the objective function for each individual ; Step 3, obtaining the sea surface temperature and the sea surface humidity from the buoy platformAs boundary constraint conditions, an inversion is carried out using the designed multi-objective genetic immune algorithm, and when it satisfies , the retrieved atmospheric temperature profile is , the relative humidity profile , and the calculated pressure profile , where is the number of atmospheric layers; Step 4, calculate the partial pressure of water vapor profile , from the atmospheric temperature profile , the partial pressure of water vapor profile , and the pressure profile , calculate the atmospheric refractive index profile.

[0006] In the above method for retrieving the tropospheric refractive index profile on a rainy day based on a buoy platform, the method for calculating the objective function value in Step 2 is as follows: Calculate the zenith atmospheric absorption coefficient and the zenith atmospheric absorption , the slant path atmospheric absorption satisfies relationship, use the slant path atmospheric microwave equation to calculate the atmospheric brightness temperature , given the observed brightness temperature , and then obtain the objective function value .

[0007] In the above method for retrieving the tropospheric refractive index profile on a rainy day based on a buoy platform, the method for calculating the zenith atmospheric absorption coefficient is as follows: ; ; ; ; where f represents the observed channel frequency; R represents the rainfall intensity ； k and α are coefficients. When the microwave radiometer operates in the horizontal polarization mode, , when the microwave radiometer operates in the vertical polarization mode, ; , , , , , , are all equation coefficients; For all path geometries in linear polarization and circular polarization: ; ; where is the path tilt angle, It is the polarization tilt angle relative to the horizontal position and can be obtained from the microwave radiometer parameters.

[0008] In the above-mentioned buoy platform-based rainy day tropospheric refractive index profile inversion method, the specific process of the multi-objective genetic immune algorithm inversion in step 3 includes: Step 3.1, sort the individuals in the population according to their non-dominated relationships in the objective function space and divide the individuals into different levels; Step 3.2, for each level of individuals, calculate its crowding degree in the objective function; identify good individuals and bad individuals in the solution space, and record the good individuals that have appeared in history; Step 3.3, using crossover and mutation operations, select parent individuals from the current population according to the selection strategy, generate a corresponding number of offspring individuals, and merge the parent individuals and offspring individuals into a new population; Step 3.4, select the next generation population according to non-dominated sorting and crowding. First, divide the individuals into different levels according to the non-dominated sorting, then select according to the crowding, and finally retain the high-level individuals and individuals with high crowding; Step 3.5, repeat steps 3.1-3.4 until satisfied , and get the inversion result.

[0009] In the above-mentioned rainy day tropospheric refractive index profile inversion method based on the buoy platform, the atmospheric refractive index profile calculation formula in step 4 is: ; in, is the atmospheric temperature profile, is the wet partial pressure profile, The air pressure profile.

[0010] The above-mentioned buoy-based rainy day tropospheric refractive index profile inversion method introduces atmospheric correction refractive index when radio waves are transmitted over long distances: ; Among them, r 0 is the mean radius of the Earth, is the height; The slope of the refractive index profile is detected. or If there is an abnormal atmospheric refractive index, the altitude will be automatically given. , and issue an alarm prompt.

[0011] The beneficial effects of the present invention are that the present invention takes into account the attitude sway of the offshore floating platform and corrects it; effectively improves the accuracy of the inversion of the tropospheric refractive index profile on rainy days, realizes real-time detection of the offshore tropospheric refractive index profile, and effectively improves the calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of the process of the present invention; Figure 2 is the inversion flowchart of the multi-objective genetic immune algorithm of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] As Figure 1 shown, this embodiment discloses a method for inverting the tropospheric refractive index profile on a rainy day based on a buoy platform, which specifically includes the following steps.

[0015] Step 1: Construct a temperature and humidity stratification knowledge base using the archived data of the nearshore sounding station , and set a threshold group , search in the knowledge base, and randomly construct m groups , where m is the population size, such as m = 80, and the pressure profile adopts the modified pressure-height empirical formula: Calculate to obtain, that is, m groups .

[0016] Step 2: Obtain the motion attitude angles (roll angle and pitch angle) of the carrying platform from the attitude sensor, and calculate the zenith angle from the attitude angles. The calculation formula is , where, is the zenith angle, is the roll and pitch attitude angle, construct m groups , and decompose the population m into s small populations.

[0017] Step 3: Distribute the sub-populations to different CPU / GPU nodes. For each individual, calculate the zenith atmospheric absorption coefficient and the zenith atmospheric absorption . The slant path atmospheric absorption satisfies relationship, and use the slant path atmospheric microwave equation to calculate the atmospheric brightness temperature , where takes 2.73K, and calculate its objective function value .

[0018] Calculation of the zenith atmospheric absorption coefficient under rainy conditions: Under rainy conditions, the atmospheric absorption mainly includes oxygen absorption, water vapor absorption and raindrop absorption, that is , where, The calculation method of can be found in ZL202410642276.3 in detail. The calculation method is specifically as follows: Rain attenuation (dB / km) can be calculated from the power-law relationship with rainfall intensity (mm / h): , (1); The values of coefficients k and α are determined by the following equations, (2); (3); where f represents the observed channel frequency; R represents the rainfall intensity ； k and α are coefficients. When the microwave radiometer operates in the horizontal polarization mode, , when the microwave radiometer operates in the vertical polarization mode, ; , , , , , , are all coefficients of the equations, and the specific values are shown in Table 1 - Table 4.

[0019] Table 1 Coefficient

[0020] Table 2 Coefficient

[0021] Table 3 Coefficient

[0022] Table 4 Coefficient

[0023] The constant value of the coefficient for horizontal polarization is given in Table 1, while the constant value of the coefficient for vertical polarization is given in Table 2. Table 3 gives the constant value of the coefficient for horizontal polarization , while Table 4 gives the constant value of the coefficient for vertical polarization .

[0024] For all path geometries in linear polarization and circular polarization, it can be calculated by the following equations using the values given in equations (2) and (3): (4); (5); Here is the path bevel, It is the polarization tilt angle relative to the horizontal position and can be obtained from the microwave radiometer parameters.

[0025] Combined with the rainfall sensor of the microwave radiometer, the above method is used to calculate , and then calculate .

[0026] Zenith atmospheric absorption Calculation: Continuous integration form: ; Converted to discrete sum form: ; Here, z represents the height.

[0027] Step 4: Obtain sea surface temperature from the buoy platform , Sea surface humidity As boundary constraints, the designed multi-objective genetic immune algorithm is used for inversion to meet The inverted atmospheric temperature profile is , relative humidity profile , calculated pressure profile ,in, is the number of atmospheric layers.

[0028] The multi-objective genetic immune algorithm corresponds the objective function of the problem to the antigen (fitness) of the invading organism, and the solution to the problem is the antibody (temperature / humidity profile) produced by the immune system. The multi-objective genetic immune algorithm is an efficient, parallel, global search method that can automatically acquire and accumulate knowledge about the search space during the search process, and can adaptively control the search process to obtain a non-inferior solution set. The algorithm has a self-regulating function, which not only retains the characteristics of the standard genetic algorithm's random global parallel search, but also avoids premature convergence to a considerable extent, ensuring rapid convergence to the local or global optimal solution, effectively improving computational efficiency.

[0029] The specific process of multi-objective genetic immune algorithm inversion is as follows: Figure 2 As shown, including: Step 4.1, sort the individuals in the population according to their non-dominated relationships in the objective function space and divide the individuals into different levels; Step 4.2, for each level of individuals, calculate its crowding degree in the objective function; identify good individuals and bad individuals in the solution space, and record the good individuals that have appeared in history; Step 4.3: Using crossover and mutation operations, select parental individuals from the current population according to the selection strategy and generate a corresponding number of offspring individuals, and merge the parental individuals and offspring individuals into a new population; Step 4.4: Select the next-generation population according to non-dominated sorting and crowding degree. First, divide the individuals into different ranks according to non-dominated sorting, and then select according to the crowding degree. Finally, retain the individuals with high ranks and high crowding degrees; Step 4.5: Repeat Steps 4.1 - 4.4 until is satisfied to obtain the inversion result.

[0030] Step 5: Calculate the partial pressure of water vapor at each layer , and the calculation method of the partial pressure of water vapor is the prior art and will not be elaborated here.

[0031] In the radio wave band, the atmospheric refractive index can be expressed as: ; where represents the dry term of the refractive index, represents the wet term of the refractive index, is the total atmospheric pressure, is the partial pressure of dry air, is the partial pressure of water vapor, , is the Kelvin temperature.

[0032] can be approximately expressed as the following equation: ; In the formula, is the absolute temperature, is the partial pressure of water vapor, is the air pressure, and the unit is .

[0033] When the radio wave is transmitted over a long distance, the atmospheric modified refractive index is introduced, where r 0 is the average radius of the earth, generally taken as , is the height, and the modified refractive index is dimensionless.

[0034] Step 6: Detect the slope of the refractive index profile. When the situation of or is detected, it indicates that there is an abnormal situation of the atmospheric refractive index, and the height will be automatically given and an alarm prompt will be issued.

[0035] The above embodiments are only exemplary embodiments of the present invention and are not used to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be regarded as falling within the protection scope of the present invention.

Claims

1. A method for inverting the refractive index profile of the troposphere on rainy days based on a buoy platform, characterized in that: The steps include: Step 1: Use the archived data of nearshore sounding stations to build a temperature and humidity stratification knowledge base Q and set the threshold group , search in the knowledge base, randomly select m groups in Q , the pressure profile is calculated using the pressure-height empirical formula with the sea surface pressure obtained by the buoy platform as the initial value, and the m groups are obtained. ; Step 2: Calculate the zenith angle and get m groups , decompose the population m into s sub-populations, distribute each sub-population to different CPU / GPU nodes, and calculate the objective function for each individual ; Step 3: Obtain sea surface temperature from the buoy platform , Sea surface humidity As boundary constraints, the designed multi-objective genetic immune algorithm is used for inversion to meet When , the inverted atmospheric temperature profile is , relative humidity profile , calculated pressure profile ,in, is the number of atmospheric layers; Step 4, calculate the moisture partial pressure profile , from the atmospheric temperature profile , wet partial pressure profile , pressure profile , calculate the atmospheric refractive index profile.

2. The method for inverting the refractive index profile of the troposphere on rainy days based on a buoy platform according to claim 1, characterized in that: The objective function value calculation method in step 2 is: Calculate the zenith atmospheric absorption coefficient under rainy conditions: and zenith atmospheric absorption , the slope is absorbed by the atmosphere to meet The atmospheric brightness temperature is calculated using the slant path atmospheric microwave equation. , it is known that the brightness temperature observed by microwave radiometer , and then get the objective function value .

3. The method for inverting the refractive index profile of the troposphere in rainy days based on a buoy platform according to claim 2, characterized in that: The zenith atmospheric absorption coefficient under the rainy day condition The calculation method is: ; ; ; ; Where f represents the observation channel frequency; R represents the rainfall intensity ； k and α are coefficients. When the microwave radiometer works in horizontal polarization mode, , when the microwave radiometer works in vertical polarization mode, ; , , , , , , are equation coefficients; For all path geometries in linear and circular polarization: ; ; in, is the path bevel, It is the polarization tilt angle relative to the horizontal position and can be obtained from the microwave radiometer parameters.

4. The method for inverting the refractive index profile of the troposphere in rainy days based on a buoy platform according to claim 1, characterized in that: The specific process of multi-objective genetic immune algorithm inversion in step 3 includes: Step 3.1, sort the individuals in the population according to their non-dominated relationships in the objective function space and divide the individuals into different levels; Step 3.2, for each level of individuals, calculate its crowding degree in the objective function; identify good individuals and bad individuals in the solution space, and record the good individuals that have appeared in history; Step 3.3, using crossover and mutation operations, select parent individuals from the current population according to the selection strategy, generate a corresponding number of offspring individuals, and merge the parent individuals and offspring individuals into a new population; Step 3.4, select the next generation population according to non-dominated sorting and crowding. First, divide the individuals into different levels according to the non-dominated sorting, then select according to the crowding, and finally retain the high-level individuals and individuals with high crowding; Step 3.5, repeat steps 3.1-3.4 until satisfied , and get the inversion result.

5. The method for inverting the refractive index profile of the troposphere in rainy days based on a buoy platform according to claim 1, characterized in that: The atmospheric refractive index profile calculation formula in step 4 is: ; in, is the atmospheric temperature profile, is the wet partial pressure profile, The air pressure profile.

6. The method for inverting the refractive index profile of the troposphere in rainy days based on a buoy platform according to claim 5, characterized in that: When radio waves are transmitted over long distances, the atmospheric refractive index correction is introduced: ; where r0 is the mean radius of the Earth, is the height; The slope of the refractive index profile is detected. or If there is an abnormal atmospheric refractive index, the altitude will be automatically given. , and issue an alarm prompt.

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