Actual sea surface geometry modeling method based on multi-physics ocean environment parameters

Abstract

The present invention relates to a method for modeling the actual sea surface geometry based on multi-physical-field ocean environmental parameters, belonging to the field of microwave remote sensing; Step 1, obtain multi-physical-field ocean environmental parameters of the region of interest; Step 2, calculate the energy spectrum E short (k, φ) of the capillary wave, and calculate the height h short (x s , y s , t) of the capillary wave sea surface undulation; Step 3, calculate the energy spectrum S g (f, φ) of the gravity wave, and calculate the comprehensive height h gravity (x g , y g , t) of the gravity wave sea surface undulation; Step 4, calculate the comprehensive height h total (x s , y s , t) of the sea surface undulation, and realize the actual sea surface geometry modeling of the multi-physical-field ocean environmental parameters; The present invention realizes the multi-scale sea surface geometry modeling of the actual ocean environment, and finally solves the problem of obtaining the amplitude mean value of sea clutter in a complex ocean environment.

Description

Technical Field

[0001] The invention belongs to the field of microwave remote sensing and relates to a method for modeling actual sea surface geometry based on multi-physical field ocean environment parameters. Background Art

[0002] Traditional research on electromagnetic scattering characteristics of the sea surface is generally based on a fully developed wind and wave spectrum theoretical model, which does not fully consider the actual marine environmental factors. The input parameters are generally wind speed and wind direction, which are inconsistent with the actual sea surface state. The echo information obtained by the existing sea clutter amplitude mean model cannot fully reflect the actual state of the sea surface, such as wave height, wave direction and wave period; therefore, the electromagnetic scattering characteristics of the real sea surface are not fully considered, and there are technical bottlenecks and cognitive level limitations in physical oceanography. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, propose an actual sea surface geometry modeling method based on multi-physical field ocean environment parameters, realize multi-scale sea surface geometry modeling of the actual ocean environment, and ultimately solve the problem of obtaining the mean amplitude of sea clutter in a complex ocean environment.

[0004] The solution of the present invention is:

[0005] The actual sea surface geometry modeling method based on multi-physics field ocean environment parameters includes the following steps:

[0006] Step 1: Select the ocean area of ​​interest and obtain the multi-physics field ocean environment parameters of the area, including the meridional wind speed u at a specific location 10 , zonal wind speed v 10 , effective wave height H s , average wave direction φ wave , average wave period Initial wave direction φ′ wave and temperature T sea ; Calculate the comprehensive wind speed U 10 and wind direction φ wind ; and for the initial wave direction φ′ wave Perform conversion processing to obtain the average wave direction φ wave ;

[0007] Step 2: Calculate and synthesize wind speed U 10 and wind direction φ wind The associated tension wave energy spectrum E short (k,φ), set the tension wave sea surface range and segmentation accuracy, calculate the tension wave sea surface fluctuation height h short (x s ,y s ,t);

[0008] Step 3: Calculate the effective wave height Hs , average wave direction φ wave , average wave period The associated gravitational wave energy spectrum S g (f,φ), set the gravity wave sea surface range and segmentation accuracy, and calculate the gravity wave sea surface comprehensive fluctuation height h gravity (x g ,y g ,t);

[0009] Step 4: Ensure that the number of grids for the tension wave sea surface is greater than the number of grids for the gravity wave sea surface, and that the gravity wave sea surface range is greater than the tension wave sea surface range. Superimpose the tension wave sea surface fluctuation height in step 2 on the gravity wave sea surface bin according to the slope of the gravity wave sea surface bin, and calculate the comprehensive sea surface fluctuation height h total (x s ,y s ,t), realize the actual sea surface geometry modeling of multi-physics field ocean environment parameters.

[0010] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, in step 1, the multi-physics field ocean environment parameters of the European mesoscale meteorological satellite reanalysis data are used to obtain the meridional wind speed u at 10 meters above the sea surface in the sea area. 10 , zonal wind speed v 10 , effective wave height H s , average wave direction φ wave , average wave period Average wave direction φ wave and temperature T sea .

[0011] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, the comprehensive wind speed U 10 for Wind direction φ wind is φ wind =arctan(v 10 / u 10 ).

[0012] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, the initial wave direction φ′ wave The range is 0°-360°; the average wave direction φ wave The conversion formula is:

[0013]

[0014] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, in step 2, the tension wave energy spectrum E short The calculation method of (k,φ) is:

[0015]

[0016] In the formula, F m It is the Elfouhaily high frequency shortwave action function;

[0017] D(k,φ,φ wind ) is the Cosine power law directional distribution function;

[0018]

[0019] Δ(k) is the Elfouhaily adverse crosswind scaling factor;

[0020] k is the discrete value of the sea surface wave number;

[0021] φ is the discrete value of the observed sea surface azimuth;

[0022] u f is the integrated wind speed U 10 associated sea surface friction wind speed;

[0023]

[0024] c is the speed of light, take 3×10 8 m / s;

[0025] c m is a constant, c m =0.23m / s.

[0026] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, in step 2, the method for setting the tension wave sea surface range and segmentation accuracy is:

[0027] Set the tension wave sea surface range to a rectangular area with a side length of L along the wind direction. x_s , the length of the side perpendicular to the wind direction is L y_s ; Side length L x_s The number of grid divisions is M s , along the side length L y_s The number of grid divisions is N s ; then the tension wave sea surface along L x_s The segmentation accuracy of the direction is Δx s =L x_s / M s ; Along L y_s The segmentation accuracy of the direction is Δy s =L y_s / N s ;

[0028] Height of tension wave sea surface fluctuation h short (x s ,y s,t) is calculated as:

[0029]

[0030] Where t is any time;

[0031] x s is the coordinate along the wind direction; x s =(m-1)Δx s ; m=1,2,…M s

[0032] y s is the coordinate of the vertical wind direction; y s =(n-1)Δy s ; n=1,2,…N s ;

[0033] E short (k,φ) is the tension wave energy spectrum;

[0034] i is the discrete value of the sea surface wave number;

[0035] j is the discrete value of the sea surface direction angle;

[0036] M is the number of sampling points of the wave number;

[0037] N is the number of sampling points of the direction angle;

[0038] Δω i is the discrete interval of angular frequency;

[0039] Δφ j is the discrete interval of the direction angle;

[0040] k i ,ω i ,φ j and φ ij (seed) respectively correspond to the wave number, angular frequency, direction angle and initial phase of the superimposed wave; and satisfy g is the acceleration due to gravity;

[0041] Get the sea surface range as L x_s ×L y_s , the mesh size is M s ×N s The tension wave sea surface coordinates each point (x s ,y s ) The sea surface fluctuation height value h short (x s ,y s ,t).

[0042] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, in step 3, the gravity wave energy spectrum S g (f,φ) is:

[0043]

[0044] Where, f is the sea surface wave frequency;

[0045] φ is the discrete value of the observed sea surface azimuth;

[0046] D(f,φ,φ wave ) is the Cosine power law directional distribution function;

[0047]

[0048] f is the frequency,

[0049] g is the acceleration due to gravity;

[0050] k is the discrete value of the sea surface wave number;

[0051] k m Take 370 as the constant.

[0052] In the above-mentioned actual sea surface geometry modeling method based on multi-physical field ocean environment parameters, in step 3, the method for setting the gravity wave sea surface range and segmentation accuracy is:

[0053] The sea surface range of gravity waves is a rectangular area with a side length of L along the wind direction. x_g , the length of the side perpendicular to the wind direction is L y_g ; Side length L x_g The number of grids is M g , along the side length L y_g The number of grid divisions is N g ; then the tension wave sea surface along L x_g The segmentation accuracy of the direction is Δx g =L x_g / M g ; Along L y_g The segmentation accuracy of the direction is Δy g =L y_g / N g ;

[0054] In order to realize the normal superposition of gravity waves and tension waves, L x_g ≥L x_s and L y_g ≥L y_s , and M g <M s and N g >N s ;

[0055] The linear superposition method is used to calculate the coordinates of any point (x g ,y g ) is the height of the gravity wave sea surface fluctuation h gravity (x g ,y g ,t) is:

[0056]

[0057] In the formula, x g is the coordinate along the wind direction; x g =(m-1)Δx g ,m=1,2,…M g ;

[0058] y g is the coordinate of the vertical wind direction; y g =(n-1)Δy g ,n=1,2,…N g ;

[0059] S g (f,φ) gravity wave energy spectrum;

[0060] i is the discrete value of the sea surface wave number;

[0061] j is the discrete value of the sea surface direction angle;

[0062] M is the number of sampling points of the wave number;

[0063] N is the number of sampling points of the direction angle;

[0064] Δω i is the discrete interval of angular frequency;

[0065] Δφ j is the discrete interval of the direction angle;

[0066] f i ,ω i ,φ j and φ ij (seed) corresponds to the frequency, angular frequency, direction angle and initial phase of the superimposed wave, and satisfies Where g is the acceleration due to gravity;

[0067] Get the sea surface range as L x_g ×L y_g , the mesh size is M g ×N g The gravity wave of each coordinate point (x g ,y g ) The sea surface fluctuation height value h gravity (x g ,yg ,t).

[0068] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, in step 4, the method of superimposing the tension wave sea surface fluctuation height on the gravity wave sea surface element according to the gravity wave sea surface element slope is:

[0069] S1, according to the tension wave sea surface grid number M s and N s , superimpose the tension wave on the gravity wave sea surface; the position of the tension wave sea surface element relative to the gravity wave sea surface can be determined by the following formula (L xs_to_xg , L ys_to_yg ):

[0070] L xs_to_xg = int(x s / Δx g )×Δx g ;

[0071] L ys_to_yg = int(y s / Δy g )×Δy g

[0072] Where, L xs_to_xg is the position of the tension wave sea surface relative to the gravity wave sea surface along the wind direction;

[0073] L ys_to_yg is the position of the tension wave sea surface relative to the gravity wave sea surface perpendicular to the wind direction;

[0074] int() is to get integer;

[0075] S2, determine the coordinates of the three points of the face element according to the face element position (x sg1 ,y sg1 ,z sg1 ), (x sg2 ,y sg2 ,z sg2 ), and (x sg3 ,y sg3 ,z sg3 ), where z sg1 、z sg2 、z sg3 They represent the sea surface coordinates of gravity waves (x sg1 ,y sg1 )、(x sg2 ,y sg2 )、(x sg3 ,y sg3 ) to obtain the coordinates of the center point of the surface element (x sg_center ,y sg_center ,zsg_center ), calculate the relative fluctuation height h of the tension wave sea surface relative to the center of the bin xs_to_xg ;

[0076] The tension wave sea surface fluctuation height is superimposed according to the gravity wave sea surface slope to generate the reconstructed sea surface fluctuation height, and the sea surface range is obtained as L x_g ×L y_g , the mesh size is M s ×N s The superimposed wave sea surface coordinates each point (x s ,y s ) The comprehensive height of the sea surface fluctuation h total (x s ,y s ,t).

[0077] In the above-mentioned actual sea surface geometry modeling method based on multi-physics field ocean environment parameters, in S2, the relative fluctuation height h of the tension wave sea surface relative to the center of the surface element is xs_to_xg for:

[0078] h xs_to_xg =z sg_center +(x s -x sg_center )×Z x +(y s -y sg_center )×Z y

[0079] In the formula, Z x and Z y are the slopes of the sea surface elements along the wind direction and perpendicular to the wind direction of the gravity wave sea surface respectively;

[0080] The comprehensive sea surface fluctuation height value h total (x s ,y s ,t) is:

[0081] h total (x s ,y s ,t)=h xs_to_xg (x s ,y s ,t)+h short (x s ,y s ,t).

[0082] The beneficial effects of the present invention compared with the prior art are:

[0083] (1) The present invention proposes an actual sea surface geometry modeling method based on multi-physics field marine environment elements provided by satellite data. The method can output a multi-physics field sea surface geometry model sample library that conforms to a specific sea area according to the selected sea area and data source. At the same time, the method can establish a marine engineering model for a specific sea area based on the sea surface electromagnetic scattering theory algorithm, which has high practical value.

[0084] (2) The present invention proposes an actual sea surface geometry modeling method based on multi-physical field marine environmental elements provided by satellite data. This method no longer uses the traditional simple wind and wave sea surface model, but integrates a variety of actual wave characteristic variables, which is more in line with the actual sea surface conditions and solves the defect that the traditional wind and wave sea surface model cannot depict the difference in wave energy under the same wind speed and wind direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 The actual sea surface geometry modeling flow chart of the present invention;

[0086] Figure 2 This is a schematic diagram of a time series of sea clutter amplitude mean values ​​generated based on 1024 groups of time-varying sea surfaces in an embodiment;

[0087] Figure 3 This is a schematic diagram of the scattering amplitude obtained based on the marine environmental parameters of the Yellow Sea in January 2017. DETAILED DESCRIPTION

[0088] The present invention will be further described below in conjunction with the embodiments.

[0089] The purpose of the present invention is to break through the shortcomings of the traditional wind wave spectrum sea surface electromagnetic scattering characteristics theory, and combine the actual wave information provided by satellite data to provide an actual sea surface geometry modeling method of multi-physics field ocean environment parameters that can be used to simulate the mean sea surface amplitude in a complex ocean environment. By adopting a multi-physics field parameter sea surface geometry model, the shortcomings of the traditional wind wave sea surface can be overcome. For the sea area with the same sea conditions, the electromagnetic distribution characteristics of the sea waves can be given based on satellite ocean data; combined with the instantaneous tension wave sea surface based on wind speed and wind direction, and the gravity wave sea surface considering wave height, wave direction and wave period, the small-scale tension wave sea wave is superimposed according to the distribution of gravity wave sea wave slope, and the multi-scale sea surface geometry modeling of the actual ocean environment is realized; combined with the surface element dual-scale electromagnetic scattering algorithm, the problem of obtaining the mean sea clutter amplitude in a complex ocean environment can be solved.

[0090] Actual sea surface geometry modeling method based on multi-physics ocean environment parameters, such as Figure 1 As shown, the specific steps include:

[0091] Step 1: Select the ocean area of ​​interest and obtain the multi-physics field ocean environment parameters of the area, including the meridional wind speed u at a specific location 10 , zonal wind speed v10 , effective wave height H s , average wave direction φ wave , average wave period Initial wave direction φ′ wave and temperature T sea ; Calculate the comprehensive wind speed U 10 and wind direction φ wind ; and for the initial wave direction φ′ wave Perform conversion processing to obtain the average wave direction φ wave ; Use the multi-physics field ocean environment parameters of the European Mesoscale Meteorological Satellite reanalysis data to obtain the meridional wind speed u at 10 meters above the sea surface in this sea area 10 , zonal wind speed v 10 , effective wave height H s , average wave direction φ wave , average wave period Average wave direction φ wave and temperature T sea .

[0092] Comprehensive wind speed U 10 for Wind direction φ wind is φ wind =arctan(v 10 / u 10 ). Wind direction φ wind The range is (-180°, 180°), and the calculated wind direction φ wind The negative value is converted to an equivalent positive value by adding 360° to the negative value, thus matching the average wave direction φ wave The numerical range of (0°, 360°) is comparable.

[0093] Since the wind direction starts from the positive half axis of the x-axis (longitude), that is, it coincides with the x-axis (longitude) as 0°, and coincides with the y-axis (latitude) as 90°; and the average wave direction adopts the direction of marine meteorology, it starts from due north, that is, it coincides with the y-axis (latitude) as 0°, and coincides with the x-axis (longitude) as 90°; therefore, it is necessary to calculate the initial wave direction φ′ wave The following conversion is used: Initial wave direction φ′ wave The range is 0°-360°; the average wave direction φ wave The conversion formula is:

[0094]

[0095] Step 2: Calculate and synthesize wind speed U 10 and wind direction φ wind The related tension wave energy spectrum E short (k,φ):

[0096] Tension wave energy spectrum Eshort The calculation method of (k,φ) is:

[0097]

[0098] In the formula, F m It is the Elfouhaily high frequency shortwave action function;

[0099] D(k,φ,φ wind ) is the Cosine power law directional distribution function;

[0100]

[0101] Δ(k) is the Elfouhaily adverse crosswind scaling factor;

[0102] k is the discrete value of the sea surface wave number;

[0103] φ is the discrete value of the observed sea surface azimuth;

[0104] u f is the integrated wind speed U 10 associated sea surface friction wind speed;

[0105]

[0106] c is the speed of light, take 3×10 8 m / s;

[0107] c m is a constant, c m =0.23m / s.

[0108] Set the tension wave sea surface range and segmentation accuracy, and calculate the tension wave sea surface fluctuation height h short (x s ,y s ,t).

[0109] The method for setting the tension wave sea surface range and segmentation accuracy is:

[0110] Set the tension wave sea surface range to a rectangular area with a side length of L along the wind direction. x_s , the length of the side perpendicular to the wind direction is L y_s ; Side length L x_s The number of grids is M s , along the side length L y_s The number of grid divisions is N s ; then the tension wave sea surface along L x_s The segmentation accuracy of the direction is Δx s =L x_s / M s ; Along L y_s The segmentation accuracy of the direction is Δy s =Ly_s / N s ;

[0111] Height of tension wave sea surface fluctuation h short (x s ,y s ,t) is calculated as:

[0112]

[0113] Where t is any time;

[0114] x s is the coordinate along the wind direction; x s =(m-1)Δx s ; m=1,2,…M s

[0115] y s is the coordinate of the vertical wind direction; y s =(n-1)Δy s ; n=1,2,…N s ;

[0116] E short (k,φ) is the tension wave energy spectrum;

[0117] i is the discrete value of the sea surface wave number;

[0118] j is the discrete value of the sea surface direction angle;

[0119] M is the number of sampling points of the wave number;

[0120] N is the number of sampling points of the direction angle;

[0121] Δω i is the discrete interval of angular frequency;

[0122] Δφ j is the discrete interval of the direction angle;

[0123] k i ,ω i ,φ j and φ ij (seed) respectively correspond to the wave number, angular frequency, direction angle and initial phase of the superimposed wave; and satisfy g is the acceleration due to gravity;

[0124] Get the sea surface range as L x_s ×L y_s , the mesh size is M s ×N s The tension wave sea surface coordinates each point (x s ,y s ) The sea surface fluctuation height value hshort (x s ,y s ,t).

[0125] Step 3: Calculate the effective wave height H s , average wave direction φ wave , average wave period The associated gravitational wave energy spectrum S g (f,φ):

[0126] Gravitational wave energy spectrum S g (f,φ) is:

[0127]

[0128] Where, f is the sea surface wave frequency;

[0129] φ is the discrete value of the observed sea surface azimuth;

[0130] D(f,φ,φ wave ) is the Cosine power law directional distribution function;

[0131]

[0132] f is the frequency,

[0133] g is the acceleration due to gravity;

[0134] k is the discrete value of the sea surface wave number;

[0135] k m Take 370 as the constant.

[0136] Set the gravity wave sea surface range and segmentation accuracy, and calculate the gravity wave sea surface comprehensive fluctuation height h gravity (x g ,y g ,t). The method for setting the gravity wave sea surface range and segmentation accuracy is:

[0137] The sea surface range of gravity waves is a rectangular area with a side length of L along the wind direction. x_g , the length of the side perpendicular to the wind direction is L y_g ; Side length L x_g The number of grids is M g , along the side length L y_g The number of grid divisions is N g ; then the tension wave sea surface along L x_g The segmentation accuracy of the direction is Δx g =L x_g / M g ; Along L y_g The segmentation accuracy of the direction is Δy g =Ly_g / N g ;

[0138] In order to realize the normal superposition of gravity waves and tension waves, L x_g ≥L x_s and L y_g ≥L y_s , and M g <M s and N g >N s ;

[0139] The linear superposition method is used to calculate the coordinates of any point (x g ,y g ) is the height of the gravity wave sea surface fluctuation h gravity (x g ,y g ,t) is:

[0140]

[0141] In the formula, x g is the coordinate along the wind direction; x g =(m-1)Δx g ,m=1,2,…M g ;

[0142] y g is the coordinate of the vertical wind direction; y g =(n-1)Δy g ,n=1,2,…N g ;

[0143] S g (f,φ) gravity wave energy spectrum;

[0144] i is the discrete value of the sea surface wave number;

[0145] j is the discrete value of the sea surface direction angle;

[0146] M is the number of sampling points of the wave number;

[0147] N is the number of sampling points of the direction angle;

[0148] Δω i is the discrete interval of angular frequency;

[0149] Δφ j is the discrete interval of the direction angle;

[0150] f i ,ω i ,φ j and φ ij (seed) corresponds to the frequency, angular frequency, direction angle and initial phase of the superimposed wave, and satisfies Where g is the gravitational acceleration; the initial phase satisfies a uniform distribution between 0 and 2π.

[0151] Get the sea surface range as L x_g ×L y_g , the mesh size is M g ×N g The gravity wave of each coordinate point (x g ,y g ) The sea surface fluctuation height value h gravity (x g ,y g ,t).

[0152] Step 4: Ensure that the number of grids for the tension wave sea surface is greater than the number of grids for the gravity wave sea surface, and that the gravity wave sea surface range is greater than the tension wave sea surface range. Superimpose the tension wave sea surface fluctuation height in step 2 on the gravity wave sea surface bin according to the slope of the gravity wave sea surface bin, and calculate the comprehensive sea surface fluctuation height h total (x s ,y s ,t), realize the actual sea surface geometry modeling of multi-physics field ocean environment parameters.

[0153] The method of superimposing the tension wave sea surface fluctuation height on the gravity wave sea surface element according to the slope of the gravity wave sea surface element is:

[0154] S1, according to the tension wave sea surface grid number M s and N s , superimpose the tension wave on the gravity wave sea surface; the position of the tension wave sea surface element relative to the gravity wave sea surface can be determined by the following formula (L xs_to_xg , L ys_to_yg ):

[0155] L xs_to_xg = int(x s / Δx g )×Δx g ;

[0156] L ys_to_yg = int(y s / Δy g )×Δy g

[0157] Where, L xs_to_xg is the position of the tension wave sea surface relative to the gravity wave sea surface along the wind direction;

[0158] L ys_to_yg is the position of the tension wave sea surface relative to the gravity wave sea surface perpendicular to the wind direction;

[0159] int() is to get integer;

[0160] S2, determine the coordinates of the three points of the face element according to the face element position (x sg1 ,y sg1 ,z sg1 ), (x sg2 ,y sg2 ,z sg2 ), and (x sg3 ,y sg3 ,z sg3 ), where z sg1 、z sg2 、z sg3 They represent the sea surface coordinates of gravity waves (x sg1 ,y sg1 )、(x sg2 ,y sg2 )、(x sg3 ,y sg3 ) to obtain the coordinates of the center point of the surface element (x sg_center ,y sg_center ,z sg_center ), calculate the relative fluctuation height h of the tension wave sea surface relative to the center of the bin xs_to_xg :

[0161] h xs_to_xg =z sg_center +(x s -x sg_center )×Z x +(y s -y sg_center )×Z y

[0162] In the formula, Z x and Z y They are the slopes of the sea surface elements along the wind direction and perpendicular to the wind direction of the gravity wave sea surface respectively.

[0163] The tension wave sea surface fluctuation height is superimposed according to the gravity wave sea surface slope to generate the reconstructed sea surface fluctuation height, and the sea surface range is obtained as L x_g ×L y_g , the mesh size is M s ×N s The superimposed wave sea surface coordinates each point (x s ,y s ) The comprehensive height of the sea surface fluctuation h total (x s ,y s ,t).

[0164] h total (x s ,y s ,t)=h xs_to_xg (x s ,ys ,t)+h short (x s ,y s ,t).

[0165] It can be seen that it is equivalent to re-refining the gravity wave sea surface according to the tension wave sea surface segmentation accuracy, thereby realizing the actual sea surface geometry modeling considering the influence of real sea wave ocean environment elements.

[0166] Given the time sampling interval and duration of the time series sea surface, repeat the actual sea surface geometry modeling method from step 2 to step 4 to obtain the time-varying sea surface geometry model database under the multi-physics field ocean environment parameters given in step 1 as the input file for the subsequent time-varying sea surface electromagnetic scattering amplitude mean simulation. Given the total duration T of the simulated sea surface total =N total Δt, Δt represents the time sampling interval, N total The default value is 1024, and the time change factor t=nΔt, n=1,2,3…N toal Substitute the data in step 2 to generate the tension wave sea surface and gravity wave sea surface respectively, and establish the actual sea surface geometric model. The 1024 sets of sea surface models finally obtained can be used as the input files for subsequent time-varying sea surface electromagnetic scattering.

[0167] The present invention can be applied to the actual ocean environment elements based on satellite data to realize the actual sea surface geometry modeling. The actual sea surface geometry model result contains a variety of actual ocean environment elements, which can be combined with the sea surface electromagnetic scattering algorithm to simulate the mean sea clutter amplitude, and can also be used as an important supplementary reference for ocean big data. The method solves the problem of obtaining the mean sea clutter amplitude in a complex ocean environment by establishing an instantaneous tension wave sea surface model combining wind speed and wind direction, and a sea surface time series sample database of a gravity wave sea surface model considering wave height, wave direction and wave period, combined with a sea surface dual-scale electromagnetic scattering theory algorithm. The specific implementation example is as follows:

[0168] Step 1: This patent example uses the European Mesoscale Meteorological Satellite Reanalysis Data (ERA-Interim), and the marine environmental elements of the Yellow Sea (34°N, 122.5°E) at 12:00 on January 8, 2017. At this time, the following were read: wind speed 9.82m / s, wind direction 298.76°, wave height 1.61m, wave direction 292.24°, and wave period 5.02s, temperature 10°C, and salinity changes very little, generally taking 33‰, based on which 1024 sets of sea surface geometry samples were generated.

[0169] Step 2: The size of the tension wave sea surface is 128m×128m, and the number of grids is 512×512, so the spatial gridding accuracy is 0.25m×0.25m, that is, L x_s =L y_s =128,M s =Ns =512,Δx s =Δy s =0.25, radar frequency is 10GHz, incident angle is 80°, and linear superposition method is used to calculate any coordinate point (x s ,y s ) is:

[0170]

[0171] Among them, E short (k i ,φ j ) is the energy spectral density of tension waves related to wind speed and direction.

[0172] Step 3: The size of the gravity wave sea surface is 128m×128m, and the number of grids is 128×128, so the spatial subdivision accuracy is 1m×1m, that is, L x_g =L y_g =128,M g =N g =128,Δx g =Δy g =1, the radar frequency is 10GHz, the incident angle is 80°, and the linear superposition method is used to calculate the coordinates of any point (x g ,y g ) is:

[0173]

[0174] Among them, S g (f,φ) is the energy spectral density of gravity waves related to wave height, wave direction and wave period.

[0175] Step 4: According to the tensile wave sea surface mesh number M s =N s =512, re-establish the tension wave superimposed gravity wave sea surface; the tension wave sea surface bin relative to the gravity wave sea surface can be determined by the following formula:

[0176] L xs_to_xg = int(x s );L ys_to_yg = int(y s )

[0177] Among them, int() means taking an integer, x s =(m-1)Δx s and s =(n-1)Δy s , and m,n=1,2,…512; L xs_to_xg and L ys_to_ygThe location of the tension wave sea surface relative to the gravity wave sea surface along the x-axis and y-axis respectively.

[0178] Step 5: Determine the coordinates of the three points of the face element according to the face element position (x sg1 ,y sg1 ,z sg1 ), (x sg2 ,y sg2 ,z sg2 ), and (x sg3 ,y sg3 ,z sg3 ), z sg1,2,3 Represents the gravity wave sea surface coordinate point (x sg1,2,3 ,y sg1,2,3 ) to obtain the coordinates of the center point of the surface element (x sg_center ,y sg_center ,z sg_center ), and then determine the relative fluctuation height of the tension wave sea surface relative to the center of the surface element as:

[0179] h xs_to_xg =z sg_center +(x s -x sg_center )×Z x +(y s -y sg_center )×Z y

[0180] Among them, Z x and Z y are the slopes of the gravity wave surface along the x-axis and y-axis given in (3b), h xs_to_xg is the height of the tension wave relative to the center of the gravity wave bin, so the final superimposed sea surface fluctuation height is

[0181] h total (x s ,y s ,t)=h xs_to_xg (x s ,y s ,t)+h short (x s ,y s ,t)

[0182] Based on this, the tension wave sea surface fluctuation height is superimposed on the gravity wave sea surface slope to generate the reconstructed sea surface fluctuation height. After the reconstructed sea surface, the sea surface range is 128×128 and the grid size is 512×512. s ,y s ) The sea surface fluctuation height value h total (x s ,ys ,t).

[0183] Step 6: Given the total duration T of the simulated sea surface total =1024×Δt, Δt means the time sampling interval is 0.005s, which is equivalent to taking a static snapshot of the sea surface sample every 0.005 seconds. The time variation factor t=0.005n, n=1,2,3…1024 is substituted into the generation of tension wave sea surface and gravity wave sea surface respectively, and the actual sea surface geometric model is established. The 1024 sets of sea surface models finally obtained can be used as the subsequent time-varying sea surface electromagnetic scattering input files.

[0184] Step 7: The dielectric constant of seawater is a complex function of the electromagnetic wave frequency, the temperature of seawater and the salinity of seawater. The dielectric constant of seawater in the sea area is corrected according to the temperature and salinity based on the common dielectric constant model. The double-scale superposition of all surface element electromagnetic scattering contributions is used to obtain the mean sea clutter amplitude (sea surface backscattering coefficient) under given multi-physical field parameters in the selected calculation sea surface area.

[0185] Step 8: Based on the Num groups of multi-physics field ocean environmental parameters obtained in step 1, 1024 groups of time-varying sea surface geometry models are generated for each group of multi-physics field ocean environmental parameters, and the corresponding mean sea clutter amplitude is obtained by using the surface element dual-scale algorithm. The mean sea clutter amplitude corresponding to the Num groups of multi-physics field ocean environmental parameters can be obtained, and the sea clutter characteristics under the actual ocean environmental parameters of the sea area can be analyzed.

[0186] The effect of the present invention is further described below through simulation experiments:

[0187] The simulation parameters are set as follows: The European Mesoscale Meteorological Satellite Database (ERA-Interim) is used to extract the marine environmental elements of the Yellow Sea (34°N, 122.5°E) at 12:00 on January 8, 2017 as an example of high sea conditions (level 5): wind speed 9.82m / s, wind direction 298.76°, wave height 1.61m, wave direction 292.24°, and wave period 5.02s, generating 1024 sets of sea surface geometry samples. The radar incident wave frequency is 10.0GHz in the X-band, and the simulation Figure 2 The calculation results of the mean values ​​of different polarization amplitudes are given. In addition, the simulation Figure 3 A scatter plot of the calculated results of the mean VV polarization amplitude in the Yellow Sea in January is given, which shows that it is very similar to the actual measured value.

[0188] Conclusion of simulation analysis: For the electromagnetic scattering echo of the sea surface in a given sea area, the actual sea surface geometry modeling method of the multi-physics field ocean environment parameters based on satellite data of the present invention is used, combined with the sea surface electromagnetic scattering theory to simulate the mean sea clutter amplitude. The result can fully consider the influence of the comprehensive effect of multi-physics fields on the sea surface electromagnetic scattering, and the simulation result is very similar to the measured value.

[0189] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for modeling actual sea surface geometry based on multi-physics field ocean environment parameters, characterized by: The steps include: Step 1: Select the ocean area of ​​interest and obtain the multi-physics field ocean environment parameters of the area, including the meridional wind speed u at the location 10 , zonal wind speed v 10 , effective wave height H s , average wave direction φ wave , average wave period Initial wave direction φ′ wave and temperature T sea ; Calculate the comprehensive wind speed U 10 and wind direction φ wind ; and for the initial wave direction φ′ wave Perform conversion processing to obtain the average wave direction φ wave ; Step 2: Calculate and synthesize wind speed U 10 and wind direction φ wind The related tension wave energy spectrum E short (k,φ), set the tension wave sea surface range and segmentation accuracy, calculate the tension wave sea surface fluctuation height h short (x s ,y s ,t); Step 3: Calculate the effective wave height H s , average wave direction φ wave , average wave period The associated gravitational wave energy spectrum S g (f,φ), set the gravity wave sea surface range and segmentation accuracy, and calculate the gravity wave sea surface comprehensive fluctuation height h gravity (x g ,y g ,t); Step 4: Ensure that the number of grids for the tension wave sea surface is greater than the number of grids for the gravity wave sea surface, and that the gravity wave sea surface range is greater than the tension wave sea surface range. Superimpose the tension wave sea surface fluctuation height in step 2 on the gravity wave sea surface bin according to the slope of the gravity wave sea surface bin, and calculate the comprehensive sea surface fluctuation height h total (x s ,y s ,t), realize the actual sea surface geometry modeling of multi-physics field ocean environment parameters; In the step 4, the method of superimposing the tension wave sea surface fluctuation height on the gravity wave sea surface bin according to the gravity wave sea surface bin slope is: S1, according to the tension wave sea surface grid number M s and N s , superimpose the tension wave on the gravity wave sea surface; the position of the tension wave sea surface element relative to the gravity wave sea surface can be determined by the following formula (L xs_to_xg , L ys_to_yg ): L xs_to_xg =int(x s / Δx g )×Δx g ; L ys_to_yg =int(y s / Δy g )×Δy g Where, L xs_to_xg is the position of the tension wave sea surface relative to the gravity wave sea surface along the wind direction; L ys_to_yg is the position of the tension wave sea surface relative to the gravity wave sea surface perpendicular to the wind direction; int() is to get integer; S2, determine the coordinates of the three points of the face element according to the face element position (x sg1 ,y sg1 ,z sg1 ), (x sg2 ,y sg2 ,z sg2 ), and (x sg3 ,y sg3 ,z sg3 ), where z sg1 、z sg2 、z sg3 They represent the sea surface coordinates of gravity waves (x sg1 ,y sg1 )、(x sg2 ,y sg2 )、(x sg3 ,y sg3 ) to obtain the coordinates of the center point of the surface element (x sg_center ,y sg_center ,z sg_center ), calculate the relative height h of the tension wave sea surface relative to the center of the bin xs_to_xg ; The tension wave sea surface fluctuation height is superimposed according to the gravity wave sea surface slope to generate the reconstructed sea surface fluctuation height, and the sea surface range is obtained as L x_g ×L y_g , the mesh size is M s ×N s The superimposed wave sea surface coordinates of each point (x s ,y s ) The comprehensive height of the sea surface h total (x s ,y s ,t); In S2, the relative fluctuation height h of the tension wave sea surface relative to the center of the surface element xs_to_xg for: h xs_to_xg =z sg_center +(x s -x sg_center )×Z x +(y s -y sg_center )×Z y In the formula, Z x and Z y are the slopes of the sea surface elements along the wind direction and perpendicular to the wind direction of the gravity wave sea surface respectively; The comprehensive sea surface fluctuation height value h total (x s ,y s ,t) is: h total (x s ,y s ,t)=h xs_to_xg (x s ,y s ,t)+h short (x s ,y s ,t)。 2. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 1 is characterized in that: In the step 1, the multi-physics field ocean environment parameters of the European Mesoscale Meteorological Satellite reanalysis data are used to obtain the meridional wind speed u at 10 meters above the sea surface in the sea area. 10 , zonal wind speed v 10 , effective wave height H s , average wave direction φ wave , average wave period Average wave direction φ wave and temperature T sea .

3. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 2 is characterized in that: The comprehensive wind speed U 10 for Wind direction φ win is φ wind =arctan(v 10 / u 10 ).

4. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 3 is characterized in that: Initial wave direction φ′ wave The range is 0°-360°; the average wave direction φ wave The conversion formula is:

5. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 4 is characterized in that: In step 2, the tension wave energy spectrum E short The calculation method of (k,φ) is: In the formula, F m It is the Elfouhaily high frequency shortwave action function; D(k,φ,φ wind ) is the Cosine power law directional distribution function; Δ(k) is the Elfouhaily adverse crosswind scaling factor; k is the discrete value of the sea surface wave number; φ is the discrete value of the observed sea surface azimuth; u f is the integrated wind speed U 10 associated sea surface friction wind speed; c is the speed of light, take 3×10 8 m / s; c m is a constant, c m =0.23m / s.

6. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 5 is characterized in that: In step 2, the method for setting the tension wave sea surface range and segmentation accuracy is: Set the tension wave sea surface range to a rectangular area with a side length of L along the wind direction. x_s , the length of the side perpendicular to the wind direction is L y_s ; Side length L x_s The number of grid divisions is M s , along the side length L y_s The number of grid divisions is N s ; then the tension wave sea surface along L x_s The segmentation accuracy of the direction is Δx s =L x_s / M s ; Along L y_s The segmentation accuracy of the direction is Δy s =L y_s / N s ; Height of tension wave sea surface fluctuation h short (x s ,y s ,t) is calculated as: Where t is any time; x s is the coordinate along the wind direction; x s =(m-1)Δx s ; m=1,2,…M s y s is the coordinate of the vertical wind direction; y s =(n-1)Δy s ; n=1,2,…N s ; E short (k,φ) is the tension wave energy spectrum; i is the discrete value of the sea surface wave number; j is the discrete value of the sea surface direction angle; M is the number of sampling points of the wave number; N is the number of sampling points of the direction angle; Δω i is the discrete interval of angular frequency; Δφ j is the discrete interval of the direction angle; k i ,ω i ,φ j and φ ij (seed) respectively correspond to the wave number, angular frequency, direction angle and initial phase of the superimposed wave; and satisfy g is the acceleration due to gravity; Get the sea surface range as L x_s ×L y_s , the mesh size is M s ×N s The tension wave sea surface coordinates each point (x s ,y s ) The sea surface fluctuation height value h short (x s ,y s ,t).

7. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 6 is characterized by: In step 3, the gravitational wave energy spectrum S g (f,φ) is: Where f is the sea surface wave frequency; φ is the discrete value of the observed sea surface azimuth; D(f,φ,φ wave ) is the Cosine power law directional distribution function; f is the frequency, g is the acceleration due to gravity; k is the discrete value of the sea surface wave number; k m Take 370 as the constant.

8. The actual sea surface geometry modeling method based on multi-physical field ocean environment parameters according to claim 7 is characterized in that: In step 3, the method for setting the gravity wave sea surface range and segmentation accuracy is: The sea surface range of gravity waves is a rectangular area with a side length of L along the wind direction. x_g , the length of the side perpendicular to the wind direction is L y_g ; Side length L x_g The number of grid divisions is M g , along the side length L y_g The number of grid divisions is N g ; then the tension wave sea surface along L x_g The segmentation accuracy of the direction is Δx g =L x_g / M g ; Along L y_g The segmentation accuracy of the direction is Δy g =L y_g / N g ; In order to realize the normal superposition of gravity waves and tension waves, L x_g ≥L x_s and L y_g ≥L y_s , and M g <M s and N g >N s ; The linear superposition method is used to calculate the coordinates of any point (x g ,y g ) is the height of the gravity wave sea surface fluctuation h gravity (x g ,y g ,t) is: In the formula, x g is the coordinate along the wind direction; x g =(m-1)Δx g ,m=1,2,…M g ; y g is the coordinate of the vertical wind direction; y g =(n-1)Δy g ,n=1,2,…N g ; S g (f,φ) gravity wave energy spectrum; i is the discrete value of the sea surface wave number; j is the discrete value of the sea surface direction angle; M is the number of sampling points of the wave number; N is the number of sampling points of the direction angle; Δω i is the discrete interval of angular frequency; Δφ j is the discrete interval of the direction angle; f i ,ω i ,φ j and φ ij (seed) corresponds to the frequency, angular frequency, direction angle and initial phase of the superimposed wave, and satisfies Where g is the acceleration due to gravity; Get the sea surface range as L x_g ×L y_g , the mesh size is M g ×N g The gravity wave sea surface coordinates of each point (x g ,y g ) The sea surface fluctuation height value h gravity (x g ,y g ,t).

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