Calculation method of sediment flux in estuaries during typhoon period

Abstract

The present invention relates to a method for calculating estuarine sediment flux during typhoon influence. The method is applicable to the field of estuarine water-sediment dynamics analysis. Based on the hydrodynamic module of the SCHISM model system, the present invention couples the sediment dynamics module with the wave dynamics module to establish a three-dimensional water-sediment-wave coupling model. Verification results show that although the model can well reproduce the high-frequency variation process of water-sediment dynamics in the Yangtze River Estuary under different weather conditions, it quantitatively underestimates the seasonal differences in SSC. To overcome the problem of seasonal differences in SSC, the present invention uses surface SSC inverted by GOCI remote sensing to correct the numerical simulation results of the model. After correction, the errors of the summer and winter SSC simulation results are reduced by an average of 36% and 38% compared with the measured errors, thereby improving the overestimation of summer SSC and the underestimation of winter SSC. The accuracy of the SSC results is significantly improved. Based on the corrected SSC results, more accurate sediment flux results with high temporal and spatial resolution will be obtained.

Description

Technical Field

[0001] The present invention relates to a method for calculating estuary sediment flux during a typhoon period, and is applicable to the field of estuary water and sediment dynamics analysis. Background Art

[0002] Although typhoons last for a short time (usually a few days), the huge wind energy generated during typhoons is transmitted to the water body in the form of surface shear stress, which on the one hand causes the wave energy on the sea surface to increase, and on the other hand forms strong wind-driven currents that increase the flow velocity, causing a large amount of sediment to be re-suspension, transported with the current and eventually settled, causing problems such as channel siltation or coastal scouring. Therefore, typhoons have a very critical impact on estuary sediment transport and topographic changes.

[0003] Although a large number of scholars have studied the movement of water and sediment in the Yangtze River Estuary during typhoons, due to the severe sea conditions during typhoons and extremely limited measured data, they can only focus on one to three typhoons or study only local points in the estuary. As a result, current research has difficulty in accurately quantitatively analyzing the sediment flux (including direction and size) in the entire estuary under the influence of typhoons, and it is also difficult to systematically analyze the differences and similarities in the impact of typhoons with different paths on the sediment dynamics in the estuary. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a method for calculating the sediment flux in an estuary during a typhoon period is provided.

[0005] The technical solution adopted by the present invention is: a method for calculating estuary sediment flux during typhoon influence, characterized by comprising:

[0006] Obtain hydrological data, atmospheric data, and GOCI water color images for the sample period of the estuary to be analyzed. The sample period includes at least one typhoon that can affect the estuary area.

[0007] The hydrological and atmospheric data within the sample period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary suspended sediment concentration (SSC) I;

[0008] Based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life, the regional average wind speed in the estuary area is calculated, and the typhoon impact period is determined from the sample time period based on the regional average wind speed;

[0009] The surface SSC of the estuary during the typhoon period was obtained by inverting the GOCI water color image during the typhoon period. The vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC. The hourly vertical distribution characteristics of the estuary SSC during the typhoon period were obtained.

[0010] Based on the hourly vertical distribution characteristics of SSC in the estuary during the typhoon period, the hourly vertical distribution of sediment flux during the typhoon period was calculated.

[0011] Based on the vertical distribution of hourly sediment flux during the typhoon period, the sediment flux during the typhoon period was calculated;

[0012] The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

[0013] The method of calculating the regional average wind speed of the estuary area based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life period within the sample time period, and selecting the typhoon impact period from the sample time period based on the regional average wind speed, includes:

[0014] Based on the ERA5 wind field during the non-typhoon life period, the regional average wind speed in the area where the estuary is located during the non-typhoon life period is calculated;

[0015] The ERA5 wind field is corrected based on the typhoon track, typhoon central pressure and central maximum wind speed during the typhoon's life, and the hourly regional average wind speed of the estuary area during the typhoon's life is calculated based on the corrected ERA5 wind field;

[0016] Determine the critical wind speed based on the hourly regional average wind speed during the typhoon's lifetime and the regional average wind speed during non-typhoon periods, so that the difference between the average of all wind speeds less than the critical wind speed among the hourly regional average wind speeds during the typhoon's lifetime and the regional average wind speed during non-typhoon periods is within a preset range;

[0017] When the regional average wind speed during the life of a typhoon is greater than the critical wind speed, the corresponding moment of the regional average wind speed is classified as within the typhoon impact period.

[0018] The ERA5 wind field correction based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life cycle includes:

[0019] ;

[0020] ;

[0021] ;

[0022] ;

[0023] in, is the wind speed; is the air pressure; the subscripts m, tc, mov, and ERA5 refer to the wind speed of the synthetic wind field, typhoon gradient wind field, typhoon transition wind speed, and initial ERA5 wind field, respectively; e, c, and n are parameters;

[0024] ;

[0025] ;

[0026] in, 、 The typhoon's central and peripheral pressures; is the distance from the typhoon center; is the maximum wind speed radius; is the air density: Determines the intensity and peakness of typhoons;

[0027] ;

[0028] ;

[0029] ;

[0030] in, is the latitude of the calculation point;

[0031] ;

[0032] The hydrodynamic module uses the SCHISM three-dimensional baroclinic model; the sediment dynamic module uses the three-dimensional sediment transport model SED3D; and the wave dynamic module uses the WWMⅢ model.

[0033] The three-dimensional sediment transport model SED3D includes:

[0034] ;

[0035] in, is the water density after considering the influence of SSC; The water density output by the state equation in the hydrodynamic module; is the total sediment component fraction; For the The concentration of each sediment component; For the Sediment density of each component.

[0036] The WWMⅢ model includes:

[0037] ;

[0038] in, is the radiation stress, which is used to calculate other forcing terms that affect the fluid momentum , Used to calculate the momentum equation in the hydrodynamic module; is the Cartesian coordinate system in the horizontal direction; 、 and Components of the radiation stress tensor defined for the spectrum.

[0039] The surface SSC of the estuary during the typhoon period is obtained based on the GOCI water color image inversion during the typhoon period, and the estuary SSC vertical distribution feature I corresponding to the time and space is corrected based on the inverted surface SSC to obtain the hourly estuary SSC vertical distribution feature II during the typhoon period, including:

[0040] Based on the GOCI water color image inversion during the typhoon period, the average value of the surface SSC in the estuary area during the typhoon period was obtained, and the average value of the surface SSC of the estuary SSC vertical distribution characteristics corresponding to time and space was used to determine the surface correction coefficient;

[0041] Based on the surface layer correction coefficient and combined with the SSC vertical distribution regression model, the correction coefficients of the remaining layers in the estuary SSC vertical distribution characteristics are determined;

[0042] Based on the correction coefficient corresponding to each layer of the estuary SSC vertical distribution characteristics, each layer in the estuary SSC vertical distribution characteristics I was corrected respectively to obtain the estuary SSC vertical distribution characteristics II.

[0043] Based on the surface layer correction coefficient and combined with the SSC vertical distribution regression model, the correction coefficients of the remaining layers in the estuary SSC vertical distribution characteristics are determined, including:

[0044] ;

[0045] ;

[0046] in, is the surface correction factor; is the average surface SSC value retrieved by GOCI during the typhoon period; For Vertical distribution characteristics of SSC in the estuary corresponding to time and space I. Average value of surface SSC; is the correction coefficient of the wth layer; is the fitting parameter of the w-th layer.

[0047] A system for calculating estuary sediment flux during typhoon period, characterized by comprising:

[0048] The data acquisition module is used to obtain hydrological data, atmospheric data and GOCI water color images within a sample time period of the estuary to be analyzed, and the sample time period includes at least one typhoon that can affect the estuary area;

[0049] The numerical simulation module is used to input the hydrological data and atmospheric data within the sample time period into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC I;

[0050] The time period selection module is used to calculate the regional average wind speed in the estuary area based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life period, and determine the typhoon impact period from the sample time period based on the regional average wind speed;

[0051] The coefficient correction module is used to obtain the surface SSC of the estuary area during the typhoon period based on the GOCI water color image inversion during the typhoon period, and to correct the corresponding time and space vertical distribution characteristics of the estuary SSC based on the inverted surface SSC I to obtain the hourly vertical distribution characteristics of the estuary SSC during the typhoon period II;

[0052] Flux calculation module I is used to calculate the hourly vertical distribution of sediment flux during the typhoon period based on the hourly vertical distribution characteristics of SSC in the estuary during the typhoon period II;

[0053] Flux calculation module II is used to calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period;

[0054] The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

[0055] A method for analyzing the impact of typhoons with different paths on estuary sediment transport and topographic changes, characterized by comprising:

[0056] Obtain hydrological data, atmospheric data, and GOCI water color images for the sample period of the estuary to be analyzed. The sample period includes at least one typhoon that can affect the estuary area.

[0057] Based on the typhoon path, typhoon center pressure and center maximum wind speed in the atmospheric data during the typhoon life, the regional average wind speed in the estuary area is calculated, and the sample time period is divided into typhoon-affected period and non-typhoon-affected period based on the regional average wind speed;

[0058] The hydrological and atmospheric data within the sample period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC during the typhoon-affected period and the non-typhoon-affected period.

[0059] The surface SSC of the estuary area during the typhoon-affected period and the non-typhoon-affected period was retrieved based on the GOCI water color image. The vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC. The hourly vertical distribution characteristics of the estuary SSC during the typhoon-affected period and the non-typhoon-affected period were obtained.

[0060] Based on the hourly vertical distribution characteristics of estuary SSC during typhoon-affected and non-typhoon-affected periods, the hourly vertical distribution of sediment flux during typhoon-affected and non-typhoon-affected periods was calculated.

[0061] Calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period;

[0062] Based on the hourly vertical distribution of sediment flux during the non-typhoon period, the sediment flux during normal weather period is calculated;

[0063] Based on the sediment flux during typhoon-affected and non-typhoon-affected periods, the contribution of typhoons to long-term sediment transport and topographic changes is measured;

[0064] The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

[0065] A storage medium stores a computer program that can be executed by a processor, wherein the computer program implements the steps of the method when executed.

[0066] A computing and analyzing device comprises a memory and a processor, wherein the memory stores a computer program executable by the processor, and is characterized in that the steps of the method are implemented when the computer program is executed.

[0067] The beneficial effects of the present invention are as follows: the present invention couples the hydrodynamic module with the sediment dynamic module and the wave dynamic module of the SCHISM model system to establish a three-dimensional water-sediment-wave coupling model. The verification results show that although the model can well reproduce the high-frequency change process of water and sediment dynamics in the Yangtze River Estuary under different weather conditions, it quantitatively underestimates the seasonal differences in SSC. In order to overcome the problem of seasonal differences in SSC, the present invention uses the surface SSC inverted by GOCI remote sensing to correct the numerical simulation results of the model. After correction, the errors of the SSC simulation results in summer and winter are reduced by an average of 36% and 38% compared with the measured errors, which improves the overestimation of SSC in summer and the underestimation of SSC in winter. The accuracy of the SSC results is significantly improved. Based on the corrected SSC results, more accurate sediment flux results with high temporal and spatial resolution will be obtained.

[0068] The present invention not only has the advantages of high temporal and spatial resolution of numerical models, but also has the accurate characteristics of GOCI remote sensing inversion data results, avoiding the technical limitations of using remote sensing or numerical models alone, and proposing a new technical route and research method for calculating accurate, high temporal and spatial resolution sediment flux in estuaries.

[0069] The present invention divides the actual impact period of typhoon on the Yangtze River estuary based on the regional average wind speed during non-typhoon periods and typhoon periods, so as to accurately calculate the impact of typhoon on sediment flux.

[0070] The present invention determines the critical wind speed based on the hourly regional average wind speed during the life of a typhoon and the regional average wind speed during non-typhoon periods, so that the difference between the average value of all wind speeds less than the critical wind speed in the hourly regional average wind speed during the life of a typhoon and the regional average wind speed during non-typhoon periods is within a preset range, thereby scientifically and accurately dividing the actual impact period of the typhoon on the estuary.

[0071] To accurately describe the increase in SSC during typhoons and improve the accuracy of sediment flux calculations during typhoons, this paper uses the average value of surface SSC retrieved from GOCI during the typhoon period to correct the surface SSC simulation results during typhoon periods. If GOCI data during typhoon periods are limited, consideration can be given to expanding the use of GOCI data throughout the typhoon's life cycle.

[0072] Commonly used reanalysis wind fields such as ERA5 and NCEP have errors in typhoon weather, such as typhoon center position offset and low typhoon intensity. The present invention calculates the typhoon model wind field (including transition wind field and gradient wind field) based on typhoon measured path, central air pressure, maximum wind speed and other data, and combines it with the initial ERA5 wind field to obtain more accurate input wind field and numerical simulation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is a flow chart of the method for calculating estuary sediment flux during typhoon influence in Example 1.

[0074] Figure 2 Comparison of the seasonal average SSC vertical distribution curves in the Yangtze River Estuary; (a) winter, (b) spring, (c) summer, and (d) autumn (the red dots are measured results. The black line is the regression equation fitting result, and the blue and red lines are the fitting results of the regression model established based on the measured data and numerical model results, respectively). DETAILED DESCRIPTION

[0075] Example 1: Figure 1 As shown, this embodiment is a method for calculating estuary sediment flux during a typhoon, which specifically includes the following steps:

[0076] S1. Obtain measured and reanalyzed hydrological, atmospheric, and topographic data and GOCI water color images within a sample period for the region where the estuary to be analyzed is located (in this case, the Yangtze River Estuary). The sample period includes at least one typhoon that can affect the estuary region.

[0077] S2. Based on the typhoon path, typhoon center pressure and center maximum wind speed during the life of the typhoon, calculate the regional average wind speed in the estuary area, and select the typhoon impact period from the sample time period based on the regional average wind speed.

[0078] This example divides the actual period of typhoon impact on the Yangtze River Estuary based on the regional average wind speed during non-typhoon periods and typhoon periods, and is used to accurately calculate the impact of typhoons on sediment flux. The specific steps are as follows:

[0079] 1) Based on the typhoon track dataset of the China coast, the sample period is divided into two periods: the period when typhoons are present in the Northwest Pacific (typhoon life period) and the period when typhoons are absent (non-typhoon period);

[0080] 2) Based on the atmospheric data during the non-typhoon period, the time series of the regional average ERA5 wind speed in the Yangtze River Estuary during the non-typhoon period (based on the results corrected by the Holland typhoon field model) is calculated and recorded as ;

[0081] Based on the relationship between the typhoon path and the Yangtze River Estuary, the distance between the typhoon center and the Yangtze River Estuary is determined. Combined with the corresponding typhoon center pressure and center maximum wind speed, the hourly regional average wind speed at the Yangtze River Estuary during the typhoon's life is calculated. ;

[0082] 3) The average wind speed in the Yangtze River Estuary during the typhoon period Summarize and arrange in ascending order to find a critical wind speed , making The average of all wind speeds is approximately equal to .

[0083] 4) When At this time, it is believed that the typhoon has a significant impact on the Yangtze River Estuary, and the corresponding time of the average wind speed in the area is classified as within the typhoon impact period.

[0084] S3. Input the measured and reanalyzed data, including hydrological data, atmospheric data, and topographic data, within the sample period into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC I.

[0085] This embodiment uses a three-dimensional water-sediment-wave coupling model for numerical simulation. The three-dimensional water-sediment-wave coupling model is established based on the hydrodynamic module coupled with the sediment dynamic module and the wave dynamic module of the SCHISM model system.

[0086] In this example, the hydrodynamic module uses a three-dimensional baroclinic model. Based on the Boussinesq and static assumptions, the governing equations, including the continuity equation (1), momentum equation (2), transport equation (3), and state equation (4), are as follows:

[0087] (1)

[0088] (2)

[0089] (3)

[0090] (4)

[0091] in, is the horizontal gradient operator; is the horizontal Cartesian coordinate system, is the vertical coordinate pointing vertically upward; is the material derivative; is the horizontal flow velocity, which includes , the components in the y direction v(x,y,z,t) ,unit ; is the vertical flow velocity, unit ; t is time, is the acceleration due to gravity, unit ; is the free elevation surface, unit ; is the water depth measured from a fixed datum, in units ; is the vertical eddy viscosity coefficient and vertical turbulent diffusion coefficient, with units of ; is the tracer concentration, such as salinity, temperature, suspended sediment concentration, etc.; represents the horizontal diffusion term, unit ; is the mass source / sink term, unit ; is the water density, including salinity S, temperature T, hydrostatic pressure The impact of the unit ; Refers to other forcing terms that affect fluid momentum, including baroclinic gradient force, horizontal viscosity force, Coriolis force, earth tidal potential, atmospheric pressure, and radiation stress. The expression is as follows:

[0092] (5)

[0093] in, is the horizontal eddy viscosity coefficient, unit ; is the Coriolis force parameter; is the z-axis unit vector; is the reference water density, unit ; is atmospheric pressure; is the effective soil elastic factor; is the Earth's tidal potential.

[0094] The closed mode of the model turbulence adopts the GLS method, which is a two-equation model including turbulent kinetic energy ( ) equation and universal scale ( ) equation, the expression is as follows:

[0095] (6)

[0096] (7)

[0097] in, and is the vertical turbulent diffusion coefficient; 、 and are model parameters; is a wall approximation function; and are the shear frequency and buoyancy frequency, respectively; is the dissipation rate. General scale is defined as:

[0098] (8)

[0099] in, ; is the turbulent mixing length; parameter 、 and Different combinations of will form different turbulence closure models, such as Model, Model, M-Y2.5 model, etc. Finally, the vertical eddy viscosity coefficient and vertical turbulent diffusion coefficient The calculation formula is:

[0100] (9)

[0101] (10)

[0102] Among them, the Schmidt number and are model parameters; and It is a stable function to measure the degree of water stratification, and its calculation formula is:

[0103] (11)

[0104] (12)

[0105] in, is the gradient Richardson number related to the water density.

[0106] In this example, the sediment dynamics module uses the three-dimensional sediment transport model SED3D. Developed from the Community Sediment Transport Model, SED3D can be coupled with the SCHISM hydrodynamics module and uses the same mesh and time step. SED3D simultaneously accounts for the movement of both cohesive and non-cohesive sediment components, including key physical processes such as convection, diffusion, sedimentation in the water column, bed deposition, and resuspension.

[0107] SED3D calculates the spatiotemporal distribution of SSC by solving the convection-diffusion equation with additional consideration of sediment source and sink terms. The governing equations and boundary conditions are as follows:

[0108] (13)

[0109] (14)

[0110] (15)

[0111] in, For the The concentration of sediment components, unit ; 、 For the The sedimentation flux and erosion flux of each component represent the sediment exchange between the water column and the bed surface; It is The settling velocity of each sediment component, unit Sediment settling velocity is the core physical quantity of sediment dynamic characteristics, affecting the vertical distribution of sediment, bed deposition and scour. The Soulsby method is used in the model to calculate sediment settling velocity, and the expression is as follows:

[0112] (16)

[0113] (17)

[0114] in, 、 Respectively The median particle size and dimensionless particle size of each sediment component, unit ; V is the kinematic viscosity coefficient of water, unit : For the The relative density of each component, For the Sediment density of each component, unit After coupling the sediment model, the state equation can take into account the effect of SSC on water density:

[0115] (18)

[0116] in, Considering the salinity S, temperature , hydrostatic pressure The water density after the influence of is the result of formula (4), the unit is ; is the total sediment fraction.

[0117] The sediment exchange between the water body and the bed is calculated in the lowest grid of the model, and the particle composition of the bed is updated accordingly. The calculation formula is:

[0118] (19)

[0119] in, For the The concentration of each sediment component in the bottom grid. ) According to Ariathurai and Arulanandan, the expression is:

[0120] (20)

[0121] (twenty one)

[0122] in, For the Bed scour rate of each sediment component, unit: kg / / s, range of variation ; is the porosity of the bed surface (dimensionless), with a default value of 0.4; For the Volume fraction of each sediment component (dimensionless); is the bottom shear stress under wave-current interaction, unit 、 Respectively The critical erosion stress of each sediment component and the dimensionless critical erosion shear stress, unit . According to Soulsby and Whitehouse calculations:

[0123] (twenty two)

[0124] In addition, according to Winterwerp's suggestion, the model does not set the critical settlement stress, and the sediment is always in a settling state.

[0125] In this embodiment, the wave dynamics module uses the WWMIII wave dynamics model. The WMWII wave dynamics module is one of the commonly used third-generation wave models, developed by Roland et al. based on the model of Hsu et al. WWMII uses an unstructured grid and solves the Eulerian approximation of the wave equation. It considers various physical processes, such as wave propagation and refraction, wind-induced waves, and wave dissipation and breakup. It is widely used in nearshore areas, estuaries, and lakes. In a Cartesian coordinate system, the governing equations of WWMIII can be written as:

[0126] (twenty three)

[0127] in, is the wave action density spectrum, is the relative frequency, The first term on the left in Eq. (23) represents the change of the wave action N over time, and the second term on the left represents the change in geographic space. The third and fourth items on the left represent the propagation in the frequency space. , spectral distribution direction space The right side of the formula Represents the energy source and sink terms, including wind energy input, four-wave interaction, three-wave interaction, white cap dissipation, wave breaking, and bottom friction.

[0128] After the SCHISM hydrodynamic module is coupled with the wave module, the radiation stress in Eq. (5) is It will be calculated according to the following method, as follows:

[0129] (twenty four)

[0130] in, 、 and Components of the radiation stress tensor defined for the spectrum. In addition, assume that the radiation stress Remains unchanged vertically.

[0131] S4. The surface SSC of the estuary during the typhoon period is obtained by inverting the GOCI water color image during the typhoon period, and the vertical distribution characteristics of the estuary SSC corresponding to time and space are corrected based on the inverted surface SSC.

[0132] To accurately describe the increase in SSC during typhoons and improve the accuracy of sediment flux calculations during typhoons, this example uses the average value of surface SSC retrieved from GOCI during the typhoon period to correct the surface SSC simulation results during the typhoon period. If GOCI data during the typhoon period are limited, consideration may be given to expanding the use of GOCI data from the typhoon's life cycle.

[0133] In this embodiment, the vertical correction coefficient is calculated to correct the SSC numerical simulation results at different water depths ( The subscripts i, w, and t represent the point number, vertical layer number, and time, respectively. represents the surface, t= represents the average value during the typhoon impact period).

[0134] S4-1. Determine the surface correction coefficient based on the average value of surface SSC during the typhoon period, inverted from the GOCI water color image, and the average value of surface SSC in the vertical distribution feature I of the estuary SSC corresponding to time and space.

[0135] Due to the data loss caused by intermittent cloud cover, the surface correction factor in this embodiment ( ) using the surface SSC inverted by GOCI during the typhoon period ( , i represents the point, w is the number of water depth layers) and the vertical distribution characteristics of the estuary SSC output in step S3 to determine the surface SSC results corresponding to time and space ( ) is calculated as follows:

[0136] (25)

[0137] S4-2. Based on the surface layer correction coefficient and combined with the SSC vertical distribution regression model, determine the correction coefficients of the remaining layers in the estuary SSC vertical distribution characteristics.

[0138] like Figure 2 As shown by the middle red line, the mathematical model established in this embodiment can well simulate the vertical distribution characteristics of SSC in the Yangtze River Estuary. Therefore, this example establishes an SSC vertical distribution regression model based on the hourly SSC simulation results of all study sections.

[0139] First, the simulation results are vertically divided according to the relative water depth. (0 and 1 represent the bottom layer and the surface layer, respectively) are divided into 21 sections, with an interval of 0.05 times the water depth. Then, the SSC of each layer in the simulation results and the surface SSC are fitted to establish an exponential relationship (26), and the fitting parameters of each layer are obtained. and It should be noted that, for the sake of simplicity of calculation, and It is only related to the vertical number of layers, but not to time and horizontal position.

[0140] (26)

[0141] Based on formula (25), if the surface SSC is calculated based on GOCI data ( ) after correction (i.e. multiplying by the correction coefficient ), in order to keep the corrected SSC in the same vertical distribution pattern, the SSC below the surface needs to be corrected according to formula (27), and then the correction coefficient of the SSC below the surface is calculated as formula (28).

[0142] (27)

[0143] in, is the corrected SSC.

[0144] (28)

[0145] S4-3. Based on the correction coefficients corresponding to each layer of the estuary SSC vertical distribution characteristics, each layer in the estuary SSC vertical distribution characteristics I is corrected respectively to obtain the hourly estuary SSC vertical distribution characteristics II during the typhoon period.

[0146] After obtaining the SSC vertical distribution regression model through the above process, the hourly estuary SSC vertical distribution characteristics of each layer section output by the numerical model are multiplied by the correction coefficient , to obtain the corrected SSC of each layer.

[0147] S5. Based on the hourly vertical distribution characteristics of SSC in the estuary during the typhoon period, calculate the hourly vertical distribution of sediment flux.

[0148] Sediment flux at each section based on hourly flow velocity (derived from the numerical model) and the corrected vertical distribution characteristics of the estuary SSC The vertical distribution calculation formula is:

[0149] (29)

[0150] in, 、 They are the hourly flow velocity perpendicular to the cross section and the flow area respectively.

[0151] S6. Calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period.

[0152] Based on the hourly sediment flux, the sediment flux on the corresponding time scale (such as month, season, year, typhoon period, etc.) of each section is calculated by integration on different time scales. for:

[0153] (30)

[0154] Accurate wind forcing is a crucial prerequisite for improving the accuracy of calculating wave energy and sediment transport during typhoons. However, numerous studies have shown that commonly used reanalysis wind fields, such as those from ERA5 and NCEP, can exhibit errors in typhoon weather, such as typhoon center position offsets and underestimation of typhoon intensity. Therefore, when simulating typhoon conditions, the typhoon model wind field (including transition and gradient wind fields) is calculated based on data such as the typhoon's measured path, central pressure, and maximum wind speed. This is then combined with the initial ERA5 wind field to obtain more accurate input wind fields and numerical simulation results.

[0155] In this embodiment, the typhoon model wind field and the initial ERA5 wind field are superimposed in a certain proportion to form a new synthetic wind field. The specific calculation formula is:

[0156] (31)

[0157] (32)

[0158] (33)

[0159] (34)

[0160] in, is the wind speed; is the air pressure; the subscripts m, tc, mov, and ERA5 refer to the wind speed of the synthetic wind field, typhoon gradient wind field, typhoon migration wind speed, and initial ERA5 wind field, respectively; e, c, and n are parameters, where n is usually 4, 9, or 10.

[0161] The gradient wind field is obtained by cyclone balance and is calculated using the Holland typhoon model, which is based on the Schloemer index pressure distribution model and introduces new parameters. , obtained using the gradient wind field, the calculation expression is:

[0162] Air pressure equation:

[0163] (35)

[0164] Wind field equation:

[0165] (36)

[0166] in, 、 The typhoon center pressure and peripheral pressure, unit is Pa; is the distance from the typhoon center, in meters; is the maximum wind speed radius, in m; is the air density, unit : Determines the intensity and peakness of a typhoon, usually .

[0167] Parameter B and These are two important parameters for calculating the wind field of the typhoon model. (other parameters are fixed), The wind speed increases gradually at the typhoon center, while the wind speed decreases at locations farther from the typhoon center, so the wind field energy is more concentrated; on the contrary, the wind speed is more evenly distributed with distance. On the other hand, the wind speed increases gradually from the typhoon center to the outside. It reaches its maximum at , and then gradually decreases: and as The increase, The wind speed changes are more gradual.

[0168] This embodiment uses the following algorithm to calculate and , the formula is as follows:

[0169] (37)

[0170] (38)

[0171] (39)

[0172] in, is the latitude of the calculation point.

[0173] Another important component of the typhoon model wind field is the transitional wind field, which is caused by the typhoon's movement. This is considered to correct the circularly symmetric gradient wind field, creating a model wind field with asymmetric wind speeds along the typhoon's path. This is because the pressure gradient is larger to the right due to the influence of the subtropical high pressure, so wind speeds on the right side of the typhoon path are generally greater than those on the left. The transitional wind field is calculated as follows:

[0174] (40)

[0175] Example 2: This example is a system for calculating estuary sediment flux during typhoon influence, which specifically includes: a data acquisition module, a time period selection module, a numerical simulation module, a coefficient correction module, a flux calculation module I and a flux calculation module II, etc.

[0176] In this embodiment, the data acquisition module is used to obtain measured and reanalyzed data such as hydrological, atmospheric, and topographic data and GOCI water color images within a sample time period of the area where the estuary to be analyzed is located. The sample time period includes at least one typhoon that can affect the area where the estuary is located.

[0177] In this example, the time period selection module is used to calculate the regional average wind speed in the estuary area based on the typhoon path, typhoon center pressure and central maximum wind speed during the typhoon's life, and select the typhoon impact period from the sample time period based on the regional average wind speed.

[0178] In this embodiment, the numerical simulation module is used to input the measured and reanalyzed data such as hydrological data, atmospheric data, and topography within the sample period into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC I.

[0179] In this example, the coefficient correction module is used to obtain the surface SSC of the estuary area during the typhoon period based on the GOCI water color image inversion during the typhoon period, and to correct the corresponding time and space vertical distribution characteristics of the estuary SSC I based on the inverted surface SSC to obtain the hourly vertical distribution characteristics of the estuary SSC II during the typhoon period.

[0180] In this example, flux calculation module I is used to calculate the hourly vertical distribution of sediment flux during the typhoon period based on the hourly vertical distribution characteristics of SSC in the estuary during the typhoon period II.

[0181] In this embodiment, the flux calculation module II is used to calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period.

[0182] In this embodiment, the three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module coupled with the sediment dynamic module and the wave dynamic module of the SCHISM model system.

[0183] Example 3: This example is a storage medium on which a computer program that can be executed by a processor is stored. When the computer program is executed, the steps of the method for calculating the sediment flux in an estuary during a typhoon period in Example 1 are implemented.

[0184] Example 4: This example is a computing and analysis device having a memory and a processor. The memory stores a computer program that can be executed by the processor. When the computer program is executed, the steps of the method for calculating estuary sediment flux during typhoon influence in Example 1 are implemented.

[0185] Example 5: This example is a method for analyzing the impact of typhoons with different paths on estuary sediment transport and topographic changes, which specifically includes the following steps:

[0186] Obtain measured and reanalyzed data on hydrology, atmosphere, topography, and other aspects of the estuary within the sample period, as well as GOCI water color images. The sample period includes at least one typhoon that can affect the estuary.

[0187] Based on the typhoon path, typhoon center pressure and center maximum wind speed in the atmospheric data during the typhoon life, the regional average wind speed in the estuary area is calculated, and the sample time period is divided into typhoon-affected period and non-typhoon-affected period based on the regional average wind speed;

[0188] The measured and reanalyzed data, including hydrological data, atmospheric data, and topographic data, during the sample period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC during the typhoon-affected period and the non-typhoon-affected period.

[0189] The surface SSC of the estuary area during the typhoon-affected period and the non-typhoon-affected period was retrieved based on the GOCI water color image. The vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC. The hourly vertical distribution characteristics of the estuary SSC during the typhoon-affected period and the non-typhoon-affected period were obtained.

[0190] Based on the hourly vertical distribution characteristics of estuary SSC during typhoon-affected and non-typhoon-affected periods, the hourly vertical distribution of sediment flux during typhoon-affected and non-typhoon-affected periods was calculated.

[0191] Calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period;

[0192] Based on the hourly vertical distribution of sediment flux during the non-typhoon period, the sediment flux during normal weather period is calculated;

[0193] Based on the sediment flux during typhoon-affected and non-typhoon-affected periods, the contribution of typhoons to long-term sediment transport and topographic changes is measured.

[0194] In this embodiment, the three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module coupled with the sediment dynamic module and the wave dynamic module of the SCHISM model system.

[0195] Example 6: This example is a storage medium on which a computer program that can be executed by a processor is stored. When the computer program is executed, the steps of the method for analyzing the impact of typhoons with different paths on estuary sediment transport and terrain changes in Example 5 are implemented.

[0196] Example 7: This example is a computing and analysis device having a memory and a processor. The memory stores a computer program that can be executed by the processor. When the computer program is executed, the steps of the method for analyzing the impact of typhoons with different paths on estuary sediment transport and terrain changes in Example 5 are implemented.

Claims

1. A method for calculating estuary sediment flux during typhoon period, characterized in that: include: Obtain hydrological data, atmospheric data, and GOCI water color images for the sample period of the estuary to be analyzed. The sample period includes at least one typhoon that can affect the estuary area. The hydrological and atmospheric data within the sample period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC I; Based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life, the regional average wind speed in the estuary area is calculated, and the typhoon impact period is determined from the sample time period based on the regional average wind speed; The surface SSC of the estuary during the typhoon period was obtained by inverting the GOCI water color image during the typhoon period. The vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC. The hourly vertical distribution characteristics of the estuary SSC during the typhoon period were obtained. Based on the hourly vertical distribution characteristics of SSC in the estuary during the typhoon period, the hourly vertical distribution of sediment flux during the typhoon period was calculated. Based on the vertical distribution of hourly sediment flux during the typhoon period, the sediment flux during the typhoon period was calculated; The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

2. The method for calculating estuary sediment flux during typhoon period according to claim 1, characterized in that: The method of calculating the regional average wind speed of the estuary area based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life period within the sample time period, and selecting the typhoon impact period from the sample time period based on the regional average wind speed, includes: Based on the ERA5 wind field during the non-typhoon life period, the regional average wind speed in the area where the estuary is located during the non-typhoon life period is calculated; The ERA5 wind field is corrected based on the typhoon track, typhoon central pressure and central maximum wind speed during the typhoon's life, and the hourly regional average wind speed of the estuary area during the typhoon's life is calculated based on the corrected ERA5 wind field; Determine the critical wind speed based on the hourly regional average wind speed during the typhoon's lifetime and the regional average wind speed during non-typhoon periods, so that the difference between the average of all wind speeds less than the critical wind speed among the hourly regional average wind speeds during the typhoon's lifetime and the regional average wind speed during non-typhoon periods is within a preset range; When the regional average wind speed during the life of a typhoon is greater than the critical wind speed, the corresponding moment of the regional average wind speed is classified as within the typhoon impact period.

3. The method for calculating estuary sediment flux during typhoon period according to claim 2, characterized in that: The ERA5 wind field correction based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life cycle includes: pp m =p tc (1-e)+ep ERA5 e=c 4 / (1+c 4 ) c=r / (nR) in, is wind speed; p is air pressure; subscripts m, tc, mov, and ERA5 refer to the wind speeds of the synthetic wind field, typhoon gradient wind field, typhoon transition wind speed, and initial ERA5 wind field, respectively; e, c, and n are parameters; Among them, p c 、p n is the typhoon center pressure and peripheral pressure; r is the distance from the typhoon center; R max is the maximum wind speed radius; ρ a is the air density: B determines the intensity and kurtosis of the typhoon; R max =exp(-0.0511*ΔP 0.7515 +4.9213) B=1.881-0.00557R max -0.01295φ ΔP=(p n -p c ) / 100 Where, φ is the latitude of the calculation point; 4. The method for calculating estuary sediment flux during a typhoon according to claim 1, characterized in that: The hydrodynamic module uses the SCHISM three-dimensional baroclinic model; the sediment dynamic module uses the three-dimensional sediment transport model SED3D; and the wave dynamic module uses the WWMⅢ model.

5. The method for calculating estuary sediment flux during typhoon period according to claim 4, characterized in that: The three-dimensional sediment transport model SED3D includes: Wherein, ρ is the water density after considering the influence of SSC; ρ0 is the water density output by the state equation in the hydrodynamic module; N sed is the total sediment fraction; C i is the concentration of the i-th sediment component; ρ s,i is the sediment density of the i-th component.

6. The method for calculating estuary sediment flux during typhoon period according to claim 4, characterized in that: The WWMⅢ model includes: in, is the radiation stress, which is used to calculate other forcing terms that affect the fluid momentum Used to calculate the momentum equation in the hydrodynamic module; (x, y) is the Cartesian coordinate system in the horizontal direction; S xx 、S xy and S yy Components of the radiation stress tensor defined for the spectrum.

7. The method for calculating estuary sediment flux during typhoon period according to claim 1, characterized in that: The surface SSC of the estuary during the typhoon period is obtained based on the GOCI water color image inversion during the typhoon period, and the estuary SSC vertical distribution feature I corresponding to the time and space is corrected based on the inverted surface SSC to obtain the hourly estuary SSC vertical distribution feature II during the typhoon period, including: Based on the GOCI water color image inversion during the typhoon period, the average value of the surface SSC in the estuary area during the typhoon period was obtained, and the average value of the surface SSC of the estuary SSC vertical distribution characteristics corresponding to time and space was used to determine the surface correction coefficient; Based on the surface layer correction coefficient and combined with the SSC vertical distribution regression model, the correction coefficients of the remaining layers in the estuary SSC vertical distribution characteristics are determined; Based on the correction coefficient corresponding to each layer of the estuary SSC vertical distribution characteristics, each layer in the estuary SSC vertical distribution characteristics I was corrected respectively to obtain the estuary SSC vertical distribution characteristics II.

8. The method for calculating estuary sediment flux during typhoon period according to claim 7, characterized in that: Based on the surface layer correction coefficient and combined with the SSC vertical distribution regression model, the correction coefficients of the remaining layers in the estuary SSC vertical distribution characteristics are determined, including: Among them, K1 is the surface correction coefficient; is the average surface SSC value retrieved by GOCI during the typhoon period; SSC typhoon For Vertical distribution characteristics of SSC in estuaries corresponding to time and space Ⅰ Average value of surface SSC; K w is the correction coefficient of the wth layer; b w is the fitting parameter of the w-th layer.

9. A system for calculating sediment flux in estuaries during typhoon periods, characterized in that: include: The data acquisition module is used to obtain hydrological data, atmospheric data and GOCI water color images within a sample time period of the estuary to be analyzed, and the sample time period includes at least one typhoon that can affect the estuary area; The numerical simulation module is used to input the hydrological data and atmospheric data within the sample time period into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC I; The time period selection module is used to calculate the regional average wind speed in the estuary area based on the typhoon path, typhoon center pressure and center maximum wind speed during the typhoon life period, and determine the typhoon impact period from the sample time period based on the regional average wind speed; The coefficient correction module is used to obtain the surface SSC of the estuary area during the typhoon period based on the GOCI water color image inversion during the typhoon period, and to correct the corresponding time and space vertical distribution characteristics of the estuary SSC based on the inverted surface SSC I to obtain the hourly vertical distribution characteristics of the estuary SSC during the typhoon period II; Flux calculation module I is used to calculate the hourly vertical distribution of sediment flux during the typhoon period based on the hourly vertical distribution characteristics of SSC in the estuary during the typhoon period II; Flux calculation module II is used to calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period; The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

10. A method for analyzing the impact of typhoons with different paths on estuary sediment transport and topographic changes, characterized in that: include: Obtain hydrological data, atmospheric data, and GOCI water color images for the sample period of the estuary to be analyzed. The sample period includes at least one typhoon that can affect the estuary area. Based on the typhoon path, typhoon center pressure and center maximum wind speed in the atmospheric data during the typhoon life, the regional average wind speed in the estuary area is calculated, and the sample time period is divided into typhoon-affected period and non-typhoon-affected period based on the regional average wind speed; The hydrological and atmospheric data within the sample period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC during the typhoon-affected period and the non-typhoon-affected period. The surface SSC of the estuary area during the typhoon-affected period and the non-typhoon-affected period was retrieved based on the GOCI water color image. The vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC. The hourly vertical distribution characteristics of the estuary SSC during the typhoon-affected period and the non-typhoon-affected period were obtained. Based on the hourly vertical distribution characteristics of estuary SSC during typhoon-affected and non-typhoon-affected periods, the hourly vertical distribution of sediment flux during typhoon-affected and non-typhoon-affected periods was calculated. Calculate the sediment flux during the typhoon period based on the hourly vertical distribution of sediment flux during the typhoon period; Based on the hourly vertical distribution of sediment flux during the non-typhoon period, the sediment flux during normal weather period is calculated; Based on the sediment flux during typhoon-affected and non-typhoon-affected periods, the contribution of typhoons to long-term sediment transport and topographic changes is measured; The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

11. A storage medium storing a computer program executable by a processor, characterized in that: When the computer program is executed, the steps of the method according to any one of claims 1 to 8 or claim 10 are implemented.

12. A computing and analysis device comprising a memory and a processor, wherein the memory stores a computer program executable by the processor, wherein: When the computer program is executed, the steps of the method according to any one of claims 1 to 8 or claim 10 are implemented.

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