Method for calculating estuary sediment flux during typhoon influence period

Abstract

The invention relates to a method for calculating estuary sediment flux during a typhoon influence period. The method is suitable for the field of estuary water-sediment dynamic analysis. A hydrodynamic module based on an SCHISM model system is coupled with a sediment power module and a wave power module, a three-dimensional water-sediment-wave coupling model is established, and a verification result shows that although the model can well reproduce the high-frequency change process of water-sediment power of the Yangtze estuary in different weathers, the seasonal difference of SSC is quantitatively underestimated; in order to overcome the problem of seasonal difference of SSC, a numerical simulation result of the model is corrected by utilizing the surface SSC subjected to GOCI remote sensing inversion, after correction, errors of summer and winter SSC simulation results are averagely reduced by 36% and 38% compared with actual measurement, overestimation of summer SSC and underestimation of winter SSC are improved, the precision of the SSC results is obviously improved, and the method has the advantages that the method is simple and convenient to operate and has a wide application prospect. Based on the corrected SSC result, a more accurate sediment flux result with high temporal-spatial resolution can be obtained.

Description

Technical Field

[0001] The invention relates to a method for calculating estuary sediment flux during typhoon influence, which 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 flow and eventually settle, causing problems such as channel siltation or coastal scour. Therefore, typhoons have a very critical impact on estuary sediment transport and terrain 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 only study local points in the estuary. As a result, current research has difficulty in making an accurate quantitative analysis of 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 similarities and differences in the effects 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 existing problems, a method for calculating the sediment flux at an estuary during the influence of a typhoon 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 within the sample time period of the estuary to be analyzed, and the sample time period contains at least one typhoon that can affect the estuary area;

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

[0008] Based on the typhoon path, typhoon center pressure and center maximum wind speed during the life of the typhoon, the regional average wind speed of 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] Based on the GOCI water color image inversion during the typhoon period, the surface SSC of the estuary area during the typhoon period was obtained, and the vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC I, and the vertical distribution characteristics of the estuary SSC hour by hour during the typhoon period II were obtained;

[0010] Based on the hourly vertical distribution characteristics of estuary SSC 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, coupling 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 path, typhoon center pressure and center maximum wind speed during the life of the typhoon, and the hourly regional average wind speed of the estuary area during the life of the typhoon is calculated based on the corrected ERA5 wind field;

[0016] Based on the regional average wind speed hourly during the life of the typhoon and the regional average wind speed during the non-typhoon period, the critical wind speed is determined so that the difference between the average value of all wind speeds less than the critical wind speed in the regional average wind speed hourly during the life of the typhoon and the regional average wind speed during the non-typhoon period 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 life of the typhoon includes:

[0019]

[0020] p m =p tc (1-e)+ep ERA5

[0021] e=c 4 / (1+c 4 )

[0022] c=r / (nR)

[0023] in, is wind speed; p is air pressure; 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] Among them, p c 、p n is the typhoon center pressure and peripheral air pressure; r is the distance from the typhoon center; R max is the maximum wind speed radius; ρ a Air density: B determines the intensity and kurtosis of a typhoon;

[0026] R max =exp(-0.0511 ＊ ΔP 0.7515 +4.9213)

[0027] B=1.881-0.00557R max -0.01295φ

[0028] ΔP=(p n -p c ) / 100

[0029] Where, φ is the latitude of the calculation point;

[0030]

[0031] 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.

[0032] The three-dimensional sediment transport model SED3D includes:

[0033]

[0034] Where ρ is the water density after considering the influence of SSC; ρ 0 N is the water density output by the state equation in the hydrodynamic module; 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 ith component.

[0035] The WWMⅢ model includes:

[0036]

[0037] 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.

[0038] 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 characteristics I corresponding to time and space are corrected based on the inverted surface SSC to obtain the hourly estuary SSC vertical distribution characteristics II during the typhoon period, including:

[0039] 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 determined to determine the surface correction coefficient;

[0040] 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;

[0041] Based on the correction coefficient corresponding to each layer of the vertical distribution characteristics of estuary SSC, each layer in the vertical distribution characteristics of estuary SSC I was corrected respectively to obtain the vertical distribution characteristics of estuary SSC II.

[0042] Based on the surface layer correction coefficient, 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:

[0043]

[0044] Among them, K 1 is the surface correction factor; is the average surface SSC inverted by GOCI during the typhoon period; SSC typhoon For Vertical distribution characteristics of estuary SSC 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.

[0045] A system for calculating estuary sediment flux during typhoon period, characterized by comprising:

[0046] The data acquisition module is used to obtain the hydrological data, atmospheric data and GOCI water color images in the sample time period of the estuary to be analyzed, and the sample time period contains at least one typhoon that can affect the estuary area;

[0047] 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;

[0048] The time period selection module is used to calculate 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, and determine the typhoon impact period from the sample time period based on the regional average wind speed;

[0049] The coefficient correction module is used to obtain the surface SSC of the estuary during the typhoon period based on the GOCI water color image inversion during the typhoon period, and to correct the vertical distribution characteristics of the estuary SSC corresponding to time and space based on the inverted surface SSC I, and obtain the hourly vertical distribution characteristics of the estuary SSC during the typhoon period II;

[0050] 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 estuary SSC during the typhoon period II;

[0051] Flux calculation module II is used to calculate the sediment flux during the typhoon period based on the vertical distribution of hourly sediment flux during the typhoon period;

[0052] The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system, coupling the sediment dynamic module and the wave dynamic module.

[0053] A method for analyzing the impact of typhoons with different paths on estuary sediment transport and terrain changes, characterized by comprising:

[0054] Obtain hydrological data, atmospheric data and GOCI water color images within the sample time period of the estuary to be analyzed, and the sample time period contains at least one typhoon that can affect the estuary area;

[0055] Based on the typhoon path, typhoon center pressure and center maximum wind speed in the atmospheric data during the life of the typhoon, 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;

[0056] The hydrological data and atmospheric data in the sample time period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of estuary SSC during the typhoon-affected period and the non-typhoon-affected period I;

[0057] The surface SSC of the estuary area during the typhoon-affected period and the non-typhoon-affected period was inverted based on the GOCI water color image, and 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.

[0058] Based on the hourly vertical distribution characteristics of estuary SSC during typhoon-affected and non-typhoon-affected periods II, the hourly vertical distribution of sediment flux during typhoon-affected and non-typhoon-affected periods was calculated;

[0059] Based on the vertical distribution of hourly sediment flux during the typhoon period, the sediment flux during the typhoon period is calculated;

[0060] Based on the vertical distribution of hourly sediment flux during the non-typhoon period, the sediment flux during normal weather period is calculated;

[0061] 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;

[0062] The three-dimensional water-sediment-wave coupling model is based on the hydrodynamic module of the SCHISM model system, coupling the sediment dynamic module and the wave dynamic module.

[0063] A storage medium stores a computer program executable by a processor, wherein the computer program implements the steps of the method when executed.

[0064] 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.

[0065] The beneficial effects of the present invention are as follows: the present invention couples the sediment dynamics module and the wave dynamics module based on the hydrodynamics module of the SCHISM model system to establish a three-dimensional water-sediment-wave coupling model, and the verification results show that although the model can well reproduce the high-frequency change process of water-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 the correction, the errors of the SSC simulation results in summer and winter are reduced by 36% and 38% on average compared with the measured errors, which improves the overestimation of the SSC in summer and the underestimation of the SSC in winter, and 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.

[0066] The present invention not only has the advantage 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.

[0067] The present invention divides the actual impact period of the typhoon on the estuary based on the regional average wind speed of the Yangtze River Estuary during non-typhoon periods and typhoon periods, so as to accurately calculate the impact of the typhoon on the sediment flux.

[0068] The present invention determines the critical wind speed based on the regional average wind speed hourly 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 regional average wind speed hourly during the life of the 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.

[0069] In order to describe the increase of SSC during typhoons as accurately as possible and improve the accuracy of sediment flux calculation during typhoons, the present invention uses the average value of GOCI inverted surface SSC during the typhoon period to correct the surface SSC simulation results during the typhoon period. If there are few GOCI data during the typhoon period, it is possible to consider expanding the use of GOCI data within the typhoon life cycle.

[0070] Commonly used reanalysis wind fields such as ERA5 and NCEP have errors such as typhoon center position offset and low typhoon intensity in typhoon weather. The present invention calculates the typhoon model wind field (including transition wind field and gradient wind field) based on the 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

[0071] Figure 1 This is a flow chart of the method for calculating estuary sediment flux during typhoon influence in Example 1.

[0072] Figure 2 Comparison of the seasonal average SSC vertical distribution curves of the Yangtze River Estuary; (a) winter, (b) spring, (c) summer, (d) autumn (the red dots are measured results. The black line is the regression relationship fitting result, and the blue line and red line are the fitting results of the regression model established based on the measured data and numerical model results, respectively).

[0073] Figure 3 Schematic diagram of the water depth distribution of the East China Sea (a), the water depth of the study area and the location of the study section (b) (the black straight line is the study section). DETAILED DESCRIPTION

[0074] 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:

[0075] S1. Obtain measured and reanalyzed data on hydrology, atmosphere, topography, etc. and GOCI water color images within a sample period of the area where the estuary to be analyzed (in this case, the Yangtze River Estuary) is located. The sample period includes at least one typhoon that can affect the estuary area.

[0076] S2. Based on the typhoon path, typhoon center pressure and center maximum wind speed during the life of the typhoon, the regional average wind speed of the estuary area is calculated, and the typhoon impact period is selected from the sample time period based on the regional average wind speed.

[0077] This embodiment divides the actual impact period of the 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 the typhoon on the sediment flux. The specific steps are as follows:

[0078] 1) Based on the typhoon track collection dataset of China's coastal waters, the sample time period is divided into two periods: the period when there are typhoons in the northwest Pacific (typhoon life period) and the period when there are no typhoons (non-typhoon period);

[0079] 2) Based on the atmospheric data during non-typhoon periods, the time series of the regional average ERA5 wind speed in the Yangtze River Estuary during non-typhoon periods (based on the results corrected by the Holland typhoon field model) is calculated and recorded as

[0080] 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 life of the typhoon is calculated.

[0081] 3) The average wind speed in the Yangtze River estuary during the typhoon period Summarize and arrange in order from small to large to find a critical wind speed Make The average of all wind speeds is approximately equal to

[0082] 4) When At that time, it was considered that the typhoon had a significant impact on the Yangtze River Estuary, and the corresponding time of the average wind speed in the area was classified as within the typhoon impact period.

[0083] S3. Input the measured and reanalyzed data such as hydrological data, atmospheric data, and topography during the sample period into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of the estuary SSC I.

[0084] 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 of the SCHISM model system coupled with the sediment dynamic module and the wave dynamic module.

[0085] In this example, the hydrodynamic module uses a three-dimensional baroclinic model. According to the Boussinesq and static assumptions, the control equations include the continuity equation (1), momentum equation (2), transport equation (3), and state equation (4) in the following form:

[0086]

[0087] ρ w =ρ(S,T,p) (4)

[0088] in, is the horizontal gradient operator; (x, y) is the Cartesian coordinate system in the horizontal direction, and z is the vertical coordinate upward; is the material derivative; is the horizontal velocity, which includes the components in the x and y directions u(x,y,z,t),v(x,y,z,t)v(x,y,z,t)v(x,y,z,t), in m / s; w(x,y,z,t) is the vertical velocity, in m / s; t is time, g is the acceleration due to gravity, in m 2 / s; η(x,y,t) is the free elevation surface, unit is m; h is the water depth measured by the fixed reference surface, unit is m; v,κ are the vertical eddy viscosity coefficient and the vertical turbulent diffusion coefficient, unit is m 2 / s; C is the tracer concentration, such as salinity, temperature, suspended sediment concentration, etc.; F h Represents the horizontal diffusion term, unit m 2 / s; Q is the mass source / sink term, unit: m 2 / s;ρ w is the water density, including the effects of salinity S, temperature T, and hydrostatic pressure p, in kg / m 3 ; 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:

[0089]

[0090] Where, μ is the horizontal eddy viscosity coefficient, unit is m 2 / s; f is the Coriolis force parameter; is the z-axis unit vector; ρ 0 is the reference water density, in kg / m 3 ;p A is the atmospheric pressure; α is the effective soil elasticity factor; is the earth's tidal potential.

[0091] The GLS method is used in the turbulent closed mode of the model. The GLS method is a two-equation model, which includes the turbulent kinetic energy (k) equation and the general scale (ψ) equation. The expression is as follows:

[0092]

[0093] in, and v ψ is the vertical turbulent diffusion coefficient; c ψ1 、c ψ2 and c ψ3 is the model parameter; F w is a wall approximation function; M and L are the shear frequency and buoyancy frequency respectively; ε is the dissipation rate. The general scale ψ is defined as:

[0094]

[0095] in, l is the turbulent mixing length; different combinations of parameters p, m and n will form different turbulent closure models, such as k-ε model, k-ω model, M-Y2.5 model, etc. Finally, the vertical eddy viscosity coefficient v and the vertical turbulent diffusion coefficient K are calculated as follows:

[0096]

[0097] Among them, the Schmidt number and σ ψ is the model parameter; s m and h It is a stable function to measure the degree of water stratification, and its calculation formula is:

[0098] s m =(0.39327-3.0858G h ) / (1-34.676G h ) / (1-6.1272G h ) (11)

[0099] s h =0.49393 / (1-34.676G h ) (12)

[0100] Among them, G h is the gradient Richardson number related to the water density.

[0101] In this embodiment, the sediment dynamics module uses the three-dimensional sediment transport model SED3D, which is developed from the Community Sediment Transport Model and can be coupled with the SCHISM hydrodynamic module and use the same grid and time step. SED3D can simultaneously consider the movement of cohesive sand and non-cohesive sand components, including important physical processes such as convection, diffusion, sedimentation in the water body, siltation and resuspension of the bed surface.

[0102] SED3D calculates the spatiotemporal distribution of SSC by solving the convection-diffusion equation with additional consideration of sediment source and sink terms. Its control equations and boundary conditions are as follows:

[0103]

[0104] Among them, C i is the concentration of the ith sediment component, in kg / m 3 ;D i 、E i is the sedimentation flux and erosion flux of the i-th component, representing the sediment exchange between the water body and the bed; w s,i is the sediment velocity of the ith sediment component, in m / s. Sediment velocity is the core physical quantity of sediment dynamic characteristics, affecting the vertical distribution of sediment, bed siltation and scouring. Soulsby is used in the model to calculate sediment velocity, and the expression is as follows:

[0105]

[0106] Among them, d 50,i , D *,i are the median particle size and dimensionless particle size of the ith sediment component, in m; V is the kinematic viscosity coefficient of water, in m 2 / s:s i =ρ s,i / ρ w is the relative density of the ith component, ρ s,i is the sediment density of the ith component, in kg / m 3 After coupling the sediment model, the state equation can take into account the effect of SSC on water density:

[0107]

[0108] Among them, ρ 0 is the water density after considering the effects of salinity S, temperature T, and hydrostatic pressure p, i.e., the result of equation (4), in kg / m 3 ; N sed is the total sediment fraction.

[0109] 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 sedimentation flux D in the model i The calculation formula is:

[0110] D i =w s,i C i,1 (19)

[0111] Among them, C i,1 is the concentration of the ith sediment component in the bottom grid. i ) According to Ariathurai and Arulanandan, the expression is:

[0112]

[0113] τ cr,i =θ cr,i gd 50,i (ρ s -ρ w ) (twenty one)

[0114] Among them, M i is the bed scour rate of the ith sediment component, in kg / m 2 / s, range 10 -5 ~10 -2 ; p is the porosity of the bed surface (dimensionless), with a default value of 0.4; f i is the volume fraction of the ith sediment component (dimensionless); is the bottom shear stress under wave-current interaction, in N / m 2 τ cr,i ,θ cr,i are the critical erosion stress and dimensionless critical erosion shear stress of the ith sediment component, in N / m 2 θ cr,i According to Soulsby and Whitehouse calculations:

[0115]

[0116] In addition, according to Winterwerp's suggestion, the model does not set the critical settlement stress, and the sediment is always in a settlement state.

[0117] In this embodiment, the wave power module uses the WWMⅢ wave power model. The WMWII wave power module is one of the commonly used third-generation wave models, which was developed by Roland et al. based on the model of Hsu et al. WWMII uses an unstructured grid and solves the Eulerian approximation wave equation. It takes into account a variety of physical processes, such as wave propagation and refraction, wind-induced waves, wave dissipation and breaking, etc. It is widely used in nearshore, estuaries and lakes. In the Cartesian coordinate system, the control equation of WWMIII can be written as:

[0118]

[0119] Among them, N(σ,θ) = E(σ,θ) / σ is the wave action density spectrum, σ is the relative frequency, and θ is the wave direction. The first term on the left side of formula (23) represents the change of the wave action N over time, the second term on the left side represents the propagation in the xy direction of the geographic space, and the third and fourth terms on the left side represent the propagation in the frequency space σ and the spectrum distribution direction space θ respectively; the right side of formula S tot =S in +S n / 4 +S n / 3 +S ds +S br +S bf Represents the energy source and sink terms, including wind energy input, four-wave interaction, three-wave interaction, white-cap dissipation, wave breaking, and the effects of bottom friction.

[0120] After the SCHISM hydrodynamic module is coupled with the wave module, the radiation stress in equation (5) is It will be calculated according to the following method, as follows:

[0121]

[0122] Among them, S xx , S xy and S yy are the components of the radiation stress tensor defined for the spectrum. In addition, assume that the radiation stress Remains unchanged vertically.

[0123] 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 I.

[0124] In order to describe the increase of SSC during typhoons as accurately as possible and improve the accuracy of sediment flux calculation during typhoons, this embodiment uses the average value of GOCI inverted surface SSC during the typhoon period to correct the surface SSC simulation results during the typhoon period. If there are few GOCI data during the typhoon period, it is possible to consider expanding the use of GOCI data within the typhoon life cycle.

[0125] In this embodiment, the vertical correction coefficient is calculated to correct the SSC numerical simulation results (SSC i,w,t The subscripts i, w, and t represent the point number, vertical layer number, and time, respectively, and w=1 represents the surface layer, and t=typhoon represents the average value during the typhoon impact period).

[0126] 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 during the typhoon period and the average value of surface SSC in the vertical distribution feature I of estuary SSC corresponding to time and space.

[0127] Due to the data loss caused by intermittent cloud cover, the surface correction factor (K 1 ) 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 (SSC) corresponding to time and space i,w＝1,typhoon ) is used for calculation, and the calculation formula is as follows:

[0128]

[0129] S4-2. 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.

[0130] like Figure 2 As shown by the red line in the middle, the mathematical model established in this embodiment can better simulate the vertical distribution characteristics of the SSC in the Yangtze River Estuary. Figure 3 The SSC vertical distribution regression model was established based on the hourly SSC simulation results of all study sections.

[0131] First, the simulation results are vertically divided according to the relative water depth h r (0 and 1 represent the bottom layer and the surface layer, respectively) is 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 parameter a of each layer is obtained w and b w It should be noted that, for the sake of simplicity of calculation, a w and b wIt is only related to the vertical number of layers, but has nothing to do with time and horizontal position.

[0132]

[0133] Based on formula (25), if the surface SSC (SSC i,1,t ) after correction (i.e. multiplying by the correction factor K 1 ), 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).

[0134]

[0135] Among them, SSC′ i,w,t is the corrected SSC.

[0136]

[0137] 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 estuary SSC vertical distribution characteristics II hourly during the typhoon period.

[0138] 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 K. w , in order to obtain the corrected SSC of each layer section.

[0139] S5. Based on the hourly vertical distribution characteristics of estuary SSC during the typhoon period II, calculate the hourly vertical distribution of sediment flux.

[0140] Sediment flux per section based on hourly flow velocity (derived from numerical model) and corrected vertical distribution characteristics of estuary SSC The vertical distribution calculation formula is:

[0141]

[0142] in, A i,w,t They are the hourly flow velocity perpendicular to the cross section and the flow area respectively.

[0143] S6. Calculate the sediment flux during the typhoon period based on the vertical distribution of the hourly sediment flux during the typhoon period.

[0144] 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:

[0145]

[0146] Accurate wind field forcing is an important prerequisite for improving the calculation accuracy of wave energy and sediment transport during typhoons. However, many studies have shown that commonly used reanalysis wind fields such as ERA5 and NCEP have errors such as typhoon center position offset and low typhoon intensity in typhoon weather. Therefore, when simulating typhoon conditions, the typhoon model wind field (including transition wind field and gradient wind field) will be calculated based on the typhoon's measured path, central air pressure, maximum wind speed and other data, and combined with the initial ERA5 wind field to obtain more accurate input wind field and numerical simulation results.

[0147] 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:

[0148]

[0149] p m =p tc (1-e)+ep ERA5 (32)

[0150] e=c 4 / (1+c 4 ) (33)

[0151] c=r / (nR) (34)

[0152] in, is the wind speed; p is the air pressure; the 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, where n is usually 4, 9, or 10.

[0153] The gradient wind field is obtained by cyclone balance and calculated using the Holland typhoon model. It is based on the Schloemer index pressure distribution model, introduces a new parameter B, and uses the gradient wind field to obtain the calculation expression:

[0154] Air pressure equation:

[0155]

[0156] Wind field equation:

[0157]

[0158] Among them, p c 、p nis the typhoon center pressure and peripheral pressure, unit is Pa; r is the distance from the typhoon center, unit is m; R max is the maximum wind speed radius, in m; ρ a is the air density, in kg / m 3 : B determines the intensity and peakness of a typhoon and is usually between 1.0 and 2.5.

[0159] Parameters B and R max are two important parameters for typhoon model wind field calculation. As parameter B increases (other parameters are fixed), R max The wind speed at the typhoon center gradually increases, while the wind speed at the location farther from the typhoon center decreases, 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 gradually increases from the typhoon center to the outside, and at R max It reaches its maximum at , and then gradually decreases: and as R max The increase of R max The wind speed changes are more gradual.

[0160] This embodiment uses the following algorithm to calculate R max and B, the formula is as follows:

[0161] R max =exp(-0.0511 ＊ ΔP 0.7515 +4.9213) (37)

[0162] B=1.881-0.00557R max -0.01295φ (38)

[0163] ΔP=(p n -p c ) / 100 (39)

[0164] Where φ is the latitude of the calculation point.

[0165] Another important component of the typhoon model wind field is the transitional wind field, which is caused by the movement of the typhoon. It is considered to correct the circularly symmetric gradient wind field, that is, to form a model wind field with asymmetric wind speed along the typhoon's path. This is because the East China Sea is usually affected by the subtropical high pressure, and the pressure gradient is larger on the right side, so the wind speed on the right side of the typhoon path is usually greater than the wind speed on the left side. The calculation expression of the transitional wind field is as follows:

[0166]

[0167] Embodiment 2: This embodiment 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.

[0168] In this embodiment, the data acquisition module is used to obtain measured and reanalyzed data such as hydrology, atmosphere, and topography, as well as 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.

[0169] 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 center maximum wind speed during the life of the typhoon, and select the typhoon impact period from the sample time period based on the regional average wind speed.

[0170] 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.

[0171] 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 estuary SSC vertical distribution characteristics I corresponding to time and space based on the inverted surface SSC to obtain the hourly estuary SSC vertical distribution characteristics II during the typhoon period.

[0172] In this example, the 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 estuary SSC during the typhoon period II.

[0173] In this embodiment, the flux calculation module II is used to calculate the sediment flux during the typhoon period based on the vertical distribution of the sediment flux hour by hour during the typhoon period.

[0174] In this embodiment, 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.

[0175] Embodiment 3: This embodiment 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 estuary sediment flux during typhoon influence in Embodiment 1 are implemented.

[0176] Embodiment 4: This embodiment is a computing and analyzing 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 Embodiment 1 are implemented.

[0177] Embodiment 5: This embodiment is a method for analyzing the impact of typhoons with different paths on estuary sediment transport and terrain changes, which specifically includes the following steps:

[0178] Obtain measured and reanalyzed data on hydrology, atmosphere, topography, etc. and GOCI water color images within the sample time period of the estuary to be analyzed. The sample time period contains at least one typhoon that can affect the estuary area.

[0179] Based on the typhoon path, typhoon center pressure and center maximum wind speed in the atmospheric data during the life of the typhoon, 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;

[0180] The measured and reanalyzed data such as hydrological data, atmospheric data, and topography during the sample period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of estuary SSC during the typhoon-affected period and the non-typhoon-affected period I;

[0181] The surface SSC of the estuary area during the typhoon-affected period and the non-typhoon-affected period was inverted based on the GOCI water color image, and 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.

[0182] Based on the hourly vertical distribution characteristics of estuary SSC during typhoon-affected periods and non-typhoon-affected periods II, the hourly vertical distribution of sediment flux during typhoon-affected periods and non-typhoon-affected periods was calculated;

[0183] Based on the vertical distribution of hourly sediment flux during the typhoon period, the sediment flux during the typhoon period is calculated;

[0184] Based on the vertical distribution of hourly sediment flux during the non-typhoon period, the sediment flux during normal weather period is calculated;

[0185] 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.

[0186] In this embodiment, 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.

[0187] Embodiment 6: This embodiment 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 Embodiment 5 are implemented.

[0188] 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 within the sample time period of the estuary to be analyzed, and the sample time period contains at least one typhoon that can affect the estuary area; The hydrological data and atmospheric data within the sample time 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 life of the typhoon, the regional average wind speed of the estuary area is calculated, and the typhoon impact period is determined from the sample time period based on the regional average wind speed; Based on the GOCI water color image inversion during the typhoon period, the surface SSC of the estuary area during the typhoon period was obtained, and the vertical distribution characteristics of the estuary SSC corresponding to time and space were corrected based on the inverted surface SSC I, and the vertical distribution characteristics of the estuary SSC hour by hour during the typhoon period II were obtained; Based on the hourly vertical distribution characteristics of estuary SSC 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, coupling the sediment dynamic module and the wave dynamic module.

2. The method for calculating estuary sediment flux during typhoon impact 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 path, typhoon center pressure and center maximum wind speed during the life of the typhoon, and the hourly regional average wind speed of the estuary area during the life of the typhoon is calculated based on the corrected ERA5 wind field; Based on the regional average wind speed hourly during the life of the typhoon and the regional average wind speed during the non-typhoon period, the critical wind speed is determined so that the difference between the average value of all wind speeds less than the critical wind speed in the regional average wind speed hourly during the life of the typhoon and the regional average wind speed during the non-typhoon period 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 period 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 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; Among them, p c 、p n is the typhoon center pressure and peripheral air pressure; r is the distance from the typhoon center; R max is the maximum wind speed radius; ρ a Air density: B determines the intensity and peakness of a 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 typhoon period 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 impact 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 ith 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 impact 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 characteristics I corresponding to time and space are corrected based on the inverted surface SSC to obtain the hourly estuary SSC vertical distribution characteristics 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 determined 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 vertical distribution characteristics of estuary SSC, each layer in the vertical distribution characteristics of estuary SSC I was corrected respectively to obtain the vertical distribution characteristics of estuary SSC 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, 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 inverted by GOCI during the typhoon period; SSC typhoon For Vertical distribution characteristics of estuary SSC 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 an estuary during a typhoon, characterized in that: include: The data acquisition module is used to obtain the hydrological data, atmospheric data and GOCI water color images in the sample time period of the estuary to be analyzed, and the sample time period contains 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 of 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 during the typhoon period based on the GOCI water color image inversion during the typhoon period, and to correct the vertical distribution characteristics of the estuary SSC corresponding to time and space based on the inverted surface SSC I, and 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 estuary SSC during the typhoon period II; Flux calculation module II is used to calculate the sediment flux during the typhoon period based on the vertical distribution of hourly 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, coupling 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 terrain changes, characterized in that: include: Obtain hydrological data, atmospheric data and GOCI water color images within the sample time period of the estuary to be analyzed, and the sample time period contains 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 life of the typhoon, 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 data and atmospheric data in the sample time period were input into the three-dimensional water-sediment-wave coupling model to obtain the hourly vertical distribution characteristics of estuary SSC during the typhoon-affected period and the non-typhoon-affected period I; The surface SSC of the estuary area during the typhoon-affected period and the non-typhoon-affected period was inverted based on the GOCI water color image, and 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 II, the hourly vertical distribution of sediment flux during typhoon-affected and non-typhoon-affected periods was calculated; Based on the vertical distribution of hourly sediment flux during the typhoon period, the sediment flux during the typhoon period is calculated; Based on the vertical distribution of hourly 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, coupling the sediment dynamic module and the wave dynamic module.

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

Images