Method for determining the boundary of land influence of typhoon spatiotemporal variation in coastal zone

Abstract

This invention relates to the field of spatial data processing technology and discloses a method for determining the impact range of typhoon spatiotemporal variations on the land boundary of a coastal zone. The method includes the following steps: acquiring historical typhoon data of the coastal zone and adjacent land areas to be analyzed and performing discrete spatial grid division; calculating the wind speed values ​​at grid points; extracting typhoon events that meet a set wind speed threshold to construct a wind field database of typhoon impacts on the disaster-causing area; extracting the spatial distribution point set of each typhoon trajectory on land from the wind field database; performing spatial geometric envelope operations to determine the typhoon entity development boundary; using an extreme value probability distribution model to fit and solve the annual maximum wind speed sequence of grid points, extracting the contour lines corresponding to the wind speed threshold as the extreme value wind speed distribution boundary; spatially overlaying the areal regions of the two boundary envelopes to obtain the union region, and extracting the outer boundary line on the side furthest from the coastline as the judgment boundary. This invention integrates objective reality and extreme value probability distribution to achieve quantitative determination of the impact range.

Description

Technical Field

[0001] This invention relates to the field of spatial data processing technology, specifically a method for determining the influence range of typhoon spatiotemporal variations on the land boundary of the coastal zone. Background Technology

[0002] Typhoons are natural disasters that significantly impact coastal zones and adjacent land areas. Accurately defining the landward boundary of a typhoon is of practical significance for disaster prevention, mitigation, and spatial planning in coastal areas. Assessing the extent of a typhoon's damage typically requires delineating the spatial extent based on baseline wind speed data and historical typhoon trajectory data.

[0003] Current technologies for obtaining baseline wind speeds largely rely directly on observation samples from ground-based meteorological stations. However, due to the uneven spatial distribution of these stations, the acquired data is prone to spatial discontinuities, making it difficult to form continuous spatial distribution data of the wind field, thus limiting the accuracy of baseline wind speed assessments. In processing typhoon trajectory data, because the speed of a typhoon changes during its movement, the time sampling interval of the original trajectory recording points is often uneven. Directly using these discrete original coordinate points for envelope calculation introduces errors in spatial geometry calculations, making it difficult to accurately extract the development boundary that closely reflects the actual impact of the typhoon.

[0004] Meanwhile, existing methods for assessing the impact range largely rely on single historical data or single probabilistic statistical models. Using only historical trajectories fails to capture long-term extreme probability trends, while relying solely on probabilistic models deviates from the objective physical reality of typhoon development. Due to the lack of quantitative calculation methods that integrate the objective physical processes of typhoon occurrence with the spatial distribution patterns of extreme probability, existing methods are one-sided in determining the comprehensive impact boundary of typhoons on the land side of the coastal zone, making it difficult to achieve accurate quantitative delineation of spatial extent. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for determining the impact range of typhoon spatiotemporal variations on the land boundary of the coastal zone. This method solves the problems of discontinuous wind field data due to uneven distribution of meteorological observation stations, spatial boundary calculation errors caused by directly using the original trajectory with uneven time sampling, and the one-sidedness and spatial bias in the determination of the impact range due to relying solely on historical data or probability models.

[0006] To achieve the above objectives, this invention provides a method for determining the impact range of typhoon spatiotemporal variations on the land boundary of the coastal zone, comprising the following steps: Historical typhoon data of the coastal zone and adjacent land area to be analyzed are obtained and discrete spatial grids are divided. Based on the historical typhoon data, the wind speed value of each discrete spatial grid point is calculated, and typhoon events that meet the set wind speed threshold are extracted to construct a typhoon impact wind field database for disaster-causing areas. Extract the spatial distribution point set of each typhoon trajectory in the land area from the typhoon impact wind field database of the disaster-causing area, perform spatial geometric envelope operation, and extract the outermost geometric contour line to determine the typhoon entity development boundary; Extract the annual maximum wind speed sequence of each discrete spatial grid point in the typhoon impact wind field database of the disaster-causing area, fit and solve the annual maximum wind speed sequence using the extreme value probability distribution model, calculate the extreme wind speed distribution field, and extract the contour lines corresponding to the set wind speed threshold as the extreme wind speed distribution boundary. The planar region encompassing the development boundary of the typhoon entity and the planar region encompassing the extreme wind speed distribution boundary are spatially overlaid to obtain the spatial union region. The final outer boundary of the spatial union region on the side furthest from the coastline is extracted as the boundary for determining the land influence range of the coastal zone.

[0007] Further, the calculation of wind speed values ​​for each discrete spatial grid point based on the historical typhoon data specifically includes: using the historical typhoon data in conjunction with a pressure-wind field model and a moving wind field model for calculation; calculating the air pressure value at the location of the discrete spatial grid point based on the pressure-wind field model, and calculating the rotating wind speed component, which characterizes the vortex kinetic energy caused by the internal pressure gradient difference of the typhoon, based on the air pressure distribution characteristics; calculating the moving wind speed component at the location of the discrete spatial grid point based on the moving wind field model; combining the rotating wind speed component and the moving wind speed component with the azimuth angle and the wind field inflow angle for vector synthesis calculation to obtain the wind speed value of the discrete spatial grid point; when the straight-line distance from the input discrete spatial grid point to the typhoon center approaches zero, the program forcibly assigns the straight-line distance to a set positive critical value; wherein, the set positive critical value is a small positive number used to avoid the occurrence of a calculation singularity with a denominator of zero.

[0008] Furthermore, the extraction of typhoon events that meet the set wind speed threshold to construct the typhoon impact wind field database for disaster-causing areas specifically includes: statistically analyzing the effective duration of wind speed values ​​greater than or equal to the set wind speed threshold at each discrete spatial grid point; selecting representative historical typhoon records from the historical typhoon data that simultaneously meet the set wind speed threshold and reach the set duration threshold, and establishing them as the typhoon impact wind field database for disaster-causing areas; wherein, the set wind speed threshold is the lower limit corresponding to a level 6 gale that can cause secondary disasters in the coastal zone, specifically 10.8 m / s, and the set duration threshold is the effective duration used as the basis for judging the impact of disasters.

[0009] Furthermore, before extracting the spatial distribution point set of each typhoon trajectory in the land area from the typhoon impact wind field database of the disaster-causing area, the process further includes: performing equidistant spatial interpolation calculation on the original trajectory recording points of each typhoon; calculating the spatial linear Euclidean distance between adjacent original typhoon center points in the same trajectory, and establishing the average reference length of each segment after interpolation based on the distance between adjacent points; based on the average reference length of the segments, under the constraint that the coordinates of the first and last endpoints of the typhoon center coordinate point sequence generated after interpolation coincide with the coordinates of the first and last endpoints of the original typhoon trajectory, performing linear coordinate mapping conversion on the corresponding original trajectory line segment according to the cumulative distance ratio to generate intermediate interpolation points; wherein, when the coordinates of two consecutive original recording points are consistent, the proportional scaling calculation of the interval is skipped and the original coordinate value of the location is directly used as the intermediate interpolation point.

[0010] Further, the spatial distribution point set of each typhoon trajectory in the land area is extracted from the typhoon impact wind field database of the disaster-causing area, and the spatial geometric envelope operation is performed. Specifically, this includes: introducing the vector spatial data of the coastline to perform geographic boundary clipping on the intermediate interpolation points, removing coordinate nodes located within the ocean area, and retaining the typhoon center coordinates projected on the land surface to form the spatial distribution point set; calling the Alpha Shape algorithm to construct a concave polygon boundary that fits the distribution characteristics of the point set, and determining the outermost continuous geometric closed line of the output as the typhoon entity development boundary.

[0011] Furthermore, the fitting and solution of the annual maximum wind speed sequence using the extreme value probability distribution model specifically includes: selecting the Weibull extreme value distribution model to fit and calculate the annual maximum wind speed sequence; constructing a log-likelihood function for the location parameter, scale parameter, and shape parameter of the Weibull extreme value distribution model, and using the maximum likelihood estimation method combined with the Newton-Raphson iterative algorithm to numerically approximate and obtain the best fitting result; wherein, the initial estimated baseline value required by the Newton-Raphson iterative algorithm is calculated in advance using the sample mean and variance of the data sequence through the method of moments, and the lower limit of the scale parameter value is limited to a set positive real number in the Newton-Raphson iterative algorithm; wherein, the set positive real number is 10. -5 .

[0012] Further, calculating the extreme wind speed distribution field and extracting the contour lines corresponding to the set wind speed threshold as the extreme wind speed distribution boundary specifically includes: combining the conversion relationship between the return period parameter and the exceedance probability, using the fitted extreme probability distribution model to calculate the extreme wind speed prediction value for the corresponding discrete spatial grid points, generating a spatial distribution data matrix; substituting the set wind speed threshold into the spatial distribution data matrix, tracking adjacent calculation nodes whose extreme wind speed prediction value is equal to the set wind speed threshold to generate an initial polyline, calling the B-spline curve smoothing algorithm to perform curvature optimization processing on the initial polyline, and obtaining continuous and smooth wind speed distribution contour lines to determine the extreme wind speed distribution boundary.

[0013] Furthermore, the spatial overlay processing of the planar region encompassing the typhoon entity development boundary and the planar region encompassing the extreme wind speed distribution boundary to obtain the spatial union region specifically includes: transforming the planar region encompassing the typhoon entity development boundary and the planar region encompassing the extreme wind speed distribution boundary to the same equal-area projection coordinate system, performing Boolean set joint calculation of two-dimensional planar polygons to obtain the spatial union region; calling pre-set coastline vector data to generate a mask polygon extending towards the land, performing spatial topological intersection operation on the spatial union region and the mask polygon, eliminating free fragmented surface elements with an area smaller than a set benchmark area threshold, and retaining the geometric planar elements projected within the range of the mask polygon as the land overlay region; wherein, the set benchmark area threshold is bound to the basic area of ​​the single grid point of the discrete spatial grid division, used to isolate the spatial topological noise caused by the computer calculation precision.

[0014] Further, extracting the final outer boundary line of the spatial union region on the side away from the coastline specifically includes: performing vector topological dimensionality reduction processing on the land superimposed region after clipping and retaining it, transforming the outer closed contour into a linear boundary loop composed of continuous line segments; performing topological difference calculation on the generated linear boundary loop and the reference coastline, eliminating the coastal line segments in the linear boundary loop whose spatial distance from the reference coastline is less than a set tolerance, and determining the continuous line segments that are separated from the coastline and extend inward into the land area after the difference erasure as the final outer boundary line; wherein, the set tolerance is calibrated based on the accuracy of the digital scale of the input coastline vector layer, and the value range is 10 to 50 meters.

[0015] Furthermore, the specific steps for performing discrete spatial grid division are as follows: dividing the continuous geographic space into several regular grid units according to a set spatial resolution, with each grid unit serving as an independent data calculation node; wherein, the spatial resolution is a grid of 0.1 degrees by 0.1 degrees or a grid of 0.05 degrees by 0.05 degrees.

[0016] This invention provides a method for determining the influence range of typhoon spatiotemporal variations on the land boundary of the coastal zone. It has the following beneficial effects: 1. This invention combines a pressure wind field model and a moving wind field model to perform wind speed vector synthesis calculation on a discrete spatial grid, reconstructing the surface wind speed matrix of historical typhoons. This overcomes the problems of uneven spatial distribution and data discontinuities in traditional meteorological station observation data, and obtains continuous wind field data that conforms to the dynamic characteristics of typhoons, thereby improving the accuracy of basic wind speed assessment.

[0017] 2. This invention performs equidistant spatial interpolation calculations on the original trajectory records of historical typhoons and calls the AlphaShape algorithm to perform envelope operations on the spatial distribution point set within the land area. This eliminates the calculation errors caused by uneven time sampling intervals due to changes in typhoon movement speed, accurately extracts the typhoon entity development boundary that conforms to the actual distribution characteristics, and reflects the actual spatial range affected by historical typhoons in the land area.

[0018] 3. This invention uses an extreme value probability distribution model to calculate and generate the extreme wind speed distribution boundary, spatially overlays it with the above-mentioned typhoon entity development boundary to obtain the union, and then uses topological difference calculation to filter out coastal segments to extract the final outer boundary. By integrating historical real-time data with extreme value probability prediction, it avoids the bias caused by relying on a single data source and realizes the quantitative delineation of the comprehensive impact range of typhoons on the land side of the coastal zone. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the method steps in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the logic principle and data flow of an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] See attached document Figure 1 and 2 This invention provides a method for determining the impact range of typhoon spatiotemporal variations on the land boundary of the coastal zone, comprising the following steps: S10: Obtain historical typhoon data for the coastal zone and adjacent land areas to be analyzed and divide the study area into discrete spatial grids. Use historical typhoon data in combination with pressure wind field model and moving wind field model to calculate the wind speed value of each discrete spatial grid point to construct the typhoon area influence wind field. Extract typhoon events that meet the set wind speed threshold conditions to construct a disaster-causing area typhoon influence wind field database. S20: Perform equidistant segmented interpolation calculation on the original trajectory recording points of each typhoon in the typhoon impact wind field database of the disaster-causing area, convert the original typhoon trajectories with different numbers of recording points into new trajectories with the same number of coordinate points, and extract the outer contour of the spatial distribution point set of each typhoon center coordinate point in the land area using the spatial geometric envelope algorithm after standardization interpolation, and determine the outermost geometric contour line as the entity development boundary of the typhoon in the land area. S30: Extract the annual maximum wind speed sequence of each discrete spatial grid point in the typhoon impact wind field database of the disaster-causing area, use the extreme value probability distribution model to perform probability fitting and solution on the annual maximum wind speed sequence, calculate the extreme value wind speed distribution field of the target area under a specific return period, and extract the wind speed distribution contour lines corresponding to the set wind speed threshold from the extreme value wind speed distribution field as the extreme value wind speed distribution boundary of the target return period. S40 spatially overlays the areal region enclosed by the typhoon entity development boundary and the areal region enclosed by the extreme wind speed distribution boundary, calculates the spatial union region of the two types of boundary enclosed regions, and extracts the final outer boundary of the spatial union region on the side away from the coastline as the boundary for determining the land influence range of the coastal zone.

[0022] See attached document Figure 1 and 2 In this embodiment, step S10 specifically includes: S110: Acquire historical typhoon data for the coastal zone and adjacent land area to be analyzed, and perform discrete spatial grid division of the study area. The coastal zone and adjacent land area to be analyzed refers to the specific geographic spatial area where the actual impact range of the typhoon needs to be determined. The historical typhoon data specifically includes the center latitude and longitude coordinates of the target typhoon at each recorded moment during its life cycle, the minimum central pressure of the typhoon, the maximum wind speed, and the typhoon center movement speed.

[0023] To ensure consistency of multi-source data during computation, timestamp alignment and outlier removal are performed on the acquired historical typhoon data to ensure that the time steps of each record match and that there are no missing entries. As a preferred method, discrete spatial gridding of the study area involves dividing the continuous geographic space into several regular grid cells according to a set spatial resolution, with each grid cell serving as an independent data computation node. This spatial resolution can be 0.1 degrees x 0.1 degrees or configured to a higher resolution of 0.05 degrees x 0.05 degrees; the specific spatial resolution value is set according to the actual computational accuracy requirements for disaster prevention and mitigation.

[0024] S120 utilizes historical typhoon data combined with pressure-wind field and moving wind field models to calculate wind speed values ​​at discrete spatial grid points, thus constructing the typhoon regional influence wind field. The actual physical wind field near the surface of a typhoon is typically composed of the superposition of a vortex rotation wind field driven by pressure gradient forces and a guiding wind field brought about by the overall movement of the typhoon. Therefore, this scheme couples the Holland model, which characterizes pressure distribution, with the Ueno model, which characterizes the movement effect, to reconstruct a more realistic dynamic wind field. For any discrete spatial grid point, the pressure value at its location is calculated based on the pressure distribution model. The purpose of this step is to quantify the spatial distribution characteristics of typhoon pressure, which exhibits an exponential decay with radial distance. The pressure model calculation formula is as follows: ; Based on the obtained air pressure distribution characteristics, the rotational wind speed component at the location of the discrete spatial grid point is calculated to characterize the vortex kinetic energy caused by the internal air pressure gradient difference of the typhoon. The formula for calculating the rotational wind speed is as follows: ; The moving wind speed component at the location of this discrete spatial grid point is calculated to compensate for the spatial asymmetric enhancement effect of the typhoon's overall movement on the wind speed in the right semicircle. The formula for calculating the moving wind speed is as follows: ; The calculated rotational wind speed component and the moving wind speed component are then combined using a vector synthesis to obtain the final wind speed value for the discrete spatial grid points. The wind speed synthesis calculation formula is as follows: ; In the formula, This indicates the straight-line distance from the center of the typhoon. Calculated air pressure at the grid points; Indicates the radius of the typhoon's maximum wind speed; This indicates the air pressure in the outer perimeter of a typhoon. This represents the lowest central pressure of a typhoon in historical typhoon data; This represents the pressure profile parameter that reflects the radial variation of air pressure. Its value range is usually between 1.0 and 2.5, and it is specifically determined by nonlinear regression relationship through the measured data of the typhoon's maximum wind speed and central air pressure. This represents the rotating wind speed component calculated from the pressure wind field model; Indicates the air density of the corresponding area; This represents the straight-line distance from a discrete spatial grid point to the typhoon center. To ensure the numerical completeness of the algorithm logic and avoid errors when calculating grid points that happen to be located at the typhoon center, this is used because... This can lead to a computational singularity in the formula where the denominator is zero, when the input... When the value approaches 0, the program forcibly assigns it a set small positive threshold value; Parameters representing the Coriolis force generated by the Earth's rotation; This represents the moving wind speed component calculated from the moving wind field model; This indicates the speed of typhoon center movement in historical typhoon data; This indicates the final wind speed at each grid point; and This is an empirical constant in the wind speed synthesis process. Its value is determined a priori based on the topographic friction coefficient and the difference in surface roughness between land and sea in the region. In this embodiment, the reasonable value range is between 0.7 and 1.0. This represents the azimuth angle of the calculation grid point relative to the center of the typhoon; Indicates the wind inflow angle; Represents an exponential function with the natural constant as its base; Represents the sine function; Represents the cosine function; This represents the constant pi. It involves the conversion of conventional geometric and physical quantities for Coriolis force parameters and azimuth angles.

[0025] S130: Extract typhoon events that meet the set wind speed threshold to construct a wind field database of typhoon impacts on disaster-causing areas. The set wind speed threshold is a wind force assessment standard used to determine whether a typhoon has a substantial disaster impact on the target area. Considering that single maximum wind speed records usually have random errors due to observation noise, the judgment of the output results should be evaluated based on spatiotemporal multi-dimensional continuous logic. Therefore, this threshold is specifically set as the lower limit corresponding to a level 6 gale that can cause secondary disasters in the coastal zone, that is, the set wind speed threshold is 10.8 m / s.

[0026] During the specific screening process, all historical typhoon data wind fields calculated using the aforementioned wind speed synthesis formula are traversed. The effective duration of the final wind speed greater than or equal to 10.8 m / s at each discrete spatial grid point is statistically analyzed as the criterion for determining the impact of the disaster. Representative historical typhoon records that meet this wind speed standard and reach the set duration threshold are selected from the established typhoon regional impact wind fields. In this embodiment, the set duration threshold is specifically set to 2 hours. This value is calibrated based on the historical meteorological disaster statistics records for coastal zone disaster prevention and mitigation. When the continuous action of gale-force winds of level 6 or above exceeds the critical duration of 2 hours, the dynamic cumulative effect of wind load will significantly trigger substantial secondary disasters such as large-scale lodging of agricultural and forestry vegetation and damage to lightweight building structures. The selected set of target typhoon events is established as a disaster-causing typhoon impact wind field database. The disaster-causing typhoon impact wind field database contains the basic parameter information of the disaster-causing typhoons and their associated spatial wind speed data matrices for each grid, providing underlying verification data support for subsequent research on the spatial expansion mechanism of dynamic processes and physical boundaries.

[0027] See attached document Figure 1 and 2 In this embodiment, step S20 specifically includes: S210 performs equidistant segmented interpolation calculations on the original trajectory records of each typhoon in the typhoon impact wind field database for the disaster-causing area. Different historical typhoons exhibit objective differences in duration within their lifecycles, resulting in varying numbers of center position coordinate points in the original typhoon trajectories sampled at fixed time intervals. To eliminate trajectory spatial morphology distortion caused by discrete time steps and statistical weight bias introduced in subsequent cluster analysis, this scheme uses an equidistant spatial interpolation algorithm to transform non-uniform discrete coordinate points with absolute time attributes into a sequence of equal coordinate points with uniform spatial scale characteristics.

[0028] Based on the original center coordinates of each typhoon trajectory, the Euclidean distance between the centers of each adjacent original typhoon on the same trajectory is calculated. The formula for calculating the straight-line distance between the centers of adjacent original typhoons is as follows: ; In the formula, Indicates the first The original typhoon center and the adjacent first The straight-line distance between the original typhoon centers; and They represent the first The x and y coordinates of the original typhoon center point in the corresponding geographic coordinate system; This indicates the total number of coordinate records contained in this specific original typhoon trajectory.

[0029] S220: Based on the distances between adjacent points obtained above, the total length of the typhoon trajectory is divided, and the average baseline length of each segment after interpolation is established. According to the spatial resolution requirements of the target analysis, a uniform total number of trajectory segments is set in the program. This operation resamples all representative disaster-causing typhoons into data structures of equal length to facilitate matrix alignment in subsequent spatial envelope analysis. The formula for calculating the average segment length is as follows: ; In the formula, This indicates that the entire original typhoon trajectory is interpolated and divided into... The average spatial reference length of each line segment after the segment; This parameter represents the total number of interpolation segments set, and as a preferred method, this parameter... The value of is determined based on the ratio between the overall latitude and longitude span of the study area and the resolution of the spatial grid. In this embodiment, the value is usually taken in the integer range of 100 to 500 to ensure that the newly generated coordinate points can capture the local curvature changes of the trajectory without causing redundant computational load.

[0030] Based on the calculated segmented baseline length, the sequence of typhoon center coordinates generated after interpolation is determined. The coordinates of the first and last endpoints of the interpolated trajectory are set to absolutely coincide with the coordinates of the first and last endpoints of the original typhoon trajectory, thereby strictly anchoring the start and dissipation positions of the typhoon's physical life cycle in geographic space. The mathematical constraint formula for the endpoint coordinates is as follows: ; ; For each intermediate interpolation point located between the first and last endpoints, a linear coordinate mapping conversion is performed on the corresponding original trajectory segment based on the cumulative distance ratio. The specific conversion formula for the coordinates of the intermediate interpolation points is as follows: ; To ensure the completeness of the interpolation algorithm, the program performs a partial squared error in the denominator of the division operation before performing the coordinate transformation described above. Singularity detection is performed on the numerical state. When the typhoon system is stationary or hovering, causing the coordinates of two consecutive original recording points to be identical, the corresponding distance... The coordinates approach 0. At this point, the algorithm skips the scaling calculation for that interval and directly uses the original coordinates of the location as the intermediate interpolation point to avoid overflow errors caused by division by zero in the underlying computer processing.

[0031] In the formula, and These represent the first and second digits of the new trajectory sequence generated by standardized interpolation. The x and y coordinates corresponding to the center point of each typhoon; Represents an integer index parameter used for line segment positioning, representing the newly generated first... The interpolation point falls exactly within the original trajectory in terms of spatial topology. The and the first Within the line segment formed by the center points. The integer index parameter must satisfy the following interval constraint formula for cumulative distance: ; S230: Extract the spatial distribution set of the typhoon center coordinates in the target land area after standardization and interpolation, and perform spatial geometric envelope operation to extract the outer contour. After performing the above coordinate mapping operation, each historical trajectory in the typhoon impact wind field database of the disaster-causing area is reconstructed into a dataset with the same number of center position coordinates. Considering that the purpose of this scheme is to quantitatively determine the disaster impact boundary of the coastal zone on the land side, the system introduces the vector spatial data of the coastline to perform geographic boundary clipping on all the acquired interpolated coordinate points. Coordinate nodes located within the ocean area are removed, and only the typhoon center coordinates projected onto the land surface are retained to form a spatial distribution set, thereby isolating the interference of non-land-based disaster-causing factors.

[0032] For the aforementioned spatially distributed point set preserved within the land area, a spatial geometric envelope algorithm is used to generate the closed contour of the polygonal perimeter. To avoid one-sided expansion caused by relying solely on the outermost single outlier point in the output results and to improve the fault tolerance of boundary determination, the Alpha Shape algorithm is used as a preferred method to construct a concave polygonal boundary that fits the distribution characteristics of the point set. An appropriate Alpha radius parameter is adaptively set according to the spatial distribution density of the point group to reasonably filter out individual discrete free points that deviate from the main path.

[0033] The outermost continuous geometric closed line output by the envelope algorithm is determined as the entity development boundary of the typhoon in the land area. This step, through spatial geometric abstraction, transforms the discrete typhoon trajectory into a continuous planar control area. This entity development boundary accurately represents the objective spatial limit of the actual arrival and impact of a historical typhoon center with disaster-causing intensity on the land surface.

[0034] See attached document Figure 1 and 2 In this embodiment, step S30 specifically includes: S310 extracts the annual maximum wind speed sequence for each discrete spatial grid point in the typhoon impact wind field database of the disaster-stricken area. Based on the fundamental axiom of independent and identically distributed systems in extreme value statistics, to ensure the reliability of future extreme condition probability predictions, the output results must be based on independent historical samples that do not interfere with each other. The wind speed data matrix in the typhoon impact wind field database of the disaster-stricken area is aggregated along the time dimension according to the natural year time window. For each fixed discrete spatial grid point, the combined peak wind speed under the influence of each typhoon event within the same year is compared, and the record with the largest value is retained as the representative sample for that year. Through year-by-year extraction, an annual maximum wind speed time series covering the research time span is constructed for each grid point. This filters out statistical noise introduced by short-term meteorological fluctuations, providing basic data input that conforms to the premise of extreme value theory for subsequent extreme value probability modeling.

[0035] S320 introduces an extreme value probability distribution model to probabilistically fit and solve the annual maximum wind speed sequence of grid points. General theories regarding the distribution characteristics of wind speed in nature indicate that the frequency of extreme strong winds does not exhibit a normally symmetrical distribution, but rather a skewed distribution with a long-tail effect. To accurately capture this spatial probability decay law, this scheme uses the Weibull extreme value distribution model to fit the extracted sequence, thereby quantifying the spatial probability of extreme typhoon wind speeds. This model structure can effectively adapt to the right-skewed distribution physical characteristics of extreme disaster data, and its cumulative distribution function formula is as follows: ; In the formula, This represents the non-exceeding probability that the annual maximum wind speed does not exceed a certain set wind speed value; This represents the annual maximum wind speed sequence variable for discrete spatial grid points, used to ensure the underlying computation of the probabilistic model holds true. The input range is strictly constrained to be no less than ; This represents the location parameter, indicating the lower limit of the maximum wind speed that may occur at this grid point; The scaling parameter controls the horizontal scaling ratio of the probability density distribution curve and the degree of data dispersion. To prevent singular anomalies caused by the denominator approaching zero in division operations, it is limited in the Newton-Raphson iterative algorithm. The lower limit of its value is a set minimum positive real number (e.g., configured as 10). -5 ); It represents the shape parameter, which determines the skewness and kurtosis characteristics of the distribution curve.

[0036] To obtain the best fit for the above model parameters, the maximum likelihood estimation method is used to solve for the parameters. A log-likelihood function is constructed for the three unknown parameters, and a system of partial derivative equations is established by taking the partial derivatives of each parameter and setting them to zero. Considering the highly nonlinear characteristics of this system of partial derivative equations, which prevent direct derivation of a mathematical analytical solution, the program employs a Newton-Raphson iterative algorithm for numerical approximation as a preferred approach. Since the nonlinear iterative mechanism is extremely sensitive to initial values, to avoid the computational engine getting stuck in local optima or divergent infinite loops, the program pre-calculates the initial baseline values ​​required for iteration using the method of moments, based on the sample mean and variance of the data sequence.

[0037] S330 utilizes the established extreme value distribution model to calculate the extreme wind speed distribution field of the target area under a specific return period, and extracts the extreme wind speed distribution boundary. Specific return period parameters are set according to the requirements of engineering disaster prevention design specifications to measure the level of defense against extreme disasters. Based on fundamental laws of probability theory, there is an inverse conversion relationship between the return period and the exceedance probability. Combining the set return period, the extreme wind speed value under the corresponding exceedance probability is calculated, and its mathematical formula is as follows: ; In the formula, This represents the predicted extreme wind speed at a discrete spatial grid point under a specific return period. This indicates the set return period parameter, the value of which is determined based on the engineering flood control level of the coastal zone. In this embodiment, it is set to 50 years or 100 years, and the system logic automatically intercepts [the data]. Illegal input parameters are used to avoid the risk of computational overflow in logarithmic field functions; It represents the logarithmic operation with the natural constant as the base.

[0038] By traversing all discrete spatial grid points within the study area and executing the above formula, a spatial distribution data matrix of extreme wind speeds for the return period covering the entire target area is generated. Spatial contour line tracing and extraction are then performed on the generated extreme wind speed distribution field. To maintain the logical consistency of the disaster-causing criteria throughout the spatial analysis scheme, the previously set level 6 wind threshold is substituted into the spatial distribution field, and all adjacent calculation nodes with predicted wind speeds equal to 10.8 m / s are traced and connected. Considering the inherent defect of jagged, broken-line deformation in the spatial contour lines obtained from pure calculations based on discrete grids, a B-spline curve smoothing algorithm is further introduced to optimize the curvature of the traced node coordinate sequence. The obtained continuous and smooth 10.8 m / s wind speed distribution contour lines are determined as the boundary of the extreme wind speed distribution for the target return period. This boundary delineates the spatial outer limit that the physical wind field of a typhoon with destructive wind intensity can reach under specific long-term probability constraints.

[0039] See attached document Figure 1 and 2 In this embodiment, step S40 specifically includes: S410, based on the topological overlay principle of spatial geographic information systems, requires unifying polygons with different spatial representation attributes into a standard reference system for geometric analysis in order to comprehensively evaluate the results of two dimensions: actual trajectory and probabilistic wind field. This involves obtaining the areal regions of the typhoon entity development boundary envelope and the areal regions of the extreme wind speed distribution boundary envelope, and then transforming both into the same geographic spatial coordinate system for spatial overlay processing. As a preferred method, an equal-area projection coordinate system is used to eliminate area deformation errors caused by the curvature of the Earth. The areal regions of the typhoon entity development boundary envelope are geometric polygons generated from the discrete point set of historical typhoon trajectories, representing the spatial range objectively reached by the center of a typhoon with destructive intensity under historical circumstances. Correspondingly, the planar region of the boundary envelope of the extreme wind speed distribution is a closed polygon of contour lines derived by the extreme distribution model based on a set return period, representing the theoretical range of the possible outward spread of the extreme wind field of a typhoon under long-sequence probability statistics.

[0040] The system performs spatial union operations to establish a comprehensive disaster prevention spatial basis that takes into account both historical objective extreme values ​​and theoretical probability predictions, avoiding biased judgments caused by relying solely on a single model or single piece of real-world data. The specific technical feature of spatial union operations is the joint calculation of Boolean sets of two-dimensional planar polygons, with the calculation formula as follows: ; In the formula, This represents the spatial union region after merging. This represents the areal region encompassing the development boundary of the input typhoon entity. This represents the planar region that encloses the boundary of the extreme wind speed distribution of the input. Operators for geometric union of spatial polygons.

[0041] S420: After obtaining the aforementioned spatial union region, it is clipped using the corresponding land base data of the coastal zone. Since the main secondary disaster prevention targets caused by typhoons in the coastal zone are located on the land side, the determination of the target analysis area requires excluding the sea surface extension. Pre-defined coastline vector data is called, and a mask polygon extending towards the land is generated. Using the coastline as a reference, the system performs a spatial topological intersection operation between the calculated spatial union region and the aforementioned mask polygon, retaining the geometric surface features projected within the range of the mask polygon. The logical expression formula for polygon intersection clipping is as follows: ; In the formula, This indicates the superimposed land area retained after land area trimming; This represents the land reference mask polygon generated from the coastline vector reference towards the land side; This refers to the geometric intersection operator for spatial polygons. Considering that when performing Boolean topological intersection operations on vector data, due to the differences in floating-point precision of the underlying coordinate nodes from different data sources, it is easy to generate geometric fragments (silver polygons) with areas much smaller than the actual physical scale at the boundary between land and water. To ensure the completeness of subsequent algorithm logic and the topological cleanliness of the output boundary, the program outputs... The system pre-configures area filtering logic. By calculating the geometric area of ​​all independent planar features, the system forcibly removes free fragmented planar features with an area smaller than a set baseline area threshold. This baseline area threshold is set based on the base area of ​​each grid point in the discrete spatial grid division in the previous steps, thereby isolating spatial topological noise purely caused by the precision of computer calculations.

[0042] S430, based on the cleaned land overlay region described above, the final outer boundary on the side furthest from the coastline is extracted as the boundary for determining the coastal zone's land influence range. Vector topological dimensionality reduction is performed on the clipped land overlay region, transforming its outer closed contour from a planar polygon into a linear boundary loop composed of continuous line segments. Within this linear boundary loop, there exists a coastal segment that conforms to and overlaps with the original coastline, and an inland segment that extends deep into the land.

[0043] To achieve the goal of extracting the outer boundary line on the side furthest from the coastline, further segment separation and topological difference calculation are performed. Specifically, a topological difference calculation is performed on the generated linear boundary loop and the baseline coastline to eliminate line segments in the boundary loop whose spatial distance from the coastline is less than a set tolerance. The physical reason for introducing the tolerance setting is that the actual geographical morphology of the coastline often presents an irregular, jagged microstructure. If a strict spatial equality judgment is applied, some coastal segments may not be effectively identified and eliminated due to slight coordinate offsets. The set tolerance value is calibrated based on the accuracy of the digital scale of the input coastline vector layer. In this embodiment, a reasonable tolerance range is configured between 10 meters and 50 meters.

[0044] The continuous line segments remaining after difference erasure constitute a boundary that extends inland from the coastline. This boundary is output and determined as the final boundary for determining the land impact range of the coastal zone. This boundary combines topographic distribution, historical disaster-causing physical upper limits, and statistical probability model upper limits to quantitatively define the geographical red line for deploying wind prevention and disaster reduction measures in space.

Claims

1. A method for determining the boundary of the influence range of the spatio-temporal variation of typhoon on the land in the coastal zone, characterized in that, Includes the following steps: Historical typhoon data of the coastal zone and adjacent land area to be analyzed are obtained and discrete spatial grids are divided. Based on the historical typhoon data, the wind speed value of each discrete spatial grid point is calculated, and typhoon events that meet the set wind speed threshold are extracted to construct a typhoon impact wind field database for disaster-causing areas. Extract the spatial distribution point set of each typhoon trajectory in the land area from the typhoon impact wind field database of the disaster-causing area, perform spatial geometric envelope operation, and extract the outermost geometric contour line to determine the typhoon entity development boundary; Extract the annual maximum wind speed sequence of each discrete spatial grid point in the typhoon impact wind field database of the disaster-causing area, fit and solve the annual maximum wind speed sequence using the extreme value probability distribution model, calculate the extreme wind speed distribution field, and extract the contour lines corresponding to the set wind speed threshold as the extreme wind speed distribution boundary. The planar region encompassing the development boundary of the typhoon entity and the planar region encompassing the extreme wind speed distribution boundary are spatially overlaid to obtain the spatial union region. The final outer boundary of the spatial union region on the side furthest from the coastline is extracted as the boundary for determining the land influence range of the coastal zone.

2. The method of claim 1, wherein the method is characterized by: Calculating the wind speed value for each discrete spatial grid point based on the historical typhoon data specifically includes: The calculations were performed using the historical typhoon data combined with the pressure wind field model and the moving wind field model. The pressure values ​​at the locations of discrete spatial grid points are calculated based on the aforementioned pressure-wind field model, and the rotational wind speed component, which characterizes the vortex kinetic energy caused by the pressure gradient difference inside the typhoon, is calculated based on the pressure distribution characteristics. The moving wind speed components at the locations of discrete spatial grid points are calculated based on the moving wind field model. The rotational wind speed component and the migrating wind speed component are combined with the azimuth angle and the wind field inflow angle to perform vector synthesis calculation, and the wind speed value of discrete spatial grid points is obtained. When the straight-line distance from the input discrete spatial grid point to the typhoon center approaches zero, the program will forcibly assign the straight-line distance to a set positive critical value. The set positive threshold value is a tiny positive number used to avoid computational singularities where the denominator is zero.

3. The method of claim 1, wherein the method is characterized by: The database of typhoon impact wind fields in disaster-causing areas, which extracts typhoon events that meet a set wind speed threshold, specifically includes: The effective duration of wind speed values ​​greater than or equal to the set wind speed threshold is statistically analyzed for each discrete spatial grid point. Representative historical typhoon records that simultaneously meet the set wind speed threshold and reach the set duration threshold are selected from the historical typhoon data and established as the typhoon impact wind field database for the disaster-causing area. The set wind speed threshold is the lower limit of a level 6 gale that can cause secondary disasters in the coastal zone, specifically 10.8 m / s. The set duration threshold is the effective duration of action used as a basis for judging the impact of the disaster.

4. The method of claim 3, wherein the method is characterized by: Before extracting the spatial distribution set of typhoon trajectories in the land area from the typhoon impact wind field database of the disaster-causing area, the following steps are also included: Perform equidistant spatial interpolation calculations on the original trajectory records of each typhoon; Calculate the spatial linear Euclidean distance between adjacent original typhoon center points in the same trajectory, and establish the average baseline length of each segment after interpolation based on the distance between adjacent points. Based on the segmented average reference length, under the constraint that the coordinates of the first and last endpoints of the typhoon center coordinate point sequence generated after interpolation coincide with the coordinates of the first and last endpoints of the original typhoon trajectory, intermediate interpolation points are generated by linear coordinate mapping on the corresponding original trajectory line segments according to the cumulative distance ratio. When the coordinates of two consecutive original recording points are the same, the scaling calculation of the interval is skipped and the original coordinate value of the location is directly used as the intermediate interpolation point.

5. The method for determining the impact range of typhoon spatiotemporal variations on the land boundary of the coastal zone according to claim 4, characterized in that, Extracting the spatial distribution set of each typhoon trajectory in the land area from the typhoon impact wind field database of the disaster-stricken area, and performing spatial geometric envelope operation specifically includes: Vector spatial data of the coastline is introduced to perform geographic boundary clipping on the intermediate interpolation points, eliminating coordinate nodes located within the ocean area, and retaining the typhoon center coordinates projected onto the land surface to form the spatial distribution point set; The Alpha Shape algorithm is called to construct a concave polygon boundary that fits the distribution characteristics of the spatial distribution point set, and the outermost continuous geometric closed line output is determined as the development boundary of the typhoon entity.

6. The method of claim 1, wherein the method is characterized by: The specific steps of fitting and solving the annual maximum wind speed sequence using an extreme value probability distribution model include: The Weibull extreme value distribution model was used to fit and calculate the annual maximum wind speed sequence; Log-likelihood functions are constructed for the location, scale, and shape parameters of the Weibull extreme value distribution model. The best fit is obtained by numerical approximation using the maximum likelihood estimation method combined with the Newton-Raphson iterative algorithm. In this process, the initial estimated benchmark value required for the Newton-Raphson iterative algorithm is calculated in advance using the sample mean and variance of the data sequence through the method of moments, and the lower limit of the scale parameter is limited to a set positive real number in the Newton-Raphson iterative algorithm. wherein the set positive real number is 10 -5 .

7. The method of claim 1, wherein the method is characterized by: Calculating the extreme wind speed distribution field and extracting the contour lines corresponding to the set wind speed threshold as the extreme wind speed distribution boundary specifically includes: By combining the conversion relationship between the return period parameter and the exceedance probability, the extreme wind speed prediction value of the corresponding discrete spatial grid point is calculated using the extreme value probability distribution model after fitting and solving, and a spatial distribution data matrix is ​​generated. Substitute the set wind speed threshold into the spatial distribution data matrix, track the adjacent calculation nodes whose extreme wind speed prediction value is equal to the set wind speed threshold to generate an initial polyline, call the B-spline curve smoothing algorithm to perform curvature optimization processing on the initial polyline, and obtain a continuous and smooth wind speed distribution contour line to determine the extreme wind speed distribution boundary.

8. The method of claim 1, wherein the method is characterized by: Specifically, obtaining the spatial union region by spatially overlaying the planar region of the typhoon entity development boundary envelope and the planar region of the extreme wind speed distribution boundary envelope includes: The planar region encompassing the boundary of the typhoon entity development and the planar region encompassing the boundary of the extreme wind speed distribution are transformed to the same equal-area projected coordinate system, and the spatial union region is obtained by performing Boolean set joint calculation of two-dimensional planar polygons. The pre-set coastline vector data is called to generate a mask polygon extending towards the land. The spatial topological intersection operation is performed on the spatial union region and the mask polygon. Free fragmented surface features with an area smaller than a set benchmark area threshold are removed, and the geometric surface features projected within the range of the mask polygon are retained as the land overlay region. The set reference area threshold is bound to the basic area of ​​a single grid point in the discrete spatial grid division, and is used to isolate spatial topological noise caused by the precision of computer calculation.

9. The method of claim 8, wherein the method further comprises: determining the boundary of the land affected by the typhoon based on the spatial and temporal variation of the typhoon. Extracting the final outer boundary of the spatial union region on the side furthest from the coastline specifically includes: The land superimposed region after cropping is subjected to vector topological dimensionality reduction processing, which transforms the outer closed contour into a linear boundary loop composed of continuous line segments; A topological difference calculation is performed on the generated linear boundary ring and the reference coastline to eliminate the coastal segments in the linear boundary ring whose spatial distance from the reference coastline is less than a set tolerance. The continuous segments that are separated from the coastline and extend into the land area after the difference is erased are determined as the final outer boundary line. The tolerance setting is determined based on the accuracy of the digital scale of the input coastline vector layer, and the value range is 10 to 50 meters.

10. The method of claim 1, wherein the method is characterized by: The specific steps for performing discrete space grid generation are as follows: The continuous geographic space is divided into several regular grid cells according to a set spatial resolution, and each grid cell serves as an independent data computing node; The spatial resolution is either a grid of 0.1 degrees by 0.1 degrees or a grid of 0.05 degrees by 0.05 degrees.

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