Method for delineating early warning areas for floating disasters based on ocean dynamic environment

Abstract

The present invention discloses a method for demarcating warning zones for floating disasters based on the ocean dynamic environment, and belongs to the field of warning zones for floating disasters at sea. The method comprises the following steps: a. selecting a protection target; b. performing characteristic analysis on the ocean dynamic environment of the sea area where the protection target is located; c. calculating the length and width of the warning zone; d. drawing the warning zone to complete the demarcation of the warning zone for floating disasters. The present invention is based on the purpose of protecting key targets or activity areas, taking into account the migration laws of floating disasters such as marine pollutants, plastic garbage, and green tides at sea, and comprehensively considering the effects of the maximum tidal current, residual current, normal wind, and unfavorable wind, and calculating the time when floating disasters arrive at the protection target, and demarcating the warning zone based on the arrival time. The warning zone obtained by this method pays more attention to specific protection targets, and the demarcated warning zone is clearer, more scientific and reasonable.

Description

Technical Field

[0001] The invention relates to the field of early warning of floating disasters at sea, and in particular to a method for demarcating early warning areas of floating disasters based on ocean dynamic environment. Background Art

[0002] Floating disasters at sea include marine pollutants, plastic waste, and green tides. In order to protect important targets such as offshore sports venues, marine aquaculture areas, ecological protection red line areas, nuclear power water intakes, and to respond to possible sudden pollution accidents and ecological disasters such as green tides, it is necessary to delineate scientific and reasonable early warning areas and deploy disposal forces to the early warning areas in advance to reduce the response time and cost when disasters occur. The delineation of early warning areas will help improve the emergency response efficiency of relevant departments, ensure that emergency plans can be quickly activated when offshore oil spills, green tides, etc. occur, and effectively organize human and material resources to respond.

[0003] However, if the warning area is set too large, it will lead to a waste of disposal resources and disposal forces; if the warning area is set too small, it will lead to a tight emergency response time and failure to complete disaster disposal in a timely and effective manner. It is crucial to scientifically and reasonably delineate the warning area.

[0004] Traditional methods for demarcating early warning areas are mainly divided into two categories: one is the statistical method, which is based on the historical records of marine oil spills or green tide disasters. Experts use experience to identify possible risk areas and formulate early warning areas accordingly. The second is the physical model method, which establishes a drift prediction model for floating objects such as marine oil spills and green tides based on physical processes, and predicts possible risk areas by simulating the physical mechanism of the occurrence and development of floating objects. Both methods start from the disaster itself and demarcate possible risk areas based on the monitoring and prediction of disasters that have already occurred. This results in the demarcation of risk areas being heavily dependent on the monitoring and prediction results of sudden disasters. Once the monitoring is not timely or the prediction is not accurate, there will be greater uncertainty and prediction errors in the demarcation of early warning areas. Summary of the invention

[0005] Based on the above technical problems, the present invention proposes a method for demarcating floating disaster warning areas based on the ocean dynamic environment.

[0006] The technical solution adopted by the present invention is:

[0007] A method for delineating a floating disaster warning zone based on an ocean dynamic environment comprises the following steps:

[0008] a. Select the target to be protected;

[0009] b. Conduct characteristic analysis of the marine dynamic environment of the sea area where the protection target is located;

[0010] c. Determine the length of the warning zone;

[0011] The length of the warning zone is the distance that floating disasters caused by the combined effects of wind and current will move within a set time in the coastal direction of the protected target location;

[0012] d. Determine the width of the warning zone;

[0013] The width of the warning zone is the distance that floating disasters caused by the combined effects of wind and current move within a set time in the offshore direction of the protected target location;

[0014] e. Draw the warning area;

[0015] Based on the length of the warning area determined in step c and the width of the warning area determined in step d, draw the warning area of ​​the protection target and complete the delineation of the floating disaster warning area.

[0016] Preferably, in step a: the protection targets include seaside parks, nuclear power plant water intakes, sailing competition areas and marine aquaculture areas.

[0017] Preferably, step b includes: collecting historical observation data on water depth, ocean current, and sea surface wind in the sea area where the protection target is located; and statistically analyzing tidal characteristics, tidal current characteristics, rising and falling tide directions, maximum tidal current velocity, residual current velocity, flow direction, and wind extremes in the sea area where the protection target is located.

[0018] Preferably, in step c:

[0019] Length of warning zone The calculation formula is as follows: ;in, ;

[0020] is the migration distance of floating disasters caused by tidal currents, and the calculation formula is as follows:

[0021] ;

[0022] Where R1 is the ocean current coefficient, is the component of the maximum tidal current velocity in the coastal direction, and T is the time;

[0023] It is the migration of floating disasters caused by wind-driven currents. The calculation formula is as follows:

[0024] ;

[0025] Where R1 is the ocean current coefficient, is the residual flow velocity, T is the time;

[0026] is the distance moved by wind, and the calculation formula is as follows:

[0027] ;

[0028] In the formula, R2 is the wind action coefficient, is the wind speed component in the coastal direction, and T is the time.

[0029] Preferably, by collecting historical observation data of ocean currents in a certain time series, using the least squares method to perform harmonic analysis and calculation, the characteristic value of the tide is obtained, and then the and ; By collecting historical observation data of the sea surface wind field near the protection target, statistically analyzing the constant wind speed and wind direction, and calculating the wind speed component in the coastal direction .

[0030] Preferably, in step d:

[0031] The calculation formula for the width of the warning area is as follows:

[0032] ;

[0033] In the formula, R2 is the wind action coefficient, is the maximum value of the wind speed statistics in the onshore wind direction, and T is the time.

[0034] Preferably, for different floating disasters, the value of R2 is different, and the value of R2 can be obtained by referring to references.

[0035] More preferably, the floating disaster is green tide of Enteromorpha or oil pollution at sea. For green tide of Enteromorpha, R2 takes the value of 0.011~0.013, and for oil pollution at sea, R2 takes the value of 0.02~0.03.

[0036] Preferably, in step e: the warning area of ​​the protection target is a rectangle, and the top edge of the rectangle is Vertical translation The width of the rectangle is measured, and then the two ends of the top edge are used as starting points to draw two sides of the rectangle vertically to the coastline; the protection target is at the center of the migration distance of floating disasters caused by the tide.

[0037] Preferably, in step e: it also includes a method of expanding the length and width of the warning area by multiples to obtain the range of the warning area in different time periods.

[0038] The beneficial technical effects of the present invention are:

[0039] The present invention starts from the purpose of protecting key targets or activity areas, and targets protected targets such as seaside parks, sailing competition areas, marine ranches, seawater aquaculture areas, nuclear power water intakes, etc., takes into account the migration laws of harmful substances such as offshore oil spills, green tides of Enteromorpha, and plastic garbage at sea, and comprehensively considers the effects of maximum tidal currents, residual currents, normal winds, and unfavorable winds to calculate the time when floating disasters arrive at the protected targets, and demarcates the early warning areas based on the arrival time. The early warning areas obtained by this method focus more on specific protected targets, and the demarcated early warning areas are clearer, more scientific, and more reasonable, which facilitates the timely activation of emergency plans and saves emergency response resources and response time.

[0040] The present invention provides a method for delineating early warning zones for floating disasters that comprehensively considers ocean dynamic environments such as ocean currents, sea surface winds, and geographic spatial locations. The method is based on the analysis of regional tidal currents and wind field environmental characteristics, combined with a floating disaster drift prediction numerical model, to quantify the duration and range of floating disasters affecting protection targets, so that 24h, 48h, and 72h early warning zones can be accurately delineated for different protection targets, thereby providing data support for relevant agencies to formulate response strategies, improving the scientificity and effectiveness of decision-making, and playing a positive role in the fields of environmental protection and disaster prevention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0042] Figure 1 It is a flow chart of the method for demarcating early warning areas of floating disasters based on the ocean dynamic environment of the present invention;

[0043] Figure 2 It is a marked schematic diagram of calculating the migration of floating disasters caused by tidal currents in a specific application example of the present invention;

[0044] Figure 3 It is a marked schematic diagram for calculating the migration of floating disasters caused by wind-driven currents in a specific application example of the present invention;

[0045] Figure 4 It is a marked schematic diagram for calculating the migration of floating disasters caused by the coastal wind direction in a specific application example of the present invention;

[0046] Figure 5 It is a marked schematic diagram for calculating the migration of floating disasters caused by the onshore wind direction in a specific application example of the present invention;

[0047] Figure 6 It is a schematic diagram of the early warning area drawn in a specific application example of the present invention;

[0048] Figure 7 It is a schematic diagram of the scope of the warning area obtained by enlarging the length and width by multiples in a specific application example of the present invention. DETAILED DESCRIPTION

[0049] like Figure 1 As shown, a method for delineating a floating disaster warning zone based on an ocean dynamic environment comprises the following steps:

[0050] a. Select the target to be protected.

[0051] Protection targets include seaside parks, nuclear power plant water intakes, sailing competition areas and marine aquaculture areas.

[0052] b. Conduct characteristic analysis of the ocean dynamic environment of the sea area where the protection target is located.

[0053] Specifically, historical observation data on water depth, ocean currents, and sea surface winds in the sea areas where the protection targets are located are collected; statistical analysis is performed on tidal characteristics, current characteristics, directions of rising and falling tides, maximum tidal velocity, residual current velocity, flow direction, and wind extremes in the sea areas where the protection targets are located.

[0054] c. Determine the length of the warning zone.

[0055] The length of the warning zone is the distance that floating disasters caused by wind and current move within a set time along the coast of the protected target. Therefore, the length is determined based on the warning time. The length of the 24h warning zone refers to the distance that floating disasters move along the coast under the action of wind and current within 24 hours.

[0056] Length of warning zone The calculation formula is as follows: ;in, .

[0057] The floating disaster migration distance caused by the tide. For the migration of floating objects caused by the tide, the average tidal velocity in the coastal direction within a tidal cycle can be used as the migration distance. Since the tidal velocity varies within the tidal cycle, half of the maximum velocity can be taken as the average velocity. The calculation formula is as follows:

[0058] ;

[0059] Where R1 is the ocean current coefficient, is the component of the maximum tidal flow velocity in the coastal direction (the maximum tidal flow velocity refers to the maximum flow velocity that may be reached due to the action of tides in a specific sea area or port under natural conditions), and T is time.

[0060] The displacement of floating objects caused by wind-driven currents is calculated based on the displacement caused by the residual current velocity within a tidal cycle. The calculation formula is as follows:

[0061] ;

[0062] Where R1 is the ocean current coefficient, is the residual flow velocity, and T is the time.

[0063] For the distance moved by wind , can be calculated according to the component of the constant wind in the coastal direction of the area ( ) is calculated using the following formula:

[0064] ;

[0065] In the formula, R2 is the wind action coefficient, is the wind speed component in the coastal direction, and T is the time.

[0066] Coastal currents are generally composed of tidal currents and wind-driven currents. Therefore, when calculating the displacement caused by the current, the displacement caused by the tidal current and the displacement caused by the wind-driven current are usually calculated separately and then superimposed.

[0067] The migration of floating hazards caused by tidal currents in the coastal direction is calculated based on the migration distance under the action of the average tidal velocity (half the maximum tidal velocity) within one tidal cycle.

[0068] For the movement of floating hazards caused by wind-driven currents in the coastal direction, the displacement caused by the residual current velocity within a tidal cycle is calculated. and By adding them together, we can obtain the migration distance of floating disasters within a tidal cycle when only considering the effect of ocean currents.

[0069] d. Determine the width of the warning zone;

[0070] The width of the warning zone is the distance that floating disasters caused by wind and current move in the set time in the offshore direction of the protected target. Therefore, the width is determined based on the warning time. The width of the 24h warning zone refers to the distance that floating disasters move toward the shore under the action of wind and current within 24 hours. Since the ocean currents in the nearshore area are generally along the coast, the distance of migration to the coast is very small and can be ignored in the calculation of this method. Only the migration distance of floating disasters under the action of the onshore wind direction is calculated.

[0071] The calculation formula is as follows:

[0072] ;

[0073] In the formula, R2 is the wind action coefficient, is the maximum value of the wind speed statistics in the onshore wind direction, and T is the time. The span of the warning zone perpendicular to the coastline, that is, the width of the warning zone.

[0074] In the above steps, the wind speeds considered for calculating the length and width of the warning zone are different. The length of the warning zone is calculated by considering the average value along the coast, while the width of the warning zone is calculated by considering the maximum value towards the coast.

[0075] For different floating disasters, R2 values ​​are different, and the R2 values ​​can be obtained by consulting references. For example, floating disasters can be Enteromorpha green tide or marine oil pollution. For Enteromorpha green tide, R2 values ​​are 0.011~0.013, and for marine oil pollution, R2 values ​​are 0.02~0.03.

[0076] e. Draw the warning area;

[0077] Based on the length of the warning area determined in step c and the width of the warning area determined in step d, draw the warning area of ​​the protection target and complete the delineation of the floating disaster warning area.

[0078] The warning area of ​​the protection target is a rectangle with the top edge of Vertical translation The width of the rectangle is measured, and then the two ends of the top edge are used as starting points to draw two sides of the rectangle vertically to the coastline; the protection target is at the center of the migration distance of floating disasters caused by the tide.

[0079] Furthermore, in step e: it also includes a method of expanding the length and width of the warning area by multiples to obtain the scope of the warning area in different time periods.

[0080] Specifically, based on the length and width of the 24h warning zone calculated in step c and step d, the 24h warning zone of the protection target is drawn using software such as geographic information system; the length and width are further expanded by multiples to obtain the range of 48h, 72h and 96h warning zones respectively.

[0081] In the above steps: the length of the warning zone is the distance that the floating disaster caused by the combined action of wind and current moves in the coastal direction within a set time or a certain period of time. The width of the warning zone is the distance that the floating disaster caused by the combined action of wind and current moves in the shoreward direction within a certain period of time.

[0082] Will and Add them together to get the displacement under the action of ocean current only and the displacement caused by wind in the coastal direction , the distance obtained is the span of the 24h warning area along the direction of the tide (the direction of the tide is parallel to the coastline), that is, the length of the warning area. Calculate the migration distance of floating disasters under the most unfavorable wind direction. Here, the most unfavorable wind direction refers to the shoreward wind direction, because the protection targets are generally in the nearshore area. The onshore wind will cause the landing of Enteromorpha, oil pollution, etc., affecting the nearshore protection targets. In addition, the ocean currents in the nearshore area are generally along the coast, and the distance of the onshore migration is very small and can be ignored. The calculated The span of the 24-hour warning zone perpendicular to the coastline, that is, the width of the warning zone.

[0083] In the above step c: by collecting historical ocean current observation data of a certain time series (not less than 25 hours), using the least squares method to perform harmonic analysis and calculation, the characteristic value of the tide is obtained, and then the and By collecting historical observation data of the sea surface wind field near the protection target, statistically analyzing the constant wind speed and wind direction, and calculating the component of the constant wind in the coastal direction, that is, the wind speed component .

[0084] Furthermore, and The specific calculation steps are as follows:

[0085] c1. Obtain continuous ocean current observation data in the study area.

[0086] c2. Perform harmonic analysis on the continuous observation data and calculate the tidal current characteristic value using the least squares method based on the harmonic equation.

[0087] c3. Calculate the maximum tidal flow velocity .

[0088] For regular semi-diurnal tidal waters, The calculation formulas are:

[0089] ;

[0090] In the formula , , , etc. represent the major axes of the tidal ellipses of different tidal components, namely, M2 tidal component, S2 tidal component, K1 tidal component, and O1 tidal component.

[0091] For regular all-day tidal waters, The calculation formulas are:

[0092] ;

[0093] For irregular diurnal tidal sea areas and irregular semi-diurnal tidal sea areas, Take the maximum of the two.

[0094] In the above steps, M2 is the lunar semi-diurnal tide, S2 is the solar semi-diurnal tide, K1 is the lunar solar declination diurnal tide, and O1 is the lunar diurnal tide. These are the most important tides in the Chinese seas. The publicly downloadable T-tide software package is usually used. With this software package, only continuous observation data of more than 24 hours is input to obtain the harmonic analysis results of the major axis of the ellipse, the minor axis of the ellipse, the residual flow, etc. of each tide.

[0095] c4. Calculate the residual flow velocity;

[0096] The residual current velocity is the vector sum of the velocity of each tidal current after harmonic analysis minus the measured current data. The measured data is the ocean current data for more than 25 hours used for harmonic analysis. The velocity of each tidal current is the velocity of the M2 tidal current, S2 tidal current, K1 tidal current, O1 tidal current, etc. mentioned above. The vector sum is the sum of the u component and v component of the velocity of each tidal current. The u component refers to the velocity in the longitudinal direction, and the v component refers to the velocity in the latitudinal direction. In other words, the residual current is the measured current minus the periodic tidal current. The tidal current is the superposition of different periodic tidal currents. For example, the M2 tidal current is the semi-diurnal tidal current caused by the gravity of the moon, and the S2 tidal current is the semi-diurnal tidal current caused by the gravity of the sun, etc. These are all fixed periods. Harmonic analysis is to strip out the corresponding velocity according to the fixed period of these tidal currents. After stripping, what is left is called residual current. It represents the average wind-driven current, density current, etc. over a period of time.

[0097] In other words, the residual current velocity is the measured current data minus the periodic tidal current velocity, that is, the measured current data minus the vector sum of the velocities of each tidal current after harmonic analysis (it needs to be clarified that the measured data refers to the continuous current observation data of 24 hours or more obtained in the study sea area for harmonic analysis, and the observation interval is not more than 1 hour. The vector sum of the velocities of each tidal current refers to the superposition of the velocities corresponding to each tidal current such as M2, S2, O1 and K1).

[0098] In the above step d: by collecting historical observation data of the sea surface wind field near the protection target, counting the maximum wind speed and wind direction, and calculating the wind force value in the shore direction .

[0099] The principle content on which the method of the present invention is based is described below:

[0100] Generally speaking, drifting objects at sea are affected by natural factors (wind, waves, tides, currents) and will not appear at the original accident site or the last reported location. The drifting motion equation of floating objects on the sea surface is as follows:

[0101] (1)

[0102] Where V represents the speed of the object, and F represents the sum of all driving forces acting on the object, generally referring to wind, wind-driven currents, surges, waves, tidal currents, etc. Refers to the wind driving force, Refers to the wave driving force, Refers to the driving force of the flow. Among them, the relative movement of the object to the water caused by the wind acting on the water part of the floating object is related to the properties of the object itself. It is necessary to quantify the drag force based on sea tests or laboratory experiments. For a given target, it is difficult to determine the exact value of the wind pressure and direction. In practice, it is generally estimated based on a large amount of experimental data. The influence of ocean currents mainly includes wind-driven currents and tidal currents. Among them, wind-driven currents are currents formed by persistent wind blowing on the sea surface. Under normal circumstances, local surface wind-driven ocean currents are generated only when the wind direction remains unchanged and lasts for 6-12 hours. Due to the repeated pulling effect of the tide, the tidal current generally keeps the target in place, thereby reducing the impact on the movement of the target at sea. The cumulative effect may pull the target into the area of ​​the current. The longshore current refers to the water flow formed by the surface water particles moving forward significantly when the waves hit the shore in the shallow water area. The upper layer flows forward and the bottom layer forms a backflow. It is generally only considered within 1 nautical mile from the shore. The impact of surge on the target can generally be ignored because the surge is the vertical movement of the water particles. The effect of waves on objects is generally ignored. On the one hand, in the short wave range, the wave drift force is mainly the wave scattering that pushes the drifter. Therefore, the drift speed is determined by the balance of the wave drift force and the flow force, which is proportional to the inclination of the wave. On the other hand, in the long wave range, the wave drift force has almost no effect on the drifter. Because the waves are almost entirely used to transport floating objects. Therefore, the drift speed is determined by the speed of the waves and is proportional to the square of the wave inclination. Therefore, in near-shore shallow waters, the effect of waves on objects less than 30m in length is generally not considered. Among the above-mentioned factors that affect the drift of the target, wind drag, wind-induced currents and tidal currents are the main ones, so calculations are usually carried out around these three factors.

[0103] Usually, the mathematical model of hydrodynamics is based on the Euler field, but to describe the motion of particles, the Lagrangian viewpoint needs to be adopted, which involves how to convert the results in the Euler field into Lagrangian particle displacement.

[0104] In the Euler field, for a two-dimensional plane problem, the velocity of any point in space can be expressed as:

[0105] (2)

[0106] Using the Lagrangian viewpoint, the velocity of any particle can be expressed as:

[0107] (3)

[0108] The above formula actually establishes a first-order ordinary differential equation for solving the displacement of the particle. Rewriting the above formula, the trajectory of the particle can be obtained by the following integral:

[0109] (4)

[0110] If every moment It is known that the motion trajectory of the particle can be calculated from the above formula through numerical integration.

[0111] Drift velocity of particles The calculation formula is:

[0112] (5)

[0113] Where:

[0114] —Velocity components resulting from wind and wave action;

[0115] —Velocity component caused by tidal current;

[0116] —Velocity components generated by circulation (including wind currents and density currents).

[0117] That is to say, first calculate the drift speed of floating disasters in the sea area; according to the force analysis of floating disasters when drifting at sea, use the Lagrangian particle tracking method to discretize the floating disasters into a certain number of particle points, consider the dragging effect of wind and flow on the particle points, and determine the wind and flow coefficients based on offshore and indoor drift tests and numerical sensitivity tests to calculate the drift speed of floating disasters.

[0118] It should be pointed out that the velocity component generated by wind and wave action is related to the windward surface and other properties of the object, which is usually obtained through offshore drift observation tests and can generally be calculated using the following formula:

[0119] (6)

[0120] Where R2 is the drag coefficient, which is generally 0.011-0.013 for Enteromorpha green tide and 0.02-0.03 for marine oil pollution. The coefficients for other floating objects can be obtained by consulting references.

[0121] In the above formulas, the flow velocity is a vector. In the application of this method, it is decomposed into two directions: along-shore direction and onshore direction.

[0122] Based on the drift speed, the drift distance (X) of an object in any period of time (dt) can be calculated:

[0123] (7)

[0124] From the above calculation formula, it can be seen that to calculate the maximum possible migration distance (X) of floating disasters within a certain warning time (dt), it is necessary to proceed in two steps. The first step is to calculate the displacement caused by ocean currents, and the second step is to calculate the displacement caused by sea surface winds.

[0125] This method integrates key factors such as ocean currents, sea surface winds and geographic spatial locations, and provides an early warning method that comprehensively considers the impact of various natural conditions. This method is goal-oriented. Unlike traditional methods, this method focuses on the protection target and delineates the early warning area for specific protection areas, which enhances the practicality and pertinence of the early warning. Through a numerical model based on physical processes, this method can scientifically quantify the impact of floating disasters on the protection target, and can provide accurate early warning areas for different time periods (24h, 48h, 72h), thereby improving the accuracy of the early warning. This method can flexibly adjust the size and time range of the early warning area according to different protection targets and needs, and has good adaptability. This method also improves the technical content and convenience of the early warning area delineation method. This method is based on a large amount of historical observation data and statistical analysis, and is data-driven, ensuring the data-driven and scientific nature of the early warning results.

[0126] By scientifically demarcating early warning areas, the present invention helps to minimize the time and cost of emergency response when a disaster occurs, reducing potential economic losses. The present invention can improve the emergency response efficiency of relevant departments and ensure that emergency plans can be quickly activated when a disaster occurs. It helps to optimize resource allocation and avoid unnecessary waste of resources. By reducing the impact of floating disasters such as offshore oil pollution and green tides on coastal social and economic activities, the present invention helps to protect residents' lives and tourism, and has significant social and economic benefits.

[0127] To sum up, the present invention embodies comprehensive advantages in terms of scientificity, practicality, accuracy, adaptability, technological advancement, environmental friendliness and socio-economic benefits, and provides an efficient and reliable solution for emergency response to emergencies such as offshore oil pollution, early warning and management of ecological disasters such as green tide disasters caused by enteromorpha.

[0128] The present invention will be further described below in conjunction with specific application examples.

[0129] Taking a sailing competition venue as an example, based on the method provided by the present invention, the early warning area for green tide disaster of Enteromorpha is delineated, and the steps are as follows:

[0130] (1) Selecting protection targets;

[0131] The protection target is a sailing venue.

[0132] (2) Analysis of the characteristics of the ocean dynamic environment in the target area;

[0133] Collect observation data on water depth, ocean currents (high tide period of no less than 25 hours), and sea surface wind (no less than 1 year in summer) in the sea area where the protection target is located.

[0134] The T-tide software package was used to harmonize and analyze the measured ocean current data, and the maximum tidal current velocity in the area was found to be 0.5 m / s; the average residual current velocity was 0.02 m / s.

[0135] Statistical analysis of the measured sea surface wind data shows that the constant wind in this area during this season is south-southeast, and the average wind speed along the coast is about 1m / s.

[0136] Statistical analysis of the measured sea surface wind data revealed that the wind level in the unfavorable wind direction (180° onshore wind direction) was 10m / s.

[0137] (3) Calculate the length and width of the warning area;

[0138] First, apply the calculation formula for the length of the warning zone ; Among them, the formula is applied , we can conclude . Apply the formula , we can conclude .

[0139] ,get .

[0140] Figure 2 The displacement caused by tides is shown (black line segment), and the protection target (sailing area) is located at the center of the line segment. and By adding them together, we can obtain the migration span caused by the ocean current in the 24h warning area along the direction of high and low tide (the direction of high and low tide is parallel to the coastline). Figure 3 The displacement caused by the residual flow (black line segment) is shown. According to the residual flow direction (45°), the displacement Then add the displacement caused by the coastal wind. Get the length of the 24h warning zone. Figure 4 shows the displacement caused by the coastal wind (black line), added to superior.

[0141] Secondly, calculate the distance that Enteromorpha moves under the action of onshore wind, and apply the formula ,get This distance is used as the span of the 24h warning zone perpendicular to the coastline, that is, the width of the warning zone. Figure 5 The displacement caused by onshore wind direction is shown (solid black line in the figure), in the onshore direction.

[0142] (4) Drawing of early warning zones by time period;

[0143] Based on the length and width of the 24-hour warning zone calculated in step (3), the 24-hour warning zone of the protection target is drawn using software such as geographic information system. Figure 6 Shows the 24h warning area range.

[0144] Expand the length and width by multiples to obtain the 48h and 72h warning areas, respectively, to form a complete warning area, such as Figure 7 shown.

Claims

1. A method for defining early warning areas for floating disasters based on the ocean dynamic environment, characterized in that The following steps are involved: a. Select the target to be protected; b. Conduct characteristic analysis of the marine dynamic environment of the sea area where the protection target is located; c. Determine the length of the warning zone; The length of the warning zone is the distance that floating disasters caused by the combined effects of wind and current will move within a set time in the coastal direction of the protected target location; d. Determine the width of the warning zone; The width of the warning zone is the distance that floating disasters caused by the combined effects of wind and current move within a set time in the offshore direction of the protected target location; e. Draw the warning area; Based on the length of the warning area determined in step c and the width of the warning area determined in step d, draw the warning area of ​​the protection target to complete the delineation of the floating disaster warning area; Step b includes: collecting historical observation data of water depth, ocean current and sea surface wind in the sea area where the protection target is located; statistically analyzing the tidal characteristics, tidal current characteristics, rising and falling tide direction, maximum tidal current velocity, residual current velocity, flow direction and wind extreme value of the sea area where the protection target is located; In step c: Warning zone length L 长 The calculation formula is as follows: 长 =L 流 +L 风 Among them, L 流 =L cur +L res ; L cur is the migration distance of floating disasters caused by tidal currents, and the calculation formula is as follows: L cur =R1×V max / 2×T; Where R1 is the ocean current coefficient, V max is the component of the maximum tidal current velocity in the coastal direction, and T is the time; L res It is the migration of floating disasters caused by wind-driven currents. The calculation formula is as follows: L res =R1×V res ×T; Where R1 is the ocean current coefficient, V res is the residual flow velocity, T is the time; L 风 is the distance moved by wind, and the calculation formula is as follows: L 风 =R2×V wnd1 ×T; Where R2 is the wind action coefficient, V wnd1 is the wind speed component in the coastal direction, T is the time; In step d: The calculation formula for the width of the warning area is as follows: L 宽 =L wnd =R2×V wnd2 ×T; Where R2 is the wind action coefficient, V wnd2 is the maximum value of wind speed statistics in the onshore wind direction, and T is time; By collecting historical observation data of ocean currents in a certain time series and using the least squares method to perform harmonic analysis and calculation, the characteristic value of the tide is obtained, and then V is obtained. max and V res ; By collecting historical observation data of the sea surface wind field near the protection target, statistically analyzing the constant wind speed and wind direction, and calculating the wind speed component V in the coastal direction wnd1 ; V max The specific calculation steps are as follows: c1. Obtain continuous ocean current observation data in the research area; c2. Perform harmonic analysis on the continuous observation data and calculate the tidal current characteristic value using the least square method based on the harmonic equation; c3. Calculate the maximum tidal flow velocity V max ; For regular semi-diurnal tidal waters, V max The calculation formula is: V max =1.295W M2 +1.245W S2 +W K1 +W O1 +W M4 +W MS4 ; Where W M2 , W S2 , W K1 , W O1 Represent the major axes of the tidal ellipses of the M2, S2, K1, O1, M4 and MS4 tides respectively; For regular all-day tidal waters, V max The calculation formula is: V max =W M2 +W S2 +1.600W K1 +1.450W O1 ; For irregular diurnal tidal areas and irregular semi-diurnal tidal areas, V max Take the maximum of the two.

2. A method for delineating early warning areas for floating disasters based on the marine dynamic environment according to claim 1, characterized in that: In step a: the protection targets include seaside parks, nuclear power plant water intakes, sailing competition areas and marine aquaculture areas.

3. The method for defining early warning areas for floating disasters based on the marine dynamic environment according to claim 1 is characterized in that: For different floating disasters, the R2 value is different, and the R2 value can be obtained by referring to references.

4. The method for defining early warning areas for floating disasters based on the marine dynamic environment according to claim 3 is characterized in that: Floating disasters include green tides of Enteromorpha or oil pollution at sea. For green tides of Enteromorpha, the R2 value is 0.011-0.013, and for oil pollution at sea, the R2 value is 0.02-0.

03.

5. The method for defining early warning areas for floating disasters based on the marine dynamic environment according to claim 1 is characterized in that: In step e: the warning area of ​​the protected target is a rectangle, and the top edge of the rectangle is L 长 Vertical translation L wnd The width of the rectangle is measured, and then the two ends of the top edge are used as starting points to draw two sides of the rectangle vertically to the coastline; the protection target is at the center of the migration distance of floating disasters caused by the tide.

6. The method for demarcating floating disaster warning areas based on the ocean dynamic environment according to claim 1 is characterized in that: Step e also includes expanding the length and width of the warning area by multiples to obtain the scope of the warning area in different time periods.

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