Method for Extracting Mesoscale Eddy and Target Catch Spatial Distribution Information in Target Sea Area

Abstract

The present invention relates to a method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area, including: obtaining mesoscale eddy data of the target sea area, target catch data, and absolute dynamic height data of the target sea area; obtaining the contour line of the eddy based on the mesoscale eddy data of the target sea area, and calculating the target catch yield within the eddy area; when the fishing location is not within the eddy area, determining whether the fishing location is within the boundary area of the eddy, and if so, calculating the target catch yield within the eddy boundary area; statistically analyzing the target catch yield in the eddy area and the target catch yield within the eddy boundary area to obtain a statistical result; and determining the spatial distribution relationship between the mesoscale eddy and the target catch yield according to the statistical result. The present invention provides information reference for the sustainable development and utilization of target resources in the target sea area.

Description

Technical Field

[0001] The present invention relates to the technical field of the application of fishery ocean environment data, and particularly to a method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area. Background Art

[0002] Scomber japonicus belongs to the Scombridae family and the Scomber genus, commonly known as mackerel. It is a warm-water small pelagic fish that lives in the water layer within 0 - 300 meters of water depth. It has phototaxis, strong swimming ability, and a general life cycle of 2 - 5 years. It is widely distributed in the western North Pacific and the Russian Far East region, and can reach the Sea of Okhotsk at the northernmost. It is one of the important marine economic fish. They have the characteristic of seasonal migration. In spring and summer, they move northward to feed, and in autumn, they move southeastward to overwinter. The Scomber japonicus fishing ground in the North Pacific belongs to a cold and warm current confluence type fishing ground, located in the confluence area of the Kuroshio warm water system and the Oyashio cold water system with a complex water mass structure. The distribution of the Scomber japonicus fishing ground and the resource changes are affected by marine environmental factors such as sea surface temperature, sea surface height, and sea surface salinity. Since 2013, domestic fishing boats have started to carry out light purse seine fishing operations in the northwest Pacific Ocean, fishing mainly for pelagic fish such as Scomber japonicus, with an annual output of up to more than 100,000 tons.

[0003] The North Pacific is located in a cold and warm current confluence area, and mesoscale eddy activities are frequent. The diameter of mesoscale eddies ranges from dozens of kilometers to hundreds of kilometers, and the duration spans from several days to several years. In the Northern Hemisphere, affected by the Coriolis force, the center of an anticyclonic eddy forms a vertically downward water body movement, which warms the water body inside it. The water body at the sea surface converges towards the center, and the sea surface height shows a positive anomaly. While the center water body of a cyclonic eddy moves vertically upward, which cools the water body inside it. The water body at the sea surface shows outward divergence, and the sea surface height is a negative anomaly.

[0004] Mesoscale eddies promote the vertical and horizontal mixing of the water body in the area where they are located, reduce the depth of the thermocline, bring the nutrients at the bottom layer to the seawater surface layer with stronger photosynthesis, increase the biological productivity, and at the same time provide rich bait for fish. Mesoscale eddies can also carry water bodies containing heat, salt, and nutrients to move in the ocean. Currently, there is no research on analyzing the distribution relationship between mesoscale eddies and the Scomber japonicus fishing ground in the North Pacific. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area, which can extract the spatial distribution information of mesoscale eddies and target catches in the target sea area from the mesoscale eddy data, target catch data, and absolute dynamic height data of the target sea area.

[0006] The technical solution adopted by the present invention to solve its technical problems is: to provide a method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area, including the following steps:

[0007] (1) Obtain the mesoscale eddy data of the target sea area, the catch data of the target, and the absolute dynamic height data of the target sea area;

[0008] (2) Based on the mesoscale eddy data of the target sea area, obtain the contour line of the eddy and calculate the target catch yield within the eddy area;

[0009] (3) When the fishing location is not within the eddy area, determine whether the fishing location is within the boundary area of the eddy. If so, calculate the target catch yield within the eddy boundary area;

[0010] (4) Statistically analyze the target catch yield in the eddy area and the target catch yield within the eddy boundary area to obtain a statistical result;

[0011] (5) According to the statistical result, determine the spatial distribution relationship between the mesoscale eddy and the target catch yield.

[0012] A preprocessing step is further included between step (1) and step (2). Specifically: remove the large-scale features above 700 km from the absolute dynamic height data through a high-pass filter; perform superposition analysis on the mesoscale eddy data, the target catch data, and the absolute dynamic height data on a daily basis.

[0013] Step (2) is specifically: use the closed absolute dynamic height isoline with the largest average geostrophic flow velocity as the boundary line of the eddy, and use the Winding Number method to statistically analyze the catch yield within the contour line of the eddy, that is, within the eddy area.

[0014] In step (3), determining whether the fishing location is within the eddy boundary area is specifically:

[0015] (31) Subtract the radius of the eddy from the distance from the fishing location to the center of the eddy to obtain the distance between the fishing location and the eddy contour line, and select the two eddies with the smallest distance values;

[0016] (32) Equally divide the connection lines between the fishing location and the centers of the two selected eddies respectively to obtain the absolute dynamic height values at the equal division points;

[0017] (33) Search for the intersection points of the connection line between the fishing location and the eddy center and the eddy contour line;

[0018] (34) Determine whether the fishing location is within the eddy boundary area according to whether the connection line from the intersection point to the fishing location is within the eddy boundary area.

[0019] In the step (31): The two vortices with the minimum distance from the fishing location to the vortex contour line are divided into four cases: both vortices are anticyclones, both vortices are cyclone vortices, the first is an anticyclone vortex and the second is a cyclone vortex, and the first is a cyclone vortex and the second is an anticyclone vortex.

[0020] The step (33) is specifically as follows: When the vortex is a cyclone vortex, find the first point with an absolute dynamic height value greater than or equal to the absolute dynamic height value on the vortex contour line from the equally divided points of the connection line in the order from the center of the vortex to the fishing location as the intersection point; when the vortex is an anticyclone vortex, find the first point with an absolute dynamic height value less than or equal to the absolute dynamic height value on the vortex contour line from the equally divided points of the connection line in the order from the center of the vortex to the fishing location as the intersection point.

[0021] In the case where the fishing location in the step (34) is located within the boundary area of the vortex, it is divided according to the absolute dynamic height isolines at a preset interval, and the vortex boundary area is divided into four areas, namely the first vortex boundary area, the second vortex boundary area, the third vortex boundary area, and the fourth vortex boundary area; the first vortex boundary area corresponds to the area between the 0m and 0.02m ADT isolines around the cyclone vortex contour line and the area between the 0m and -0.02m ADT isolines around the anticyclone vortex contour line; the second vortex boundary area corresponds to the area between the 0.02m and 0.04m ADT isolines around the cyclone vortex contour line and the area between the -0.02m and -0.04m ADT isolines around the anticyclone vortex contour line; the third vortex boundary area corresponds to the area between the 0.04m and 0.06m ADT isolines around the cyclone vortex contour line and the area between the -0.04m and -0.06m ADT isolines around the anticyclone vortex contour line; the fourth vortex boundary area corresponds to the area between the 0.06m and 0.08m ADT isolines around the cyclone vortex contour line and the area between the -0.06m and -0.08m ADT isolines around the anticyclone vortex contour line.

[0022] The step (34) is specifically as follows: When the vortex is a cyclone vortex, if the maximum absolute dynamic height value on the connection line from the intersection point to the fishing location is less than or equal to the value of the isoline around the vortex contour line, then the connection line is located within the corresponding isoline around the vortex contour line; when the vortex is an anticyclone vortex, if the minimum absolute dynamic height value on the connection line from the intersection point to the fishing location is greater than or equal to the value of the isoline around the vortex contour line, then the connection line is located within the corresponding isoline around the vortex contour line.

[0023] The target catch yields in the vortex region and the vortex boundary region are stored in the form of a three-dimensional matrix, and a cyclonic vortex dictionary variable and an anti-cyclonic vortex dictionary variable are respectively constructed with the identification number of the vortex as the key of the dictionary and the cumulative yield as the value of the dictionary.

[0024] In step (4), the yields in the sea current divergence area and the sea current convergence area where the vortices interact are also counted.

[0025] Beneficial effects

[0026] Due to the adoption of the above technical solutions, compared with the prior art, the present invention has the following advantages and positive effects: The present invention superimposes fishing data, vortex spatial distribution data, and absolute dynamic height with days as the time unit, searches for the catch yields in the vortex region and the vortex boundary region, counts the yields in each region of the vortex, so as to obtain the mesoscale vortex and target catch spatial distribution information in the target sea area. In the present invention, the vortex boundary region is divided into four regions, and the total catch yields in each region are calculated respectively. A cyclonic vortex dictionary variable and an anti-cyclonic vortex dictionary variable are respectively constructed with the identification number of the vortex as the key of the dictionary and the cumulative yield as the value of the dictionary, which can track the yields of each vortex in its vortex region and vortex boundary region during the entire life cycle. According to the different polarities of the two vortices with the smallest distance from the fishing location to the vortex contour line, the yields in the sea current divergence area and the sea current convergence area are counted. According to the calculation results, the influence of the mesoscale vortex in the target sea area on the spatial distribution of the target fishery resources can be quantitatively analyzed in detail, providing information reference for the sustainable development and utilization of the target resources in the target sea area. Description of the drawings

[0027] Figure 1 is a flowchart of an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of each variable in an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of the sea current divergence area and the sea current convergence area between the vortices in an embodiment of the present invention;

[0030] Figure 4 is a vortex trajectory diagram of the top 20 Japanese mackerel yields in the vortex region and the boundary region in 2018 in an embodiment of the present invention. Detailed implementation manners

[0031] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0032] Embodiments of the present invention relate to a method for extracting information on the spatial distribution of mesoscale eddies and target catches in a target sea area, as Figure 1 shown, including the following steps: obtaining mesoscale eddy data, target catch data, and absolute dynamic height data of the target sea area; obtaining the contour line of the eddy based on the mesoscale eddy data of the target sea area, and calculating the target catch yield within the eddy area; when the fishing location is not within the eddy area, determining whether the fishing location is within the boundary area of the eddy, and if so, calculating the target catch yield within the eddy boundary area; statistically analyzing the target catch yield in the eddy area and the target catch yield within the eddy boundary area to obtain a statistical result; and determining the spatial distribution relationship between the mesoscale eddy and the target catch yield according to the statistical result.

[0033] Hereinafter, taking the North Pacific as the target sea area and Japanese mackerel as the target, the present invention will be further described.

[0034] 1. Obtaining and preprocessing North Pacific mesoscale eddy data, Japanese mackerel catch data, and absolute dynamic height data

[0035] The absolute dynamic topography (ADT) data is grid data of multi-source satellite fusion produced by DUACS (data unification and altimeter combination system) and published by CMEMS (Copernicus marine environment monitoring service) (http: / / marine.copernicus.eu / services-portfolio / access-to-products / ), with a spatial accuracy of 1 / 4° and a time accuracy of one day. The diameter of mesoscale eddies is mainly between 100 and 300 km, so it is necessary to filter out the large-scale features in the ADT data. The ADT data is passed through a high-pass filter to remove large-scale features above 700 km.

[0036] The mesoscale vortex data is produced by DUACS and released by AVISO (https: / / www.aviso.altimetry.fr / en / data / products / value-added-products / global-mesoscale-eddy-trajectory-product.html). The time accuracy of the vortex data is in days, and the continuous period is more than 7 days. Through the vortex data, characteristic data of the vortex can be obtained, such as the vortex radius, vortex identification number, vortex contour line, ADT value on the vortex contour line, etc. The study area is the Japanese mackerel fishing ground in the North Pacific: 140°E - 170°E, 30°N - 50°N.

[0037] The catch data of Japanese mackerel comes from the purse seine fishing logs of fishing operations in the high seas of the North Pacific from April to December 2018 provided by the High Seas Purse Seine Technical Group of the China National Fisheries Association. The fishing data comes from a total of 61 fishing boats of 11 fishing enterprises. The fishing time is from April 1, 2018 to December 16, 2018, for a total of 260 days. The data records include date, longitude, latitude, yield, etc. The main variety of the catch is Japanese mackerel, accounting for about 90%, and other miscellaneous fish include sardines, squids and saury, etc. The total catch tonnage from April to December is 140,500 tons, and the catch tonnage for each month is 9,500 tons, 18,700 tons, 19,200 tons, 20,800 tons, 19,300 tons, 21,900 tons, 15,300 tons, 13,900 tons, and 1,900 tons respectively. The mesoscale vortex data, Japanese mackerel catch data and absolute dynamic topography data are superimposed and analyzed by day. The fishing data is stored in an access database and read through sql statements in the program. The vortex and ADT data are stored in nc files.

[0038] 2. Spatial relationship between vortices and fishing locations

[0039] The spatial distribution relationship between the fishing locations and the eddies is divided into three cases. First, the fishing location is within the eddy area. Second, the fishing location is within the eddy boundary area. Third, the fishing location is outside the eddy boundary area. Here, the eddy boundary area is divided into four regions. The first eddy boundary region corresponds to the area between the 0 m and 0.02 m ADT isopleths around the Cyclonic eddy (CE) contour line and the area between the 0 m and -0.02 m ADT isopleths around the Anticyclonic eddy (AE) contour line. The second eddy boundary region corresponds to the area between the 0.02 m and 0.04 m ADT isopleths around the CE contour line and the area between the -0.02 m and -0.04 m ADT isopleths around the AE contour line. The third eddy boundary region corresponds to the area between the 0.04 m and 0.06 m ADT isopleths around the CE contour line and the area between the -0.04 m and -0.06 m ADT isopleths around the AE contour line. The fourth eddy boundary region corresponds to the area between the 0.06 m and 0.08 m ADT isopleths around the CE contour line and the area between the -0.06 m and -0.08 m ADT isopleths around the AE contour line.

[0040] The area of eddy interaction is divided into a Flows divergent (FD) area and a Flows convergent (FC) area. The FD area is located between two anticyclonic eddies (as shown in Figure 3 ). If the two eddies with the smallest distance from the fishing location to the eddy contour line are both anticyclonic (AE - AE), then the fishing location is considered to be in the FD area. The FC area is located between two cyclonic eddies or between an anticyclonic eddy and a cyclonic eddy. If the two eddies with the smallest distance from the fishing location to the eddy contour line are both cyclonic eddies (CE - CE), or the first is an anticyclonic eddy and the second is a cyclonic eddy (AE - CE), or the first is a cyclonic eddy and the second is an anticyclonic eddy (CE - AE), then the fishing location is considered to be in the FC area.

[0041] 3. Calculation of the yield within the eddy area

[0042] For the absolute dynamic height ADT, the time resolution of the eddy data is in days. Therefore, the catch yield is matched by day with the ADT and the eddy data. According to the input date, the absolute dynamic height ADT, the eddies, and the yield of that day are extracted. The eddies within the study area are represented as eddy t,j , where t ∈ (1,..., T) represents the serial number of the input date, and T = 260. j ∈ (1,..., J) represents the serial number of the eddy, and J represents the total number of eddies on day t. The eddy contour line is represented as eddy_contour t,j。The vortex center is denoted as eddy_center t,j , and its longitude and latitude are set as lon_eddy t,j and lat_eddy t,j 。The catch is denoted as catch t,i , where \(i\in(1,\ldots,I)\) represents the serial number of fishing records, and \(I\) represents the total number of fishing times on day \(t\). The fishing location is denoted as catch_point t,i , and its corresponding longitude and latitude are set as lon_catch t,i and lat_catch t,i 。

[0043] The contour line of the vortex is the closed ADT isoline with the maximum average geostrophic flow velocity. The WindingNumber method is used to count the catch production within this closed isoline. Let the variable catch_A_in be the total production inside the anticyclonic vortex, and the variable catch_C_in be the total production inside the cyclonic vortex. The calculation formulas are as follows:

[0044] catch_A_in = \(\{\sum catch t,i | wn\neq0, t\in(1,\ldots,T), i\in(1,\ldots,I), j\in(1,\ldots,J), eddy t,j is AE\}\),

[0045] catch_C_in = \(\{\sum catch t,i | wn\neq0, t\in(1,\ldots,T), i\in(1,\ldots,I), j\in(1,\ldots,J), eddy t,j is CE\}\).

[0046] where \(wn = winding\_number(catch\_point t,i , eddy\_contour t,j )\). When \(wn\neq0\), it means that the fishing location catch_point t,i is within the vortex contour line eddy_contour t,j . To trace the total production inside each vortex along its trajectory line during its life cycle, a dictionary variable is established with the vortex identification number as the key and the accumulated production as the value. The dictionary variables for tracing the production inside the anticyclonic vortex and the cyclonic vortex are set as dict_A_in and dict_C_in respectively. The calculation formulas are as follows:

[0047]

[0048]

[0049] where, track_nmuberp Indicates the vortex identification number, eddy_track_number t,j Indicates the vortex eddy t,j The identification number, where P represents the total number of vortex identification numbers in 2018.

[0050] 4. Calculation of the yield within the vortex boundary region

[0051] If the fishing location is not within the vortex region, it is necessary to calculate whether the fishing location is within the vortex boundary region.

[0052] 1) Calculate the distance between the fishing location and the vortex boundary

[0053] The distance between the fishing location and the vortex boundary is equal to the distance between the fishing location and the vortex center minus the vortex radius. The distance between the fishing location and the vortex center is calculated using the spherical cosine formula. The fishing location catch_point t,i The distance from the vortex eddy t,j The calculation expression for the distance to the contour line is as follows:

[0054]

[0055] where radius_eddy t,j represents the radius of the j-th vortex at time t, and Earth_radius represents the radius of the Earth. The distances {D t,i from catch_point t,j to the contour lines of the J vortices {eddy t,i,j |j ∈ (1,..., J)} in the study area are sorted in ascending order from smallest to largest. The two vortices with the smallest distance values are selected for analysis. The two vortices with the closest distance from the contour line to the fishing location catch_point t,i are denoted as eddy t,i,1 and eddy t,i,2 . The combinations of the two vortices with the closest distance are divided into four cases: AE - AE, CE - CE, AE - CE, CE - AE, where AE - AE means that both the first - closest and second - closest vortices are anticyclonic vortices, AE - CE means that the first - closest vortex is an anticyclonic vortex and the second - closest is a cyclonic vortex, and so on.

[0056] 2) Calculate the absolute dynamic height value on the line connecting the fishing location and the vortex center

[0057] Let the line connecting the fishing location catch_point t,i and the center of the vortex eddy t,i,q be line t,i,q, where \(q\in(1,2)\). When \(q = 1\), it represents the vortex with the closest boundary distance to the fishing location. When \(q = 2\), it represents the vortex with the second-closest boundary distance to the fishing location. The longitude and latitude of the vortex center are denoted as \(lon\_eddy\) t,i,q , \(lat\_eddy\) t,i,q . Let the step size \(step = 0.01\). Let the length of the longitude interval be \(long\_lon\) t,i,q \(= abs(lon\_catch\) t,i \(- lon\_eddy\) t,i,q ). Let the length of the latitude interval be \(long\_lat\) t,i,q \(= abs(lat\_catch\) t,i \(- lat\_eddy\) t,i,q ). Divide the longitude interval according to the step size \(step\). The number of divided segments is \(N\_lon\) t,i,q \(= round(long\_lon\) t,i,q \( / step)\), where the \(round\) function represents rounding to the nearest integer, and \(abs\) represents taking the absolute value. Divide the latitude interval in the same way according to the step size \(step\). The number of divided segments is \(N\_lat\) t,i,q \(= round(long\_lat\) t,i,q \( / step)\). Select \(N\) t,i,q \(= max(N\_lon\) t,i,q , \(N\_lat\) t,i,q ) as the number of equally spaced segments of the connection line \(line\) t,i,q .

[0058] The equally spaced points (including the starting point vortex center) on the connection line \(line\) t,i,q are denoted as \(points\) t,i,q \(= \{point\) t,i,q,k | \(k\in(0,...,N\) t,i,q ) \}. The longitude calculation formula for the equally spaced points \(points\) t,i,q is: \(lon\_points\) t,i,q \(= \{x|x = lon\_eddy\) t,i,q +(lon\_catch\) t,i \(- lon\_eddy\) t,i,q ) / N t,i,q * \(k\), \(k\in(0,..,N\) t,i,q ) \}. The latitude calculation formula for the equally spaced points \(points\) t,i,q is: \(lat\_points\) t,i,q \(= \{x|x = lat\_eddy\) t,i,q +(lat\_catch\) t,i \(- lat\_eddy\) t,i,q ) / N t,i,q*k, k ∈ (0,.., N t,i,q )}. After obtaining the longitude and latitude coordinates of the points on the connection line, the equally divided points points t,i,q on the connection line line t,i,q can be obtained by linear interpolation, and the ADT values on the equally divided points are denoted as ADT_points t,i,q = {ADT_points t,i,q,k | k ∈ (0,..., N t,i,q )}, where ADT_points t,i,q,k represents the ADT value at the equally divided point k.

[0059] 3) Find the intersection points of the vortex contour line and the connection line between the fishing location and the vortex center

[0060] If eddy t,i,q is a cyclone vortex, the ADT value at the vortex center is less than the value on its boundary. Therefore, the ADT value from the vortex center to the intersection point is less than or equal to the value at the intersection point. The intersection point of the vortex eddy t,i,q contour line and the connection line line t,i between the fishing location catch_point t,i,q and the vortex eddy t,i,q center is denoted as intersect_point t,i,q . According to the order from the vortex center to the fishing location, find the first point among the N t,i,q equally divided points (excluding the vortex center) on the connection line line t,i,q whose ADT value is greater than or equal to the ADT on the vortex boundary, and take this point as the intersection point intersect_point t,i,q . The serial number of the equally divided point where the intersection point intersect_point t,i,q is located on the connection line line t,i,q is denoted as intersect_point_k t,i,q , and the calculation expression is:

[0061]

[0062] where ADD_eddy_contour t,i,q represents the ADT value on the vortex eddy t,i,q contour line. If eddy t,i,q is an anticyclone vortex, the ADT value at the vortex center is greater than the value on its boundary. Therefore, the ADT value from the vortex center to the intersection point is greater than or equal to the value at the intersection point. According to the order from the vortex center to the fishing location, from the connection line line t,i,q of the N t,i,qFind the first point among the equally divided points (excluding the vortex center) where the ADT value is less than or equal to the ADT on the vortex boundary as the intersection point. intersect_point_k t,i,q Calculation expression of:

[0063]

[0064] 4) Determine whether the fishing location is within the vortex boundary area

[0065] There are four cases where the fishing location is within the vortex boundary area. They are respectively that the fishing location is within the ADT isolines of 0m and 0.02m, 0.02m and 0.04m, 0.04 and 0.06m, 0.06 and 0.08m around the contour line of the cyclonic vortex, or within the ADT isolines of 0m and -0.02m, -0.02m and -0.04m, -0.04 and -0.06m, -0.06 and -0.08m around the contour line of the anticyclonic vortex. According to whether the connection line ( Figure 2 the black solid line in) from the intersection point to the fishing location is within the vortex boundary area to judge whether the fishing location is within the vortex boundary area. When the vortex is a cyclonic vortex, if the maximum ADT value on the connection line from the intersection point to the fishing location is less than or equal to the value of the isoline around the vortex contour line, the connection line is within the corresponding isoline around the vortex contour line; when the vortex is an anticyclonic vortex, if the minimum ADT value on the connection line from the intersection point to the fishing location is greater than or equal to the value of the isoline around the vortex contour line, the connection line is within the corresponding isoline around the vortex contour line.

[0066] Take the fishing location catch_point t,i and the vortex eddy t,i,q as an example to illustrate. Use flag t,i,q,1 = TURE to indicate that the first case is satisfied, flag t,i,q,1 = FALSE to indicate that the first case is not satisfied. Similarly, there are flag t,i,q,2 , flag t,i,q,3 , flag t,i,q,4 . When the vortex eddy t,i,q is a cyclonic vortex, whether the connection line from the intersection point intersect_point t,i,q to the fishing location catch_point t,i is outside the vortex contour line and within the 0.02m ADT isoline around the vortex contour line can be judged by the following formula:

[0067]

[0068] where intersect_point_k t,i,q is the intersection point intersect_point t,i,qThe serial number of the equally divided points on the connection line t,i,q The intersection point t,i,q The connection line to the fishing location t,i Whether the connection line from the intersection point

[0069]

[0070] flag t,i,q,3 and flag t,i,q,4 and so on

[0071] When the eddy t,i,q is an anticyclonic eddy, the ADT value on the eddy contour line is greater than the ADT value on the contour line around it. The intersection point t,i,q The connection line to the fishing location t,i is outside the eddy contour line and inside the -0.02m ADT contour line around the eddy contour line, which can be judged by the following formula:

[0072]

[0073] The intersection point t,i,q The connection line to the fishing location t,i is outside the -0.02m ADT contour line around the air eddy contour line and inside the -0.04m ADT contour line around the eddy contour line, which can be judged by the following formula:

[0074]

[0075] flag t,i,q,3 and flag t,i,q,4 and so on

[0076] 5. Saving of calculation results

[0077] Use the three-dimensional matrix catch_count l,m,n to count the yields of various situations, where l ∈ (1,..., 4) represents the fishing location t,i The four combinations of the two eddies t,i,1 and eddy t,i,2 with the smallest distances from the fishing location to the eddy edge: AE - AE, CE - CE, CE - AE, AE - CE. m ∈ (1,..., 3) represents the fishing location t,i and the eddy t,i,1, eddy t,i,2 The relationship with the vortex boundary region of t,i,2 is divided into three cases: only located within the vortex boundary region of eddy t,i,1 only located within the vortex boundary region of eddy t,i,2 only located within the vortex boundary region of eddy t,i,1 , eddy t,i,2 and within the vortex boundary regions of both eddies. n ∈ (1,..., 4) represents the four cases where catch_point t,i is located within the vortex boundary region. For example, catch_count 1,1,1 represents the two eddies eddy t,i,1 , eddy t,i,2 with the smallest distances from the fishing location to the vortex edge, which is AE, i.e., the AE - AE combination, and the fishing location is only located within the first vortex boundary region of eddy t,i,1 . The calculation expression of catch_count 1,1,1 is as follows:

[0078] catch_count 1,1,1 = {∑catch t,i |eddy t,i,1 is AE, eddy t,i,2 is AE, flag t,i,1,1 = TRUE, flag t,i,2,1 = FALSE}.

[0079] To track the production within the boundary regions of each vortex throughout its entire life cycle, a cyclonic vortex dictionary dict_C and an anticyclonic vortex dictionary dict_A are established, with the vortex identification number as the key of the dictionary and the cumulative production as the value of the dictionary. The dictionary variable expressions are as follows:

[0080] dict_A[eddy_track_number t,i,q = {∑catch t,i |eddy t,i,q is AE, flag t,i,q,1 || flag t,i,q,2 || flag t,i,q,3 || flag t,i,q,4 = TRUE},

[0081] dict_C[eddy_track_number t,i,q = {∑catch t,i |eddy t,i,q is CE, flag t,i,q,1 || flag t,i,q,2 || flag t,i,q,3 || flagt,i,q,4 = TRUE}.

[0082] Among them, eddy_track_number t,i,q represents the identification number of the eddy, and "||" represents the logical operation OR. t,i,q The identification number of eddy, "||" represents the logical operation OR.

[0083] 6. Statistics of the yield in each region

[0084] The yield in the cyclonic eddy region is catch_C_in, and the yield in the anticyclonic eddy region is catch_A_in. The calculation formula for the yield in the boundary region between the cyclonic eddy and the anticyclonic eddy:

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] Among them, catch_C and catch_A respectively represent the total yields in the boundary regions between the cyclonic eddy and the anticyclonic eddy, catch_A_and_A represents the total yield in the boundary regions between two anticyclonic eddies in the case of AE - AE, catch_C_and_C represents the total yield in the boundary regions between two cyclonic eddies in the case of CE - CE, and catch_A_and_C represents the total yield in the boundary regions between two vortices in the cases of AE - CE and CE - AE. The fishing location catch_point t,i The two eddies with the smallest distance to the eddy contour line t,i,1 eddy t,i,2 Four cases of eddy: AE - AE, CE - CE, CE - AE, AE - CE. AE - AE corresponds to FD, and if it is CE - CE, AE - CE, CE - AE, it corresponds to FC.

[0091] Yield in the FD region:

[0092] Yield of CE - CE in the FC region:

[0093] Total yield of AE - CE and CE - AE in the FC region:

[0094]

[0095] 7. Analysis of the Relationship between the Catch Yield of Scomber japonicus and the Spatial Distribution of Eddies

[0096] Taking the mesoscale eddy data, Scomber japonicus catch data, and absolute dynamic height data in 2018 as examples, the spatio-temporal distributions of mesoscale eddies and Scomber japonicus catches were analyzed. The production proportion in the cyclonic eddy region was 9.48%, the production proportion in the anticyclonic eddy region was 6.91%, and the total production proportion in the eddy region was 16.39% (Table 1). The production proportion in the cyclonic eddy region was 2.57% more than that in the anticyclonic eddy region. The production proportions in the first boundary region, second boundary region, third boundary region, and fourth boundary region of the cyclonic eddy were 13.70%, 19.79%, 11.99%, and 6.31% respectively, all greater than 5.56%, 5.15%, 4.07%, and 2.85% of the anticyclonic eddy. The total production proportions in the boundary regions of the cyclonic eddy and the anticyclonic eddy were 51.79% and 17.63% respectively, and the production in the boundary region of the cyclonic eddy exceeded that of the anticyclonic eddy by 34.16% (Table 2). The catch yield of Scomber japonicus was mainly distributed in the boundary region of the cyclonic eddy, and the production proportion in the second boundary region of the cyclonic eddy was the highest. The production proportion in the boundary region of the anticyclonic eddy was significantly less than that of the cyclonic eddy. The production proportion in the boundary region where it was located in both eddies at the same time was relatively small. The production proportions in the boundary regions where it was located in both AE and AE, CE and CE, and AE and CE at the same time were 2.34%, 2.34%, and 3.21% respectively, and the production proportion in the boundary region where it was located in both AE and CE at the same time was slightly higher. The total production proportion in the boundary region of the eddy was 75.38%. The total production proportion of the eddy region plus the boundary region of the eddy was 91.77%.

[0097] Table 1 Proportion of Scomber japonicus Production in the Mesoscale Eddy Region of the North Pacific in 2018

[0098] A C Total Vortex region 6.91 9.48 16.39

[0099] Table 2 Proportion of Scomber japonicus Production in the Boundary Regions of Cyclonic and Anticyclonic Eddies in the North Pacific in 2018

[0100] A C A and A C and C A and C Total First boundary region 5.56 13.70 0.02 0.27 0.65 20.20 Second boundary region 5.15 19.79 0.08 1.14 1.22 27.37 Third boundary region 4.07 11.99 0.12 0.87 0.72 17.78 Fourth boundary region 2.85 6.31 0.19 0.06 0.62 10.03 Total 17.63 51.79 0.41 2.34 3.21 75.38

[0101] Table 3 Proportion of Scomber japonicus Production in the Sea Current Divergence Region and Sea Current Convergence Region of Eddy Interaction in 2018

[0102]

[0103] The catch production in the FD area accounted for 7.77%. The production in the CE-CE area of the FC area accounted for 12.19%. The production in the AE-CE and CE-AE areas of the FC area reached 55.42%, which is greater than the sum of the previous two, indicating that the catch is mainly located in the vortex boundary area between the cyclonic and anticyclonic vortices in the sea current convergence area (Table 3). In the FD and FC areas, the production proportions of the first vortex boundary area, the second boundary area, the third boundary area, and the fourth boundary area are 20.20%, 27.37%, 17.78%, and 10.03% respectively. Among them, the production proportion in the second vortex boundary area is the highest, followed by the first vortex boundary area.

[0104] 8. Tracking the Production of Mesoscale Vortices

[0105] Along each vortex trajectory line, track the production of Japanese mackerel in the vortex area and the vortex influence area during the life cycle of each vortex. Among the top 20 vortices with the production proportion of Japanese mackerel in the vortex area and the vortex boundary area, there are 5 anticyclonic vortices and 15 cyclonic vortices. The production proportion of these 20 vortices is about 90.28%. Among the top 10 vortices with the production proportion of Japanese mackerel in the vortex area and the vortex boundary area, there are 3 anticyclonic vortices and 7 cyclonic vortices. The production proportion of these 10 vortices is about 74.25%, indicating that the production of Japanese mackerel is mainly distributed in the vortex area and the vortex boundary area of these vortices.

[0106] Table 4 The Top 20 Vortices with the Production Proportion of Japanese Mackerel in the Vortex Area and the Vortex Boundary Area in 2018

[0107]

[0108] The trajectory lines of the top 20 vortices with the production proportion of Japanese mackerel in the vortex area and the vortex boundary area are mainly in the area of 145°E - 155°E, 37.5°N - 45°N, and their trajectories are as Figure 4 shown. The vortex with the first production proportion is a cyclonic vortex, with the generation location at 148.50°E, 41.12°N, the end location at 147.81°E, 40.37°N, the generation time on May 2, 2018, and the end time on June 18, 2018. The vortex with the second production proportion is a cyclonic vortex, with the generation location at 153.24°E, 43.00°N, the end location at 151.43°E, 42.63°N, the generation time on September 8, 2018, and the end time on October 18, 2018. The vortex with the third production proportion is an anticyclonic vortex, with the generation location at 150.74°E, 41.24°N, the end location at 150.50°E, 43.41°N, the generation time on June 5, 2018, and the end time on August 31, 2018.

[0109] In 2018, there were 503 cyclonic eddy trajectory lines and 436 anticyclonic eddy trajectory lines in the study area, and the yield of chub mackerel was mainly concentrated near a few of these trajectory lines. From the above analysis, it can be seen that the influence of mesoscale eddies in the North Pacific on the distribution of chub mackerel is significant. The absolute dynamic height data is less affected by cloud cover. Therefore, in the absence of data such as sea surface temperature, the spatial distribution of mesoscale eddies can be obtained based on the absolute dynamic height to assist in fishing operations.

Claims

1. A method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area, characterized in that, it includes the following steps: (1) Obtain the mesoscale eddy data, target catch data, and absolute dynamic height data of the target sea area; (2) Based on the mesoscale eddy data of the target sea area, obtain the contour line of the eddy and calculate the target catch yield within the eddy area. Specifically: Take the closed absolute dynamic height isoline with the maximum average geostrophic flow velocity as the contour line of the eddy, and use the WindingNumber method to count the catch yield within the contour line of the eddy, that is, within the eddy area; (3) When the fishing location is not within the eddy area, determine whether the fishing location is within the eddy boundary area. If so, calculate the target catch yield within the eddy boundary area; where, the determination of whether the fishing location is within the eddy boundary area is specifically: (31) Subtract the radius of the eddy from the distance from the fishing location to the center of the eddy to obtain the distance between the fishing location and the eddy contour line, and select the two eddies with the smallest distance values; (32) Equally divide the lines connecting the fishing location to the centers of the two selected eddies respectively to obtain the absolute dynamic height values at the equal division points; (33) Search for the intersection points of the line connecting the fishing location to the center of the eddy and the eddy contour line; (34) Determine whether the fishing location is within the eddy boundary area according to whether the line connecting the intersection point to the fishing location is within the eddy boundary area. Specifically: When the eddy is a cyclonic eddy, if the maximum absolute dynamic height value on the line connecting the intersection point to the fishing location is less than or equal to the value of the isoline around the eddy contour line, then the line is within the corresponding isoline around the eddy contour line; when the eddy is an anti-cyclonic eddy, if the minimum absolute dynamic height value on the line connecting the intersection point to the fishing location is greater than or equal to the value of the isoline around the eddy contour line, then the line is within the corresponding isoline around the eddy contour line; (4) Statistically analyze the target catch yield in the eddy area and the target catch yield within the eddy boundary area to obtain the statistical results; (5) According to the statistical results, determine the spatial distribution relationship between the mesoscale eddy and the target catch yield.

2. The method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area according to claim 1, characterized in that, a preprocessing step is further included between step (1) and step (2). Specifically: Remove the large-scale features above 700 km from the absolute dynamic height data through a high-pass filter; Perform superposition analysis on the mesoscale eddy data, target catch data, and absolute dynamic height data on a daily basis.

3. The method for extracting the spatial distribution information of mesoscale eddies and target catches in a target sea area according to claim 1, characterized in that, in step (31): The two eddies with the smallest distance from the fishing location to the eddy contour line are divided into four cases: both eddies are anti-cyclonic, both eddies are cyclonic eddies, the first is an anti-cyclonic eddy and the second is a cyclonic eddy, and the first is a cyclonic eddy and the second is an anti-cyclonic eddy.

4. The method for extracting the spatial distribution information of mesoscale eddies and target catches in the target sea area according to claim 1, characterized in that, step (33) is specifically as follows: when the eddy is a cyclonic eddy, find the first point with an absolute dynamic height value greater than or equal to the absolute dynamic height value on the eddy contour line from the equal division points of the connection line in the order from the center of the eddy to the fishing location as the intersection point; when the eddy is an anticyclonic eddy, find the first point with an absolute dynamic height value less than or equal to the absolute dynamic height value on the eddy contour line from the equal division points of the connection line in the order from the center of the eddy to the fishing location as the intersection point.

5. The method for extracting the spatial distribution information of mesoscale eddies and target catches in the target sea area according to claim 1, characterized in that, in the case where the fishing location in step (34) is within the boundary area of the eddy, it is divided according to the absolute dynamic height contour lines at a preset interval, and the eddy boundary area is divided into four areas, namely the first eddy boundary area, the second eddy boundary area, the third eddy boundary area and the fourth eddy boundary area; the first eddy boundary area corresponds to the area between the 0m and 0.02m ADT contour lines around the cyclonic eddy contour line and the area between the 0m and -0.02m ADT contour lines around the anticyclonic eddy contour line; the second eddy boundary area corresponds to the area between the 0.02m and 0.04m ADT contour lines around the cyclonic eddy contour line and the area between the -0.02m and -0.04m ADT contour lines around the anticyclonic eddy contour line; the third eddy boundary area corresponds to the area between the 0.04m and 0.06m ADT contour lines around the cyclonic eddy contour line and the area between the -0.04m and -0.06m ADT contour lines around the anticyclonic eddy contour line; the fourth eddy boundary area corresponds to the area between the 0.06m and 0.08m ADT contour lines around the cyclonic eddy contour line and the area between the -0.06m and -0.08m ADT contour lines around the anticyclonic eddy contour line.

6. The method for extracting the spatial distribution information of mesoscale eddies and target catches in the target sea area according to claim 1, characterized in that, the target catch yields in the eddy area and the eddy boundary area are saved in the form of a three-dimensional matrix, and a cyclonic eddy dictionary variable and an anticyclonic eddy dictionary variable are respectively constructed with the identification number of the eddy as the key of the dictionary and the cumulative yield as the value of the dictionary.

7. The method for extracting the spatial distribution information of mesoscale eddies and target catches in the target sea area according to claim 1, characterized in that, in step (4), the yields in the sea current divergence area and the sea current convergence area where the eddies interact are also statistically calculated.

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