Tropical cyclone sea surface wind field inversion method, device, equipment, medium and product

Abstract

The present application discloses a method, device, equipment, medium and product for inverting the sea surface wind field of a tropical cyclone, and relates to the field of marine remote sensing technology. The method comprises determining the position of the tropical cyclone eyewall from a C-band VV polarized synthetic aperture radar image under tropical cyclone sea conditions, and then determining the center of the tropical cyclone; determining the line connecting each point in the sea surface wind field in the synthetic aperture radar image and the center of the tropical cyclone, and taking the counterclockwise tangent direction of the line as the wind direction of each point in the sea surface wind field; inverting the tropical cyclone wind field according to the wind direction of each point in the sea surface wind field and a geophysical function model to obtain the wind speed of each point in the sea surface wind field; using an empirical function to perform wind speed saturation adjustment on the wind speed of each point in the sea surface wind field, and obtaining the adjusted wind speed of each point in the sea surface wind field. The present application can overcome the difficulties of high wind speed saturation and wind direction estimation, and improve the accuracy of tropical cyclone wind field inversion by C-band VV polarized synthetic aperture radar.

Description

Technical Field

[0001] The present application relates to the field of marine remote sensing technology, and in particular to a method, device, equipment, medium and product for inverting tropical cyclone sea surface wind fields. Background Art

[0002] The definition of tropical cyclone intensity and size is based on measurements of sea surface winds (the wind field at 10 meters above the sea surface). Therefore, the retrieval of sea surface winds under tropical cyclone conditions is fundamental to tropical cyclone intensity research and is of great significance for tropical cyclone forecasting and disaster prevention and mitigation.

[0003] Remote sensing, with its high frequency of observations, wide temporal and spatial coverage, and excellent real-time performance, is a powerful means of monitoring tropical cyclone paths. Compared to passive remote sensing, which primarily operates in the visible and infrared bands, microwave remote sensing can observe around the clock and is less affected by atmospheric windows. Synthetic Aperture Radar (SAR), with its high resolution, can accurately invert surface wind field information for tropical cyclones, making it of great significance in tropical cyclone monitoring and forecasting. SAR primarily uses the Bragg resonance between electromagnetic waves and capillary gravity waves on the sea surface to obtain the Normalized Radar Cross Section (NRCS), which is very sensitive to changes in sea surface roughness caused by wind at 10 meters above the sea surface. However, for VV polarized SAR imagery, there are two problems: high wind speed saturation and difficulty in estimating wind direction. Summary of the Invention

[0004] The purpose of this application is to provide a method, device, equipment, medium and product for tropical cyclone sea surface wind field inversion, which can overcome the difficulties of high wind speed saturation and wind direction estimation and improve the tropical cyclone wind field inversion accuracy of C-band VV polarization synthetic aperture radar.

[0005] To achieve the above objectives, this application provides the following solutions.

[0006] In a first aspect, the present application provides a method for inverting a tropical cyclone sea surface wind field, comprising: determining the position of a tropical cyclone eyewall from a C-band VV polarized synthetic aperture radar image under tropical cyclone sea conditions; determining the center of the tropical cyclone based on the position of the tropical cyclone eyewall; determining a line connecting each point in the sea surface wind field in the synthetic aperture radar image and the center of the tropical cyclone, and taking the counterclockwise tangent direction of the line as the wind direction of each point in the sea surface wind field; inverting the tropical cyclone wind field based on the wind direction of each point in the sea surface wind field and a geophysical function model to obtain the wind speed of each point in the sea surface wind field; performing wind speed saturation adjustment on the wind speed of each point in the sea surface wind field using an empirical function to obtain the adjusted wind speed of each point in the sea surface wind field; and constituting the sea surface wind field under tropical cyclone sea conditions with the adjusted wind speed of each point in the sea surface wind field and the wind direction of each point in the sea surface wind field.

[0007] Optionally, determining the position of the tropical cyclone eyewall from a C-band VV polarization synthetic aperture radar image under tropical cyclone sea conditions specifically includes: selecting a position in the synthetic aperture radar image where the backscatter signal gradient changes the most; and determining all selected positions where the backscatter signal gradient changes the most as the tropical cyclone eyewall position.

[0008] Optionally, the center of the tropical cyclone is determined based on the position of the tropical cyclone eyewall, specifically including: determining the area enclosed by the position of the tropical cyclone eyewall as the tropical cyclone eye area; extracting the center of the tropical cyclone eye area and determining it as the center of the tropical cyclone.

[0009] Optionally, the tropical cyclone wind field is inverted according to the wind direction of each point in the sea surface wind field and the geophysical function model to obtain the wind speed of each point in the sea surface wind field, specifically including: according to the wind direction of each point in the sea surface wind field, using the formula , calculate the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar; where, is the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar, is the wind speed at 10 meters above the sea surface, is the synthetic aperture radar incident angle, is the azimuth angle of synthetic aperture radar observation, 、 and are the first, second and third coefficients related to wind speed and synthetic aperture radar incident angle respectively; according to the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar, the wind speed at each point in the sea surface wind field is obtained using the geophysical function model.

[0010] Optionally, the empirical function is: Where, is the adjusted wind speed at each point in the sea surface wind field, is the wind speed at each point in the sea surface wind field, 、 、 are the first, second and third parameters obtained by fitting respectively.

[0011] Optionally, , , .

[0012] In a second aspect, the present application provides a tropical cyclone sea surface wind field inversion device, comprising: an eyewall determination module, a cyclone center determination module, a wind direction calculation module, a wind speed calculation module, a wind speed adjustment module and a wind field inversion module.

[0013] The eyewall determination module is used to determine the position of the tropical cyclone eyewall from the C-band VV polarization synthetic aperture radar image under tropical cyclone sea conditions. The cyclone center determination module is used to determine the center of the tropical cyclone based on the position of the tropical cyclone eyewall. The wind direction calculation module is used to determine the line connecting each point in the sea surface wind field in the synthetic aperture radar image and the tropical cyclone center, and take the counterclockwise tangent direction of the line as the wind direction at each point in the sea surface wind field. The wind speed calculation module is used to invert the tropical cyclone wind field based on the wind direction at each point in the sea surface wind field and the geophysical function model to obtain the wind speed at each point in the sea surface wind field. The wind speed adjustment module is used to perform wind speed saturation adjustment on the wind speed at each point in the sea surface wind field using an empirical function to obtain the adjusted wind speed at each point in the sea surface wind field. The wind field inversion module is used to combine the adjusted wind speed at each point in the sea surface wind field and the wind direction at each point in the sea surface wind field to form the sea surface wind field under tropical cyclone sea conditions.

[0014] In a third aspect, the present application provides a computer device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement any of the above-described methods for inverting the tropical cyclone sea surface wind field.

[0015] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the above-mentioned methods for inverting the tropical cyclone sea surface wind field.

[0016] In a fifth aspect, the present application provides a computer program product, comprising a computer program, which, when executed by a processor, implements any of the above-mentioned methods for inverting the tropical cyclone sea surface wind field.

[0017] According to the specific embodiments provided in this application, this application has the following technical effects.

[0018] The present application provides a method, apparatus, equipment, medium and product for inverting the sea surface wind field of a tropical cyclone. By determining the center of the tropical cyclone, the wind direction in the sea surface wind field under tropical cyclone sea conditions is obtained, thereby overcoming the difficulty of estimating the wind direction. The wind speed at each point in the sea surface wind field is adjusted for saturation using an empirical function, thereby overcoming the difficulty of high wind speed saturation, thereby improving the accuracy of tropical cyclone wind field inversion using a C-band VV polarization synthetic aperture radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic flow chart of a method for inverting the sea surface wind field of a tropical cyclone provided in one embodiment of the present application.

[0021] Figure 2 A schematic diagram of the functional modules of a tropical cyclone sea surface wind field inversion device provided in one embodiment of the present application.

[0022] Figure 3 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0025] In an exemplary embodiment, Figure 1 As shown, a method for inverting the sea surface wind field of a tropical cyclone is provided, including the following steps 101 to 106.

[0026] Step 101: Determine the position of the tropical cyclone eyewall from a C-band VV polarization synthetic aperture radar image of the tropical cyclone sea state.

[0027] Step 102: Determine the center of the tropical cyclone based on the position of the tropical cyclone eyewall.

[0028] Step 103: Determine the line connecting each point in the sea surface wind field in the synthetic aperture radar image and the center of the tropical cyclone, and take the counterclockwise tangent direction of the line as the wind direction at each point in the sea surface wind field.

[0029] Step 104: Based on the wind direction at each point in the sea surface wind field and the geophysical function model, the tropical cyclone wind field is inverted to obtain the wind speed at each point in the sea surface wind field.

[0030] Step 105: Using the empirical function, the wind speed at each point in the sea surface wind field is saturated and adjusted to obtain the adjusted wind speed at each point in the sea surface wind field.

[0031] Step 106: The adjusted wind speed at each point in the sea surface wind field and the wind direction at each point in the sea surface wind field are combined to form a sea surface wind field under tropical cyclone sea conditions.

[0032] By implementing steps 101 to 106, the center of a tropical cyclone can be determined, and the wind direction and speed of the tropical cyclone wind field can be obtained. This improves the problem of high wind speed saturation and difficulty in estimating wind direction in VV polarimetric SAR images. The method of this application can monitor tropical cyclone intensity in real time, thereby significantly reducing losses caused by typhoons.

[0033] In another exemplary embodiment of the present application, the above step 101 can be replaced by the following steps 201 to 202.

[0034] Step 201: Selecting a position in the synthetic aperture radar image where the gradient change of the backscattered signal is the largest.

[0035] Step 202: Determine the position where all selected backscatter signal gradients have the largest change as the tropical cyclone eyewall position.

[0036] In another exemplary embodiment of the present application, the above step 102 can be replaced by the following steps 301 to 302.

[0037] Step 301: Determine the area enclosed by the tropical cyclone eyewall as the tropical cyclone eye area.

[0038] The eye area of ​​a tropical cyclone is also called the eye area of ​​a typhoon.

[0039] Step 302: Extract the center of the tropical cyclone eye area and determine it as the tropical cyclone center.

[0040] If the tropical cyclone eye is a regular ellipse, the intersection of the major and minor axes is the cyclone center. If the tropical cyclone eye is not a regular ellipse, it is approximated to a regular ellipse, and the intersection of the major and minor axes of the approximate regular ellipse is the cyclone center.

[0041] In another exemplary embodiment of the present application, the above step 104 can be replaced by the following steps 401 to 402.

[0042] Step 401: Based on the wind direction at each point in the sea surface wind field, use the formula , calculate the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar.

[0043] Where, is the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar; is the wind speed at 10 meters above the sea surface; is the synthetic aperture radar incident angle; is the azimuth of SAR observation, that is, the angle between the projection of SAR wave velocity on the sea surface and the wind direction; 、 and are the first coefficient, the second coefficient and the third coefficient related to wind speed and synthetic aperture radar incident angle respectively.

[0044] Step 402: According to the standard backscatter coefficient of the VV polarization of the C-band synthetic aperture radar, the wind speed at each point in the sea surface wind field is obtained using a geophysical function model.

[0045] The geophysical function model is the CMOD5.N geophysical function model.

[0046] In another exemplary embodiment of the present application, the empirical function is: .

[0047] Where, is the adjusted wind speed at each point in the sea surface wind field, is the wind speed at each point in the sea surface wind field, 、 、 are the first parameter, second parameter, and third parameter obtained by fitting respectively. For example, , , .

[0048] Through the method provided in this application, the sea surface wind field observation process of the C-band VV polarization SAR satellite can determine the center position of the tropical cyclone, determine the wind direction in the tropical cyclone wind field, and then invert and improve the wind speed in the tropical cyclone wind field, which is conducive to the monitoring of the tropical cyclone sea surface wind field.

[0049] With the increasing number of SAR satellites, it has become possible to coordinate observations of tropical cyclone sea surface wind fields using multi-source SAR satellites. Based on the method of this application, multiple, high-precision and comprehensive observations of tropical cyclones can be further carried out using SAR satellite networking or multi-source satellite networking.

[0050] Based on the same inventive concept, embodiments of the present application also provide a tropical cyclone sea surface wind field inversion device for implementing the aforementioned tropical cyclone sea surface wind field inversion method. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more tropical cyclone sea surface wind field inversion device embodiments provided below can be found in the above-mentioned limitations of the tropical cyclone sea surface wind field inversion method and will not be repeated here.

[0051] In an exemplary embodiment, Figure 2 As shown, a tropical cyclone sea surface wind field inversion device is provided, which includes: an eyewall determination module, a cyclone center determination module, a wind direction calculation module, a wind speed calculation module, a wind speed adjustment module and a wind field inversion module.

[0052] The eyewall determination module is used to determine the position of the tropical cyclone eyewall from the C-band VV polarization synthetic aperture radar image under tropical cyclone sea conditions. The cyclone center determination module is used to determine the center of the tropical cyclone based on the position of the tropical cyclone eyewall. The wind direction calculation module is used to determine the line connecting each point in the sea surface wind field in the synthetic aperture radar image and the tropical cyclone center, and take the counterclockwise tangent direction of the line as the wind direction at each point in the sea surface wind field. The wind speed calculation module is used to invert the tropical cyclone wind field based on the wind direction at each point in the sea surface wind field and the geophysical function model to obtain the wind speed at each point in the sea surface wind field. The wind speed adjustment module is used to perform wind speed saturation adjustment on the wind speed at each point in the sea surface wind field using an empirical function to obtain the adjusted wind speed at each point in the sea surface wind field. The wind field inversion module is used to combine the adjusted wind speed at each point in the sea surface wind field and the wind direction at each point in the sea surface wind field to form the sea surface wind field under tropical cyclone sea conditions.

[0053] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 3As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O) and a communication interface. The processor, memory and input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the sea surface wind field under tropical cyclone sea conditions. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for inverting the sea surface wind field of a tropical cyclone is implemented.

[0054] Those skilled in the art will understand that Figure 3 The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present application and does not constitute a limitation on the computer device to which the solution of the present application is applied. A specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement. In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps of the above-mentioned method embodiments when executing the computer program.

[0055] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0056] In an exemplary embodiment, a computer program product is provided, including a computer program. When the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0057] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0058] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0059] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0060] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for inverting the sea surface wind field of a tropical cyclone, characterized in that: include: Determine the location of the tropical cyclone eyewall from C-band VV polarized synthetic aperture radar images under tropical cyclone sea conditions; Determine the center of a tropical cyclone based on the position of the tropical cyclone's eyewall; Determine the line connecting each point in the sea surface wind field in the synthetic aperture radar image and the center of the tropical cyclone, and take the counterclockwise tangent direction of the line as the wind direction at each point in the sea surface wind field; Based on the wind direction and geophysical function model at each point in the sea surface wind field, the tropical cyclone wind field is inverted to obtain the wind speed at each point in the sea surface wind field; The wind speed at each point in the sea surface wind field is adjusted to saturation using the empirical function to obtain the adjusted wind speed at each point in the sea surface wind field; The adjusted wind speed at each point in the sea surface wind field and the wind direction at each point in the sea surface wind field constitute the sea surface wind field under tropical cyclone sea conditions.

2. The tropical cyclone sea surface wind field inversion method according to claim 1, characterized in that: Determine the location of the tropical cyclone eyewall from C-band VV-polarized synthetic aperture radar images under tropical cyclone sea conditions, specifically: Selecting a position in the synthetic aperture radar image where the gradient change of the backscattered signal is the largest; The location with the largest gradient change of all selected backscatter signals is determined as the location of the tropical cyclone eyewall.

3. The tropical cyclone sea surface wind field inversion method according to claim 1, characterized in that: Determine the center of a tropical cyclone based on the position of its eyewall, including: The area enclosed by the tropical cyclone eyewall is determined as the tropical cyclone eye area; Extract the center of the tropical cyclone eye area and determine it as the tropical cyclone center.

4. The tropical cyclone sea surface wind field inversion method according to claim 1, characterized in that: Based on the wind direction and geophysical function model at each point in the sea surface wind field, the tropical cyclone wind field is inverted to obtain the wind speed at each point in the sea surface wind field, including: According to the wind direction at each point in the sea surface wind field, use the formula , calculate the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar; where, is the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar, is the wind speed at 10 meters above the sea surface, is the synthetic aperture radar incident angle, is the azimuth angle of synthetic aperture radar observation, 、 and are the first coefficient, the second coefficient and the third coefficient related to wind speed and synthetic aperture radar incident angle respectively; According to the standard backscatter coefficient of VV polarization of C-band synthetic aperture radar, the wind speed at each point in the sea surface wind field is obtained using the geophysical function model.

5. The tropical cyclone sea surface wind field inversion method according to claim 1, characterized in that: The empirical function is: ； Where, is the adjusted wind speed at each point in the sea surface wind field, is the wind speed at each point in the sea surface wind field, 、 、 are the first, second and third parameters obtained by fitting respectively.

6. The tropical cyclone sea surface wind field inversion method according to claim 5, characterized in that: ， ， 。 7. A tropical cyclone sea surface wind field inversion device, characterized in that: include: The eyewall determination module is used to determine the location of the tropical cyclone eyewall from the C-band VV polarization synthetic aperture radar image under tropical cyclone sea conditions; A cyclone center determination module is used to determine the center of a tropical cyclone based on the position of the tropical cyclone eye wall; The wind direction calculation module is used to determine the line connecting each point in the sea surface wind field in the synthetic aperture radar image and the center of the tropical cyclone, and take the counterclockwise tangent direction of the line as the wind direction at each point in the sea surface wind field; The wind speed calculation module is used to invert the tropical cyclone wind field based on the wind direction and geophysical function model at each point in the sea surface wind field to obtain the wind speed at each point in the sea surface wind field; The wind speed adjustment module is used to perform wind speed saturation adjustment on the wind speed at each point in the sea surface wind field using an empirical function to obtain the adjusted wind speed at each point in the sea surface wind field; The wind field inversion module is used to construct the sea surface wind field under tropical cyclone sea conditions by combining the adjusted wind speed and wind direction at each point in the sea surface wind field.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the tropical cyclone sea surface wind field inversion method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for inverting the tropical cyclone sea surface wind field according to any one of claims 1 to 6 is implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the method for inverting the tropical cyclone sea surface wind field according to any one of claims 1 to 6 is implemented.

Images