A method for inverting typhoon wind speed based on extremely low frequency noise
Through the energy inversion method based on extremely low frequency noise pulsation, the problem that existing typhoon monitoring methods are difficult to accurately invert typhoon high wind speed areas is solved, and typhoon wind speed monitoring with high time resolution is achieved, which reduces the difficulty of data acquisition and provides new ideas for typhoon monitoring.
Patent Information
- Application Number
- CN202310056420.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-01-18
- Publication Date
- 2025-05-30
- Estimated Expiration
- 2043-01-18
AI Technical Summary
The existing typhoon monitoring methods are difficult to accurately invert the wind speed in typhoon high-wind speed areas and rainfall areas, and the meteorological reconnaissance aircraft is difficult to operate, is highly dangerous and is expensive to fly.
Using an energy inversion method based on extremely low frequency noise ground pulsation, the geopulsation frequency bands stimulated by typhoons are screened, the weighted center position of the equivalent source area of the geopulsation is calculated, the Rayleigh wave energy is obtained, and the maximum wind speed of the typhoon is output through the inversion target model.
It improves the time resolution of typhoon wind speed monitoring, reduces the difficulty of data acquisition, fills the gap in the inversion of typhoon intensity by ground pulsation signals, and provides new ideas for typhoon monitoring.
Smart Images
Figure CN116203651B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for inverting typhoon wind speed, and more particularly to a method for inverting the maximum wind speed of a typhoon based on the energy of a specific seismic phase in extremely low frequency noise ground pulsation. Background Art
[0002] Typhoons are highly destructive disastrous weather systems that mainly cause casualties and economic losses through strong winds, heavy rains, and storm surges. The northwest Pacific Ocean is the most active sea area for strong tropical storms, with one-third of the world's typhoons concentrated here every year. Improving the monitoring ability of typhoon process intensity is a necessary measure for disaster prevention and mitigation.
[0003] At present, satellite remote sensing and meteorological aircraft reconnaissance are mainly used for typhoon monitoring. Satellite remote sensing technology is difficult to accurately invert the wind speed in high wind speed areas and rainfall areas of typhoons; while meteorological reconnaissance aircraft have problems such as high operation difficulty, high danger, and expensive flight costs. Therefore, there is an urgent need for a new typhoon intensity monitoring method to supplement and mutually verify the traditional methods.
[0004] Inverting typhoon intensity through ocean noise is a feasible new method. However, the currently selected noises are all above 10 Hz, and some even reach several kHz. The noise attenuates quickly during propagation and is difficult to collect. Therefore, hydrophones must be arranged in advance on the typhoon path, and noise signals can be effectively collected only when the typhoon passes near the observation device. In recent years, typhoon-excited extremely low frequency noise (ground pulsation) has been used to observe and study typhoons. Scientists have achieved typhoon positioning based on ground pulsation signals, but the research on inverting typhoon intensity using ground pulsation signals has developed slowly and remains only at the stage of statistical analysis, lacking more specific research starting from specific seismic phases. Summary of the Invention
[0005] In order to solve the problems in the background art, the present invention provides a method for inverting typhoon wind speed based on extremely low frequency noise.
[0006] The technical solution adopted by the present invention is as follows:
[0007] The method for inverting typhoon wind speed of the present invention includes the following steps:
[0008] Step 1) During the movement of the typhoon on the ocean surface, for each typhoon center path point during the movement of the typhoon, according to the sea surface equivalent pressure distribution of extremely low frequency noise of each frequency excited by the waves within the sea area range of the typhoon movement path, that is, the ground pulsation, the ground pulsation frequency band excited by the typhoon is screened, and the sea surface equivalent pressure distribution in this frequency band is used as the ground pulsation equivalent source area.
[0009] Step 2) For each typhoon center path point during the typhoon movement, according to the position of the ground motion equivalent source area, perform weighted calculation to obtain the weighted center position of the ground motion equivalent source area at the current moment; it is necessary to ensure that the time resolution of the weighted center position is the same as the time resolution of the typhoon wind speed.
[0010] Step 3) For each typhoon center path point during the typhoon movement, according to the typhoon center path point and its weighted center position, calculate the distance that the wave propagates from the typhoon center path point to the weighted center position, and then obtain the average time delay data of the wave propagating from the typhoon center path point to the weighted center position.
[0011] Step 4) According to the OBS data and average time delay data of several ocean bottom seismographs OBS pre - arranged within the sea area range of the typhoon movement path during the typhoon, use short - time Fourier transform for time - frequency analysis to obtain the spectral information of the OBS data of each ocean bottom seismograph OBS, and then calculate the Rayleigh wave energy obtained by each ocean bottom seismograph OBS within the Rayleigh wave frequency band range.
[0012] Step 5) Energy loss will occur during the propagation of Rayleigh waves from the weighted center of the ground motion equivalent source area to the OBS; for the Rayleigh wave energy obtained by each ocean bottom seismograph OBS, perform compensation calculation on the Rayleigh wave energy obtained by the ocean bottom seismograph OBS to obtain the Rayleigh wave energy of the ground motion at the weighted center position of the ground motion equivalent source area; according to the Rayleigh wave energy of the ground motion at the weighted center position of the ground motion equivalent source area obtained by each ocean bottom seismograph OBS, take the average value to obtain the noise source intensity of the ground motion equivalent source area, and it is necessary to ensure that its time resolution is consistent with the wind speed data.
[0013] Step 6) Establish an inversion target model for the maximum typhoon wind speed, input the noise source intensity of the ground motion equivalent source area and the maximum wind speed data of the typhoon into the inversion target model, and the inversion target model outputs the inversion index and inversion coefficient.
[0014] Step 7) Establish an optimal fitting inversion model for the typhoon according to the inversion index and inversion coefficient. After repeating steps 1) - 5) for the sea - surface equivalent pressure distribution of the extremely low - frequency noise ground motion of each frequency excited by the waves within the sea area range of the typhoon movement path of the typhoon to be monitored, obtain the noise source intensity of the ground motion equivalent source area when the center of the typhoon to be monitored moves to each typhoon center path point. Input the noise source intensity of the ground motion equivalent source area when the center of the typhoon to be monitored moves to each typhoon center path point into the optimal fitting inversion model for the typhoon, and the optimal fitting inversion model for the typhoon outputs the maximum wind speed when the center of the typhoon to be monitored moves to each typhoon center path point, and finally realizes the inversion of the typhoon wind speed.
[0015] In the above step 1), the sea surface equivalent pressure distribution of the extremely low-frequency noise ground pulsation at each frequency excited by the sea waves within the sea area of the typhoon moving path is specifically the sea surface equivalent pressure of the extremely low-frequency noise ground pulsation at each grid point within the sea area with the preset grid longitude and latitude resolution for each frequency of the extremely low-frequency noise ground pulsation; the frequency range of the extremely low-frequency noise ground pulsation is 0.05 Hz - 0.5 Hz.
[0016] The sea surface equivalent pressure distribution of the extremely low-frequency noise ground pulsation can be specifically obtained from the French Research Institute for Exploitation of the Sea (IFREMER), or can also be calculated in the following way: Input the terrain data and wind speed data of the simulated sea area of the typhoon path into the WAVEWATCHⅢ sea wave forecasting model to simulate the sea wave fields at different time periods within the simulated sea area. Specifically, a wave field can be constructed every three hours. Calculate the sea surface equivalent pressure generated by the sea waves at each frequency at each moment in each corresponding time period through this sea wave field to obtain the distribution grid of the equivalent source area of the extremely low-frequency noise ground pulsation excited by the sea waves at different frequencies at each moment. The longitude and latitude resolution of the equivalent source area distribution grid is 0.5°, that is, the grid size is 0.5° * 0.5°, and higher resolutions can also be used. Each moment refers to: According to the time-frequency diagram of the OBS data, find out the time when the ground pulsation signal is excited by the typhoon, and determine the moment at a certain time interval (such as 3 hours).
[0017] In the above step 1), for each typhoon center path point during the typhoon movement, according to the sea surface equivalent pressure distribution of the extremely low-frequency noise ground pulsation at each frequency excited by the sea waves within the sea area of the typhoon moving path, screen out the ground pulsation frequency band excited by the typhoon, and use the sea surface equivalent pressure distribution in this frequency band as the ground pulsation equivalent source area. Specifically, for the grid where the sea surface equivalent pressure of the extremely low-frequency noise ground pulsation at each frequency is located, obtain the grids whose distance from the typhoon center path point is less than the preset distance at the current frequency as the optimal grids and obtain their quantity. Compare the quantities of the optimal grids under the extremely low-frequency noise ground pulsation at each frequency, and select the extremely low-frequency noise ground pulsation at one frequency with the largest quantity of the optimal grids as the optimal ground pulsation; screen out the grids where each sea surface equivalent pressure greater than the preset intensity threshold in the sea surface equivalent pressure of the optimal ground pulsation are the most optimal grids, and each optimal grid constitutes the ground pulsation equivalent source area excited by the typhoon. The ground pulsation equivalent source area is located near the typhoon center path point (lon, lat) of the typhoon, and the range near the typhoon center path point is a rectangular frame of [lon - 23, lon + 7, lat - 15, lat + 5].
[0018] In the above step 2), the weighted center position of the ground pulsation equivalent source area at the current moment is specifically as follows:
[0019]
[0020]
[0021] Among them, Lon and Lat are respectively the longitude and latitude of the weighted center position; α i represents the weight of the i-th grid point in the equivalent source area of ground motion; lon i and lat i are respectively the longitude and latitude of the i-th grid point in the equivalent source area of ground motion.
[0022] The weight α of the i-th grid point in the equivalent source area of ground motion is specifically as follows: i Specifically as follows:
[0023]
[0024]
[0025]
[0026] Among them, p2l represents the source area intensity of the i-th grid point in the equivalent source area of ground motion; p2l all represents the sea surface equivalent pressure of each grid point in the equivalent source area of ground motion; p2l i represents the sea surface equivalent pressure of the i-th grid point in the equivalent source area of ground motion.
[0027] In the said step 3), according to the typhoon center path points and their weighted center positions, calculate the distance that the wave propagates from the typhoon center path point to the weighted center position, and then obtain the average time delay data of the wave propagating from the typhoon center path point to the weighted center position, specifically as follows:
[0028]
[0029]
[0030]
[0031] Among them, dis t represents the distance that the wave propagates from the typhoon center path point to the weighted center position at time t; Lon t and Lat t respectively represent the longitude and latitude of the weighted center position at time t; and respectively represent the longitude and latitude of the typhoon center path point at time t; △T t represents the time delay data of the wave propagating from the typhoon center path point to the weighted center position at time t; c grepresents the wave group velocity at the current wave frequency; △T represents the average time delay data of the wave propagating from the typhoon center path point to the weighted center position; N represents the total number of preset moments.
[0032] Since the positions of the typhoon center and the weighted center of the equivalent source area change continuously with time, the calculated value of the wave propagation distance dis t is not exactly the same as the actual value. Therefore, the average value of the time delays of wave propagation at all moments during the typhoon is calculated to obtain the average time delay of the ground motion process excited by the typhoon, which is used as the time delay value for calculation.
[0033] In step 4), according to the OBS data and average time delay data of several ocean bottom seismographs OBS pre-arranged within the sea area of the typhoon movement path during the typhoon movement, short-time Fourier transform is used for time-frequency analysis to obtain the spectral information of the OBS data of each ocean bottom seismograph OBS, and then the Rayleigh wave energy obtained by each ocean bottom seismograph OBS is calculated within the Rayleigh wave frequency band range, specifically for each ocean bottom seismograph OBS as follows:
[0034]
[0035] E t+△T represents the Rayleigh wave energy obtained by the ocean bottom seismograph OBS at time t + △T; f 2 and f 1 respectively represent the upper and lower limits of the frequency band of the Rayleigh wave; stft() represents the short-time Fourier transform, and data t+△T represents the OBS data of the ocean bottom seismograph OBS at time t + △T, that is, the data of the amplitude change of the ground motion recorded by the ocean bottom seismograph OBS with time; nfft represents the number of sampling points of the ocean bottom seismograph OBS, and stft(data t+△T , nfft) represents the spectral information obtained by short-time Fourier transform of the OBS data of the ocean bottom seismograph OBS at time t + △T; the Rayleigh wave energy obtained by the ocean bottom seismograph OBS is used as the energy of the extremely low-frequency noise ground motion propagating from the weighted center position of the ground motion equivalent source area to the ocean bottom seismograph OBS.
[0036] When performing short-time Fourier transform, a hanning window with an overlap rate of 50% and a window length of 200 is specifically used to calculate the spectrum of the ground motion signal excited by the typhoon. The short-time Fourier transform algorithm reflects the change of the signal with time by taking out a small segment of the signal each time, adding a window, and then performing Fourier transform, and can show the moments when each spectral component appears.
[0037] In step 5), for the Rayleigh wave energy obtained by each ocean bottom seismograph (OBS), compensation calculation is performed on the Rayleigh wave energy obtained by the OBS to obtain the Rayleigh wave energy of ground roll at the weighted center position of the equivalent source area of ground roll, specifically as follows:
[0038] log 10 (E 0t )=log 10 (E t+△T )+log 10 (r)+2×B×r×log 10 (e)
[0039] Among them, E 0t represents the noise source intensity obtained by the OBS at time t under the current typhoon; E t+△T represents the Rayleigh wave energy obtained by the OBS at time t + △T; r represents the propagation distance of the Rayleigh wave; B represents the preset inelastic attenuation coefficient of the propagation medium.
[0040] The preset inelastic attenuation coefficient is determined according to the propagation medium in the study area according to the actual situation. For example, in the area near Reunion Island, when the ground roll frequency is in the range of 0.1 - 0.35 Hz, the inelastic attenuation coefficient B can be set to 0.00084.
[0041] In step 6), the established inversion target model minL of the maximum typhoon wind speed is specifically as follows:
[0042]
[0043] Among them, L represents the residual function; V j represents the maximum wind speed of the typhoon at time j; n and k represent the inversion index and inversion coefficient; E 0j represents the noise source intensity obtained by the OBS at time j under the current typhoon.
[0044] The specific data of the maximum wind speed of the typhoon is the data of the International Best Track Archive for Climate Stewardship (IBTrACS).
[0045] In step 7), the established optimal fitting inversion model of the typhoon is specifically as follows:
[0046]
[0047] Among them, V 1j represents the maximum wind speed of the typhoon to be monitored at time j; E 1jDenote the noise source intensity obtained by the ocean bottom seismograph OBS at the j-th moment under the typhoon to be monitored.
[0048] Use the least squares method in the logarithmic space to obtain the best fitting model, and realize the inversion of typhoon wind speed through extremely low frequency noise.
[0049] The beneficial effects of the present invention are as follows:
[0050] The present invention realizes the inversion of the maximum wind speed of typhoons starting from specific seismic phases in extremely low frequency noise. Using extremely low frequency noise to invert wind speed improves the time resolution of previous satellite remote sensing wind speed data, avoids the problem of rapid attenuation of high-frequency noise used in previous studies, and reduces the difficulty of data collection; at the same time, studying the wind speed of typhoons starting from extremely low frequency noise fills the gap in inverting typhoon intensity using ground pulsation signals, proves the feasibility of inverting typhoon wind speed starting from Rayleigh waves, and provides a new idea for typhoon monitoring. Description of the Drawings
[0051] Figure 1 It is a schematic diagram of the technical route of the present invention;
[0052] Figure 2 It is a schematic diagram of the process of typhoon-excited ground pulsation. Specific Embodiments
[0053] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.
[0054] As Figure 1 shown, the method for inverting typhoon wind speed of the present invention includes the following steps:
[0055] Step 1) During the movement of the typhoon on the ocean surface, for each typhoon center path point during the movement of the typhoon, according to the extremely low frequency noise of each frequency excited by the waves within the sea area of the typhoon movement path, that is, the sea surface equivalent pressure distribution of ground pulsation, screen out the ground pulsation frequency band excited by the typhoon, and use the sea surface equivalent pressure distribution in this frequency band as the ground pulsation equivalent source area.
[0056] In step 1), the sea surface equivalent pressure distribution of the extremely low frequency noise ground pulsation of each frequency excited by the waves within the sea area of the typhoon movement path is specifically, for each frequency of the extremely low frequency noise ground pulsation, within the sea area range with a preset grid longitude and latitude resolution, the sea surface equivalent pressure of the extremely low frequency noise ground pulsation at each grid point; the frequency range of the extremely low frequency noise ground pulsation is 0.05Hz - 0.5Hz.
[0057] The specific distribution of the sea surface equivalent pressure of the extremely low frequency noise ground pulsation can be obtained from the French Research Institute for Exploitation of the Sea (IFREMER), or can also be calculated in the following way: Input the terrain data and wind speed data of the simulated sea area range of the typhoon path into the WAVEWATCHⅢ wave forecasting model to simulate the wave fields at different time periods within the simulated sea area range. Specifically, a wave field can be constructed every three hours. Calculate the sea surface equivalent pressure generated by the waves of each frequency at each moment in each corresponding time period through this wave field, and obtain the distribution grid of the equivalent source area of the extremely low frequency noise ground pulsation excited by the waves of different frequencies at each moment. The longitude and latitude resolution of the equivalent source area distribution grid is 0.5°, that is, the grid size is 0.5° * 0.5°, and higher resolutions can also be used. Each moment refers to: According to the time-frequency diagram of the OBS data, find out the time when the ground pulsation signal is excited by the typhoon, and determine the moment at a certain time interval (such as 3 hours).
[0058] In step 1), for each typhoon center path point during the typhoon movement, according to the distribution of the sea surface equivalent pressure of the extremely low frequency noise ground pulsation of each frequency excited by the waves within the sea area range of the typhoon movement path, screen out the ground pulsation frequency band excited by the typhoon, and use the sea surface equivalent pressure distribution in this frequency band as the ground pulsation equivalent source area. Specifically, for the grid where the sea surface equivalent pressure of the extremely low frequency noise ground pulsation of each frequency is located, obtain the grids whose distance from the typhoon center path point is less than the preset distance at the current frequency as the optimal grids and obtain their quantity. Compare the quantities of the optimal grids under the extremely low frequency noise ground pulsation of each frequency, and select the extremely low frequency noise ground pulsation of one frequency with the largest quantity of the optimal grids as the optimal ground pulsation; Screen out the grids where each sea surface equivalent pressure greater than the preset intensity threshold in the sea surface equivalent pressure of the optimal ground pulsation is located as the optimal grids, and each optimal grid constitutes the ground pulsation equivalent source area excited by the typhoon. The ground pulsation equivalent source area is located near the typhoon center path point (lon, lat) of the typhoon, and the range near the typhoon center path point is a rectangular frame of [lon - 23, lon + 7, lat - 15, lat + 5].
[0059] In step 2), for each typhoon center path point during the typhoon movement, according to the position of the ground pulsation equivalent source area, perform weighted calculation to obtain the weighted center position of the ground pulsation equivalent source area at the current moment; It is necessary to ensure that the time resolution of the weighted center position is the same as the time resolution of the typhoon wind speed at the same time.
[0060] In step 2), the weighted center position of the ground pulsation equivalent source area at the current moment is specifically as follows:
[0061]
[0062]
[0063] Among them, Lon and Lat are the longitude and latitude of the weighted center position; α i represents the weight of the i-th grid point in the equivalent source area of ground motion; lon i and lat i are the longitude and latitude of the i-th grid point in the equivalent source area of ground motion, respectively.
[0064] The weight α of the i-th grid point in the equivalent source area of ground motion i is specifically as follows:
[0065]
[0066]
[0067]
[0068] Among them, p2l represents the source area intensity of the i-th grid point in the equivalent source area of ground motion; p2l all represents the sea surface equivalent pressure of each grid point in the equivalent source area of ground motion; p2l i represents the sea surface equivalent pressure of the i-th grid point in the equivalent source area of ground motion.
[0069] Step 3): For each typhoon center path point during the typhoon movement, according to the typhoon center path point and its weighted center position, calculate the distance that the wave propagates from the typhoon center path point to the weighted center position, and then obtain the average time delay data of the wave propagating from the typhoon center path point to the weighted center position.
[0070] In step 3), according to the typhoon center path point and its weighted center position, calculate the distance that the wave propagates from the typhoon center path point to the weighted center position, and then obtain the average time delay data of the wave propagating from the typhoon center path point to the weighted center position, specifically as follows:
[0071]
[0072]
[0073]
[0074]
[0075] Among them, dis t represents the distance that the wave propagates from the typhoon center path point to the weighted center position at time t; Lon t and Lat t respectively represent the longitude and latitude of the weighted center position at time t; and respectively represent the longitude and latitude of the typhoon center path point at time t; △T t represents the time delay data of the wave propagating from the typhoon center path point to the weighted center position at time t; c g represents the wave group velocity at the current wave frequency; △T represents the average time delay data of the wave propagating from the typhoon center path point to the weighted center position; N represents the total number of preset times.
[0076] Since the weighted center positions of the typhoon center and the equivalent source area change with time, the calculated value of the wave propagation distance dis t is not exactly the same as the actual value. Therefore, the average value of the time delays of the waves propagating at all times during the typhoon is obtained, and the average time delay of the ground motion process excited by the typhoon is obtained and used as the time delay value for calculation.
[0077] Step 4) According to the OBS data and the average time delay data of a number of ocean bottom seismographs OBS pre-arranged within the sea area range of the typhoon movement path during the typhoon, perform time-frequency analysis using the short-time Fourier transform to obtain the spectral information of the OBS data of each ocean bottom seismograph OBS, and then calculate the Rayleigh wave energy obtained by each ocean bottom seismograph OBS within the Rayleigh wave frequency band range.
[0078] In step 4), according to the OBS data and the average time delay data of a number of ocean bottom seismographs OBS pre-arranged within the sea area range of the typhoon movement path during the typhoon movement, perform time-frequency analysis using the short-time Fourier transform to obtain the spectral information of the OBS data of each ocean bottom seismograph OBS, and then calculate the Rayleigh wave energy obtained by each ocean bottom seismograph OBS within the Rayleigh wave frequency band range. Specifically for each ocean bottom seismograph OBS as follows:
[0079]
[0080] E t+△T represents the Rayleigh wave energy obtained by the ocean bottom seismograph OBS at time t + △T; f 2 and f 1 respectively represent the upper and lower limits of the frequency band of the Rayleigh wave; stft() represents the short-time Fourier transform, data t+△T represents the OBS data of the ocean bottom seismograph OBS at time t + △T, that is, the data of the amplitude of the ground motion recorded by the ocean bottom seismograph OBS changing with time; nfft represents the number of sampling points of the ocean bottom seismograph OBS, stft(data t+△T , nfft) represents the spectral information obtained after the OBS data of the ocean bottom seismograph OBS at time t + △T is subjected to the short-time Fourier transform; the Rayleigh wave energy obtained by the ocean bottom seismograph OBS is used as the energy of the extremely low-frequency noise ground motion propagating from the weighted center position of the ground motion equivalent source area to the ocean bottom seismograph OBS.
[0081] When performing short-time Fourier transform, a Hanning window with an overlap rate of 50% and a window length of 200 is specifically used to calculate the spectrum of the ground pulsation signal excited by the typhoon. The short-time Fourier transform algorithm reflects the change of the signal over time by taking a small segment of the signal each time, windowing it, and then performing Fourier transform, and can display the moments when each spectral component appears.
[0082] In step 5), energy loss will occur during the propagation of Rayleigh waves from the weighted center of the ground pulsation equivalent source area to the OBS; for the Rayleigh wave energy obtained by each ocean bottom seismograph OBS, compensation calculation is performed on the Rayleigh wave energy obtained by the ocean bottom seismograph OBS to obtain the Rayleigh wave energy of the ground pulsation at the weighted center position of the ground pulsation equivalent source area; according to the Rayleigh wave energy of the ground pulsation at the weighted center position of the ground pulsation equivalent source area obtained by each ocean bottom seismograph OBS, the noise source intensity of the ground pulsation equivalent source area is obtained by taking the average value, and its time resolution needs to be consistent with the wind speed data.
[0083] In step 5), for the Rayleigh wave energy obtained by each ocean bottom seismograph OBS, compensation calculation is performed on the Rayleigh wave energy obtained by the ocean bottom seismograph OBS to obtain the Rayleigh wave energy of the ground pulsation at the weighted center position of the ground pulsation equivalent source area, specifically as follows:
[0084] log 10 (E 0t ) = log 10 (E t+△T ) + log 10 (r) + 2 × B × r × log 10 (e)
[0085] Among them, E 0t represents the noise source intensity obtained by the ocean bottom seismograph OBS at time t under the current typhoon; E t+△T represents the Rayleigh wave energy obtained by the ocean bottom seismograph OBS at time t + △T; r represents the propagation distance of the Rayleigh wave; B represents the preset inelastic attenuation coefficient of the propagation medium.
[0086] The preset inelastic attenuation coefficient is determined according to the propagation medium in the study area according to the actual situation. For example, in the area near Reunion Island, when the ground pulsation frequency is in the range of 0.1 - 0.35 Hz, the inelastic attenuation coefficient B can be set to 0.00084.
[0087] In step 6), an inversion target model for the maximum wind speed of the typhoon is established, and the noise source intensity of the ground pulsation equivalent source area and the maximum wind speed data of the typhoon are input into the inversion target model, and the inversion target model outputs an inversion index and an inversion coefficient.
[0088] In step 6), the established inversion target model minL for the maximum wind speed of the typhoon is specifically as follows:
[0089]
[0090] Among them, L represents the residual function; V j represents the maximum wind speed of the typhoon at time j; n and k represent the inversion index and inversion coefficient; E 0j represents the noise source intensity obtained by the ocean bottom seismograph OBS at time j under the current typhoon.
[0091] The maximum wind speed data of the typhoon is specifically the data of the International Best Track Archive for Climate Stewardship (IBTrACS).
[0092] Step 7): Establish an optimal fitting inversion model for the typhoon according to the inversion index and inversion coefficient. After repeating steps 1)-5) for the sea surface equivalent pressure distribution of the extremely low-frequency noise ground pulsation of each frequency excited by the waves within the sea area of the typhoon movement path of the typhoon to be monitored, obtain the noise source intensity of the ground pulsation equivalent source area when the center of the typhoon to be monitored moves to each typhoon center path point. Input the noise source intensity of the ground pulsation equivalent source area when the center of the typhoon to be monitored moves to each typhoon center path point into the optimal fitting inversion model of the typhoon. The optimal fitting inversion model of the typhoon outputs the maximum wind speed when the center of the typhoon to be monitored moves to each typhoon center path point, and finally realizes the inversion of the typhoon wind speed.
[0093] In step 7), the established optimal fitting inversion model for the typhoon is specifically as follows:
[0094]
[0095] Among them, V 1j represents the maximum wind speed of the typhoon to be monitored at time j; E 1j represents the noise source intensity obtained by the ocean bottom seismograph OBS at time j under the typhoon to be monitored.
[0096] Use the least squares method in the logarithmic space to obtain the optimal fitting model, and realize the inversion of the typhoon wind speed through the extremely low-frequency noise.
[0097] The present invention inverses the typhoon wind speed by extracting the energy of Rayleigh waves in the extremely low-frequency noise ground pulsation. As Figure 2As shown in the figure, through the comparative analysis of the distribution of the equivalent source area of ground pulsation and the typhoon path, a reasonable intensity threshold is set for the equivalent source area, so that the position points with intensity above the threshold in the equivalent source area are concentrated near the typhoon center. The position points with intensity greater than the threshold are regarded as the equivalent source area of ground pulsation excited by the typhoon. On this basis, the weighted center position of the equivalent source area excited by the typhoon is obtained. In order to obtain the noise source intensity at the weighted center position of the equivalent source area, the ground pulsation signals received by multiple OBSs are extracted, the short-time Fourier transform is used to calculate the energy of the Rayleigh wave component at the OBS, and the noise source intensity of the weighted center of the equivalent source area is obtained after propagation loss compensation. Then, the least squares method is used to fit the Rayleigh wave energy and the maximum wind speed data of the typhoon, and finally the relationship between the maximum wind speed of the typhoon and the Rayleigh wave energy in the ground pulsation excited by the typhoon is inversely obtained, realizing the inversion of the maximum wind speed of the typhoon from a specific seismic phase in extremely low-frequency noise.
[0098] The above description is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for inverting typhoon wind speed based on extremely low frequency noise, characterized in that: The method comprises the following steps: Step 1) During the movement of the typhoon over the ocean surface, for each typhoon center path point during the typhoon movement, according to the extremely low frequency noise of each frequency excited by the waves within the sea area of the typhoon movement path, that is, the sea surface equivalent pressure distribution of the earth tremors, filter out the earth tremor frequency band excited by the typhoon, and use the sea surface equivalent pressure distribution in this frequency band as the earth tremor equivalent source area; Step 2) For each typhoon center path point during the typhoon movement, according to the position of the earth tremor equivalent source area, perform weighted calculation to obtain the weighted center position of the earth tremor equivalent source area at the current moment; Step 3) For each typhoon center path point during the typhoon movement, according to the typhoon center path point and its weighted center position, calculate the distance that the wave propagates from the typhoon center path point to the weighted center position, and further obtain the average time delay data of the wave propagating from the typhoon center path point to the weighted center position; Step 4) According to the OBS data and the average time delay data of several ocean bottom seismographs OBS pre-arranged within the sea area of the typhoon movement path during the typhoon, use short-time Fourier transform for time-frequency analysis to obtain the spectral information of the OBS data of each ocean bottom seismograph OBS, and further calculate the Rayleigh wave energy obtained by each ocean bottom seismograph OBS within the Rayleigh wave frequency band range; Step 5) For the Rayleigh wave energy obtained by each ocean bottom seismograph OBS, perform compensation calculation on the Rayleigh wave energy obtained by the ocean bottom seismograph OBS to obtain the Rayleigh wave energy of the earth tremors at the weighted center position of the earth tremor equivalent source area; according to the Rayleigh wave energy of the earth tremors at the weighted center position of the earth tremor equivalent source area obtained by each ocean bottom seismograph OBS, take the average value to obtain the noise source intensity of the earth tremor equivalent source area; Step 6) Establish an inversion target model for the maximum typhoon wind speed, input the noise source intensity of the earth tremor equivalent source area and the maximum typhoon wind speed data into the inversion target model, and the inversion target model outputs an inversion index and an inversion coefficient; Step 7) Establish a typhoon best-fit inversion model according to the inversion index and the inversion coefficient. After repeating steps 1)-5) for the sea surface equivalent pressure distribution of the earth tremors of the extremely low frequency noise of each frequency excited by the waves within the sea area of the typhoon movement path of the typhoon to be monitored, obtain the noise source intensity of the earth tremor equivalent source area when the center of the typhoon to be monitored moves to each typhoon center path point. Input the noise source intensity of the earth tremor equivalent source area when the center of the typhoon to be monitored moves to each typhoon center path point into the typhoon best-fit inversion model, and the typhoon best-fit inversion model outputs the maximum wind speed when the center of the typhoon to be monitored moves to each typhoon center path point, and finally realizes the inversion of the typhoon wind speed.
2. The method for inverting typhoon wind speed based on extremely low frequency noise according to claim 1, characterized in that: In step 1), the sea surface equivalent pressure distribution of the extremely low-frequency noise ground pulsation at each frequency excited by the sea waves within the sea area of the typhoon movement path is specifically the sea surface equivalent pressure of the extremely low-frequency noise ground pulsation at each grid point within the sea area with the preset grid longitude and latitude resolution for each frequency of the extremely low-frequency noise ground pulsation; the frequency range of the extremely low-frequency noise ground pulsation is 0.05 Hz - 0.5 Hz.
3. A method for inverting typhoon wind speed based on extremely low-frequency noise according to claim 2, characterized in that: In step 1), for each typhoon center path point during the typhoon movement, according to the sea surface equivalent pressure distribution of the extremely low-frequency noise ground pulsation at each frequency excited by the sea waves within the sea area of the typhoon movement path, the ground pulsation frequency band excited by the typhoon is screened out, and the sea surface equivalent pressure distribution in this frequency band is used as the ground pulsation equivalent source area. Specifically, for the grid where the sea surface equivalent pressure of the extremely low-frequency noise ground pulsation at each frequency is located, the grid with a distance less than the preset distance from the typhoon center path point at the current frequency is obtained as the optimal grid and its quantity is obtained. The quantities of the optimal grids under the extremely low-frequency noise ground pulsation at each frequency are compared, and the extremely low-frequency noise ground pulsation at one frequency with the largest quantity of the optimal grids is selected as the optimal ground pulsation; the grids where each sea surface equivalent pressure greater than the preset intensity threshold in the sea surface equivalent pressure of the optimal ground pulsation are the most optimal grids, and each optimal grid constitutes the ground pulsation equivalent source area excited by the typhoon.
4. A method for inverting typhoon wind speed based on extremely low-frequency noise according to claim 2, characterized in that: In step 2), the weighted center position of the ground pulsation equivalent source area at the current moment is specifically as follows: where Lon and Lat are the longitude and latitude of the weighted center position; α i represents the weight of the i-th grid point in the equivalent source area of ground pulsation; lon i and lat i are the longitude and latitude of the i-th grid point in the equivalent source area of ground pulsation, respectively.
5. A method for inverting typhoon wind speed based on extremely low-frequency noise according to claim 4, characterized in that: The weight α of the i-th grid point in the equivalent source area of ground pulsation i Specifically as follows: Among them, p2l represents the source area intensity of the i-th grid point in the equivalent source area of ground pulsation; p2l all represents the sea surface equivalent pressure of each grid point in the equivalent source area of ground pulsation; p2l i represents the sea surface equivalent pressure of the i-th grid point in the equivalent source area of ground pulsation.
6. A method for inverting typhoon wind speed based on extremely low-frequency noise according to claim 1, characterized in that: In step 3), according to the typhoon center path point and its weighted center position, the distance that the wave propagates from the typhoon center path point to the weighted center position is calculated, and then the average time delay data of the wave propagating from the typhoon center path point to the weighted center position is obtained. Specifically as follows: Among them, dis t represents the distance that the wave propagates from the typhoon center path point to the weighted center position at time t; Lon t and Lat t respectively represent the longitude and latitude of the weighted center position at time t; and respectively represent the longitude and latitude of the typhoon center path point at time t; △T t represents the time delay data that the wave propagates from the typhoon center path point to the weighted center position at time t; c g represents the wave group velocity at the current wave frequency; △T represents the average time delay data that the wave propagates from the typhoon center path point to the weighted center position; N represents the total number of preset time instants.
7. A method for inverting typhoon wind speed based on extremely low-frequency noise according to claim 1, characterized in that: In step 4), according to the OBS data of a plurality of ocean bottom seismographs OBS pre-arranged within the sea area of the typhoon movement path during the typhoon movement and the average time delay data, time-frequency analysis is performed using the short-time Fourier transform to obtain the spectral information of the OBS data of each ocean bottom seismograph OBS, and then the Rayleigh wave energy obtained by each ocean bottom seismograph OBS is calculated within the Rayleigh wave frequency band range. Specifically for each ocean bottom seismograph OBS as follows: E t+△T represents the Rayleigh wave energy obtained by the Ocean Bottom Seismograph (OBS) at time t + △T; f 2 and f 1 respectively represent the upper and lower limits of the frequency band of the Rayleigh wave; stft() represents the Short-Time Fourier Transform, and data t+△T represents the OBS data of the Ocean Bottom Seismograph (OBS) at time t + △T, that is, the data of the amplitude change of the ground pulsation recorded by the Ocean Bottom Seismograph (OBS) over time; nfft represents the number of sampling points of the Ocean Bottom Seismograph (OBS), and stft(data t+△T , nfft) represents the spectral information obtained after the short-time Fourier transform of the OBS data of the Ocean Bottom Seismograph (OBS) at time t + △T; the Rayleigh wave energy obtained by the Ocean Bottom Seismograph (OBS) is the energy of the extremely low-frequency noise ground pulsation propagating from the weighted center position of the ground pulsation equivalent source area to the Ocean Bottom Seismograph (OBS).
8. A method for inverting typhoon wind speed based on extremely low-frequency noise according to claim 1, characterized in that: In step 5), for the Rayleigh wave energy obtained by each Ocean Bottom Seismograph (OBS), compensation calculation is performed on the Rayleigh wave energy obtained by the OBS to obtain the Rayleigh wave energy of ground pulsation at the weighted center position of the ground pulsation equivalent source area, specifically as follows: log 10 (E 0t )=log 10 (E t+△T )+log 10 (r)+2×B×r×log 10 (e) Among them, E 0t represents the noise source intensity obtained by the ocean bottom seismograph OBS at time t under the current typhoon; E t+△T represents the Rayleigh wave energy obtained by the ocean bottom seismograph OBS at time t + △T; r represents the propagation distance of the Rayleigh wave; B represents the preset inelastic attenuation coefficient.
9. A method for inverting typhoon wind speed based on extremely low frequency noise according to claim 1, characterized in that: In step 6), the inversion target model minL of the maximum typhoon wind speed is established as follows: Among them, L represents the residual function; V j represents the maximum wind speed of the typhoon at time j; n and k represent the inversion index and inversion coefficient; E 0j represents the noise source intensity obtained by the ocean bottom seismograph OBS at time j under the current typhoon.
10. A method for inverting typhoon wind speed based on extremely low frequency noise according to claim 1, characterized in that: In step 7), the best-fit inversion model of the typhoon is established as follows: Among them, V 1j represents the maximum wind speed of the typhoon to be monitored at time j; E 1j represents the noise source intensity obtained by the ocean bottom seismograph OBS at time j under the typhoon to be monitored.