Method for estimating kernel scale of typhoon with eyes by using static meteorological satellite image

Abstract

The invention discloses a method for estimating the kernel scale of a typhoon with eyes by using a stationary meteorological satellite image. The method is characterized by comprising the following steps: step 1, acquiring brightness temperature data of an infrared channel of a stationary satellite; 2, determining a typhoon high-rise center through a man-machine interaction method; 3, projecting the brightness temperature Tb of the infrared window area to a rectangular coordinate system, and calculating an intermediate parameter Rw; step 4, calculating an eye wall radius Reye; 5, typhoon clear eyes and typhoon non-clear eyes are recognized; step 6, establishing a relational expression between the maximum wind speed radius RMW of the typhoon clear eye and the eye wall radius; and step 7, establishing a relational expression between the maximum wind speed radius RMW of the typhoon non-clear eye and the eye wall radius. Therefore, a more accurate typhoon high-rise center can be obtained by the man-machine interaction method, objective standards of clear eye typhoons and non-clear eye typhoons are formulated, a currently lacked inversion method of the maximum wind speed radius RMW of the non-clear eye typhoons is researched and developed, and the accuracy of the typhoon kernel scale is improved.

Description

Technical Field

[0001] The present invention relates to a method for estimating the scale of a typhoon, and more particularly to a method for estimating the inner core scale of an eyewall typhoon using geostationary meteorological satellite images. Background Art

[0002] A typhoon is one of the most disastrous weather systems on Earth. Accurate estimation of typhoon intensity and scale is crucial for understanding typhoon development and evolution and improving typhoon forecasts. The position, intensity, and scale of a typhoon are closely related to typhoon disasters. The position and intensity determine the area where the disaster occurs and the maximum degree of damage, while the scale determines the scope of its direct and secondary disaster impacts. Scale is one of the key elements in typhoon analysis and forecasting. Typhoon scale can be divided into inner core scale and outer core scale. The inner core scale is usually characterized by the radius of maximum wind (RMW); the outer core scale is characterized by the radius of the wind circle at different sea surface wind speeds, such as 34-kt (1 kt = 0.5144 m / s -1 ), 24-kt, 16-kt, or 5-kt. These scale data provided by the "Best Track" dataset are the most commonly used in actual research. However, the research by Combot et al. (2020) shows that the uncertainty of the RMW provided by the "Best Track" dataset is between 25% and 40%. In fact, in the northwestern Pacific Ocean, this uncertainty is even greater, often between 30% and 60% (Zhuge et al., 2024). Past research has mainly focused on the outer core scale or the inner core scale in the North Atlantic and northeastern Pacific Ocean regions, while there has been little research on the inner core scale in the northwestern Pacific Ocean. This lack is largely due to the lack of reliable inner core scale data.

[0003] For decades, the monitoring methods of typhoon scale have been continuously improved. Currently, for the observation of typhoon wind fields (and typhoon scales), the most recognized method is aircraft detection. However, operational aircraft detection is only carried out in the waters of the North Atlantic and the Northeast Pacific, with strong limitations. Even if aircraft observation data are obtained, the information collected along its flight path usually only covers about 2% of the complete "α" mode of the cyclone wind field, and the sampling is also significantly insufficient (Sampson & Knaff, 2017). Spaceborne wind field observation instruments include microwave radiometers, microwave scatterometers, microwave imagers, etc. The spatial resolution of such instruments is usually relatively coarse. For example, the advantage of the L-band radiometer is that it is mostly not affected by precipitation, but its performance is often poor when the wind speed is below 30 kt, and the spatial resolution of the retrieved sea surface wind field is mostly between 40 and 60 km, making it difficult to observe features at smaller scales such as the eyewall. Microwave scatterometers belong to active observations. Although they can cover the wind field well, the observed spatial resolution is in the range of 25 - 50 km. In addition, there are significant gaps in the scatterometer scans in the tropical region, which may lead to the phenomenon of missing some wind field sampling or omitting consecutive multiple observations (Sampson & Knaff, 2017). The optical imager on geostationary satellites has the characteristic of high temporal resolution, but infrared radiation cannot penetrate the thick clouds of typhoons. So far, it has played a limited role in monitoring typhoon wind fields and scales.

[0004] In recent years, the C-band Synthetic Aperture Radar (SAR) has developed rapidly. By combining single polarization and cross polarization, it can obtain high-precision (below 5 kt), high-level resolution (hundred-meter level) sea surface wind even under extreme wind speeds (such as 140 kts), and there will be no microwave saturation (Tsukada & Horinouchi, 2023). The main disadvantage of SAR is the low observation frequency. Generally, about 5 SAR samples can be obtained in each typhoon life history stage, and at most no more than 20 times. Therefore, there is a contradiction between the accuracy and the time frequency of the typhoon inner core scale data. If a reliable relationship can be established between the geostationary satellite infrared cloud images with high spatio-temporal resolution and the high spatial resolution and high-precision SAR wind fields, it is possible to obtain typhoon scale products with high frequency and reliable accuracy.

[0005] Foreign experts have made attempts in this regard. The research by Kossin et al. (2007) showed that the R eye estimated based on infrared cloud images has a high correlation with the RMW observed by aircraft. They further classified typhoons with eyes into symmetric clear eyes and asymmetric non-clear eyes, and initially established an estimation method for the RMW of clear-eye typhoons. Tsukada & Horinouchi (2023) re-evaluated the R eyeThe relationship with the RMW was studied, and the infrared estimation method for the RMW of a clear - eye typhoon was revised. However, the criterion for distinguishing a clear - eye from a non - clear - eye typhoon is too strict and lacks objectivity, resulting in only 21 clear - eye typhoon samples from SAR being found in 7 years (2015 - 2021). The objective discrimination standard between clear - eye and non - clear - eye typhoons still needs to be clarified, and the research on the RMW estimation algorithm for non - clear - eye typhoons based on satellite infrared cloud images is currently scarce.

[0006] The existing relationship between geostationary satellite cloud images and the typhoon inner - core scale has a relatively strict criterion for distinguishing clear - eye typhoons from non - clear - eye typhoons, resulting in a small number of samples for fitting the RMW, lacking objectivity, and only considering the relationship between geostationary satellite cloud images and the inner - core scale in the case of clear - eye typhoons, lacking a method for estimating the inner - core scale in the case of non - clear - eye typhoons. Summary of the Invention

[0007] In view of the deficiencies of the prior art, the present invention provides a method for estimating the inner - core scale of an eyewall typhoon using geostationary meteorological satellite images, establishing a reliable relationship between geostationary satellite cloud images and the SAR inner - core scale. The aim is to establish a connection between high - temporal - resolution geostationary satellite brightness temperature data and high - spatial - resolution and high - precision SAR wind field data, effectively overcoming the contradiction that it is difficult to coordinate the accuracy and time frequency of inner - core scale data, and providing more accurate inner - core scale data of eyewall typhoons. In addition, the present invention will formulate an objective standard for distinguishing clear - eye typhoons from non - clear - eye typhoons, simultaneously establish a reliable relationship between satellite cloud images of clear - eye typhoons and non - clear - eye typhoons and the SAR inner - core scale, objectively evaluate the accuracy of this method, and finally obtain inner - core scale data of eyewall typhoons with high temporal resolution and reliable accuracy.

[0008] To achieve the above - mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for estimating the inner - core scale of an eyewall typhoon using geostationary meteorological satellite images, comprising the following steps:

[0010] Step 1: Obtain the brightness temperature data of the infrared channel of the geostationary satellite:

[0011] Perform quality control on the SAR wind field data, and extract the information of the brightness temperature T b of the infrared window area of all pixel points within the typhoon central region on the equal - longitude - latitude satellite cloud image;

[0012] Step 2: Determine the typhoon upper - layer center by a human - machine interaction method:

[0013] Combine the typhoon RGB composite image and cloud - track wind, and use a human - machine interaction method to determine the typhoon upper - layer center within the typhoon central region;

[0014] Step 3: Use the brightness temperature T bProject onto the rectangular coordinate system and calculate the intermediate parameter R w :

[0015] Taking the typhoon upper-level center determined in Step 2 as the origin, project the infrared window region brightness temperature T b onto the rectangular coordinate system according to equidistant azimuth and calculate the intermediate parameter R w ; The X-axis of the rectangular coordinate system points due east and the Y-axis points due north;

[0016] Step 4. Calculate the eyewall radius R eye :

[0017] Based on the intermediate parameter R calculated in Step 3 w , calculate the highest brightness temperature T corresponding to all pixel points within the range of radius r ≤ R w in the typhoon center region max and the average brightness temperature T w in the adjacent range where r ≥ R top , and then calculate the temperature threshold T for identifying the typhoon eye region th ;

[0018] Based on the calculated temperature threshold T th , identify all typhoon eye regions in the typhoon center region, and calculate the minimum circumscribed circle radius corresponding to each typhoon eye region one by one, then the eyewall radius R of the corresponding typhoon eye region can be obtained eye ;

[0019] Step 5. Identify the clear eye and non-clear eye of the typhoon:

[0020] Formulate an objective criterion for distinguishing the clear eye and non-clear eye of the typhoon, and identify the clear eye and non-clear eye of the typhoon based on the formulated objective criterion;

[0021] When the typhoon eye region is identified as the clear eye of the typhoon, go to Step 6;

[0022] When the typhoon eye region is identified as the non-clear eye of the typhoon, go to Step 7;

[0023] Step 6. Establish the relationship between the maximum wind speed radius and the eyewall radius of the clear eye of the typhoon:

[0024] Based on the eyewall radius R corresponding to each clear eye of the typhoon identified in Step 5 eye , combined with the typhoon intensity in the typhoon center region, establish the relationship between the maximum wind speed radius RMW est and the eyewall radius R eye by fitting;

[0025] Step 7. Establish the relationship between the maximum wind speed radius and the eyewall radius of the non-clear eye of the typhoon:

[0026] Based on the eye wall radius R' corresponding to each non-clear eye of the typhoon identified in Step Five eye and combined with the typhoon intensity in the typhoon center area, establish the maximum wind speed radius RMW' of the non-clear eye of the typhoon by fitting est and the relationship with the eye wall radius R' eye ;

[0027] The eye wall radius R' of the non-clear eye of the typhoon eye is calculated as follows:

[0028] First, based on the average brightness temperature T within the adjacent range of different radii r≥R w , set the temperature threshold T' for identifying the eye area of the non-clear eye of the typhoon top , and then, based on the calculated temperature threshold T' Th , identify all the typhoon eye areas corresponding to the non-clear eyes within the typhoon center area, and calculate the minimum circumscribed circle radius corresponding to each typhoon eye area one by one, then the eye wall radius R' of the corresponding typhoon eye area can be obtained th . eye .

[0029] Preferably, in Step One, the typhoon center area specifically refers to the range within ±2.5° of the typhoon center.

[0030] Preferably, in Step Two, when determining the typhoon upper-level center, first use the human-computer interaction method to preliminarily obtain the typhoon upper-level center within the range of ±2.5° of the typhoon center; then, with the preliminary upper-level center as the origin, use the human-computer interaction method again within the range of ±0.5° to obtain the final upper-level center.

[0031] Preferably, in Step Three, the intermediate parameter R w is specifically obtained through the following steps:

[0032] Calculate the brightness temperature standard deviation σ(r): within the selected typhoon center area, for different radii r, calculate the brightness temperature standard deviation σ(r) of all pixel points within the ring from r to r+δ1 in turn and discard the area where the temperature is higher than -10°C; r represents the distance relative to the typhoon upper-level center, and δ1 is a preset value;

[0033] Based on the brightness temperature standard deviation σ(r), obtain the inner edge radius of the eye wall characteristic layer The inner edge radius of the eye wall characteristic layer is the radius r corresponding to the maximum negative gradient of the brightness temperature standard deviation σ(r);

[0034] Calculate the azimuth-averaged brightness temperature Calculate the azimuth-averaged brightness temperature within the ring, and δ2 is a preset value;

[0035] Calculate the average bright temperature T of the narrow ring b (r): Set narrow rings with width w for different radii r within the range of and calculate the average bright temperature T of each narrow ring b (r);

[0036] Based on the calculated azimuth-averaged bright temperature and the average bright temperature T of the narrow ring b (r), obtain the intermediate variable R w ; The intermediate variable R w is the radius r corresponding to the closest value between the average bright temperature T b (r) of the narrow ring and the azimuth-averaged bright temperature .

[0037] Preferably, in step four, the calculation of the eyewall radius R eye is specifically carried out through the following steps:

[0038] Calculate the temperature threshold T for identifying the typhoon eye area th , and the calculation formula is:

[0039]

[0040] In the formula: T max represents the highest bright temperature value corresponding to all pixel points within the range of 0 ≤ r ≤ R w ; T top represents the average bright temperature of the pixel points within the ring of R w ≤ r ≤ R w +δ3, where δ3 is a preset value;

[0041] Extract the typhoon eye area: Based on the calculated temperature threshold T th perform typhoon eye area extraction so that the bright temperature T b of the infrared window area of the typhoon eye area satisfies:

[0042] T b ≥ T th ;

[0043] Calculate the eyewall radius R eye : The eyewall radius R eye is the minimum circumscribed circle radius of the typhoon eye area.

[0044] Preferably, in step five, the identification of the clear typhoon eye and the non-clear typhoon eye specifically includes the following steps:

[0045] Calculate the maximum distance R -50 from the -50°C isotherm T -50 near the typhoon eye area to the typhoon upper-level center;

[0046] Define the cold area and the warm area: within the ring where R -50 ≤r≤R -50 +δ4, the pixels with the bright temperature T b <-50°C in the infrared window area are marked as the cold area, while the pixels with the bright temperature T b >-50°C are marked as the warm area; δ4 is a preset value;

[0047] Formulate an objective criterion for differentiating the clear eye of a typhoon from the non-clear eye of a typhoon, and identify the clear eye and non-clear eye of a typhoon based on the formulated objective criterion;

[0048] The objective criterion for differentiating the clear eye of a typhoon from the non-clear eye of a typhoon includes the objective identification criterion for the clear eye and the objective identification criterion for the non-clear eye;

[0049] The objective identification criterion for the clear eye includes two determination conditions:

[0050] A1. The actual area of the typhoon eye region is not less than 40% of the area of its circumscribed circle;

[0051] B1. The cold area is not invaded by the warm area in all azimuth angles, or the number of warm area pixels invading the cold area does not exceed 20;

[0052] When the typhoon eye region simultaneously meets the above two determination conditions, the typhoon eye region is identified as the clear eye of the typhoon and proceeds to step six;

[0053] The objective identification criterion for the non-clear eye includes four determination conditions:

[0054] A2. The actual area of the typhoon eye region is less than 40% of the area of its circumscribed circle;

[0055] B2. R -50 -R eye >δ5; δ5 is a preset value;

[0056] C2. The cold area is invaded by the warm area, and the number of pixels included in the warm area exceeds 20;

[0057] D2. The cold area is completely cut off by the warm area, and the eye wall radius R eye estimated according to the clear eye rule exceeds the eye wall radius threshold δ6;

[0058] When the typhoon eye region meets one of the above four determination conditions, the typhoon eye region is identified as the non-clear eye of the typhoon and proceeds to step seven.

[0059] Preferably, in step seven, the temperature threshold T' th of the non-clear eye of the typhoon is calculated as follows:

[0060]

[0061] In the formula: Ttop Indicates the average bright temperature of the pixel points within the ring of R w ≤r≤R w +δ3, where δ3 is a preset value;

[0062] The eyewall radius R' of the non-clear eye of the typhoon eye is the radius of the smallest circumscribed circle of the eye area of the non-clear eye of the typhoon; the eye area of the non-clear eye of the typhoon is the area where the bright temperature T b ≥T' th in the infrared window area of the non-clear eye of the typhoon.

[0063] Preferably, in step six, the maximum wind speed radius RMW of the clear eye of the typhoon est and the eyewall radius R eye have the following relationship:

[0064] RMW est = 0.7R eye - 0.14V max + 13.22

[0065] where: V max represents the intensity of the typhoon.

[0066] Preferably, in step seven, the maximum wind speed radius RMW' of the non-clear eye of the typhoon est and the eyewall radius R' eye have the following relationship:

[0067] RMW' est = 0.45R' eye - 0.15V max + 37.14

[0068] where: V max represents the intensity of the typhoon.

[0069] Another technical object of the present invention is to provide an electronic device, including a memory, a processor, and a computer program stored on the memory and running on the processor. The computer program runs to execute the method for estimating the scale of the typhoon kernel with an eye using geostationary meteorological satellite images as described above.

[0070] Compared with the current technology, the above technical solution has the following beneficial effects:

[0071] (1) Using the human-computer interaction method to obtain a more accurate typhoon high-level center helps to accurately calculate R eye in the case of a clear eye and R' eye in the case of a non-clear eye;

[0072] (2) A more objective criterion for differentiating between typhoons with a clear eye and those without a clear eye was established, obtaining more fitting samples and making the fitting relationship more persuasive.

[0073] (3) As shown in the appendix Figure 4 , a method for calculating typhoon inner core scale data in the case of typhoons without a clear eye, which is currently lacking, was developed.

[0074] (4) The RMW calculated by the fitting relationship of the present invention est is reliable. As shown in the appendix Figure 5 , the correlation coefficient between RMW est and RMW SAR is 0.94, the mean absolute error MAE is 5.46 km, and the root mean square error RMSE is 7.35 km. Therefore, the present invention can improve the problem of large errors in typhoon inner core scale data existing in current research. Description of the Drawings

[0075] Figure 1 is a flowchart of a method for estimating the inner core scale of a typhoon with an eye using geostationary satellite images;

[0076] Figure 2 takes Typhoon LAN No. 21 in 2017 at 09:30 on October 21, 2017 as an example, and shows the eye area range and R calculated on the infrared satellite cloud image eye figure;

[0077] Figure 3 is a schematic diagram of a clear eye and a non-clear eye. In the figure: (a) shows the schematic diagram of T -50 , R -50 , T th , R eye , (b) shows the schematic diagram of a clear eye, (c) shows the schematic diagram of the first type of non-clear eye, (d) shows the schematic diagram of the second type of non-clear eye, (e) shows the schematic diagram of the third type of non-clear eye, and (f) shows the schematic diagram of the fourth type of non-clear eye;

[0078] Figure 4 is a comparison chart of temperature threshold curves in the cases of clear eyes and non-clear eyes;

[0079] Figure 5 is a comparison chart of the maximum wind speed radius RMW est calculated by the present invention and the observed maximum wind speed radius RMW SAR ; Detailed Embodiment

[0080] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0081] The present invention defines the RMW value as the typhoon inner-core scale, and formulates an objective criterion for distinguishing a clear eye of a typhoon from a non-clear eye of a typhoon, obtaining a more persuasive sample size. In addition, extensive previous studies have shown that there is a certain relationship between the typhoon scale and intensity. Therefore, when developing the inner-core scale inversion algorithm, the present invention also considers the typhoon intensity (V max ), and fits the radius of the eye wall R eye , the typhoon intensity V max and the radius of maximum wind RMW est of the SAR, develops a method for estimating the inner-core scale of a typhoon with an eye based on geostationary satellite images, and objectively evaluates the accuracy of the inversion algorithm.

[0082] The present invention selects 88 typhoons with eyes in the northwestern Pacific Ocean from 2016 to 2023, for which the SAR has undergone quality control, as samples, and develops a method for estimating the inner-core scale of a typhoon with an eye using geostationary satellite images.

[0083] Figure 1 The method flow for estimating the inner-core scale of a typhoon with an eye using geostationary satellite images is shown, including the following steps:

[0084] Step 1: Obtain the brightness temperature data of the infrared channel of the geostationary satellite:

[0085] Data preprocessing. Perform quality control on the SAR wind field data, and remove the data in three cases: (a) the image covers less than two quadrants, (b) the inner-core area is affected by land, and (c) there is a disagreement between the analyzed RMW and the first peak of the wind speed profile; select the brightness temperature data of the infrared channel of the geostationary satellite at the nearest whole hour or half hour to the SAR recording time, and use the range of ±2.5° centered on the typhoon center as the calculation area, denoted as the typhoon center area.

[0086] Step 2: Determine the typhoon upper-level center by a human-computer interaction method:

[0087] First, interpolate the typhoon center recorded by JTWC to the corresponding time of the geostationary satellite data, use the interpolation center as the origin, and combine the typhoon RGB composite image and the cloud drift wind in the typhoon center area (the range of ±2.5° centered on the typhoon center) to obtain a preliminary typhoon upper-level center. Then, use the obtained preliminary upper-level center as the origin, and use the human-computer interaction method once again within the range of ±0.5° to obtain the final typhoon upper-level center.

[0088] Step 3: Project the brightness temperature T b of the infrared window area onto a rectangular coordinate system and calculate the intermediate parameter R w :

[0089] Using the typhoon upper-level center obtained in Step 2 as the origin, project the brightness temperature T bProject it onto a rectangular coordinate system according to the equidistant azimuth projection. The X-axis of the rectangular coordinate system points due east, and the Y-axis points due north.

[0090] Intermediate parameter R w Specifically, it is obtained through the following steps:

[0091] Calculate the standard deviation of brightness temperature σ(r): within the selected typhoon center area, for different radii r, calculate the standard deviation of brightness temperature σ(r) of all pixel points within the ring from r to r + δ1 in sequence and discard the area where the temperature is higher than -10°C, that is, record the standard deviation of brightness temperature σ(r) in the area where the temperature is higher than -10°C as missing and it will no longer participate in the subsequent calculations; r represents the distance relative to the typhoon upper-level center, with the unit of km, and δ1 is a preset value; through research, the preset value of δ1 is 30 km.

[0092] Based on the standard deviation of brightness temperature σ(r), obtain the inner radius of the eyewall characteristic layer Inner radius of the eyewall characteristic layer It is the radius r corresponding to the maximum negative gradient of the standard deviation of brightness temperature σ(r).

[0093] Calculate the azimuth-averaged brightness temperature Calculate The azimuth-averaged brightness temperature within the ring, and δ2 is a preset value; through research, the preset value of δ2 is 30 km.

[0094] Calculate the average brightness temperature T b (r): within Set narrow rings with a width of w for different radii r within the range of, and calculate the average brightness temperature T b (r); through research, the width w of the narrow ring is taken as 1 km.

[0095] Based on the calculated azimuth-averaged brightness temperature And the average brightness temperature T of the narrow ring b (r), obtain the intermediate variable R w ; Intermediate variable R w Is the average brightness temperature T of the narrow ring b (r) and the azimuth-averaged brightness temperature The radius r corresponding to the closest time. In other words, when the average brightness temperature T b (r) of each narrow ring is compared with the azimuth-averaged brightness temperature When the difference between the two is the smallest, it can be determined that the radius r corresponding to the average brightness temperature T b (r) of the narrow ring is the intermediate variable R w .

[0096] To calculate the average azimuth angle, the projected brightness temperature data is interpolated into the polar coordinate system at a resolution of 1 km in radius and 0.5° in azimuth angle to construct an average azimuth radial profile.

[0097] Step 4. Calculate the eyewall radius R eye :

[0098] Based on the intermediate parameter R calculated in Step 3 w , calculate the highest brightness temperature T corresponding to all pixel points within the range of radius r ≤ R w within the typhoon center area max and the average brightness temperature T w within the adjacent range of radius r ≥ R top , and then calculate the temperature threshold T for identifying the typhoon eye area th ;

[0099] Based on the calculated temperature threshold T th , identify all typhoon eye areas within the typhoon center area, and calculate the minimum circumscribed circle radius corresponding to each typhoon eye area one by one, then the eyewall radius R of the corresponding typhoon eye area can be obtained eye .

[0100] Specifically, the calculation of the eyewall radius R eye includes the following steps:

[0101] Calculate the temperature threshold T for identifying the typhoon eye area th , and the calculation formula is:

[0102]

[0103] In the formula: T max represents the highest brightness temperature value corresponding to all pixel points within the range of 0 ≤ r ≤ R w ; T top represents the average brightness temperature of the pixel points within the ring of R w ≤ r ≤ R w + δ3, where δ3 is a preset value; through research, the preset value of δ3 is 30 km.

[0104] Extract the typhoon eye area: Based on the calculated temperature threshold T th to extract the typhoon eye area, so that the brightness temperature T b of the infrared window area of the typhoon eye area satisfies:

[0105] T b ≥ T th ;

[0106] Calculate the eyewall radius R eye : The eyewall radius R eye is the minimum circumscribed circle radius of the typhoon eye area.

[0107] It should be specifically pointed out here that the temperature threshold T for identifying the typhoon eye area th does not distinguish whether the typhoon eye area is a clear eye situation or a non-clear eye situation.

[0108] Appendix Figure 2 Taking Typhoon LAN (No. 21 in 2017) at 09:30 on October 21, 2017 as an example, the eye area range and eye wall radius R calculated on the infrared satellite cloud image eye Figure. The dotted line in the figure represents the temperature threshold T for identifying the typhoon eye area th , and the solid circle is the minimum circumscribed circle of the area where T b ≥T th , and its radius is the eye wall radius R eye . The eye wall radius R eye will be used to distinguish clear eye typhoons and non-clear eye typhoons.

[0109] Step 5. Identify clear eye typhoons and non-clear eye typhoons:

[0110] Using the eye wall radius R calculated in Step 4 eye formulate an objective criterion for distinguishing clear eye typhoons and non-clear eye typhoons, and identify clear eye typhoons and non-clear eye typhoons based on the formulated objective criterion; when the typhoon eye area is identified as a clear eye typhoon, go to Step 6; when the typhoon eye area is identified as a non-clear eye typhoon, go to Step 7;

[0111] The identification of clear eye typhoons and non-clear eye typhoons specifically includes the following steps:

[0112] Calculate the maximum distance R -50 from the -50°C isotherm T -50 near the typhoon eye area to the typhoon upper-level center;

[0113] Define the cold area and the warm area: within the ring where R -50 ≤r≤F -50 +δ4, the pixels with infrared window region brightness temperature T b <-50°C are recorded as the cold area, while the pixels with infrared window region brightness temperature T b >-50°C are recorded as the warm area; δ4 is a preset value, and through testing, its value can be 15 km;

[0114] Formulate an objective criterion for distinguishing clear eye typhoons and non-clear eye typhoons, and identify clear eye typhoons and non-clear eye typhoons based on the formulated objective criterion;

[0115] The objective criterion for distinguishing clear eye typhoons and non-clear eye typhoons includes the objective identification criterion for clear eyes and the objective identification criterion for non-clear eyes;

[0116] The objective recognition criteria for a clear eye of a typhoon include two judgment conditions:

[0117] A1. The actual area of the typhoon eye region is not less than 40% of the area of its circumscribed circle;

[0118] B1. The cold region is not invaded by the warm region at all azimuths, or the number of warm-region pixels invading the cold region does not exceed 20;

[0119] When the typhoon eye region simultaneously meets the above two judgment conditions, the typhoon eye region is recognized as a clear eye of the typhoon and proceeds to Step Six;

[0120] The objective recognition criteria for a non-clear eye of a typhoon include four judgment conditions:

[0121] A2. The actual area of the typhoon eye region is less than 40% of the area of its circumscribed circle;

[0122] B2. R -50 -R eye > δ5; δ5 is a preset value, and through research, its value is 10 km;

[0123] C2. The cold region is invaded by the warm region, and the number of pixels included in the warm region exceeds 20;

[0124] D2. The cold region is completely cut off by the warm region, and the eyewall radius R estimated in Step Four eye exceeds the eyewall radius threshold δ6, and the eyewall radius threshold δ6 can be set to 200 km.

[0125] When the typhoon eye region meets one of the above four judgment conditions, the typhoon eye region is recognized as a non-clear eye of the typhoon and proceeds to Step Seven.

[0126] Appendix Figure 3 (a) is a schematic diagram of T -50 、R -50 、T th 、R eye schematic diagram, (b) clear eye schematic diagram, (c) first type of non-clear eye schematic diagram, (d) second type of non-clear eye schematic diagram, (e) third type of non-clear eye schematic diagram, and (f) fourth type of non-clear eye schematic diagram.

[0127] Among 88 typhoons with eyes, 65 were recognized as clear eye cases and 23 were recognized as non-clear eye cases.

[0128] Step Six. Establish the relationship between the maximum wind speed radius and the eyewall radius of the clear eye of the typhoon:

[0129] Based on the eyewall radius R corresponding to each clear eye of the typhoon identified in Step Five eye , combined with the typhoon intensity in the typhoon center region, establish the maximum wind speed radius RMW of the clear eye of the typhoon by fitting estRelationship with the radius R of the eyewall eye is as follows:

[0130] RMW est = 0.7R eye - 0.14V max + 13.22

[0131] In the formula: V max represents the intensity of the typhoon.

[0132] Step 7. Establish the relationship between the radius of the maximum wind speed of the non-clear eye of the typhoon and the radius of the eyewall:

[0133] Based on the radius R' of the eyewall corresponding to each non-clear eye of the typhoon identified in Step 5 eye , combined with the intensity of the typhoon in the typhoon center area, establish the radius RMW' of the maximum wind speed of the non-clear eye of the typhoon est and the radius R' of the eyewall eye by fitting;

[0134] The radius R' of the eyewall of the non-clear eye of the typhoon eye is calculated by the following method:

[0135] First, based on the average brightness temperature T w in the adjacent range of different radii r ≥ R top , set the temperature threshold T' for identifying the eye area of the non-clear eye of the typhoon th , and then based on the calculated temperature threshold T' th , identify all the typhoon eye areas corresponding to the non-clear eyes in the typhoon center area, and calculate the minimum circumscribed circle radius corresponding to each typhoon eye area one by one, then the radius R' of the eyewall of the corresponding typhoon eye area can be obtained eye .

[0136] Specifically, the calculation formula of the temperature threshold T' of the non-clear eye of the typhoon th is as follows:

[0137]

[0138] In the formula: T top represents the average brightness temperature of the pixel points in the non-clear eye of the typhoon within the ring of R w ≤ r ≤ R w + δ3, where δ3 is a preset value;

[0139] The radius R' of the eyewall of the non-clear eye of the typhoon eye is the minimum circumscribed circle radius of the eye area of the non-clear eye of the typhoon; the eye area of the non-clear eye of the typhoon is the area where the brightness temperature T b ≥ T' th in the infrared window area of the non-clear eye of the typhoon.

[0140] Therefore, the radius of maximum wind speed RMW' of the non-clear eye of a typhoon est and the radius of the eyewall R' eye have the following relationship:

[0141] RMW' est = 0.45R' eye - 0.15V max + 37.14

[0142] where: V max represents the intensity of the typhoon.

[0143] Appendix Figure 4 is a comparison chart of the temperature thresholds T th , T' th calculated for the cases of clear-eye typhoons and non-clear-eye typhoons. The theoretical basis for setting the temperature threshold in the non-clear-eye case is based on the research of Kossin et al. (2007) (hereinafter referred to as K07). K07 pointed out that in most cases, the average brightness temperature within the range of R w ≤ r ≤ R w + 30 km around the typhoon eye area generally does not exceed -50°C, because this range is often the cold area of the typhoon. However, in the vicinity of the eye area of some typhoons, there are not only cold areas, but often multiple or even large warm areas (T b > -50°C) existing, which leads to the calculated average brightness temperature T top being on the high side, and sometimes even reaching -30°C. K07 pointed out that in this case, a higher temperature threshold should be set to correctly find the eye area. Therefore, the present invention formulates a more detailed temperature threshold, that is, when T b ≤ -60°C, the temperature threshold T' th is the same as that in the clear-eye case; within the range of -60°C to -50°C, a higher temperature threshold T' th is set compared to the clear-eye case; in fact, very few typhoons have an average brightness temperature T top value that can exceed -30°C. Therefore, when T b > -50°C, the temperature threshold T' th set by the present invention is also higher than the temperature threshold T th in the clear-eye case.

[0144] Appendix Figure 5 is a comparison chart of the radius of maximum wind speed RMW est calculated by using the method provided by the present invention for 88 typhoons with eyes SAR and the observed radius of maximum wind speed RMW est and the observed radius of maximum wind speed RMW SARThe correlation coefficient is 0.94, the mean absolute error MAE is 5.46 km, and the root mean square error RMSE is 7.35 km. The results show that the method for calculating the scale data of the typhoon inner core with eyes in the present invention is reliable.

[0145] Based on the same inventive concept, the present invention also provides an electronic device, which includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the method in the above embodiments.

[0146] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and the operating system of the terminal is stored in this storage space. And, one or more instructions suitable for being loaded and executed by the processor are also stored in this storage space. These instructions may be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The one or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the steps of the method in the above embodiments.

[0147] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The solutions in the embodiments of the present invention can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript, etc.

[0148] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in Figure 1 one or more of the flows Figure 1 or a plurality of flows and / or blocks

[0149] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that realizes the functions specified in Figure 1 one or more of the flows Figure 1 or a plurality of flows and / or blocks

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in Figure 1 one or more of the flows Figure 1 or a plurality of flows and / or blocks

Claims

1. A method for estimating the size of the inner core of an eye typhoon using stationary meteorological satellite images, characterized in that: The following steps are included: Step 1: Obtain the brightness temperature data of the infrared channel of the geostationary satellite: The quality control of SAR wind field data was performed, and the infrared window brightness temperature T of all pixel points in the typhoon center area was extracted from the satellite cloud images with equal longitude and latitude. b information; Step 2: Determine the typhoon high-level center using human-computer interaction method: Combining the typhoon RGB composite image and cloud track wind, a human-computer interaction method is used to determine the typhoon high-level center in the typhoon center area; Step 3: Set the infrared window area brightness temperature T b Project to rectangular coordinate system and calculate intermediate parameters R w : Taking the typhoon high-level center determined in step 2 as the origin, the infrared window area brightness temperature T b Project into the rectangular coordinate system according to the equidistant orientation and calculate the intermediate parameter R w ; The X-axis of the rectangular coordinate system points to the east, and the Y-axis points to the north; Step 4: Calculate the eyewall radius R eye : Based on the intermediate parameter R calculated in step 3 w Calculate the radius r≤R in the typhoon center area w The highest brightness temperature T corresponding to all pixels in the range max And the radius r ≥ R w The average brightness temperature T in the vicinity of top , and then calculate the temperature threshold T for identifying the typhoon eye area th ; Based on the calculated temperature threshold T th , identify all typhoon eye areas in the typhoon center area, and calculate the minimum circumscribed circle radius corresponding to each typhoon eye area one by one, and then obtain the eye wall radius R of the corresponding typhoon eye area eye ; Step 5: Identify the clear eye and unclear eye of a typhoon: To formulate objective criteria for distinguishing the clear eye of a typhoon from the unclear eye of a typhoon, and to identify the clear eye of a typhoon from the unclear eye of a typhoon based on the formulated objective criteria; When the typhoon eye area is identified as a clear typhoon eye, proceed to step six; When the typhoon eye area is identified as a non-clear typhoon eye, proceed to step seven; Step 6: Establish the relationship between the maximum wind speed radius of the typhoon clear eye and the eye wall radius: Based on the eyewall radius R corresponding to each typhoon clear eye identified in step 5 eye , combined with the typhoon intensity in the typhoon center area, the maximum wind speed radius RMW of the typhoon clear eye is established by fitting est and the eyewall radius R eye The relationship between Step 7: Establish the relationship between the maximum wind speed radius of the typhoon's non-clear eye and the eyewall radius: Based on the eyewall radius R′ corresponding to the unclear eye of each typhoon identified in step 5 eye , combined with the typhoon intensity in the typhoon center area, the maximum wind speed radius RMW′ of the typhoon non-clear eye is established by fitting est and the eyewall radius R′ eye The relationship between The eyewall radius R′ of a typhoon with an unclear eye eye Calculated in the following way: First, based on different radii r≥R w The average brightness temperature T in the vicinity of top , set the temperature threshold T′ for identifying the typhoon's non-clear eye th , and then based on the calculated temperature threshold T′ th , identify the typhoon eye areas corresponding to all the typhoon non-clear eyes in the typhoon center area, and calculate the minimum circumscribed circle radius corresponding to each typhoon eye area one by one, and then obtain the eye wall radius R′ of the corresponding typhoon eye area eye .

2. The method for estimating the size of the inner core of an eye typhoon using a stationary meteorological satellite image according to claim 1, characterized in that: In step 1, the typhoon center area specifically refers to the range of ±2.5° from the typhoon center.

3. The method for estimating the size of the inner core of an eye typhoon using a stationary meteorological satellite image according to claim 1, characterized in that: In step 2, when determining the high-level center of the typhoon, the human-computer interaction method is first used within the range of ±2.5° of the typhoon center to preliminarily obtain the high-level center of the typhoon; then, taking the preliminary high-level center as the origin, the human-computer interaction method is used again within the range of ±0.5° to obtain the final high-level center.

4. The method for estimating the size of the inner core of an eye typhoon using geostationary meteorological satellite images according to claim 1, characterized in that: In step 3, the intermediate parameter R w The specific steps are as follows: Calculate the brightness temperature standard deviation σ(r): In the selected typhoon center area, for different radii r, calculate the brightness temperature standard deviation σ(r) of all pixels within the ring from r to r+δ1 and discard the areas with temperature higher than -10℃; r represents the distance relative to the typhoon high-level center, and δ1 is a preset value; Based on the brightness temperature standard deviation σ(r), the inner radius of the eyewall characteristic layer is obtained Inner radius of the eyewall characteristic layer is the radius r corresponding to the maximum value of the negative gradient of the brightness temperature standard deviation σ(r); Calculate the azimuth mean brightness temperature calculate The azimuthal average brightness temperature within the ring, δ2 is the preset value; Calculate the average brightness temperature T of the narrow ring b (r): in In the range of , set narrow rings with width w for different radii r, and calculate the average brightness temperature T of each narrow ring b (r); Based on the calculated azimuthal average brightness temperature The average brightness temperature of the narrow ring is T b (r), get the intermediate variable R w ; Intermediate variable R w is the average brightness temperature of the narrow ring T b (r) and azimuth average brightness temperature The radius r corresponding to the closest approach.

5. The method for estimating the size of the inner core of an eye typhoon using a stationary meteorological satellite image according to claim 1, characterized in that: In step 4, the eyewall radius R eye The calculation is carried out through the following steps: Calculate the temperature threshold T for identifying the typhoon eye area th , the calculation formula is: Where: T max It means 0≤r≤R w The highest brightness temperature value corresponding to all pixels in the range; T top Indicates that it is in R w ≤r≤R w + Average brightness temperature of pixels within the δ3 ring, δ3 is a preset value; Extract the typhoon eye area: Based on the calculated temperature threshold T th The typhoon eye area is extracted so that the infrared window area brightness temperature T b satisfy: T b ≥T th ; Calculate the eyewall radius R eye : Eyewall radius R eye It is the minimum circumscribed circle radius of the typhoon eye area.

6. The method for estimating the size of the inner core of an eye typhoon using geostationary meteorological satellite images according to claim 1, characterized in that: In step 5, the identification of the typhoon clear eye and the typhoon unclear eye specifically includes the following steps: Calculate the -50℃ isotherm T near the typhoon eye area -50 The maximum distance R to the typhoon's upper center -50 ; Definition of cold and warm areas: In R -50 ≤r≤R -50 In the ring of +δ4, the infrared window brightness temperature T b Pixels with a temperature < -50°C are recorded as cold areas, while the infrared window area has a brightness temperature T b Pixels with a temperature of >-50℃ are recorded as warm areas; δ4 is the preset value; To formulate objective criteria for distinguishing the clear eye of a typhoon from the unclear eye of a typhoon, and to identify the clear eye of a typhoon from the unclear eye of a typhoon based on the formulated objective criteria; Objective standards for distinguishing a typhoon's clear eye from a typhoon's unclear eye, including objective identification standards for clear eyes and objective identification standards for unclear eyes; The clear eye objective identification standard includes two judgment conditions: A1. The actual area of ​​the typhoon eye is not less than 40% of the area of ​​its circumscribed circle; B1. The cold area is not invaded by the warm area in all azimuths, or the number of warm area pixels invading the cold area does not exceed 20; When the typhoon eye area meets the above two judgment conditions at the same time, the typhoon eye area is identified as a typhoon clear eye and enters step 6; the objective identification standard for non-clear eyes includes four judgment conditions: A2. The actual area of ​​the typhoon eye is less than 40% of the area of ​​its circumscribed circle; B2, R -50 -R eye >δ5; δ5 is the preset value; C2, the cold area is invaded by the warm area, and the number of pixels included in the warm area exceeds 20; D2, the cold area is completely cut off by the warm area, and the eye wall radius R is estimated according to the clear eye rule eye Exceeding the eyewall radius threshold δ6; When the typhoon eye area meets one of the above four judgment conditions, the typhoon eye area is identified as a non-clear typhoon eye and enters step seven.

7. The method for estimating the size of the inner core of an eye typhoon using geostationary meteorological satellite images according to claim 1, characterized in that: In step 7, the temperature threshold T′ of the typhoon's non-clear eye th The calculation formula is as follows: Where: T top Indicates that the typhoon is not in a clear eye and is in R w ≤r≤R w + Average brightness temperature of pixels within the δ3 ring, δ3 is a preset value; The eyewall radius R′ of a typhoon with an unclear eye eye is the minimum circumscribed circle radius of the typhoon's unclear eye area; the typhoon's unclear eye area is the brightness temperature T of the infrared window area in the typhoon's unclear eye. b ≥T′ th area.

8. The method for estimating the size of the inner core of an eye typhoon using geostationary meteorological satellite images according to claim 1, characterized in that: In step 6, the maximum wind speed radius RMW of the typhoon's clear eye est and the eyewall radius R eve The relationship is as follows: <h2 style=";text-align:left;direction:ltr">RMW<h2 style=";text-align:left;direction:ltr"> est <h2 style=";text-align:left;direction:ltr"> <0.7R<h2 style=";text-align:left;direction:ltr"> eye <h2 style=";text-align:left;direction:ltr"> -0.14V<h2 style=";text-align:left;direction:ltr"> max <h2 style=";text-align:left;direction:ltr"> +13.22 Where: V max Characterizes the intensity of a typhoon.

9. The method for estimating the size of the inner core of an eye typhoon using geostationary meteorological satellite images according to claim 1, characterized in that: In step 7, the maximum wind speed radius RMW′ of the typhoon's non-clear eye est and the eyewall radius R′ eye The relationship is: RMW′ est =0.45R′ eye -0.15V max +37.14 Where: V max Characterizes the intensity of a typhoon.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the computer program runs to execute the method for estimating the inner core size of an eye typhoon using stationary meteorological satellite images as described in any one of claims 1 to 9.

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