Method for representing collaborative change of pole sharp torrent and subtropical west wind torrent

Abstract

The invention discloses a method for representing collaborative change of pole tip torrent and subtropical west wind torrent, which belongs to the field of atmospheric science and comprises the following steps: acquiring weft wind data of the upper layer of a troposphere in a target area; according to the weft wind data, identifying a pole tip jet active area and a subtropical west wind jet active area; calculating the average value of the weft wind in the pole tip torrent active area to obtain a pole tip torrent index PJ, and calculating the average value of the weft wind in the sub-tropical west wind torrent active area to obtain a sub-tropical torrent index SJ; carrying out standardization processing to obtain a standardized pole tip torrent index Std-PJI and a standardized subtropical torrent index Std-SJI; and according to the symbol combination of the Std-SJI and the Std-PJI and the absolute value size relationship thereof, the double-rapid-stream collaborative change is divided into eight phases. According to the invention, the pole sharp torrent and the sub-tropical torrent have collaborative change characteristics in position and intensity, and the method can be applied to real-time monitoring of extreme weather and climate events in business.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric science and technology, and in particular relates to a method for characterizing the coordinated changes of the polar front jet stream and the subtropical westerly jet stream. Background Art

[0002] Currently, the main methods for characterizing the coordinated changes of the Polar Front Jet (PJ) and the Subtropical Westerly Jet (SJ) fall into two categories: The first is the Empirical Orthogonal Function (EOF) method, which decomposes the mean wind field using EOF to extract the first two modes representing different states of the coordinated changes between the two jets. This method depends on the spatiotemporal extent of the analysis field, and the resulting modes are significantly affected by the data's temporal length and spatial resolution. The second is the univariate index method, which defines the radial position index of the jets using the latitude of the maximum wind speed within the active areas of the two jets, characterizes the jet intensity using the total wind speed, and analyzes the coordinated changes through the relative magnitudes of the two indices. This type of method only focuses on a single variable of position or intensity, making it difficult to quantify the coupling relationship between the two jets in terms of position and intensity.

[0003] The existing technology has the following shortcomings: First, the EOF method cannot separate the coordinated change characteristics of the jet stream's position and intensity, and the univariate index method can only reflect a single physical quantity (such as position or intensity), ignoring the position-intensity coupling effect and lacking co-variables; Second, the existing characterization results are limited by the spatiotemporal range of the data, making it difficult to meet the needs of real-time monitoring and unable to support extended-range weather forecasting and model evaluation, thus limiting its operational applications; Finally, the univariate index method lacks the ability to quantify the "lead-lag response" of the dual jet streams and the "seesaw" pattern of north-south opposite displacement, resulting in insufficient capture of mid-to-high latitude circulation adjustment signals and inadequate characterization of dynamic processes. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for characterizing the coordinated changes of the polar front jet stream and the subtropical westerly jet stream, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for characterizing the coordinated changes of the polar front jet stream and the subtropical westerly jet stream, comprising:

[0006] Acquire zonal wind data in the upper troposphere of the target area;

[0007] Based on the zonal wind data, identify active areas of polar front jet stream and active areas of subtropical westerly jet stream;

[0008] The average zonal wind value within the active area of ​​the polar front jet stream is calculated to obtain the polar front jet stream index PJ, and the average zonal wind value within the active area of ​​the subtropical westerly jet stream is calculated to obtain the subtropical jet stream index SJ.

[0009] The polar front jet index PJ and the subtropical jet index SJ are standardized to obtain the standardized polar front jet index Std-PJI and the standardized subtropical jet index Std-SJI.

[0010] Establish a coordinate system with Std-SJI as the abscissa and Std-PJI as the ordinate;

[0011] Based on the sign combinations of Std-SJI and Std-PJI and the relationship between their absolute values, the co-variation of the two jet streams is divided into eight phases.

[0012] Preferably, the target area is East Asia, with the active area of ​​the polar front jet stream defined as 50°–70°N and the active area of ​​the subtropical westerly jet stream defined as 25°–45°N.

[0013] Preferably, the time resolution of the zonal wind data is 6 hours or 1 day, and the horizontal resolution is 1°×1°.

[0014] Preferably, the process of identifying active areas of extreme frontal jet streams includes:

[0015] Regions with zonal wind speeds ≥ 30 m / s were selected; when the analysis period was summer, the wind speed threshold for active polar front jet stream areas was set to 25 m / s.

[0016] Preferably, the symbol combination is used to characterize the movement of the rapid flow position;

[0017] The absolute value is used to characterize the intensity of the jet stream.

[0018] Preferably, the rules for dividing the eight phases include:

[0019] When Std-PJI≤0 and Std-SJI<0, if |Std-PJI|>|Std-SJI|, it is mode 1; if |Std-PJI|≤|Std-SJI|, it is mode 2. Mode 1 corresponds to the two jet streams moving towards each other, dominated by the subtropical jet stream, and mode 2 corresponds to the two jet streams moving towards each other, dominated by the polar front jet stream.

[0020] When Std-PJI < 0 and Std-SJI ≥ 0, if |Std-PJI| > |Std-SJI|, it is mode 3; if |Std-PJI| ≤ |Std-SJI|, it is mode 4. Mode 3 corresponds to the southward co-current jet stream dominated by the polar front jet stream, and mode 4 corresponds to the southward co-current jet stream dominated by the subtropical jet stream.

[0021] When Std-PJI≥0 and Std-SJI>0, if |Std-PJI|≤|Std-SJI|, it is mode 5; if |Std-PJI|>|Std-SJI|, it is mode 6. Mode 5 corresponds to the subtropical jet stream-dominated double jet stream moving in opposite directions, and mode 6 corresponds to the polar front jet stream-dominated double jet stream moving in opposite directions.

[0022] When Std-PJI > 0 and Std-SJI ≤ 0, if |Std-PJI| > |Std-SJI|, it is mode 7; if |Std-PJI| ≤ |Std-SJI|, it is mode 8. Mode 7 corresponds to the northward co-current jet stream dominated by the polar front jet stream, and mode 8 corresponds to the northward co-current jet stream dominated by the subtropical jet stream.

[0023] Preferably, the eight phases are associated with Meiyu season weather events; wherein mode 3, mode 4, mode 5, and mode 6 are associated with the occurrence of Meiyu season precipitation.

[0024] Preferably, when in mode 5, it is determined to be a phase with a high incidence of continuous heavy rain during the plum rain season.

[0025] Preferably, the plum rain season event in a flood-prone year is associated with mode 5, and the plum rain season event in a dry year is associated with mode 4.

[0026] In a second aspect, the present invention also discloses a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in the first aspect.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] This invention discloses a method for characterizing the coordinated changes of the polar front jet stream and the subtropical westerly jet stream, comprising the following steps: First, acquiring zonal wind data in the upper troposphere of the target area; second, identifying active areas of the polar front jet stream and the subtropical westerly jet stream based on the zonal wind data; third, calculating the average zonal wind value within the active polar front jet stream area to obtain the polar front jet stream index PJ, and calculating the average zonal wind value within the active subtropical westerly jet stream area to obtain the subtropical jet stream index SJ; further, standardizing the polar front jet stream index PJ and the subtropical jet stream index SJ to obtain the standardized polar front jet stream index Std-PJI and the standardized subtropical jet stream index Std-SJI; establishing a coordinate system with Std-SJI as the abscissa and Std-PJI as the ordinate; finally, dividing the coordinated changes of the two jet streams into eight phases based on the sign combination and absolute value relationship of Std-SJI and Std-PJI.

[0029] This invention addresses the technical problem that current methods for characterizing the coordinated changes in jet streams cannot simultaneously reflect the coordinated changes in both the location and intensity of the jet streams. It recognizes the coordinated changes in location and intensity between the polar front jet stream and the subtropical jet stream, and how these coordinated changes can significantly influence East Asian weather and climate change. This invention establishes a comprehensive characterization method that can simultaneously reflect the radial positional shifts of both jet streams and their own intensity changes. Based on this method, a comprehensive index for jet stream coordinated changes is developed, providing an analytical tool for understanding the mechanisms by which mid-to-high latitude circulation adjustments influence weather and climate change. Furthermore, this invention's technical solution, as a comprehensive monitoring index, can also be directly applied to the real-time monitoring of extreme weather and climate events in operational settings. Attached Figure Description

[0030] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 A flowchart illustrating the establishment of the comprehensive index for rapid flow synergistic change in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the selection criteria for the key area of ​​the jet stream synergistic change index in an embodiment of the present invention, wherein (a) is a schematic diagram of the frequency of zonal winds and jet stream cores at 300 hPa in the upper troposphere during the Meiyu season in East Asia from 1979 to 2020, and (b) is a schematic diagram of the spatial distribution of zonal winds at 300 hPa during the Meiyu season precipitation return.

[0033] Figure 3 The diagrams above illustrate the distribution of zonal wind at 300 hPa in different modes of the comprehensive index of jet stream synergy in this invention. (a) shows the distribution of zonal wind at 300 hPa in mode 1, (b) shows the distribution of zonal wind at 300 hPa in mode 2, (c) shows the distribution of zonal wind at 300 hPa in mode 3, (d) shows the distribution of zonal wind at 300 hPa in mode 4, (e) shows the distribution of zonal wind at 300 hPa in mode 5, (f) shows the distribution of zonal wind at 300 hPa in mode 6, (g) shows the distribution of zonal wind at 300 hPa in mode 7, and (h) shows the distribution of zonal wind at 300 hPa in mode 8.

[0034] Figure 4 This is a scatter plot of the comprehensive index of the coordinated changes in the Meiyu season jet stream from 1979 to 2020, according to an embodiment of the present invention.

[0035] Figure 5 This is a scatter plot of the comprehensive index of the coordinated changes in the jet stream during the plum rain season in a typical drought or flood year, according to an embodiment of the present invention.

[0036] Figure 6 This is a scatter plot of the comprehensive index of the coordinated changes of rainstorms and jet streams during the typical Meiyu season from 1979 to 2020, according to an embodiment of the present invention.

[0037] Figure 7 This is a scatter plot of the synergistic variation index of plum rain, torrential rain and jet stream in a typical drought and flood year according to an embodiment of the present invention. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a method for characterizing the coordinated changes of the polar front jet stream and the subtropical westerly jet stream, including:

[0042] S1. Obtain zonal wind data in the upper troposphere of the target area;

[0043] The target area is East Asia, with the active area of ​​the polar front jet stream defined as 50°–70°N and the active area of ​​the subtropical westerly jet stream defined as 25°–45°N.

[0044] The zonal wind data are derived from ERA-5 reanalysis data, with a time resolution of 6 hours or daily and a horizontal resolution of 1°×1°.

[0045] S2. Based on the zonal wind data, identify the active areas of the polar front jet stream and the active areas of the subtropical westerly jet stream;

[0046] Furthermore, the process of identifying active areas of polar front jet streams includes:

[0047] Regions with zonal wind speeds ≥ 30 m / s were selected; when the analysis period was summer, the wind speed threshold for active polar front jet stream areas was set to 25 m / s.

[0048] Specifically, the active jet stream area is determined by calculating the center of the highest wind speed over a global area using the 300hPa zonal wind every day or every 6 hours. The center wind speed of the highest wind speed center is ≥30m / s (this can be relaxed to 25m / s in summer, considering that the intensity of the polar front jet stream is relatively weak). The latitude and longitude range is recorded based on the concentrated area of ​​the jet stream center.

[0049] S3. Calculate the average zonal wind value within the active area of ​​the polar front jet stream to obtain the polar front jet stream index PJ, and calculate the average zonal wind value within the active area of ​​the subtropical westerly jet stream to obtain the subtropical jet stream index SJ.

[0050] Specifically, the jet stream co-variance index is calculated by calculating the average zonal wind value within the active regions of the two jet streams. (Daily average, pentad average, monthly average, and annual average can be calculated depending on the situation), and are represented as the polar front jet stream index PJ and the subtropical westerly jet stream index SJ.

[0051] S4. Standardize the polar front jet index PJ and the subtropical jet index SJ respectively to obtain the standardized polar front jet index Std-PJI and the standardized subtropical jet index Std-SJI.

[0052] S5. Establish a coordinate system with Std-SJI as the abscissa and Std-PJI as the ordinate;

[0053] S6. Based on the sign combination of Std-SJI and Std-PJI and the relationship between their absolute values, the co-variation of the two jet streams is divided into eight phases.

[0054] Furthermore, the symbol combination is used to characterize the movement of the rapid flow position;

[0055] The absolute value is used to characterize the intensity of the jet stream.

[0056] The rules for dividing the eight phases include:

[0057] When Std-PJI≤0 and Std-SJI<0, if |Std-PJI|>|Std-SJI|, it is mode 1; if |Std-PJI|≤|Std-SJI|, it is mode 2. Mode 1 corresponds to the two jet streams moving towards each other, dominated by the subtropical jet stream, and mode 2 corresponds to the two jet streams moving towards each other, dominated by the polar front jet stream.

[0058] When Std-PJI < 0 and Std-SJI ≥ 0, if |Std-PJI| > |Std-SJI|, it is mode 3; if |Std-PJI| ≤ |Std-SJI|, it is mode 4. Mode 3 corresponds to the southward co-current jet stream dominated by the polar front jet stream, and mode 4 corresponds to the southward co-current jet stream dominated by the subtropical jet stream.

[0059] When Std-PJI≥0 and Std-SJI>0, if |Std-PJI|≤|Std-SJI|, it is mode 5; if |Std-PJI|>|Std-SJI|, it is mode 6. Mode 5 corresponds to the subtropical jet stream-dominated double jet stream moving in opposite directions, and mode 6 corresponds to the polar front jet stream-dominated double jet stream moving in opposite directions.

[0060] When Std-PJI > 0 and Std-SJI ≤ 0, if |Std-PJI| > |Std-SJI|, it is mode 7; if |Std-PJI| ≤ |Std-SJI|, it is mode 8. Mode 7 corresponds to the northward co-current jet stream dominated by the polar front jet stream, and mode 8 corresponds to the northward co-current jet stream dominated by the subtropical jet stream.

[0061] Specifically, to simultaneously characterize the coordinated changes in both position and intensity of the two jet streams, based on the signs and relative magnitudes of the absolute values ​​of Std-PJI and Std-SJI, the absolute value of the exponent represents the jet stream intensity, and the sign of the exponent represents the jet stream positional movement. Std-SJI is defined as the X-axis coordinate, and Std-PJI as the Y-axis coordinate. The coordinated changes of the two jet streams are divided into the following eight phases, with different phases corresponding to different jet stream intensities and positional states, reflecting different mid-to-high latitude atmospheric circulation states:

[0062] Mode 1: Dominated by the subtropical jet stream, with two jet streams flowing towards each other.

[0063] That is, when the exponent has Std-PJI≤0 and Std-SJI<0, if |Std-PJI|>|Std-SJI|;

[0064] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0065] In terms of radial position: the polar front jet stream moves towards the equator, while the subtropical westerly jet stream moves towards the poles.

[0066] Mode 2: Dominated by the extreme front jet stream, with two jet streams flowing towards each other.

[0067] That is, when the exponent has Std-PJI≤0 and Std-SJI<0, if |Std-PJI|≤|Std-SJI|;

[0068] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0069] In terms of radial position: the polar front jet stream moves towards the equator, while the subtropical westerly jet stream moves towards the pole.

[0070] Mode 3: Dominated by the extreme front jet stream, with both jet streams flowing southward in the same direction.

[0071] That is, when the exponent has Std-PJI < 0 and Std-SJI ≥ 0, if |Std-PJI| > |Std-SJI|;

[0072] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0073] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the equator simultaneously.

[0074] Mode 4: Dominated by the subtropical jet stream, with both jet streams flowing southward in the same direction.

[0075] That is, when the exponent has Std-PJI<0 and Std-SJI≥0, if |Std-PJI|≤|Std-SJI|;

[0076] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0077] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the equator simultaneously.

[0078] Mode 5: Dominated by the subtropical jet stream, with two jet streams flowing in opposite directions.

[0079] That is, when the exponent has Std-PJI≥0 and Std-SJI>0, if |Std-PJI|≤|Std-SJI|;

[0080] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0081] In terms of radial position: the polar front jet stream moves towards the polar region, while the subtropical westerly jet stream moves towards the equator.

[0082] Mode 6: Dominated by a high-speed jet stream, with two jet streams flowing in opposite directions.

[0083] That is, when the exponent has Std-PJI≥0 and Std-SJI>0, if |Std-PJI|>|Std-SJI|;

[0084] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0085] In terms of radial position: the polar front jet stream moves towards the polar region, while the subtropical westerly jet stream moves towards the equator.

[0086] Mode 7: Dominated by the extreme front jet stream, with both jet streams flowing northward.

[0087] That is, when the exponent has Std-PJI>0 and Std-SJI≤0, if |Std-PJI|>|Std-SJI|;

[0088] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0089] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the poles at the same time.

[0090] Mode 8: Dominated by the subtropical jet stream, with both jet streams flowing northward.

[0091] That is, when the exponent has Std-PJI>0 and Std-SJI≤0, if |Std-PJI|≤|Std-SJI|;

[0092] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0093] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the poles at the same time.

[0094] The comprehensive method for the coordinated changes of the polar front jet stream and the subtropical jet stream established in this invention can better grasp the comprehensive characteristics of the coordinated changes in position and intensity of the polar front jet stream and the subtropical westerly jet stream in mid-to-high latitude regions. It can provide certain forecasting basis for the influence of jet stream coordinated changes on the occurrence and development of extreme weather and climate events in my country, such as the onset and end of the plum rain season in the Yangtze River Basin and the occurrence and development of continuous heavy precipitation events during the flood season.

[0095] Example 1:

[0096] Combined with appendix Figure 2 Taking the summer plum rain season from 1979 to 2020 as an example, the analysis focuses on the daily radial position and intensity variation characteristics of the polar front jet stream and the subtropical westerly jet stream during the East Asian summer plum rain season over the past 42 years. Depending on the specific circumstances, the analysis can also be conducted using data at the annual, monthly, pentad, or hourly scales.

[0097] Step 1: Identify the key active areas of the polar front jet stream and the subtropical westerly jet stream.

[0098] The distribution areas of the two jet stream cores were clearly defined: The centers of maximum wind speed in East Asia were calculated using 300 hPa zonal winds over 6-hour intervals. A jet stream center was defined as one that met the following two conditions: (a) the central wind speed was ≥30 m / s (the threshold could be relaxed to 25 m / s due to the relatively weak intensity of the polar front jet stream in summer); (b) the wind speeds at the eight grid points surrounding the center of maximum wind speed were all lower than the wind speed at the center of maximum wind speed. Using jet stream center distribution maps from 42 years, the centers of maximum wind speed in high latitudes and mid-to-low latitudes corresponded to the active areas of the polar front jet stream and the subtropical jet stream, respectively, and their latitudinal ranges were recorded (e.g., ...). Figure 2 (as shown in a).

[0099] Step 2: Establish a comprehensive index for the coordinated changes in the intensity and location of upper-level jet streams.

[0100] The regions mentioned above that are correlated with the intensity of Meiyu rainfall were selected as key areas for jet stream synergistic changes (e.g., Figure 2As shown in b), the zonal wind average within the key jet stream region is represented as the jet stream composite index. The absolute value of the index represents the jet stream intensity, and the index sign represents the jet stream position movement. These are denoted as EAPJI and EASJI. Furthermore, the index is standardized and denoted as Std-EAPJI and Std-EASJI.

[0101] Step 3: A comprehensive characterization method for the coordinated changes in radial position and intensity of the polar front jet stream and the subtropical westerly jet stream.

[0102] Based on the signs and relative absolute values ​​of Std-EAPJI and Std-EASJI, Std-EASJI is defined as the X-axis coordinate, and Std-EAPJI as the Y-axis coordinate. The coordinated change of the two jet streams is defined as the following eight phases, with each phase corresponding to different jet stream intensities and radial positions. Calculating the jet stream index at different times will yield its distribution in the phase diagram and the corresponding atmospheric background circulation conditions:

[0103] Mode 1: Dominated by the subtropical jet stream, with two jet streams flowing towards each other.

[0104] That is, when the exponent has Std-EAPJI≤0 and Std-EASJI<0, if |Std-EAPJI|>|Std-EASJI|;

[0105] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0106] In terms of radial position: the polar front jet stream moves towards the equator, while the subtropical westerly jet stream moves towards the poles.

[0107] Mode 2: Dominated by the extreme front jet stream, with two jet streams flowing towards each other.

[0108] That is, when the exponent has Std-EAPJI≤0 and Std-EASJI<0, if |Std-EAPJI|≤|Std-EASJI|;

[0109] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0110] In terms of radial position: the polar front jet stream moves towards the equator, while the subtropical westerly jet stream moves towards the pole.

[0111] Mode 3: Dominated by the extreme front jet stream, with both jet streams flowing southward in the same direction.

[0112] That is, when the exponent has Std-EAPJI<0 and Std-EASJI≥0, if |Std-EAPJI|>|Std-EASJI|;

[0113] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0114] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the equator simultaneously.

[0115] Mode 4: Dominated by the subtropical jet stream, with both jet streams flowing southward in the same direction.

[0116] That is, when the exponent has Std-EAPJI<0 and Std-EASJI≥0, if |Std-EAPJI|≤|Std-EASJI|;

[0117] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0118] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the equator simultaneously.

[0119] Mode 5: Dominated by the subtropical jet stream, with two jet streams flowing in opposite directions.

[0120] That is, when the exponent has Std-EAPJI≥0 and Std-EASJI>0, if |Std-EAPJI|≤|Std-EASJI|;

[0121] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0122] In terms of radial position: the polar front jet stream moves towards the polar region, while the subtropical westerly jet stream moves towards the equator.

[0123] Mode 6: Dominated by a high-speed jet stream, with two jet streams flowing in opposite directions.

[0124] That is, when the exponent has Std-EAPJI≥0 and Std-EASJI>0, if |Std-EAPJI|>|Std-EASJI|;

[0125] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0126] In terms of radial position: the polar front jet stream moves towards the polar region, while the subtropical westerly jet stream moves towards the equator.

[0127] Mode 7: Dominated by the extreme front jet stream, with both jet streams flowing northward.

[0128] That is, when the exponent has Std-EAPJI>0 and Std-EASJI≤0, if |Std-EAPJI|>|Std-EASJI|;

[0129] In terms of jet stream intensity: the polar front jet stream is stronger, while the subtropical jet stream is weaker.

[0130] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the poles at the same time.

[0131] Mode 8: Dominated by the subtropical jet stream, with both jet streams flowing northward.

[0132] That is, when the exponent has Std-EAPJI>0 and Std-EASJI≤0, if |Std-EAPJI|≤|Std-EASJI|;

[0133] In terms of jet stream intensity: the subtropical jet stream is stronger, while the polar front jet stream is weaker.

[0134] In terms of radial position: the polar front jet stream and the subtropical jet stream move towards the poles at the same time.

[0135] Example 2:

[0136] This example focuses on the East Asian region. Based on the Polar Front Jet Index (EAPJI) and the Subtropical Westerly Jet Index (EASJI), the coordinated changes in the intensity and location of the two jet streams are divided into eight modes according to the above definitions. These eight modes correspond to different jet stream co-evolution patterns and different jet stream intensity changes. The jet stream co-evolution index and the trend of emergency jet stream evolution are shown in Table 1.

[0137] Table 1

[0138]

[0139] Figure 3 This is a composite image of the 300 hPa upper-level wind field for eight modes of coordinated changes in the East Asian jet stream. In mode 1 ( Figure 3 In mode 2 (a), the subtropical westerly jet stream has two centers, with the jet stream morphology slightly exhibiting a northeast-southwest orientation, and the main body of the jet stream being significantly northward. At this time, the polar front jet stream is relatively weak and located further south. Figure 3 In mode b), the subtropical jet stream center is shifted westward, with a strong jet stream core over Xinjiang, my country, while the jet stream core over Northeast my country disappears. Simultaneously, the corresponding strong center of the polar front jet stream is located near the Sea of ​​Okhotsk. In mode 3 ( Figure 3 In mode c), the subtropical westerly jet stream is weaker, located further south, with its central axis near 35ºN. The jet stream core appears over the Sea of ​​Japan, and the polar front jet stream distribution is similar to that of phase 2, but slightly stronger. In mode 4 ( Figure 3 In mode 5 (d), the subtropical jet stream was significantly stronger than normal, the jet stream core over the Sea of ​​Japan intensified, and merged with the jet stream core over western my country into a single center, controlling the Yellow River and Huai River basins in my country. Meanwhile, the polar front jet stream remained relatively southerly, but its intensity was weaker. Figure 3In mode 6 (e), the subtropical westerly jet stream is very strong, with its main body located in the Yellow River and Huai River basins of my country, its axis around 32°N, and a merged jet stream core existing in East Asia. The polar front jet stream is located at a higher latitude at this time, with its core located in the northern part of the East Siberian Plain. Figure 3 In mode f), two more jet stream cores reappear within the subtropical westerly jet stream region, located over the Huanghuai region and Xinjiang, my country, respectively. Their overall intensity is relatively weak, while the polar front jet stream remains strong and positioned further north. In mode 7 ( Figure 3 In mode 8, the jet core over Xinjiang, my country, is similar to that in phase 6, while the jet core in the Yangtze-Huaihe River basin is weaker. The corresponding polar front jet stream controls the region north of Siberia. Figure 3 In phase h), two weak jet centers of the subtropical westerly jet stream control the airspace over Xinjiang and the vicinity of Northeast my country. Compared to phase 7, the position of the polar front jet stream remains unchanged, but its jet core intensity weakens. The subtropical westerly jet stream is relatively weak and its position is significantly northward, while the axis of the polar front jet stream remains basically around 75ºN. The eight modes synthesized based on the comprehensive index of jet stream synergy clearly reflect the different characteristics of the synergistic changes in position and intensity between the East Asian polar front jet stream and the subtropical jet stream.

[0140] In this embodiment, the eight phases are associated with weather events during the plum rain season; among them, mode 3, mode 4, mode 5, and mode 6 are associated with the occurrence of precipitation during the plum rain season.

[0141] When in mode 5, it is determined to be a phase with a high incidence of continuous heavy rain during the plum rain season.

[0142] The plum rain season event in flood-prone years is associated with mode 5, while the plum rain season event in dry years is associated with mode 4.

[0143] This implementation provides the application of the comprehensive index of rapid flow coordination change:

[0144] The Meiyu season is a unique product of the phased northward advance of the East Asian summer monsoon. Its occurrence and development are significantly affected by the adjustment of mid-to-high latitude atmospheric circulation. Next, we will examine the ability of the jet stream comprehensive characterization method to indicate East Asian climate change by using special weather and climate events during the Meiyu season. Figure 4 The relationship between the comprehensive index of the coordinated variation of the East Asian westerly jet stream and the Meiyu season is presented. Looking at the distribution of all Meiyu seasons, Meiyu occurs most frequently in mode 5 and least frequently in mode 1. This means that East Asian Meiyu often occurs when two jet streams are moving southward in the same direction or in opposite directions. Overall, Meiyu is more likely to occur when the subtropical westerly jet stream is dominant.

[0145] Further statistical analysis of the frequency of different duration events in various phases of the Meiyu season revealed that, in Mode 3, events lasting more than 3 days occurred significantly more frequently than other continuous events. In Mode 4, the frequency of events lasting more than 3 days was similar to that of short-duration events lasting 2-3 days. The results for Mode 5 were similar to those for Mode 3, with frequent occurrences of long-duration events. Clearly, long-duration events during the Meiyu season primarily occurred in Modes 3 and 5, with a significantly lower frequency in Mode 4. The distribution of continuous events during the Meiyu season based on the jet stream co-variance index (considering only the number of days with an index intensity ≥ 1, where d is the number of days) is shown in Table 2.

[0146] Table 2

[0147]

[0148] Further exploration of the indicative effect of this comprehensive index on typical plum rain events, such as... Figure 5 As shown.

[0149] In flood-prone years, the Meiyu season mostly occurs during Mode 5, meaning that the Meiyu season in flood-prone years is often characterized by the jet stream moving in the opposite direction to the subtropical westerly jet stream, corresponding to a longer duration and higher rainfall. Secondly, this event mostly occurs during Modes 3 and 4. At this time, the two jet streams are in a southward-moving mode, and active cold air and abundant dynamic lifting conditions provide a favorable circulation background for precipitation during the Meiyu season in flood-prone years. However, the Meiyu season in flood-prone years almost never occurs during Modes 1 and 8, accounting for less than 3%.

[0150] For the plum rain season in dry years, the most frequent phase is Mode 4, accounting for 21.3%, which is the southward-moving mode dominated by the polar front jet stream. This corresponds to a relatively short duration of the plum rain season in dry years, along with less rainfall. This also reflects the increased activity of mid-to-high latitude cold air in dry years, which can effectively strengthen the polar front jet stream. The rapid southward movement of cold air also helps to enhance the temperature gradient on both sides of the subtropical jet stream, thus accelerating the westerly winds. Secondly, this type of event occurs more frequently in Modes 5 and 6, accounting for 16.9% and 15.7% respectively, which are modes where the two jet streams move in opposite directions. Unlike the plum rain season in flooded years, the plum rain area in dry years still has some distribution in Modes 1 and 8, which is clearly closely related to the significantly less precipitation during the plum rain season in dry years.

[0151] Further exploration of the index's indicative role in heavy rainfall during the plum rain season, such as... Figure 6As shown, the results indicate that Meiyu season torrential rains occurred most frequently in Mode 5, accounting for 26.3%, followed by Mode 4, accounting for 25.6%. In both of these modes, the subtropical westerly jet stream dominated the jet stream co-evolution, suggesting that the occurrence of Meiyu season torrential rains may be more easily regulated by the subtropical westerly jet stream. Modes 3 and 6 occurred relatively less frequently, but still accounted for more than 15%, indicating that under conditions of weak subtropical westerly jet streams, the circulation evolution dominated by the polar front jet stream can also trigger Meiyu season torrential rains, but the frequency of occurrence is relatively low. Similarly, the analysis of the persistence of torrential rains occurring in different modes revealed that, similar to the frequency of persistent events during the Meiyu season, Meiyu season torrential rains lasting more than 3 days occurred most frequently in Mode 5, with a frequency of up to 27 days. However, unlike Mode 6, persistent torrential rains still reached 21 days, but were mostly torrential rains lasting 3 to 4 days. The distribution of persistent Meiyu season torrential rain events based on the jet stream co-evolution index is shown in Table 3.

[0152] Table 3

[0153]

[0154] Studies on torrential rains during the plum rain season in both drought and flood years have found that, for example Figure 7 As shown, heavy rainfall in flood years is concentrated in mode 5, accounting for 29.4%, while the probability of occurrence in modes 4 and 6 is 21.1% each, followed by mode 3. The occurrence and development of heavy rainfall often require abundant water vapor supply and active convection, combined with... Figure 6 The analysis reveals that in Mode 5, the strong subtropical westerly jet stream provides a favorable dynamic lifting environment, while the active mid-latitude cold air pushes the two jet streams in opposite directions. Simultaneously, the intense confrontation with the low-latitude warm and humid airflow in the Yangtze River basin is also a significant factor contributing to the occurrence of torrential rains during the Meiyu season. In contrast, the most frequent torrential rains in dry years occur in Mode 4, corresponding to the southward location of the polar front jet stream caused by the high-latitude meridional circulation.

[0155] The above analysis reveals that the jet stream coordination index effectively indicates the differences between Meiyu season torrential rainfall and drought / flood years. Meiyu season torrential rainfall is concentrated in Modes 4 and 5, when the subtropical westerly jet stream is strong, providing favorable dynamic lifting conditions for the rainfall. Prolonged and persistent torrential rainfall occurs more frequently in Mode 5, possibly due to the frequent occurrence of persistent events during this period. In flood years, torrential rainfall is concentrated in Mode 5, with the polar front jet stream shifting northward and the mid-to-high latitude circulation exhibiting a zonal distribution; the torrential rainfall is longer and heavier. Conversely, in drought years, torrential rainfall is concentrated in Mode 4, with the polar front jet stream shifting southward, mid-to-high latitude disturbances being more active, and the duration of the torrential rainfall being significantly shorter.

[0156] Example 2

[0157] This embodiment also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method described in Embodiment 1.

[0158] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for characterizing the coordinated changes of the polar front jet stream and the subtropical westerly jet stream, characterized in that, The following steps are involved: Acquire zonal wind data in the upper troposphere of the target area; Based on the zonal wind data, identify active areas of polar front jet stream and active areas of subtropical westerly jet stream; The average zonal wind value within the active area of ​​the polar front jet stream is calculated to obtain the polar front jet stream index PJ, and the average zonal wind value within the active area of ​​the subtropical westerly jet stream is calculated to obtain the subtropical jet stream index SJ. The polar front jet index PJ and the subtropical jet index SJ are standardized to obtain the standardized polar front jet index Std-PJI and the standardized subtropical jet index Std-SJI. Establish a coordinate system with Std-SJI as the abscissa and Std-PJI as the ordinate; Based on the sign combinations of Std-SJI and Std-PJI and the relationship between their absolute values, the co-variation of the two jet streams is divided into eight phases.

2. The method according to claim 1, characterized in that, The target area is East Asia, with the active area of ​​the polar front jet stream defined as 50°–70°N and the active area of ​​the subtropical westerly jet stream defined as 25°–45°N.

3. The method according to claim 1, characterized in that, The time resolution of the zonal wind data is 6 hours or 1 day, and the horizontal resolution is 1°×1°.

4. The method according to claim 1, characterized in that, The process of identifying active areas of extreme fronts and jet streams includes: Regions with zonal wind speeds ≥ 30 m / s were selected; when the analysis period was summer, the wind speed threshold for active polar front jet stream areas was set to 25 m / s.

5. The method according to claim 1, characterized in that, The symbol combination is used to characterize the movement of the jet stream position; The absolute value is used to characterize the intensity of the jet stream.

6. The method according to claim 1, characterized in that, The rules for dividing the eight phases include: When Std-PJI≤0 and Std-SJI<0, if |Std-PJI|>|Std-SJI|, it is mode 1; if |Std-PJI|≤|Std-SJI|, it is mode 2. Mode 1 corresponds to the two jet streams moving towards each other, dominated by the subtropical jet stream, and mode 2 corresponds to the two jet streams moving towards each other, dominated by the polar front jet stream. When Std-PJI < 0 and Std-SJI ≥ 0, if |Std-PJI| > |Std-SJI|, it is mode 3; if |Std-PJI| ≤ |Std-SJI|, it is mode 4. Mode 3 corresponds to the southward co-current jet stream dominated by the polar front jet stream, and mode 4 corresponds to the southward co-current jet stream dominated by the subtropical jet stream. When Std-PJI≥0 and Std-SJI>0, if |Std-PJI|≤|Std-SJI|, it is mode 5; if |Std-PJI|>|Std-SJI|, it is mode 6. Mode 5 corresponds to the subtropical jet stream-dominated double jet stream moving in opposite directions, and mode 6 corresponds to the polar front jet stream-dominated double jet stream moving in opposite directions. When Std-PJI > 0 and Std-SJI ≤ 0, if |Std-PJI| > |Std-SJI|, it is mode 7; if |Std-PJI| ≤ |Std-SJI|, it is mode 8. Mode 7 corresponds to the northward co-current jet stream dominated by the polar front jet stream, and mode 8 corresponds to the northward co-current jet stream dominated by the subtropical jet stream.

7. The method according to claim 6, characterized in that, The eight phases were correlated with Meiyu season weather events; among them, mode 3, mode 4, mode 5, and mode 6 were correlated with the occurrence of Meiyu season precipitation.

8. The method according to claim 6, characterized in that, When in mode 5, it is determined to be a phase with a high incidence of continuous heavy rain during the plum rain season.

9. The method according to claim 6, characterized in that, The plum rain season event in flood-prone years is associated with mode 5, while the plum rain season event in dry years is associated with mode 4.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1-9.

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