A method for characterizing polar front jet stream and subtropical westerly jet stream cooperative variation

Abstract

The application discloses a method for characterizing the cooperative variation of polar front jet and subtropical westerly jet, and belongs to the field of atmospheric science, and comprises the following steps: obtaining the zonal wind data of the upper troposphere of a target area; identifying the polar front jet active area and the subtropical westerly jet active area according to the zonal wind data; calculating the average value of the zonal wind in the polar front jet active area to obtain a polar front jet index PJ, and calculating the average value of the zonal wind in the subtropical westerly jet active area to obtain a subtropical jet index SJ; performing standardization processing to obtain a standardized polar front jet index Std-PJI and a standardized subtropical jet index Std-SJI; and according to the sign combination of Std-SJI and Std-PJI and the absolute value size relationship, the cooperative variation of the double jets is divided into eight phases. The application has the cooperative variation characteristics of the polar front jet and the subtropical jet in position and intensity, and can be applied to the real-time monitoring of extreme weather and climate events in business.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of atmospheric science, and particularly relates to a method for characterizing the coordinated variation of polar front jet and subtropical westerly jet. BACKGROUND

[0002] Currently, the methods for characterizing the coordinated variation of polar front jet (PJ) and subtropical westerly jet (SJ) mainly include two types: the first type is the empirical orthogonal function (EOF) method, which decomposes the average wind field by the EOF method, extracts the first two modes to represent the different states of the coordinated variation of the double jets, and the method depends on the time and space range of the analysis field, and the obtained modes are significantly affected by the time length and spatial resolution of the data. The second type is the single variable index method, which defines the jet radial position index according to the latitude of the maximum wind speed in the active area of the two jets, and represents the jet intensity by the total wind speed, and analyzes the coordinated variation by the relative size of the double indexes; this type of method only focuses on a single variable such as position or intensity, and cannot quantify the coupling relationship between the position and intensity of the double jets.

[0003] The prior art has the following defects: first, the EOF method cannot separate the coordinated variation characteristics of the jet position and intensity, and the single variable index method can only reflect a single physical quantity (such as position or intensity), ignores the position-intensity coupling effect, and misses the coordinated variable; second, the existing characterization results are restricted by the time and space range of the data, and it is difficult to meet the real-time monitoring requirements, and cannot support the extended period weather forecast and model evaluation, and the business application is limited; finally, the single variable index method lacks quantification ability for the "leading-lag response" and "seesaw" pattern of the north-south reverse displacement of the double jets, which leads to insufficient capture of the adjustment signal of the mid-high latitude circulation and insufficient description of the dynamic process. SUMMARY

[0004] To solve the above technical problems, the application provides a method for characterizing the coordinated variation of polar front jet and subtropical westerly jet to solve the problems existing in the prior art.

[0005] To achieve the above purpose, in a first aspect, the application provides a method for characterizing the coordinated variation of polar front jet and subtropical westerly jet, comprising:

[0006] obtaining the zonal wind data of the upper troposphere of a target area;

[0007] According to the zonal wind data, identifying the polar front jet active area and the subtropical westerly jet active area;

[0008] calculating the average of the zonal wind in the polar jet active region to obtain a polar jet index PJ, and calculating the average of the zonal wind in the subtropical westerly jet active region to obtain a subtropical jet index SJ;

[0009] standardizing the polar jet index PJ and the subtropical jet index SJ to obtain a standardized polar jet index Std-PJI and a standardized subtropical jet index Std-SJI, respectively;

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

[0011] According to the sign combination of Std-SJI and Std-PJI and the absolute value size relationship, the double-jet cooperative change is divided into eight phases.

[0012] Preferably, the target area is the East Asian region, and the polar jet active region is defined as 50°-70°N, and the subtropical westerly jet active region is defined as 25°-45°N.

[0013] Preferably, the time resolution of the zonal wind data is every 6 hours or every day, and the horizontal resolution is 1°x1°.

[0014] Preferably, the process of identifying the polar jet active region comprises:

[0015] Screening the region with zonal wind speed ≥30m / s; wherein when the analysis period is summer, the wind speed threshold of the polar jet active region is set to 25m / s.

[0016] Preferably, the sign combination is used to represent the jet position movement.

[0017] The absolute value size is used to represent the jet intensity.

[0018] Preferably, the eight phases are divided according to the following rules:

[0019] When Std-PJI≤0 and Std-SJI<0, if |Std-PJI|>|Std-SJI|, it is mode 1, and if |Std-PJI|≤|Std-SJI|, it is mode 2; wherein mode 1 corresponds to the double-jet head-on mode dominated by the subtropical jet, and mode 2 corresponds to the double-jet head-on mode dominated by the polar jet;

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

[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; wherein mode 5 corresponds to a subtropical jet stream dominated double jet stream back-and-forth mode, and mode 6 corresponds to a polar front jet stream dominated double jet stream opposite mode;

[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; wherein mode 7 corresponds to a polar front jet stream dominated double jet stream northward mode, and mode 8 corresponds to a subtropical jet stream dominated double jet stream northward mode.

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

[0024] Preferably, when in mode 5, it is determined that it is a Meiyu period persistent heavy rain high-occurrence phase.

[0025] Preferably, a flood year Meiyu period event is associated with mode 5, and a drought year Meiyu period event is associated with mode 4.

[0026] In a second aspect, the present application also discloses a computer readable storage medium, which has a computer program stored thereon, and the computer program is executed by a processor to realize the steps of the method in the first aspect.

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

[0028] The present application discloses a method for characterizing the coordinated variation of a polar front jet stream and a subtropical westerly jet stream, comprising the following steps: first, obtaining the zonal wind data of the upper troposphere of a target region; second, identifying a polar front jet stream active area and a subtropical westerly jet stream active area according to the zonal wind data; third, calculating the average value of the zonal wind in the polar front jet stream active area to obtain a polar front jet stream index PJ, and calculating the average value of the zonal wind in the subtropical westerly jet stream active area to obtain a subtropical jet stream index SJ; further, performing standardization processing on the polar front jet stream index PJ and the subtropical jet stream index SJ respectively to obtain a standardized polar front jet stream index Std-PJI and a standardized subtropical jet stream index Std-SJI; establishing a coordinate system with Std-SJI as the abscissa and Std-PJI as the ordinate; finally, according to the sign combination of Std-SJI and Std-PJI and the absolute value size relationship, the coordinated variation of the double jet streams is divided into eight phases.

[0029] The present application aims at the technical problem that the current representation of the cooperative change of the jet stream cannot reflect the cooperative change of the position and intensity of the jet stream at the same time, and the cooperative change of the polar front jet and the subtropical jet in position and intensity can significantly affect the weather and climate change in East Asia, and the present application establishes a comprehensive representation method that can reflect the radial position swing of the two jet streams and the intensity change of the jet stream itself at the same time, and develops a set of comprehensive index of the cooperative change of the jet stream based on this, which provides an analysis means for grasping the mechanism of the adjustment of the circulation at middle and high latitudes affecting the weather and climate change. In addition, the technical solution of the present application can also be directly applied to the real-time monitoring of extreme weather and climate events in business as a comprehensive monitoring index. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of this application, are intended to provide further understanding of the application and are incorporated herein in their entirety. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 Flow chart for the comprehensive index of the cooperative change of the jet stream of the embodiments of the present application;

[0032] Figure 2 Schematic diagram for the basis for selecting the key area of the index of the cooperative change of the jet stream of the embodiments of the present application, wherein (a) is a schematic diagram of the 300 hPa zonal wind and the jet core frequency in the upper troposphere during the Meiyu period in East Asia from 1979 to 2020, and (b) is a schematic diagram of the spatial distribution of the 300 hPa zonal wind regression during the Meiyu period;

[0033] Figure 3 Schematic diagram of the 300 hPa zonal wind distribution of the comprehensive index of the cooperative change of the jet stream of the embodiments of the present application in different modes, wherein (a) is a schematic diagram of the 300 hPa zonal wind distribution of mode 1, (b) is a schematic diagram of the 300 hPa zonal wind distribution of mode 2, (c) is a schematic diagram of the 300 hPa zonal wind distribution of mode 3, (d) is a schematic diagram of the 300 hPa zonal wind distribution of mode 4, (e) is a schematic diagram of the 300 hPa zonal wind distribution of mode 5, (f) is a schematic diagram of the 300 hPa zonal wind distribution of mode 6, (g) is a schematic diagram of the 300 hPa zonal wind distribution of mode 7, and (h) is a schematic diagram of the 300 hPa zonal wind distribution of mode 8;

[0034] Figure 4 Scatter plot of the comprehensive index of the cooperative change of the jet stream during the Meiyu period from 1979 to 2020 of the embodiments of the present application;

[0035] Figure 5 Scatter plot of the comprehensive index of the cooperative change of the jet stream during the Meiyu period of typical dry and wet years of the embodiments of the present application;

[0036] Figure 6 A typical 1979-2020 Meiyu period rainstorm jet stream coordinated variation comprehensive index scatter plot of an embodiment of the present application;

[0037] Figure 7 A typical Meiyu rainstorm jet stream coordinated variation index scatter plot of a dry and wet year of an embodiment of the present application. DETAILED DESCRIPTION

[0038] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

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

[0040] Embodiment one

[0041] As Figure 1 shown, the present embodiment provides a method for characterizing the coordinated variation of polar front jet and subtropical westerly jet, comprising:

[0042] S1, obtaining zonal wind data of the upper troposphere of a target region;

[0043] The target region is the East Asian region, the polar front jet active area is defined as 50°-70°N, and the subtropical westerly jet active area is defined as 25°-45°N.

[0044] The zonal wind data is derived from ERA-5 reanalysis data, with a time resolution of every 6 hours or every day and a horizontal resolution of 1°x1°.

[0045] S2, identifying the polar front jet active area and the subtropical westerly jet active area according to the zonal wind data;

[0046] Further, the process of identifying the polar front jet active area comprises:

[0047] Screening the area with a zonal wind speed ≥30m / s; wherein when the analysis period is summer, the wind speed threshold of the polar front jet active area is set to 25m / s.

[0048] Specifically, determining the jet active area: using the daily or 6-hour 300hPa zonal wind to calculate the wind speed maximum center of the global region, and the center wind speed value of the wind speed maximum center is ≥30m / s (considering the weak intensity of the polar front jet in summer, it can be relaxed to 25m / s); according to the jet center concentration area, record the latitude and longitude range.

[0049] S3, calculating the average value of the zonal wind in the polar front jet active area to obtain a polar front jet index PJ, and calculating the average value of the zonal wind in the subtropical westerly jet active area to obtain a subtropical jet index SJ;

[0050] Specifically, a jet collaborative change index is calculated: the average values of the zonal wind in the active areas of the two jets are calculated (the daily average, the candidate average, the monthly average, and the annual average can be calculated as appropriate), which are represented by the polar front jet index PJ and the subtropical westerly jet index SJ.

[0051] S4, the polar front jet index PJ and the subtropical jet index SJ are respectively standardized to obtain a standardized polar front jet index Std-PJI and a standardized subtropical jet index Std-SJI;

[0052] S5, a coordinate system is established with Std-SJI as the horizontal coordinate and Std-PJI as the vertical coordinate;

[0053] S6, according to the sign combination of Std-SJI and Std-PJI and the absolute value size relationship, the double-jet collaborative change is divided into eight phases.

[0054] Further, the sign combination is used to represent the jet position movement.

[0055] The absolute value size is used to represent the jet intensity.

[0056] The division rules of the eight phases include:

[0057] When Std-PJI≤0 and Std-SJI<0, if |Std-PJI|>|Std-SJI|, it is mode 1, and if |Std-PJI|≤|Std-SJI|, it is mode 2; wherein, mode 1 corresponds to a double-jet head-on mode dominated by the subtropical jet, and mode 2 corresponds to a double-jet head-on mode dominated by the polar front jet;

[0058] When Std-PJI<0 and Std-SJI≥0, if |Std-PJI|>|Std-SJI|, it is mode 3, and if |Std-PJI|≤|Std-SJI|, it is mode 4; wherein, mode 3 corresponds to a double-jet same direction southward mode dominated by the polar front jet, and mode 4 corresponds to a double-jet same direction southward mode dominated by the subtropical jet;

[0059] When Std-PJI≥0 and Std-SJI>0, if |Std-PJI|≤|Std-SJI|, it is mode 5, and if |Std-PJI|>|Std-SJI|, it is mode 6; wherein, mode 5 corresponds to a double-jet back-to-back mode dominated by the subtropical jet, and mode 6 corresponds to a double-jet back-to-back mode dominated by the polar front jet.

[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; wherein, mode 7 corresponds to the polar front jet dominated double jet same direction northward mode, mode 8 corresponds to the subtropical jet dominated double jet same direction northward mode.

[0061] Specifically, in order to simultaneously represent the cooperative variation characteristics of the two jets in terms of position and intensity, the absolute value of the index is used to represent the jet intensity, and the sign of the index is used to represent the jet position movement, according to the sign and the relative size of the absolute value of Std-PJI and Std-SJI. The cooperative variation of the two jets is divided into the following eight phases, different phases correspond to different jet intensity and position state, reflecting different mid-high latitude atmospheric circulation state:

[0062] Mode 1: dominated by subtropical jet, two jets move in opposite directions.

[0063] That is, when the index appears Std-PJI≤ 0 and Std-SJI< 0, if |Std-PJI| > |Std-SJI|, it is mode 1.

[0064] In terms of jet intensity: the subtropical jet is strong, and the polar front jet is weak.

[0065] From the radial position: the polar front jet moves towards the equator, and the subtropical westerly jet moves towards the pole.

[0066] Mode 2: dominated by polar front jet, two jets move in opposite directions.

[0067] That is, when the index appears Std-PJI≤ 0 and Std-SJI< 0, if |Std-PJI| ≤ |Std-SJI|, it is mode 2.

[0068] In terms of jet intensity: the polar front jet is strong, and the subtropical jet is weak.

[0069] From the radial position: the polar front jet moves towards the equator, and the subtropical westerly jet moves towards the pole.

[0070] Mode 3: dominated by polar front jet, two jets move in the same direction southward.

[0071] That is, when the index appears Std-PJI< 0 and Std-SJI≥ 0, if |Std-PJI| > |Std-SJI|, it is mode 3.

[0072] In terms of jet intensity: the polar front jet is strong, and the subtropical jet is weak.

[0073] From the radial position: the polar front jet moves equatorward while the subtropical jet moves equatorward.

[0074] Modality 4: The subtropical jet is dominant, and the two jets move southward.

[0075] That is, when the index appears Std-PJI < 0 and Std-SJI ≥ 0, if |Std-PJI| ≤ |Std-SJI| in the case of;

[0076] In the intensity of the jet: the subtropical jet is strong, and the polar front jet is weak.

[0077] From the radial position: the polar front jet moves equatorward while the subtropical jet moves equatorward.

[0078] Modality 5: The subtropical jet is dominant, and the two jets move away from each other.

[0079] That is, when the index appears Std-PJI ≥ 0 and Std-SJI > 0, if |Std-PJI| ≤ |Std-SJI| in the case of;

[0080] In the intensity of the jet: the subtropical jet is strong, and the polar front jet is weak.

[0081] From the radial position: the polar front jet moves equatorward while the subtropical jet moves equatorward.

[0082] Modality 6: The polar front jet is dominant, and the two jets move away from each other.

[0083] That is, when the index appears Std-PJI ≥ 0 and Std-SJI > 0, if |Std-PJI| > |Std-SJI| in the case of;

[0084] In the intensity of the jet: the polar front jet is strong, and the subtropical jet is weak.

[0085] From the radial position: the polar front jet moves equatorward while the subtropical jet moves equatorward.

[0086] Modality 7: The polar front jet is dominant, and the two jets move northward.

[0087] That is, when the index appears Std-PJI > 0 and Std-SJI ≤ 0, if |Std-PJI| > |Std-SJI| in the case of;

[0088] In the intensity of the jet: the polar front jet is strong, and the subtropical jet is weak.

[0089] From the radial position: the polar front jet moves equatorward while the subtropical jet moves equatorward.

[0090] Mode 8: Subtropical jet is dominant, and two jets move northward in the same direction.

[0091] That is, when the index appears Std-PJI> 0 and Std-SJI≤ 0, if |Std-PJI|≤ |Std-SJI|, the case is;

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

[0093] From the radial position: the polar front jet and the subtropical jet move to the polar direction at the same time.

[0094] The comprehensive method of the coordinated variation of the polar front jet and the subtropical jet established by the application can better grasp the comprehensive characteristics of the position and intensity of the polar front jet and the subtropical westerly jet in the middle and high latitude regions, and can provide certain prediction basis for the occurrence and development of the extreme weather and climate events influenced by the coordinated variation of the jets, such as the occurrence and development of the Meiyu period in the Yangtze River Basin, and the occurrence and development of the persistent heavy rainfall event in the flood season.

[0095] Example 1:

[0096] Combined with the attached Figure 2 Taking the summer Meiyu period from 1979 to 2020 as an example, the radial position and intensity coordinated variation characteristics of the polar front jet and the subtropical westerly jet in the Meiyu period in East Asia in the past 42 years are analyzed. According to the specific situation, the analysis object can also be analyzed on the basis of annual, monthly, hourly and hourly data.

[0097] First step: clear the active key area of the polar front jet and the subtropical westerly jet.

[0098] Determine the distribution area of the two jets: use the 6-hourly 300 hPa zonal wind to calculate the wind speed center of East Asia, and when the wind speed center meets the following two conditions, it is recorded as a jet center: (a) the center wind speed value is greater than or equal to 30 m / s (since the summer polar front jet is weak, the threshold can be appropriately widened to 25 m / s); (b) the wind speed values of the 8 grid points around the wind speed center are less than the wind speed value of the wind speed center. Using the jet center distribution map of 42 years, the wind speed centers corresponding to high latitudes and middle and low latitudes correspond to the active areas of the polar front jet and the subtropical jet respectively, and the latitude range is recorded (such as shown in a of Figure 2 ).

[0099] Second step: establish a comprehensive index of the coordinated variation of the upper jet intensity and position.

[0100] Select the region related to Meiyu precipitation in the above region as the key region of the coordinated variation of the jets (such as Figure 2The average value of the zonal wind in the critical area of the jet stream is represented as the jet stream comprehensive index, the absolute value of the index represents the intensity of the jet stream, and the sign of the index represents the position of the jet stream, marked as EAPJI and EASJI. Further, the index is standardized and marked as Std-EAPJI and Std-EASJI.

[0101] Third step: comprehensive representation of the coordinated changes of the polar front jet and the subtropical westerly jet in radial position and intensity.

[0102] According to the sign and relative size of the absolute value of Std-EAPJI and Std-EASJI, Std-EASJI is defined as the X-axis coordinate, and Std-EAPJI is defined as the Y-axis coordinate. The coordinated changes of the two jets are defined as the following eight phases. Each phase corresponds to a different coordinated change state of the intensity and radial position of the jet stream. Calculating the jet stream index at different times will give the distribution in the phase diagram and the corresponding atmospheric background circulation conditions:

[0103] Mode 1: dominated by the subtropical jet, with the two jets moving in opposite directions.

[0104] That is, when the index appears Std-EAPJI≤0 and Std-EASJI<0, if |Std-EAPJI|>|Std-EASJI|, then

[0105] In terms of jet stream intensity: the subtropical jet is strong, and the polar front jet is weak.

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

[0107] Mode 2: dominated by the polar front jet, with the two jets moving in opposite directions.

[0108] That is, when the index appears Std-EAPJI≤0 and Std-EASJI<0, if |Std-EAPJI|≤|Std-EASJI|, then

[0109] In terms of jet stream intensity: the polar front jet is strong, and the subtropical jet is weak.

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

[0111] Mode 3: dominated by the polar front jet, with the two jets moving in the same direction towards the south.

[0112] That is, when the index appears Std-EAPJI<0 and Std-EASJI≥0, if |Std-EAPJI|>|Std-EASJI|, then

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

[0114] From the radial position: the polar front jet and the subtropical jet move to the equator at the same time.

[0115] Mode 4: The subtropical jet is dominant, and the two jets move southward in the same direction.

[0116] That is, when the index appears Std-EAPJI < 0 and Std-EASJI ≥ 0, if |Std-EAPJI| ≤ |Std-EASJI|, then

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

[0118] From the radial position: the polar front jet and the subtropical jet move to the equator at the same time.

[0119] Mode 5: The subtropical jet is dominant, and the two jets move away from each other.

[0120] That is, when the index appears Std-EAPJI ≥ 0 and Std-EASJI > 0, if |Std-EAPJI| ≤ |Std-EASJI|, then

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

[0122] From the radial position: the polar front jet moves to the polar direction and the subtropical westerly jet moves to the equator.

[0123] Mode 6: The polar front jet is dominant, and the two jets move away from each other.

[0124] That is, when the index appears Std-EAPJI ≥ 0 and Std-EASJI > 0, if |Std-EAPJI| > |Std-EASJI|, then

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

[0126] From the radial position: the polar front jet moves to the polar direction and the subtropical westerly jet moves to the equator.

[0127] Mode 7: The polar front jet is dominant, and the two jets move northward in the same direction.

[0128] That is, when the index appears Std-EAPJI > 0 and Std-EASJI ≤ 0, if |Std-EAPJI| > |Std-EASJI|, then

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

[0130] From the radial position: the polar front jet moves to the polar direction with the subtropical jet.

[0131] Mode 8: The subtropical jet is dominant, and the two jets move northward.

[0132] That is, when the index appears Std-EAPJI> 0 and Std-EASJI≤ 0, if |Std-EAPJI|≤ |Std-EASJI|, then

[0133] In terms of jet intensity: the subtropical jet is strong, and the polar front jet is weak.

[0134] From the radial position: the polar front jet moves to the polar direction with the subtropical jet.

[0135] Example 2:

[0136] This example focuses on East Asia. According to the polar front jet index EAPJI and the subtropical westerly jet index EASJI, the coordinated changes in the intensity and position of the two jets are divided into the following eight modes according to the above definition. These eight modes correspond to different jet coordination evolution patterns and different jet intensity changes. The jet coordination change index corresponds to the jet evolution trend, as shown in Table 1.

[0137] Table 1

[0138]

[0139] Figure 3 The 300 hPa high-altitude wind field synthesis chart of the eight modes of East Asian jet coordination change. In mode 1 (a in Figure 3 , there are two centers of the subtropical westerly jet, and the jet shape slightly presents a northeast-southwest direction, with the jet main position obviously northward. At this time, the polar front jet is weak, and the position is southward. In mode 2 (b in Figure 3 , the subtropical jet center is westward, and the jet core over Xinjiang in China is strong, while the jet core in the northeast of China disappears. At the same time, the polar front jet center corresponding to this phase is located near the Okhotsk Sea. In mode 3 (c in Figure 3 , the subtropical westerly jet is weak, and the position is southward, with the center axis located near 35ºN, and the jet core appears over the Sea of Japan. The polar front jet distribution is similar to phase 2, but the intensity is slightly stronger. In mode 4 (d in Figure 3 , the subtropical jet is significantly strong, and the jet core over the Sea of Japan is enhanced, merging with the jet core over the western region of China to form a center controlling the Huang-Huai River basin, while the polar front jet position remains relatively southward, but the intensity is weak. In mode 5 (e in Figure 3e) in FIG. 6, the subtropical westerly jet is very strong, the main body of the jet is located in the Huang-Huai River basin of China, and the axis is located near 32ºN, and there is a merged jet core in the East Asian region. The polar front jet is located at a relatively high latitude, and the jet core is located in the northern part of the Siberian Plain. In mode 6 (f) in FIG. 6, Figure 3 the subtropical westerly jet region again appears two jet cores, which are located in the Huang-Huai River basin of China and over Xinjiang of China, respectively, and the overall intensity is weak. At this time, the polar front jet is strong and still located northward. In mode 7 (g) in FIG. 6, Figure 3 the jet core over Xinjiang of China is similar to that in phase 6, and the jet core in the Jianghuai River basin is weaker. The polar front jet corresponding to this phase controls the area north of Siberia. In mode 8 (h) in FIG. 6, Figure 4 the two weak jet centers of the subtropical westerly jet control the area near Xinjiang of China and the Northeast China. Compared with phase 7, the polar front jet in this phase has the same position, but the jet core intensity is weakened. The subtropical westerly jet is in a weak state, and the position is obviously northward, while the polar front jet axis basically maintains near 75ºN. The eight modes synthesized based on the jet coordination change comprehensive index clearly reflect the different characteristics of the coordination change of the East Asian polar front jet and the subtropical jet position and intensity.

[0140] In this embodiment, the eight phases are associated with the Meiyu period weather event; modes 3, 4, 5, 6 and 6 are related to the occurrence of Meiyu period precipitation.

[0141] When in mode 5, it is determined that it is a Meiyu period persistent heavy rain high-occurrence phase.

[0142] The Meiyu period event in a flood year is associated with mode 5, and the Meiyu period event in a drought year is associated with mode 4.

[0143] The present embodiment provides an application of the jet coordination change comprehensive index:

[0144] Meiyu is a unique product of the seasonal northward advance of the East Asian summer monsoon, and its occurrence and development will be significantly affected by the adjustment of the atmospheric circulation at middle and high latitudes. Next, the Meiyu period special weather and climate events will be used to test the indication ability of the jet comprehensive representation method for East Asian climate change. Figure 5 The relationship between the East Asian westerly jet coordination change comprehensive index and the Meiyu period is given. From the distribution of all Meiyu periods, Meiyu occurs most in mode 5 and least in mode 1. That is, Meiyu occurs more in the case of two jets moving southward and moving away from each other. Overall, Meiyu is more likely to occur in the case dominated by the subtropical westerly jet.

[0145] Further statistics of the occurrence frequency of different phase events during the Meiyu period showed that in mode 3, the occurrence frequency of events lasting more than 3 days was significantly higher than that of the remaining continuous events. In mode 4, the occurrence frequency of events lasting more than 3 days was similar to that of short continuous events lasting 2-3 days. In mode 5, the results were similar to those in phase 3, and long continuous events occurred frequently. Obviously, long continuous events during the Meiyu period occurred more frequently in modes 3 and 5, and the frequency of occurrence in mode 4 was significantly lower. The distribution of the jet stream cooperative change index during the Meiyu period (only considering days with index intensity ≥ 1, d is the number of days) is shown in Table 2.

[0146] Table 2

[0147]

[0148] Further exploration of the indicating effect of the comprehensive index on typical Meiyu events is shown in Table 3. Figure 6

[0149] During the flood year, the Meiyu period often occurs in mode 5, i.e., the Meiyu period of the flood year occurs in the state of the subtropical westerly jet stream dominated by the backward movement of the jet stream, corresponding to a longer duration and higher rainfall during the Meiyu period. Secondly, this event often occurs in modes 3 and 4. At this time, the two jets are in the same southward mode, and the active cold air and abundant dynamic lifting conditions provide a favorable circulation background for the Meiyu period precipitation. The Meiyu of the flood year does not occur in modes 1 and 8, accounting for less than 3%.

[0150] For the Meiyu period of the dry year, the phase with the highest occurrence frequency is mode 4, accounting for 21.3%, i.e., the same southward mode dominated by the polar front jet. This corresponds to a relatively short duration of the Meiyu period and a relatively small amount of Meiyu. At the same time, this also reflects that the cold air in the dry year is relatively active in the middle and high latitudes, which can effectively enhance the intensity of the polar front jet, and the rapid southward movement of the cold air is also conducive to enhancing the temperature gradient on both sides of the subtropical jet and accelerating the westerly. Secondly, this type of event often occurs in modes 5 and 6, accounting for 16.9% and 15.7%, respectively, i.e., the two jets are in the backward movement mode. Unlike the Meiyu period of the flood year, the Meiyu area in modes 1 and 8 still exists to some extent during the Meiyu period of the dry year, which is obviously related to the significantly lower rainfall during the Meiyu period of the dry year.

[0151] Further exploration of the indicating effect of the index on the Meiyu period rainstorm is shown in Table 4. Figure 7 ​As 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 6 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... ​ 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] The embodiment also discloses a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the steps of the method in the embodiment one.

[0158] The above merely illustrates the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope 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, Includes the following steps: 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 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; 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; 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.

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 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.

6. The method according to claim 1, 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.

7. The method according to claim 1, 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.

8. 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 1-7.

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