A sea and land wind identification method and system for the Bohai Sea Rim area

Abstract

The invention discloses a method and system for identifying sea and land breezes in the Bohai Sea Rim area. The method comprises: obtaining an average vertical profile variable field according to coastline data; decomposing the flow field in the Bohai Sea Rim area into divergent wind and curl wind based on the stream function and velocity potential in the Bohai Sea Rim area; projecting the original wind, divergent wind and curl wind respectively to the vertical profile direction of the coastline to obtain normal original, divergent and curl velocities, and obtaining a wind flux data set that meets the conditions in the closed area of ​​the coastline based on the normal original velocity; performing preliminary identification of sea and land breeze events in combination with the normal original, divergent and curl velocities and the wind flux data set that meets the conditions, and performing accurate identification of sea and land breeze events based on the average vertical profile variable field and the preliminary identification result; the invention can accurately identify sea and land breeze events in the Bohai Sea Rim area, and provide refined structural feature information of sea and land breezes for numerical forecasting business models.

Description

Technical Field

[0001] The invention relates to a method and system for identifying sea and land winds in the Bohai Sea Rim area, belonging to the technical field of meteorology. Background Art

[0002] As an important mesoscale weather phenomenon, sea and land breeze events are a local circulation weather system that cannot be ignored in the forecast of disastrous weather and pollution diffusion in meteorological forecasting business. It is particularly important to accurately identify sea and land breeze events in business forecasting. In the existing sea and land breeze event identification technology, the identification of sea and land breeze is mostly based on the change of wind speed and direction, the temperature difference between sea and land, large-scale background wind field, cloud cover, solar radiation, etc. For example, Borne K et al. proposed a series of conditions such as the need for wind direction and speed to change on the 700 hPa isobaric surface; the temperature difference between sea and land needs to be greater than 3℃; the change of near-surface wind direction needs to be greater than 30°; the sharp change ratio of wind direction peak needs to be greater than 6, etc., to identify sea and land breeze from multiple meteorological elements; however, the restriction of too many meteorological elements and conditions will lead to the omission of some similar sea and land breeze events, low identification accuracy, and cannot provide the refined structural feature information of sea and land breeze for the numerical forecasting business model; in addition, the strong locality of sea and land breeze also makes other identification methods may not be applicable to the identification of sea and land breeze events in the Bohai Bay area. In recent years, with the rapid development of high-resolution numerical models and high-performance computing, more refined observation and research on sea and land breezes can be carried out. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a method and system for identifying sea and land breezes in the Bohai Rim region, which can accurately identify sea and land breeze events in the Bohai Rim region, obtain accurate quantitative results, and provide refined structural characteristic information of sea and land breezes for the numerical forecasting business model.

[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0005] In one aspect, the present invention provides a method for identifying sea and land winds in the Bohai Sea Rim region, comprising:

[0006] Acquire coastline data of a certain section of the Bohai Sea Rim area, and obtain an average vertical profile variable field of the coastline based on the coastline data;

[0007] Based on the stream function and velocity potential of the underlying surface in the Bohai Rim area, the flow field in the Bohai Rim area is decomposed into divergent wind and curl wind.

[0008] The original wind and the divergent wind and the curl wind are projected to the vertical section direction of the coastline respectively to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and based on the normal original velocity, a wind flux data set that meets the conditions in the closed area of ​​the coastline is obtained;

[0009] Combine the normal original velocity, normal divergence velocity, normal curl velocity and qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, which include: type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of sea and land breeze events;

[0010] Based on the average vertical profile variable field and the preliminary identification results, accurate identification of sea and land breeze events is performed to obtain accurate quantitative results, which include: preliminary identification results, height of sea and land breeze events, approximate boundaries of circulation, penetration distance, and average transport volume per second.

[0011] Optionally, the acquiring of coastline data of a certain section of the Bohai Sea Rim region and obtaining an average vertical profile variable field of the coastline according to the coastline data includes:

[0012] Obtain the coastline data of a certain section of the Bohai Sea area, and confirm the scope of the coastline study area based on the coastline data, wherein the coastline data includes the function of the coastline;

[0013] Based on the function of the coastline and the scope of the coastline study area, determine the latitude and longitude coordinates of several vertical sections within the scope of the coastline study area and the starting point and end point of each vertical section, wherein the starting point and end point of the vertical section are both the intersection points of the vertical section and the boundary of the coastline study area;

[0014] Obtain the horizontal and vertical wind speeds at the starting and ending points of each vertical section;

[0015] Based on the latitude and longitude coordinates, horizontal wind speed and vertical wind speed of the starting point and end point of each vertical section, each vertical section is interpolated to obtain the variable field of each vertical section;

[0016] The vertical profile variable fields are spatially averaged to obtain the average vertical profile variable field of the coastline.

[0017] Optionally, the formula for spatially averaging each vertical profile variable field is expressed as follows:

[0018]

[0019] in, represents the i-th variable field obtained by interpolation; n represents the number of vertical profiles on the coastline; represents the average vertical profile variable field.

[0020] Optionally, the decomposition of the flow field in the Bohai Rim region into divergent wind and curl wind based on the stream function and velocity potential of the underlying surface in the Bohai Rim region includes:

[0021] According to the velocity in the flow field around Bohai Sea, the vorticity and divergence in the Bohai Sea area are determined;

[0022] Based on the automatic search method, determine the search information and the location information of the discretized grid points where the inner and outer boundaries of the Bohai Rim region are located, wherein the search information includes the number of areas where data are missing;

[0023] Based on the harmonic-cosine spectrum expansion perturbation method, the internal component is determined according to the position information, the vorticity and the divergence, wherein the internal component includes an average component and a perturbation component, the average component includes a stream function average component and a velocity potential average component, and the perturbation component includes a stream function perturbation component and a velocity potential perturbation component;

[0024] Determine the stream function and velocity potential of the underlying surface in the Bohai Sea region according to the component corresponding to the data missing area, the internal component and the harmonic component, wherein the component corresponding to the data missing area is determined by using the Green's function method, the harmonic component is determined by using the harmonic-cosine spectrum expansion method, the component corresponding to the data missing area includes the stream function component and the velocity potential component corresponding to the data missing area, and the harmonic component includes the stream function harmonic component and the velocity potential harmonic component;

[0025] Based on Helmholtz's law, the flow field in the Bohai Sea area is decomposed into divergent wind and curl wind according to the stream function and velocity potential of the underlying surface in the Bohai Sea area.

[0026] Optionally, based on the normal original velocity, a wind flux dataset meeting the conditions in the closed area of ​​the coastline is obtained, including:

[0027] Based on the wind flux formula, the daily wind flux data at the height of 50m-200m above the ground in the closed area of ​​the coastline are calculated respectively; wherein the daily wind flux data includes the wind flux at each moment of the day and the next day; the wind flux formula is expressed as follows:

[0028]

[0029]

[0030] in, represents the wind flux at the tth moment on the mth coastline at height z; represents the wind flux at the tth moment at height z; Represents the normal original velocity at the z height above the ground The value at the xth interval point on the m-segment coastline; z 50m-200m; n represents the number of interval points on each section of the coastline, which is equivalent to the number of vertical sections on the coastline; m represents any section of the coastline in the closed area of ​​the coastline;

[0031] The daily wind flux data at a height of 50m-200m above the ground are conditionally screened to obtain the wind flux data set that meets the conditions in the closed area of ​​the coastline.

[0032] Optionally, the wind flux daily data at a height of 50m-200m above the ground are subjected to conditional screening to obtain a wind flux data set that meets the conditions in a closed area of ​​the coastline, including:

[0033] If the wind flux in the daily data of wind flux at a height of 50m-200m above the ground has a negative value within one day, and the wind flux in the daily data of wind flux at a height of 50m above the ground has a positive value after sunrise, then the screening condition is met;

[0034] If the wind flux in the daily data of wind flux at a height of 50m-200m above the ground has a positive value before sunset on the second day, and the wind flux in the daily data of wind flux at a height of 50m above the ground has a negative value after sunset on the current day and before sunrise on the second day, then the screening condition is met;

[0035] The wind fluxes that meet the screening conditions are used to form a wind flux dataset that meets the conditions in the closed area of ​​the coastline.

[0036] Optionally, the combining of the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, wherein the preliminary identification step comprises:

[0037] Type Identification:

[0038] If both the normal original velocity and the normal divergence velocity are positive, it is judged to be a similar sea breeze event;

[0039] If a similar sea breeze event ends within one day and the start time is after sunrise and before sunset, it is identified as a sea breeze event;

[0040] If both the normal original velocity and the normal divergence velocity are negative, it is judged to be a land wind event;

[0041] If a similar land wind event ends within one day and the start time is after sunset and before sunrise on the next day, it is identified as a land wind event;

[0042] Start and end time:

[0043] When both the normal original velocity and the normal divergence velocity are positive / negative, it is recorded as the start time of the sea breeze / land breeze event;

[0044] When the normal original velocity or normal divergence velocity changes from the original positive / negative value, it is recorded as the end time of the sea breeze / land breeze event;

[0045] Duration:

[0046] Based on the start and end time of the sea breeze / land breeze event, the duration of the sea breeze / land breeze event is obtained;

[0047] Average Strength:

[0048] The average value of the normal original velocity at a preset height above the ground during the sea breeze / land breeze event is taken as the average intensity of the sea breeze / land breeze event;

[0049] Maximum Strength:

[0050] The maximum value of the normal original velocity at a preset height above the ground during the sea breeze / land breeze event is taken as the maximum intensity of the sea breeze / land breeze event;

[0051] Average background wind strength:

[0052] The average value of the normal curl velocity at a preset height above the ground during the sea breeze / land breeze event is taken as the average background wind intensity of the sea breeze / land breeze event;

[0053] Strongest moment;

[0054] The moment when the maximum value of the normal original velocity at a preset height above the ground during the sea breeze / land breeze event occurs is taken as the strongest moment of the sea breeze / land breeze event.

[0055] Optionally, based on the average vertical profile variable field and the preliminary identification result, accurate identification of sea and land wind events is performed to obtain accurate quantitative results, wherein the accurate quantitative results, wherein the accurate identification process includes:

[0056] Sea and land breeze height:

[0057] On the basis of the average vertical profile variable field, the height above the coastline where the normal original velocity in the average vertical profile first turns is the height of the sea breeze / land breeze event;

[0058] Approximate circulation boundary:

[0059] Based on the average vertical profile variable field, the integral of the normal original velocity with height in the average vertical profile is When it is equal to 0, it is the approximate boundary of the circulation; among them, the integral of the normal original velocity with the height z in the average vertical section is The formula is as follows:

[0060]

[0061] in, represents the normal original velocity;

[0062] Penetration distance:

[0063] Based on the integration of the normal raw velocity with height in the average vertical profile , where the sea surface / land surface is equal to 0, and the distance from the coastline, the penetration distance of the sea breeze / land breeze event is obtained;

[0064] Average delivery volume per second:

[0065] In the average vertical profile, the average sea breeze / land breeze transport per second is calculated based on the height of the sea breeze / land breeze event, as follows:

[0066]

[0067] in, is the average delivery volume per second, when the above formula is When , it is the average sea breeze transport per second. When the above formula is When , it is the average land wind transport per second; is the height of the sea breeze event; is the height of the land wind event.

[0068] On the other hand, the present invention provides a sea and land wind identification system for the Bohai Sea Rim region, comprising:

[0069] The average vertical profile variable field acquisition module is used to acquire the coastline data of a certain section of the Bohai Sea Rim area, and obtain the average vertical profile variable field of the coastline according to the coastline data;

[0070] Decomposition module, used to decompose the flow field in the Bohai Rim into divergent wind and curl wind based on the stream function and velocity potential of the underlying surface in the Bohai Rim;

[0071] A wind flux data set acquisition module is used to project the original wind and the divergent wind and the curl wind respectively to the vertical section direction of the coastline to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and based on the normal original velocity, obtain a wind flux data set that meets the conditions in the closed area of ​​the coastline;

[0072] A preliminary identification module is used to combine the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, wherein the preliminary identification results include: the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of the sea and land breeze event;

[0073] The precise quantitative module is used to accurately identify the sea and land breeze events based on the average vertical profile variable field and the preliminary identification results, and obtain precise quantitative results. The precise quantitative results include: preliminary identification results, the height of the sea and land breeze events, the approximate boundary of the circulation, the penetration distance, and the average transport volume per second.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] The method for identifying sea and land breezes in the Bohai Rim region proposed in the present invention obtains the average vertical profile variable field, the normal original velocity, the normal divergence velocity and the normal curl velocity in the Bohai Rim region, accurately and quantitatively identifies sea and land breeze events, and obtains the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity, strongest moment, height, circulation approximate boundary, penetration distance and average per second transport volume of sea and land breeze events in the Bohai Rim region. The method has high identification accuracy, and provides refined structural feature information of sea and land breezes for numerical forecasting business models.

[0076] The sea and land breeze identification system for the Bohai Rim region proposed in the present invention identifies sea and land breeze events based on a preliminary identification module and an accurate quantification module, and can supplement the missing sea and land breeze modules in the post-processing of weather and ocean numerical forecast models in the Bohai Rim region such as Tianjin, Shandong, and Liaoning. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor, among which:

[0078] Figure 1 The flow chart of the sea and land wind identification method for the Bohai Sea Rim region in an embodiment of the present invention is shown;

[0079] Figure 2 The schematic diagram of the average vertical profile variable field in the embodiment of the present invention is shown;

[0080] Figure 3 A schematic diagram of normal original velocity, normal divergence velocity and normal curl velocity in an embodiment of the present invention is shown;

[0081] Figure 4 The schematic diagram of the closed area of ​​the coastline in the embodiment of the present invention is shown;

[0082] FIG5( a ) is a schematic diagram of an average vertical profile of a sea breeze event with a clear boundary in an embodiment of the present invention;

[0083] FIG5( b ) is a schematic diagram of an average vertical profile of a land breeze event with a clear boundary according to an embodiment of the present invention;

[0084] FIG6 (a) shows a severe pollution event at a height of 50 m above the ground in an embodiment of the present invention. and and line graphs of pollutant concentrations;

[0085] FIG6( b ) shows a non-severe pollution event at a height of 50 m above the ground in an embodiment of the present invention. and and line graphs of pollutant concentrations;

[0086] FIG. 7 ( a ) is a schematic diagram showing an average vertical cross-section of a heavy pollution event according to an embodiment of the present invention;

[0087] FIG. 7( b ) is a schematic diagram of an average vertical cross-section of a non-severe pollution event in an embodiment of the present invention. DETAILED DESCRIPTION

[0088] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0089] The application principle of the present invention is described in detail below in conjunction with the accompanying drawings.

[0090] Embodiment 1:

[0091] like Figure 1 As shown, an embodiment of the present invention provides a method for identifying sea and land winds in the Bohai Sea Rim region, comprising the following steps:

[0092] S01: Acquire coastline data of a certain section of the Bohai Sea Rim area, and obtain the average vertical profile variable field of the coastline according to the coastline data;

[0093] S02: Based on the stream function and velocity potential of the underlying surface in the Bohai Rim region, the flow field in the Bohai Rim region is decomposed into divergent wind and curl wind;

[0094] S03: projecting the original wind and the divergent wind and the curl wind respectively to the vertical section direction of the coastline to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and obtaining a wind flux data set that meets the conditions in the closed area of ​​the coastline based on the normal original velocity;

[0095] S04: combining the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set, performing preliminary identification of the sea and land breeze events, and obtaining preliminary identification results, wherein the preliminary identification results include: the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of the sea and land breeze events;

[0096] S05: Based on the average vertical profile variable field and the preliminary identification results, accurately identify the sea and land breeze events to obtain accurate quantitative results, which include: preliminary identification results, height of the sea and land breeze events, approximate boundaries of circulation, penetration distance, and average transport volume per second.

[0097] The present invention proposes a sea and land breeze identification method for the Bohai Rim region, which can accurately and quantitatively identify sea and land breeze events, and obtain the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity, strongest moment, height, circulation approximate boundary, penetration distance, and average per second transport volume of sea and land breeze events in the Bohai Rim region. The identification accuracy is high, and refined structural feature information of sea and land breezes is provided for the numerical forecasting business model.

[0098] In this embodiment, step S01 obtains coastline data of a certain section of the Bohai Sea Rim area, and obtains the average vertical profile variable field of the coastline according to the coastline data, specifically including:

[0099] Obtain the coastline data of a certain section of the Bohai Sea area, and confirm the scope of the coastline study area based on the coastline data, wherein the coastline data includes the function of the coastline;

[0100] Based on the function of the coastline and the scope of the coastline study area, determine the latitude and longitude coordinates of several vertical sections within the scope of the coastline study area and the starting point and end point of each vertical section, wherein the starting point and end point of the vertical section are both the intersection points of the vertical section and the boundary of the coastline study area;

[0101] Obtain the horizontal and vertical wind speeds at the starting and ending points of each vertical section;

[0102] Based on the latitude and longitude coordinates, horizontal wind speed and vertical wind speed of the starting point and end point of each vertical section, each vertical section is interpolated to obtain the variable field of each vertical section;

[0103] The vertical profile variable fields are spatially averaged to obtain the average vertical profile variable field of the coastline.

[0104] Specifically, the coastline data, i.e., the function of the coastline, is confirmed by the endpoints at both ends of the coastline, such as Figure 2 As shown, in this embodiment, the coastline is the AB segment in the figure. The longitude and latitude coordinates of point A (a1, b1) and the longitude and latitude coordinates of point B (a2, b2) are known. Based on the principle of two points determining a straight line, the function y=kx+b of the coastline of segment AB is obtained;

[0105] Specifically, the confirmation of the scope of the coastline study area includes: adding and subtracting the intercept △b on the basis of the coastline function to obtain two functions y1=kx+b+△b and y2=kx+b-△b parallel to the coastline function, refer to Figure 2 The line segments A1B1 and A2B2 in the figure are as follows; based on the coastline function, the endpoints at both ends of the coastline and the two functions parallel to the coastline function, the scope of the coastline study area is confirmed, that is, the quadrilateral A1B1B2A2 in the figure.

[0106] Specifically, based on the function of the coastline section and the scope of the coastline study area, determine the latitude and longitude coordinates of several vertical sections within the coastline study area and the starting and ending points of each vertical section, including:

[0107] A plurality of interval points are set in the coastline with an interval resolution of △d, and the latitude and longitude coordinates of the plurality of interval points are obtained based on the endpoints at both ends of the coastline;

[0108] Based on the interval points, a vertical profile of the coastline is made to obtain several vertical profiles;

[0109] By intersecting several vertical sections with the boundary of the coastline study area, the latitude and longitude coordinates of the starting point and end point of each vertical section are obtained; that is, several vertical sections intersect with line segment A1B1 to obtain the starting point of each vertical section, and intersect with line segment A2B2 to obtain the end point of each vertical section.

[0110] Specifically, based on the latitude and longitude coordinates, horizontal wind speed and vertical wind speed of the starting point and end point of each vertical profile, each vertical profile is interpolated to obtain the variable field of each vertical profile, including:

[0111] On the basis of the known latitude and longitude coordinates, horizontal wind speed and vertical wind speed of the starting point and end point of each vertical profile, the height resolution in the vertical direction is first set. In this embodiment, the height resolution is set to 50m, and the interpolation function is used to perform upward interpolation (linear interpolation) on each vertical profile; then, with the interval point of each vertical profile as the center, horizontal interpolation (quadratic interpolation) is performed between the starting point and the end point of the vertical profile, with positive values ​​on the land surface and negative values ​​on the sea surface, to obtain the variable field of each vertical profile.

[0112] Specifically, the spatial average of each vertical profile variable field is performed to obtain the average vertical profile variable field of the coastline, such as Figure 2 The red surface shown in the figure is the average vertical profile variable field of the AB coastline. The spatial average formula is as follows:

[0113]

[0114] in, Indicates the variable field obtained by interpolation; n indicates the number of vertical profiles on the coastline, or the number of interval points; represents the average vertical profile variable field.

[0115] In this embodiment, in step S02, based on the stream function and velocity potential of the underlying surface in the Bohai Rim region, the flow field in the Bohai Rim region is decomposed into divergent wind and curl wind, specifically including:

[0116] S021: Obtain the stream function and velocity potential of the underlying surface in the Bohai Rim area, including:

[0117] According to the velocity in the flow field around Bohai Sea, the vorticity and divergence in the Bohai Sea area are determined;

[0118] Based on the automatic search method, determine the search information and the location information of the discretized grid points where the inner and outer boundaries of the Bohai Rim region are located, wherein the search information includes the number of areas where data are missing;

[0119] Based on the harmonic-cosine spectrum expansion perturbation method, the internal component is determined according to the position information, the vorticity and the divergence, wherein the internal component includes an average component and a perturbation component, the average component includes a stream function average component and a velocity potential average component, and the perturbation component includes a stream function perturbation component and a velocity potential perturbation component;

[0120] Determine the stream function and velocity potential of the underlying surface in the Bohai Sea region according to the component corresponding to the data missing area, the internal component and the harmonic component, wherein the component corresponding to the data missing area is determined by using the Green's function method, the harmonic component is determined by using the harmonic-cosine spectrum expansion method, the component corresponding to the data missing area includes the stream function component and the velocity potential component corresponding to the data missing area, and the harmonic component includes the stream function harmonic component and the velocity potential harmonic component;

[0121] Specifically, the stream function and velocity potential formulas of the underlying surface in the Bohai Sea area are expressed as follows:

[0122]

[0123]

[0124] in, represents the stream function of the underlying surface in the Bohai Sea area; represents the velocity potential of the underlying surface in the Bohai Sea area; , They represent the stream function component and velocity potential component corresponding to the data missing area respectively; k represents the kth data missing area; K represents the number of data missing areas; , denote the average component of stream function and the average component of velocity potential respectively; , represent the stream function disturbance component and the velocity potential disturbance component respectively; , They represent the harmonic components of the stream function and the harmonic components of the velocity potential, respectively.

[0125] S022:

[0126] Based on Helmholtz's basic law, according to the stream function ψ and velocity potential χ of the underlying surface in the Bohai Sea area, the flow field in the Bohai Sea Rim area is decomposed into divergent wind and curl wind, and the formula is as follows:

[0127]

[0128] Specifically, the flow field (horizontal wind field) in the Bohai Sea Rim Divergent wind and rotating wind Two parts; ∇ is the vector gradient operator, χ and ψ represent the velocity potential and stream function respectively, here is a unit vector in the vertical direction.

[0129] In this embodiment, in step S03, the original wind and the divergent wind and the curl wind are projected to the vertical section direction of the coastline respectively to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and based on the normal original velocity, a wind flux data set that meets the conditions in the closed area of ​​the coastline is obtained, specifically including:

[0130] S031: Projecting the original wind and the divergent wind and the curl wind respectively to the vertical section direction of the coastline to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity; specifically, the original wind is obtained by observation or simulation, and the divergent wind and the curl wind are obtained by decomposing the stream function and the velocity potential obtained in step S021 according to the Helmholtz basic law; Figure 3 As shown, is the original wind, which is the vector synthesis of the east-west wind (u) and the north-south wind (v); the original wind is projected to the vertical section direction to obtain the normal original velocity , projected to the coastline direction is the tangential original velocity Similarly, the divergent wind and the curl wind are processed similarly to obtain the normal divergent velocity and the normal curl velocity ;

[0131] S032: Based on the wind flux formula, the daily wind flux data at the height of 50m-200m above the ground in the closed area of ​​the coastline are calculated respectively; wherein the daily wind flux data includes the wind flux at each moment of the day and the next day; the wind flux formula is expressed as follows:

[0132]

[0133]

[0134] in, represents the wind flux at the tth moment on the mth coastline at height z; represents the wind flux at the tth moment at height z; Represents the normal original velocity at the z height above the ground The value at the xth interval point on the m-segment coastline; z 50m-200m; n represents the number of interval points on each coastline; m represents any coastline in the closed area of ​​the coastline. Figure 4 As shown, it includes AB, BC, CD, DE, and AE segments;

[0135] S033: Conditionally screen the daily wind flux data at a height of 50m-200m above the ground to obtain a wind flux data set that meets the conditions in the closed area of ​​the coastline, including:

[0136] Since the altitude resolution is set to 50m, the following two filter conditions are set:

[0137] Sea breeze condition: If the wind flux in the daily data of wind flux at 50m, 100m, 150m, and 200m above the ground has a negative value within a day, and the wind flux in the daily data of wind flux at 50m above the ground has a positive value after sunrise, then the screening condition is met;

[0138] Land wind conditions: If the wind flux in the daily data of wind flux at 50m, 100m, 150m, and 200m above the ground has a positive value before sunset on the second day, and the wind flux in the daily data of wind flux at 50m above the ground has a negative value after sunset on the current day and before sunrise on the next day, then the screening conditions are met;

[0139] The wind fluxes that meet the screening conditions are used to form a wind flux dataset that meets the conditions in the closed area of ​​the coastline.

[0140] In this embodiment, in step S04, the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set are combined to perform preliminary identification of the sea and land breeze event to obtain a preliminary identification result, wherein the preliminary identification result includes: the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of the sea and land breeze event, and specifically includes the following steps:

[0141] Type identification:

[0142] Sea breeze event: If both the normal original velocity and the normal divergence velocity are positive, it is judged as a similar sea breeze event; on this basis, if a similar sea breeze event ends within one day and the start time is after sunrise and before sunset, it is identified as a sea breeze event;

[0143] Land breeze event: If both the normal original velocity and the normal divergence velocity are negative, it is judged as a land breeze event. On this basis, if a land breeze event ends within one day and the start time is after sunset and before sunrise on the next day, it is identified as a land breeze event.

[0144] Start and end time ( , ):

[0145] When the normal original velocity and the normal divergence velocity When both are positive / negative values, it is recorded as the start time of the sea breeze / land breeze event. ;

[0146] When the normal original velocity Or normal divergence velocity When the original positive / negative value changes, it is recorded as the end time of the sea breeze / land breeze event. ;

[0147] Duration ( ):

[0148] Based on the start and end time of the sea breeze / land breeze event, the duration of the sea breeze / land breeze event is obtained, and the formula is as follows:

[0149]

[0150] Average intensity ( ):

[0151] The average value of the normal original velocity at a height of 50m above the ground during the sea breeze / land breeze event is taken as the average intensity of the sea breeze / land breeze event. The formula is as follows:

[0152]

[0153] in, represents the normal original velocity at the height z=50m above the ground at time t; in this embodiment, the preset height is 50m;

[0154] Maximum strength ( ):

[0155] The maximum value of the normal original velocity at a height of 50m above the ground during the sea breeze / land breeze event is taken as the maximum intensity of the sea breeze / land breeze event;

[0156]

[0157] in, It indicates the time when the maximum value of the normal original velocity at a height of 50m occurs during the sea breeze / land breeze event;

[0158] Average background wind intensity ( ):

[0159] The average value of the normal curl velocity at 50m above the ground during the sea breeze / land breeze event is taken as the average background wind intensity of the sea breeze / land breeze event. The formula is as follows:

[0160]

[0161] in, It represents the normal curl velocity at the height z=50m above the ground at time t;

[0162] Strongest moment;

[0163] The moment when the maximum value of the normal original velocity at a height of 50 m above the ground occurs during the sea breeze / land breeze event is taken as the strongest moment of the sea breeze / land breeze event.

[0164] In this embodiment, in step S05, based on the average vertical profile variable field and the preliminary identification result, the sea and land breeze events are accurately identified to obtain accurate quantitative results, which include: preliminary identification results, height of the sea and land breeze events, circulation approximate boundary, penetration distance, average per second delivery, specifically including:

[0165] Based on the average vertical profile variable field and the preliminary identification results, sea breeze and land breeze events with clear boundaries are extracted, and the height, circulation approximate boundary, penetration distance, and average sea breeze (land breeze) transport per second of all sea breeze and land breeze events with clear boundaries are calculated, as follows:

[0166] Sea and land breeze height ( ):

[0167] Based on the average vertical profile variable field, the height above the coastline where the normal original velocity in the average vertical profile first turns is the height of the sea breeze / land breeze event. ;

[0168] Approximate circulation boundary:

[0169] Based on the average vertical profile variable field, the integral of the normal original velocity with height in the average vertical profile is When it is equal to 0, it is the approximate boundary of the circulation; among them, the integral of the normal original velocity with the height z in the average vertical section is The formula is as follows:

[0170] =

[0171] in, represents the normal original velocity;

[0172] Penetration distance (D S , D L ):

[0173] Based on the integration of the normal raw velocity with height in the average vertical profile The distance between the point on the sea / land equals 0 and the coastline, and the penetration distance D of the sea breeze / land breeze event is obtained. S / D L ;

[0174] Average delivery volume per second ( ):

[0175] In the average vertical profile, the average sea breeze / land breeze transport per second is calculated based on the height of the sea breeze / land breeze event, as follows:

[0176]

[0177] in, is the average delivery volume per second, when the above formula is When , it is the average sea breeze transport per second. When the above formula is When , it is the average land wind transport per second; is the height of the sea breeze event; is the height of the land wind event.

[0178] As shown in Figure 5 (a) and Figure 5 (b), they are schematic diagrams of the average vertical profiles of sea breeze events and land breeze events with clear boundaries, respectively. In the figure, the center line is the coastline, the left side is the land, and the right side is the sea surface. The solid line outline represents the boundary of the sea and land breeze events.

[0179] Embodiment 2:

[0180] The embodiment of the present invention provides a sea and land wind identification system for the Bohai Sea Rim region, comprising:

[0181] The average vertical profile variable field acquisition module is used to acquire the coastline data of a certain section of the Bohai Sea Rim area, and obtain the average vertical profile variable field of the coastline according to the coastline data;

[0182] Decomposition module, used to decompose the flow field in the Bohai Rim into divergent wind and curl wind based on the stream function and velocity potential of the underlying surface in the Bohai Rim;

[0183] A wind flux data set acquisition module is used to project the original wind and the divergent wind and the curl wind respectively to the vertical section direction of the coastline to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and based on the normal original velocity, obtain a wind flux data set that meets the conditions in the closed area of ​​the coastline;

[0184] A preliminary identification module is used to combine the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, wherein the preliminary identification results include: the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of the sea and land breeze event;

[0185] The precise quantitative module is used to accurately identify the sea and land breeze events based on the average vertical profile variable field and the preliminary identification results, and obtain precise quantitative results. The precise quantitative results include: preliminary identification results, the height of the sea and land breeze events, the approximate boundary of the circulation, the penetration distance, and the average transport volume per second.

[0186] Embodiment 3:

[0187] In this embodiment, based on the sea and land breeze identification method for the Bohai Sea Rim region proposed in Example 1, a severe pollution event in Tianjin was compared with a non-severe pollution event to study the quantitative comparative analysis of the role of sea breeze in the diffusion of pollutants;

[0188] According to the hourly pollutant concentration data of the stations from the National Urban Air Quality Real-time Publishing Platform (cnemc.cn), the pollution days and pollutant concentration data of the severe pollution events and non-severe pollution events in Tianjin area were obtained;

[0189] Based on step S03 in Example 1, the normal original velocity on the pollution day of the severe pollution event and the non-severe pollution event is obtained. and the normal divergence velocity ;

[0190] Using step S04 and step S05 in Example 1, a preliminary analysis is performed on the severe pollution incident and the non-severe pollution incident, respectively, as follows:

[0191] According to the pollutant concentration data (O3) in Tianjin area and the normal original velocity during the pollution day and the normal divergence velocity , respectively plotting the hourly distribution of severe pollution events and non-severe pollution events at a height of 50m above the ground and As well as the pollutant concentration line graph, as shown in Figures 6(a) and 6(b); in Figure 6(a), the sunrise and sunset times of the pollution day based on the severe pollution event, and the normal original velocity and the normal divergence velocity It can be judged that sea breeze event 1 occurred on that day; it can be seen in the figure that in sea breeze event 1, with the occurrence of sea breeze, the concentration of O3 pollutants gradually increased; until the sea breeze ended, the pollutant concentration reached the highest, and a severe pollution event occurred; in Figure 6 (b), based on the sunrise and sunset time of the pollution day of the non-severe pollution event, and the normal original velocity and the normal divergence velocity It can be judged that sea breeze event 2 occurred on that day; it can be seen in the figure that in sea breeze event 2, non-pollution events also showed an increase in concentration as the sea breeze developed, but because the 8-hour average O3 concentration reached 156μg / m 3 , and no serious pollution incident occurred.

[0192] In the preliminary analysis of severe pollution events and non-severe pollution events, the preliminary identification steps of sea and land breeze events proposed in the present invention can be used, combined with pollutant concentration data, to better judge the impact of sea and land breeze on the Tianjin area;

[0193] Based on the preliminary analysis of the above-mentioned severe pollution incidents and non-severe pollution incidents, the precise identification steps proposed by the present invention are used to accurately analyze severe pollution incidents and non-severe pollution incidents, as follows:

[0194] Based on step S01 in Example 1, the average vertical profile of the heavy pollution event and the non-pollution event is obtained, and the height, circulation approximate boundary, and penetration distance of the sea and land breeze events in the heavy pollution event and the non-pollution event are obtained by step S05; as shown in Figure 7 (a), the height of the sea breeze event 1 of the heavy pollution event reaches 650m, and the inland penetration distance reaches 94km; in contrast, as shown in Figure 7 (b), the average height of the sea breeze event 2 of the non-pollution event is only 1 / 3 of that of the sea breeze event 1, and the inland penetration distance is less than 1 / 2. Whether in terms of height or inland penetration distance, the scale of the sea breeze circulation of the heavy pollution event is greater than that of the non-pollution event in both horizontal and vertical directions.

[0195] In summary, based on the sea and land breeze identification method proposed in the present invention, the refined structural characteristic information of the sea and land breeze is provided. The longer the penetration distance of the sea breeze event with a clear boundary, the more likely it is that the pollutants will be transported and accumulated inland. This method can be well applied to the quantitative analysis of a severe pollution event in Tianjin.

[0196] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A method for identifying sea and land winds in the Bohai Sea Rim region, characterized in that: include: Acquire coastline data of a certain section of the Bohai Sea Rim area, and obtain an average vertical profile variable field of the coastline based on the coastline data; Based on the stream function and velocity potential of the underlying surface in the Bohai Rim area, the flow field in the Bohai Rim area is decomposed into divergent wind and curl wind. The original wind and the divergent wind and the curl wind are projected to the vertical section direction of the coastline respectively to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and based on the normal original velocity, a wind flux data set that meets the conditions in the closed area of ​​the coastline is obtained; Combine the normal original velocity, normal divergence velocity, normal curl velocity and qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, which include: type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of sea and land breeze events; Based on the average vertical profile variable field and the preliminary identification results, accurate identification of sea and land breeze events is performed to obtain accurate quantitative results, which include: preliminary identification results, height of sea and land breeze events, approximate boundaries of circulation, penetration distance, and average transport volume per second.

2. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 1, characterized in that: The method of acquiring coastline data of a certain section of the Bohai Sea Rim region and obtaining an average vertical profile variable field of the coastline according to the coastline data includes: Obtain the coastline data of a certain section of the Bohai Sea area, and confirm the scope of the coastline study area based on the coastline data, wherein the coastline data includes the function of the coastline; Based on the function of the coastline and the scope of the coastline study area, determine the latitude and longitude coordinates of several vertical sections within the scope of the coastline study area and the starting point and end point of each vertical section, wherein the starting point and end point of the vertical section are both the intersection points of the vertical section and the boundary of the coastline study area; Obtain the horizontal and vertical wind speeds at the starting and ending points of each vertical section; Based on the latitude and longitude coordinates, horizontal wind speed and vertical wind speed of the starting point and end point of each vertical section, each vertical section is interpolated to obtain the variable field of each vertical section; The spatial average of each vertical profile variable field is performed to obtain the average vertical profile variable field of the coastline.

3. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 2, characterized in that: The formula for spatially averaging the variable fields of each vertical profile is expressed as follows: ， in, represents the i-th variable field obtained by interpolation; n represents the number of vertical profiles on the coastline; represents the average vertical profile variable field.

4. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 2, characterized in that: Based on the stream function and velocity potential of the underlying surface in the Bohai Rim region, the flow field in the Bohai Rim region is decomposed into divergent wind and curl wind, including: According to the velocity in the flow field around Bohai Sea, the vorticity and divergence in the Bohai Sea area are determined; Based on the automatic search method, determine the search information and the location information of the discretized grid points where the inner and outer boundaries of the Bohai Rim region are located, wherein the search information includes the number of areas where data are missing; Based on the harmonic-cosine spectrum expansion perturbation method, the internal component is determined according to the position information, the vorticity and the divergence, wherein the internal component includes an average component and a perturbation component, the average component includes a stream function average component and a velocity potential average component, and the perturbation component includes a stream function perturbation component and a velocity potential perturbation component; Determine the stream function and velocity potential of the underlying surface in the Bohai Sea region according to the component corresponding to the data missing area, the internal component and the harmonic component, wherein the component corresponding to the data missing area is determined by using the Green's function method, the harmonic component is determined by using the harmonic-cosine spectrum expansion method, the component corresponding to the data missing area includes the stream function component and the velocity potential component corresponding to the data missing area, and the harmonic component includes the stream function harmonic component and the velocity potential harmonic component; Based on Helmholtz's law, the flow field in the Bohai Sea area is decomposed into divergent wind and curl wind according to the stream function and velocity potential of the underlying surface in the Bohai Sea area.

5. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 3, characterized in that: Based on the normal original velocity, a wind flux dataset that meets the conditions in the closed area of ​​the coastline is obtained, including: Based on the wind flux formula, the daily wind flux data at the height of 50m-200m above the ground in the closed area of ​​the coastline are calculated respectively; wherein the daily wind flux data includes the wind flux at each moment of the day and the next day; the wind flux formula is expressed as follows: ， ， in, represents the wind flux at the tth moment on the mth coastline at height z; represents the wind flux at the tth moment at height z; Represents the normal original velocity at the z height above the ground The value at the xth interval point on the m-segment coastline; z 50m-200m; n represents the number of interval points on each section of the coastline, which is equivalent to the number of vertical sections on the coastline; m represents any section of the coastline in the closed area of ​​the coastline; The daily wind flux data at a height of 50m-200m above the ground are conditionally screened to obtain the wind flux data set that meets the conditions in the closed area of ​​the coastline.

6. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 5, characterized in that: The wind flux daily data at a height of 50m-200m above the ground are subjected to conditional screening to obtain a wind flux data set that meets the conditions in the closed area of ​​the coastline, including: If the wind flux in the daily data of wind flux at a height of 50m-200m above the ground has a negative value within one day, and the wind flux in the daily data of wind flux at a height of 50m above the ground has a positive value after sunrise, then the screening condition is met; If the wind flux in the daily data of wind flux at a height of 50m-200m above the ground has a positive value before sunset on the second day, and the wind flux in the daily data of wind flux at a height of 50m above the ground has a negative value after sunset on the current day and before sunrise on the second day, then the screening condition is met; The wind fluxes that meet the screening conditions are used to form a wind flux dataset that meets the conditions in the closed area of ​​the coastline.

7. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 6, characterized in that: The method combines the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, wherein the preliminary identification step includes: Type Identification: If both the normal original velocity and the normal divergence velocity are positive, it is judged to be a similar sea breeze event; If a similar sea breeze event ends within one day and the start time is after sunrise and before sunset, it is identified as a sea breeze event; If both the normal original velocity and the normal divergence velocity are negative, it is judged to be a land wind event; If a similar land wind event ends within one day and the start time is after sunset and before sunrise on the next day, it is identified as a land wind event; Start and end time: When both the normal original velocity and the normal divergence velocity are positive / negative, it is recorded as the start time of the sea breeze / land breeze event; When the normal original velocity or normal divergence velocity changes from the original positive / negative value, it is recorded as the end time of the sea breeze / land breeze event; Duration: Based on the start and end time of the sea breeze / land breeze event, the duration of the sea breeze / land breeze event is obtained; Average Strength: The average value of the normal original velocity at a preset height above the ground during the sea breeze / land breeze event is taken as the average intensity of the sea breeze / land breeze event; Maximum Strength: The maximum value of the normal original velocity at a preset height above the ground during the sea breeze / land breeze event is taken as the maximum intensity of the sea breeze / land breeze event; Average background wind strength: The average value of the normal curl velocity at a preset height above the ground during the sea breeze / land breeze event is taken as the average background wind intensity of the sea breeze / land breeze event; Strongest moment: The moment when the maximum value of the normal original velocity at a preset height above the ground during the sea breeze / land breeze event occurs is taken as the strongest moment of the sea breeze / land breeze event.

8. The method for identifying sea and land winds in the Bohai Sea Rim region according to claim 7, characterized in that: Based on the average vertical profile variable field and the preliminary identification results, accurate identification of sea and land wind events is performed to obtain accurate quantitative results, wherein the accurate quantitative results include: Sea and land breeze height: On the basis of the average vertical profile variable field, the height above the coastline where the normal original velocity in the average vertical profile first turns is the height of the sea breeze / land breeze event; Approximate circulation boundary: Based on the average vertical profile variable field, the integral of the normal original velocity with height in the average vertical profile is When it is equal to 0, it is the approximate boundary of the circulation; among them, the integral of the normal original velocity with the height z in the average vertical section is The formula is as follows: = ， in, represents the normal original velocity; Penetration distance: Based on the integration of the normal raw velocity with height in the average vertical profile , where the sea surface / land surface is equal to 0, and the distance from the coastline, the penetration distance of the sea breeze / land breeze event is obtained; Average delivery volume per second: In the average vertical profile, the average sea breeze / land breeze transport per second is calculated based on the height of the sea breeze / land breeze event, as follows: ， in, is the average delivery volume per second, when the above formula is When , it is the average sea breeze transport per second. When the above formula is When , it is the average land wind transport per second; is the height of the sea breeze event; is the height of the land wind event.

9. A sea and land wind identification system for the Bohai Sea Rim region, characterized in that: include: The average vertical profile variable field acquisition module is used to acquire the coastline data of a certain section of the Bohai Sea Rim area, and obtain the average vertical profile variable field of the coastline according to the coastline data; Decomposition module, used to decompose the flow field in the Bohai Rim into divergent wind and curl wind based on the stream function and velocity potential of the underlying surface in the Bohai Rim; A wind flux data set acquisition module is used to project the original wind and the divergent wind and the curl wind respectively to the vertical section direction of the coastline to obtain the normal original velocity, the normal divergent velocity and the normal curl velocity, and based on the normal original velocity, obtain a wind flux data set that meets the conditions in the closed area of ​​the coastline; A preliminary identification module is used to combine the normal original velocity, the normal divergence velocity, the normal curl velocity and the qualified wind flux data set to perform preliminary identification of sea and land breeze events to obtain preliminary identification results, wherein the preliminary identification results include: the type, start and end time, duration, average intensity, maximum intensity, average background wind intensity and strongest moment of the sea and land breeze event; The precise quantitative module is used to accurately identify the sea and land breeze events based on the average vertical profile variable field and the preliminary identification results, and obtain precise quantitative results. The precise quantitative results include: preliminary identification results, the height of the sea and land breeze events, the approximate boundary of the circulation, the penetration distance, and the average transport volume per second.

Images