CN116449461A - Automatic identifying method for south branch groove - Google Patents

Automatic identifying method for south branch groove Download PDF

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CN116449461A
CN116449461A CN202310708181.2A CN202310708181A CN116449461A CN 116449461 A CN116449461 A CN 116449461A CN 202310708181 A CN202310708181 A CN 202310708181A CN 116449461 A CN116449461 A CN 116449461A
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south
derivative
point
contour line
contour
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CN116449461B (en
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胡文东
张永凯
舒红平
郝艳琼
张高三
肖天贵
陈艳
罗飞
甘建红
张莹
熊太松
邵建
王超
陶静怡
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Chengdu University of Information Technology
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Abstract

The invention provides an automatic identification method of a south branch groove, which comprises the following steps: reading a high vacancy potential height field and analyzing the contour line; filtering the contour line of the potential height field; constructing each contour line data point sequence; calculating to obtain a first derivative and a second derivative of each contour line; identifying the minimum value point of each contour line as a groove line node; detecting whether a slot line node exists in a south branch slot active area; detecting whether the north contour line of the designated area is closed or not, and determining a south branch groove starting node; sequentially connecting the minimum value points of all the contour lines from north to south to form south branch groove nodes; judging whether the distance between the north and south nodes is smaller than a preset threshold value, if so, no south branch slot exists; otherwise, curve fitting is carried out on the south branch groove to determine the position of the south branch groove. According to the invention, the south branch groove line is automatically identified through derivation, so that the efficiency and normalization of weather forecast are improved, the weather situation is accurately judged in time, and the service capacity and automation level of the weather forecast are improved.

Description

Automatic identifying method for south branch groove
Technical Field
The invention belongs to the technical field of weather, and particularly relates to an automatic identification method of a south branch groove.
Background
The south branch groove is an important weather system affecting the south area of China and often appears in regions of Yunnan, sichuan, guizhou, guangxi and the like of China. In the winter half a year, when the south branch groove cloud system moves to the areas of the Yangtze river basin such as the Guangxi, guangdong, hunan and the like of China along with the east of the west wind air current, precipitation can be brought to the areas, and the system is one of important precipitation weather systems in the south of China. The method has the advantages of accurately analyzing the south branch groove, judging the position, the strength and other characteristics of the south branch groove, and having important significance for weather forecast, disaster prevention and reduction. The south branch groove has long moving time and wide influence area. However, the weather service has been limited to manual analysis, the manual analysis process is complex, the efficiency is low, the error judgment is easy to occur according to the individuals, and the judgment of the forecasting personnel on the weather situation is influenced. By automatically identifying the south branch groove, the efficiency and normalization of weather forecast are improved, misjudgment of artificial factors is greatly reduced, and correct judgment is timely made on weather conditions.
Disclosure of Invention
Aiming at the defects in the prior art, the automatic identifying method for the south branch groove provided by the invention automatically identifies the south branch groove line through derivation, improves the efficiency and accuracy of weather forecast, greatly reduces misjudgment, makes correct judgment on weather situation in time, and promotes the improvement of the business capability and automation level of weather forecast.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the scheme provides an automatic identification method of a south branch groove, which comprises the following steps:
s1, reading a high vacancy potential height field, and analyzing an contour line;
s2, filtering the contour line of the potential height field;
s3, extracting data points of all contour lines of the potential height field after filtering treatment from north to south and from west to east one by one, and constructing all contour line data point sequences;
s4, calculating to obtain a first derivative and a second derivative of each contour line according to coordinates of each contour line data point;
s5, identifying the minimum value point of each contour line by utilizing the first derivative and the second derivative, and taking the minimum value point of each contour line as a groove line node;
s6, detecting whether a slot line node exists in a south-branch slot active area, if so, entering a step S7; otherwise, no south branch groove exists, and the process is ended;
s7, detecting whether the north contour line of the designated area is closed, if so, taking the geometric center point of the closed contour line as a south branch slot starting node; otherwise, taking the minimum value point of the north contour line as the south branch groove starting node;
s8, sequentially connecting the minimum value points of all the contour lines from north to south to form south support groove nodes;
s9, judging whether the distance between the north and south nodes is smaller than a preset threshold value, and if yes, no south branch groove exists; otherwise, curve fitting is carried out on the south branch groove according to each node of the south branch groove, the position of the south branch groove is determined, and the identification of the south branch groove is completed.
The beneficial effects of the invention are as follows: the invention converts the problem of finding the south-branch groove line into the minimum value of the finding function, and according to the property of the derivative and the method for finding the minimum value of the function, the south-branch groove line is automatically identified by derivation, so that the efficiency and the accuracy of weather forecast are improved, misjudgment is greatly reduced, correct judgment is made on weather situation in time, and the service capability and the automation level of the weather forecast are improved.
Further, the S2 specifically is: the following is used for carrying out filtering treatment on the contour line of the potential height field:
wherein ,representing the filtered potential height field, +.>Representing the intensity coefficient of the filter, < >>Coordinates representing contour data points, ++>Representing natural constants.
The beneficial effects of the above-mentioned further scheme are: according to the invention, the two-dimensional Gaussian filter is selected for processing, so that the contour line noise elimination becomes smoother, and the method is suitable for weather system analysis.
Still further, the expression of the first derivative is as follows:
wherein ,representing the first derivative, +.>Representation->First derivative of> and />Respectively shown inyAndxincrement of direction, ++> and />Respectively representyCoordinate +.>And->Location of the place (s)/(s)> and />Respectively representxCoordinate in->And->Location of the place (s)/(s)>Position sequence number representing point on contour, +.>Representation ofThe contour line is at->The position of the partyThe position of the direction;
the expression of the second derivative is as follows:
wherein ,representing the second derivative>Representation->Second derivative of> and />Respectively indicate-> and />First derivative of> and />Respectively expressed in +.> and />The function value of the position, and />Respectively indicate the contour line at +.> and />The first derivative of the two points.
The beneficial effects of the above-mentioned further scheme are: according to the invention, the south branch groove line is automatically identified through derivation, so that the efficiency and normalization of weather forecast are improved, misjudgment is greatly reduced, correct judgment is timely made on weather situation, and the service capability and automation level of weather forecast are improved.
Still further, the determining conditions of the minimum value points of the contour lines are as follows:
wherein ,representation->Absolute value of>Representation->First derivative of>Representation->Second derivative of>Representation->First derivative of> and />Respectively representyCoordinate +.>And->Location of the place (s)/(s)>Representing the sequence number of the location of the point on the contour.
The beneficial effects of the above-mentioned further scheme are: the method determines whether a specific point in the contour line data point sequence is a local minimum value point or not through specific values of first-order and second-order derivatives. Any one of the two conditions is satisfied, namely the local minimum point.
Still further, the judging condition for detecting whether the north-most contour line of the designated area is closed is as follows:
wherein ,first point +.>And (3) the last point->Is used for the distance of (a),representing a certain potentialFirst point of the altitude contour, +.>Representing the last point of a potential height contour.
The beneficial effects of the above-mentioned further scheme are: in this application, when S < = 20km, the start and end points of the contour line can be considered to coincide, and the contour line is closed.
Still further, the step S9 specifically includes:
determining the distance between the north and south nodesI.e. if the length is less than 100km, if so, there is no south branch slot; otherwise, curve fitting is carried out on the south branch groove according to each node of the south branch groove, and the position of the south branch groove is determined according to the fitting result, so that the identification of the south branch groove is completed.
Still further, the southwest and northest node distancesThe expression of (2) is as follows:
wherein , and />Respectively representing the north-most nodesxAndycoordinates of-> and />Respectively representing the south-most nodesxAndycoordinates.
The beneficial effects of the above-mentioned further scheme are: when the distance between the north and south nodes is large enough, the existence of the south branch slot is judged, and then smoothing processing is carried out and the position of the south branch slot is calculated.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a function of the present embodimentAnd its first order derivative function->Schematic diagram.
FIG. 3 is a schematic diagram of the second derivative and its properties in the present embodiment.
Fig. 4 is a schematic diagram of a slot line in the western wind belt in this embodiment.
FIG. 5 is an exemplary diagram of a 500hPa potential high field contour in this embodiment.
Fig. 6 is a diagram showing an example of a 500hPa potential high field contour after filtering in this embodiment.
Fig. 7 is a schematic diagram of minimum point screening in the present embodiment.
FIG. 8 is a diagram of the geometric center points of the minimum points and the closed contour in the present embodiment.
Fig. 9 is a schematic diagram of a first slot line in the present embodiment.
Fig. 10 is a schematic diagram of a second slot line in the present embodiment.
Fig. 11 is a schematic diagram of a third slot line in the present embodiment.
Fig. 12 is a schematic diagram of a fourth slot line in the present embodiment.
Detailed Description
The following description of specific embodiments of the invention is provided to facilitate understanding of the invention by those skilled in the art. It should be understood that the invention is not limited to the specific embodiments, but is capable of numerous modifications within the spirit and scope of the invention as hereinafter defined and defined by the appended claims as will be apparent to those skilled in the art all falling within the true spirit and scope of the invention as hereinafter claimed.
Examples
In this embodiment, the derivative, also called derivative, is in the calculusImportant basic concepts. As shown in FIG. 2 (in FIG. 2, O represents the origin, A and A 0 Representing a functionAny two points on the curve, the coordinates of which are +.>And，/>is a function->First derivative of> and />Respectively shown inyAndxincrement of direction), set a function->At the point->Defined in a certain neighborhood when the argument +.>At->There is an increment->，(/>) Also in this neighborhood, the corresponding function gets the increment +.>The method comprises the steps of carrying out a first treatment on the surface of the If->And->Ratio of whenThe time limit exists, then the function->At the point->Where can be derived and this limit is called a function +.>At the pointThe derivative at->Or->The mathematical notation can be expressed as:
（1）
wherein ,representation->First derivative of>Representing derivative operations,/->Representing the difference +.>Limitation when approaching 0, < >> and />Respectively shown inyAndxincrement of direction, ++>Indicated at the spot->Function of->，/>Representation dot->A function value at the location.
Function ofAt the point->Is>Geometric meaning of (2): representing the point of the function curveThe slope of the tangent at this point, i.e. the geometric meaning of the first derivative, is the tangent slope of the function curve at this point. The properties of the first derivative are shown as: when the function monotonically increases, the first derivative is greater than 0; when the function monotonically decreases, the first derivative is less than 0. As shown in fig. 2, when the first derivative at point a is greater than 0, the function monotonically increases; when the first derivative is less than 0, the function monotonically decreases.
In this embodiment, the second derivative is a derivative of the first derivative. If it isFunction ofIs>At the point->The recipe of the recipe is called->Is a function of>At the point->The second derivative of the location, denoted +.>. The mathematical notation can be expressed as:
（2）
wherein ,representation->Second derivative of>Indicating when delta +>Approaching the limit of 0 a,representation->First derivative of>To be at the pointx 0 First derivative at.
Function ofAt the point->Second derivative of>Geometric meaning of (2): the change rate of the tangential slope of the curve can be reflected, and the concave-convex characteristic of the function image is reflected from the graph. The method is characterized in that when the second derivative of the function at a certain point is larger than 0, the function curve is concave at the certain point; when the second derivative of the function at a point is less than 0, the function curve is convex at that point. As shown in fig. 3, at B 3 Left side of dot, function->The second derivative of (2) is smaller than 0, and the function image is a concave curve; at B 3 Right side of dot, function->The second derivative of (2) is larger than 0, and the function image is a convex curve; at B 3 Point, function->The second derivative of (2) is equal to 0, and the primary function image is not concave and not convex.
In this embodiment, the extremum of the function can be found by combining the properties of the first derivative and the second derivative. When a functionWhen the first derivative is equal to 0 and the second derivative is greater than 0 at a point, the point is the minimum point of the function; when the function->When the first derivative is equal to 0 at a certain point and the second derivative is less than 0, the point is the function maximum point.As shown in fig. 3, at B 1 A point, the first derivative of the original function is equal to 0, and the second derivative is smaller than 0, the point being the maximum point of the original function; at B 2 The first derivative of the original function is equal to 0, and the second derivative is greater than 0, which is the minimum point of the original function.
In this embodiment, the temperature of the air is successively reduced from the ground to the high temperature, and if the air block rises, the water vapor in the air is saturated due to the temperature reduction, and is condensed into water drops and ice crystals to form clouds and precipitation. In the northern hemisphere, the south is close to the ocean and the air temperature is high, so that the atmosphere contains more water vapor and is moist, and the atmosphere is warm and moist air; the water vapor in the north is little and cold, and is dry and cold air. The pressure of air is also decreasing from the ground to the high air. At sea level, the air pressure is generally about 1000hPa, and the air pressure can be reduced to about 500hPa when the air pressure reaches 5500 meters. This altitude 500hPa weather map is often analyzed aloft during meteorological operations. At 500hPa has been generally far from the ground surface, the friction is negligible and small. The atmosphere is in quasi-rotational motion, i.e. the wind blows along the contour of the potential altitude field. So at high altitudes, the potential altitude field contours reflect the wind conditions.
In this embodiment, the western wind flow is prevailing at the high altitude in the northern hemisphere, and is called western wind zone. Fluctuations in the flow of west wind are often generated and are represented on the weather map as southerly extending grooves and northward projecting ridges, as shown in fig. 4, three data of 5480, 5520 and 5560 in fig. 4 are potential height fields, and the corresponding lines of northwest dry cold air lines are 500hPa potential height contours, which represent the flow. The corresponding lines of the west wind grooves are groove lines, the front (east side) is southwest warm-humid air flow, and the rear (west side) is northwest dry-cold air flow. The grooves in the Western wind zone are called Western wind grooves, and as can be seen in FIG. 4, the nodes of the Western wind groove line are the southwest points in the neighborhood of the potential altitude field contour, i.e., the minimum points on the contour.
In this embodiment, the western wind trough is a long and narrow region extending from a low value position in the western wind zone on the high altitude isobologram, and is also called a slot line because it is shown as a line in the weather map. The front of the trough, i.e. the eastern side of the trough line, is southwest warm and humid air flow, and the rear of the trough, i.e. the western side of the trough, is northwest dry and cool air flow. Because of different densities of cold and warm air, warm and humid air in front of the tank rises due to lighter weight, and after the air flow rises, the air is colder due to high altitude, water vapor in the air condenses, and overcast and rainy weather is generated in the area; the dry and cold air density behind the groove is large and sinks, and the original water drop ice crystal in the area is heated to be gaseous due to the fact that the lower layer is warmer, and the weather of the area is clear. Therefore, the characteristics of the position, the strength and the like of the groove line have indication significance for weather analysis and forecast.
In this embodiment, when the west wind passes through the Qinghai-Tibet plateau, the west wind is affected by the huge topographic power of the Qinghai-Tibet plateau, and the west wind band is divided into two branches of north and south, wherein the west wind groove appearing on the south branch west wind flow is called a south branch groove. The geographic position is between 10 DEG and 30 DEG in north latitude and 75 DEG and 95 DEG in east longitude. The south branch groove generally disappears from the beginning of the 10 th month to the next 6 th month. The south branch groove can cause a large-scale cooling and precipitation weather in southwest areas under the cooperation of cold air, and can influence the downstream south China and China to Jianghuai areas. The position of the south branch groove, the water vapor transmission, the low-altitude rapid flow, the cold air strength and other conditions are different, so that the weather difference and the rainfall intensity are determined.
In this embodiment, the node of the west wind slot is the minimum point of the contour of the potential altitude field, so that the problem of finding the south branch slot can be converted into the minimum of finding the contour function. According to the nature of the derivative and the method for searching the minimum value of the function, as shown in fig. 1, the invention provides an automatic identifying method of a south branch slot, which comprises the following implementation steps:
s1, reading a high vacancy potential height field, and analyzing an contour line;
in this embodiment, the bit-potential-height field lattice point data is read, and the bit-potential-height field and the contour thereof are obtained according to the bit-potential-height field lattice point data H, as shown in fig. 5.
In this embodiment, there is a lot of noise in fig. 5, which is represented by contours that are not smooth. At high altitude, the friction force mainly generated by the lower pad surface is small and can be ignored, the atmosphere only receives the air pressure gradient force and the ground deflection force in the horizontal direction, and the two forces are balanced, and the motion state is quasi-ground wind deflection. In this case not only the high altitude wind speed is high, but also the wind direction is parallel to the contour of the potential altitude field. The observation fact shows that on the weather scale, the high air flow is quite smooth, so that the contour line of the potential height field is quite smooth, the high-frequency fluctuation everywhere in fig. 5 is noise and has no weather meaning, and the high-frequency fluctuation must be eliminated when weather analysis is performed, otherwise, a large amount of meaningless interference occurs.
S2, filtering the contour line of the potential height field;
in this embodiment, the gaussian filtering is a linear smoothing filtering, and mainly replaces the data of a certain point with the average value of the data around the certain point. The purpose is to remove sharp changes in the image and to smooth the image. Since the data of the potential height field is two-dimensional, two-dimensional gaussian filtering is selected for processing. The formula is:
（3）
wherein ,representing the filtered potential height field, +.>Representing the intensity coefficient of the filter, < >>Representing data points, ++>Representing natural constant->The larger the value, the smoother the processed image.
In this embodiment, the two-dimensional potential height field is filtered by a gaussian filtering method, so that the contour line is smoother, and noise having no weather significance is eliminated, as shown in fig. 6. In the process of eliminating noise, in the formula (3)The larger the value, the smoother the processed image, but the smaller the area of the closed system, so that on one hand, noise interference is effectively eliminated, and on the other hand, the original state is kept. Through experiments, get ∈ ->The effect is best =5.
S3, extracting data points of all contour lines of the potential height field after filtering treatment from north to south and from west to east one by one, and constructing all contour line data point sequences;
in this embodiment, each contour line is sequentially extracted from north to south for the contour line of the potential height fieldCoordinate data of->Thereby constructing a sequence of data points for each contour, for example:
for example: the first contour line at the north endIs defined as: (65.00,49.37), (65.25,49.39), (65.5,49.43), (65.75,49.48), (65.81,49.5), (66.0,49.58), (66.25,49.70), (66.33,49.75), (66.5,49.95), (66.54,50.00).... Second contour line->Is defined as: (112.25,50.00), (112.29,49.75), (112.36,49.50), (112.46,49.25), (112.50,49.17), (112.59,49.00), (112.75,48.76), (112.76,48.75), (112.95,48.50), (113.00,48.44), (113.17,48.25), (113.25,48.17), (113.42,48.00), (113.50,47.93), (113.71,47.75), (113.75,47.72), (114.00,47.54), (114.06,47.50), (114.25,47.39), (114.50,47.27), (114.56,47.25), (114.75,47.19), (115.00,47.15)....
S4, calculating to obtain a first derivative and a second derivative of each contour line according to coordinates of each contour line data point;
in this embodiment, for each contour line L, the coordinate data of each point is substituted into the formulas (1) and (2), and the first-order derivative and the second-order derivative of each point of each contour line are obtained.
In this embodiment, since all the obtained discrete data of each contour line is not an analytical function, discretization should be performed when the first derivative is obtained by applying the formula (1) and the second derivative is obtained by the formula (2).
After discretizing the formula (1), the derivative calculation is carried out by using two adjacent points, the limit is not required, the corresponding difference is required, and then the corresponding difference is calculated for a certain contour lineGo up to some point->The first derivative difference of (2) is calculated as:
（4）
wherein ,representing the first derivative, +.>Representation->First derivative of> and />Respectively shown inyAndxincrement of direction, ++> and />Respectively representyCoordinate +.>And->Location of the place (s)/(s)> and />Respectively representxCoordinate in->And->Location of the place (s)/(s)>Position sequence number representing point on contour, +.>Indicating that the contour line is at +.>A location at which to locate.
For the first point to the last point of the contour lineFrom the formula (4) a certain contour line +.>Go up to some point->Is>. Co-calculable +.>First derivative value of individual points, first derivative curve thus formed>Wherein each point is +.>。
In this embodiment, the second derivative can be obtained from the first derivative by performing discretization calculation of the difference using the formula (2). For a certain pointThe second derivative difference calculation formula of (2) is:
（5）
wherein ,representing the second derivative>Representation->Second derivative of> and />Respectively indicate-> and />First derivative of> and />Respectively expressed in +.> and />The function value of the position, and />Respectively indicate the contour line at +.> and />The first derivative of the two points.
Thereby obtaining a certain contour lineWherein each point is +.>. As with the first derivative calculation, a derivative value can be calculated using a point and its subsequent points, so that the resulting second derivative sequences together amount to the original sequence length +.>。
S5, identifying the minimum value point of each contour line by utilizing the first derivative and the second derivative, and taking the minimum value point of each contour line as a groove line node;
in this embodiment, a function has the following features at the minimum point: that is, the first derivative of the point is 0 and the second derivative is greater than 0, and the identification is performed according to the condition, as shown in fig. 7, the solid line is the original function, and the two dotted lines are the first derivative and the second derivative, respectively, in the figure, the first derivative is zero and the second derivative is less than zero. This is the maximum point. This point is excluded. The first derivative is zero and the second derivative is greater than zero. This point is the minimum point.
Since the computation is performed using the difference for discrete points rather than the derivative of a continuous function, the computation result is not exactly equal to a data point of 0, but rather data very close to 0 is obtained. In this case, by a comparative test, it is determined that one of the following 2 conditions is satisfied, that is, it can be determined as the minimum point:
（6）
（7）
wherein ,representation->Absolute value of>Representation->First derivative of>Representation->Second derivative of>Representation->First derivative of> and />Respectively representyCoordinate +.>And->Location of the place (s)/(s)>Representing the sequence number of the location of the point on the contour.
In this embodiment, the mathematical meaning of the formula (6) is the same as that of the conventional formula, and only the case that the numerical value is difficult to satisfy the strict 0 under the differential condition is considered. (7) The formula shows that if the first derivative of the previous point is negative, i.e. the curve is in a falling phase, the value is decreasing; the first derivative of a point is then turned to a positive value, i.e. the value starts to increase, and the curve between the two points must have a turning process from decreasing to increasing, and must have a minimum value, so the point at the rear is taken as the minimum value point.
S6, detecting whether a slot line node exists in a south-branch slot active area, if so, entering a step S7; otherwise, no south branch groove exists, and the process is ended;
in this embodiment, according to the active area of the south branch slot, detection is performed by taking the north latitude of 10 ° to 30 ° and the east longitude of 75 ° to 95 ° as the identification area, if no minimum point of the contour line exists, no south branch slot exists, and exit is ended.
S7, detecting whether the north contour line of the designated area is closed, if so, taking the geometric center point of the closed contour line as a south branch slot starting node; otherwise, taking the minimum value point of the north contour line as the south branch groove starting node;
in this embodiment, in addition to the linear contour in the contour image of the potential height field, there is also a closed contour in the low-voltage or high-voltage center. The slot line generally extends from a lowest value point within the closed contour, so for such contours, the slot line start node can be found by looking for its geometric center point.
In this embodiment, if a minimum point is detected in the above region, it is detected whether the region has a closed contour. According to the weather principle, if a closed contour is present, the starting position of the groove should be at the minimum point within the closed contour. The analysis finds that the minimum point is highly coincident with the geometric center point of the closed contour, so the geometric center point is used as the starting point of the south-branch slot in the region.
If the contour is closed, its first point coincides with the last point. However, in the actual contour analysis process, since the self-contained error is calculated, the set closed contour judgment conditions are as follows, taking the error into consideration through analysis:
（8）
wherein ,representing a first point representing a contour of a potential height>And (3) the last point->Distance of->First point representing a potential height contour line, +.>Representing the last point of the contour of the potential height of the strip.
If S<=20 km, i.e. the first point of a contour of potential heightAnd (3) the last point->If the distance of the line is less than or equal to 20km, the contour line is considered to be closed.
For a closed contour line, comparing the coordinates of each point on the contour line to obtain 4 endpoints of the southwest, the northst, the easiest and the westest on the contour line, obtaining the coordinates of the geometric center of the contour line by averaging, and taking the geometric center point as the initial node of the south branch groove.
The minimum point on the value line is then used as the second node of the south-branch slot. As shown in fig. 8, fig. 8 is a schematic diagram of a minimum point (dot) and a closed contour geometric center point (cross).
In this embodiment, if equation (8) is not satisfied, the contour is not closed, and the minimum point in the identified area on the contour is taken as the starting node of the south-branch slot.
S8, sequentially connecting the minimum value points of all the contour lines from north to south to form south support groove nodes;
in this embodiment, each contour line is analyzed from north to south one by one, and if a minimum value point is detected in the identification area, the method continues to the node sequence of the south branch slot until all the analyses are completed.
S9, judging whether the distance between the north and south most nodes is smaller than a preset threshold value, if yes, no south supporting slot exists, otherwise, performing curve fitting on the south supporting slot according to each node of the south supporting slot, determining the position of the south supporting slot, and completing the identification of the south supporting slot, wherein the method specifically comprises the following steps:
determining the distance between the north and south nodesI.e. if the length is less than 100km, if so, there is no south branch slot; otherwise, curve fitting is carried out on the south branch groove according to each node of the south branch groove, and the position of the south branch groove is determined according to the fitting result, so that the identification of the south branch groove is completed.
The distance between the north and south nodesThe expression of (2) is as follows:
wherein , and />Respectively representing the north-most nodesxAndycoordinates of-> and />Respectively representing the south-most nodesxAndycoordinates.
In this embodiment, the south-branch node representation length is calculated according to equation (8). The south branch groove is a weather scale system, and the geometrical scale of the weather scale is in the order of 1000 km. If S <100km, the scale is too small to be considered as a south branch slot. In this case, there is no south slot, and the exit is ended.
And if the condition is not satisfied, carrying out slot line fitting. Weather theory suggests that the score line is a relatively smooth curve. After the nodes of the slotline are obtained, the nodes are connected into a round curve through Bessel function and output as the identified southbound slotline result, see FIGS. 9-12.
According to the invention, the south branch groove line is automatically identified through derivation, so that the efficiency and normalization of weather forecast are improved, misjudgment is greatly reduced, correct judgment is timely made on weather situation, and the service capability and automation level of weather forecast are improved.

Claims (7)

1. The automatic identifying method for the south branch groove is characterized by comprising the following steps of:
s1, reading a high vacancy potential height field, and analyzing an contour line;
s2, filtering the contour line of the potential height field;
s3, extracting data points of all contour lines of the potential height field after filtering treatment from north to south and from west to east one by one, and constructing all contour line data point sequences;
s4, calculating to obtain a first derivative and a second derivative of each contour line according to coordinates of each contour line data point;
s5, identifying the minimum value point of each contour line by utilizing the first derivative and the second derivative, and taking the minimum value point of each contour line as a groove line node;
s6, detecting whether a slot line node exists in a south-branch slot active area, if so, entering a step S7; otherwise, no south branch groove exists, and the process is ended;
s7, detecting whether the north contour line of the designated area is closed, if so, taking the geometric center point of the closed contour line as a south branch slot starting node; otherwise, taking the minimum value point of the north contour line as the south branch groove starting node;
s8, sequentially connecting the minimum value points of all the contour lines from north to south to form south support groove nodes;
s9, judging whether the distance between the north and south nodes is smaller than a preset threshold value, and if yes, no south branch groove exists; otherwise, curve fitting is carried out on the south branch groove according to each node of the south branch groove, the position of the south branch groove is determined, and the identification of the south branch groove is completed.
2. The automatic identifying method of a south rest slot according to claim 1, wherein the step S2 is specifically: the following is used for carrying out filtering treatment on the contour line of the potential height field:
wherein ,representing the filtered potential height field, +.>Representing the intensity coefficient of the filter, < >>Coordinates representing contour data points, ++>Representing natural constants.
3. The automatic identification method of a south-branch slot according to claim 1, wherein the expression of the first derivative is as follows:
wherein ,representing the first derivative, +.>Representation->First derivative of> and />Respectively shown inyAndxincrement of direction, ++> and />Respectively representyCoordinate +.>And->Location of the place (s)/(s)> and />Respectively representxOn the coordinatesIn the first placeAnd->Location of the place (s)/(s)>Position sequence number representing point on contour, +.>Indicating that the contour line is at +.>The position of the partyThe position of the direction;
the expression of the second derivative is as follows:
wherein ,representing the second derivative>Representation->Second derivative of> and />Respectively represent and />First derivative of> and />Respectively expressed in +.> and />Function value of the place->Andrespectively indicate the contour line at +.> and />The first derivative of the two points.
4. The automatic south-branch gutter identification method according to claim 1, wherein the determination condition of each contour minimum point is as follows:
wherein ,representation->Absolute value of>Representation->First derivative of>Representation->Second derivative of>Representation ofFirst derivative of> and />Respectively representyCoordinate +.>And->At the contour pointyDirection position(s) (I)>Representing the sequence number of the location of the point on the contour.
5. The automatic identifying method of a south rest slot according to claim 1, wherein the determining condition for detecting whether the north contour line of the designated area is closed is:
wherein ,first point +.>And (3) the last point->Distance of->First point representing a potential height contour line, +.>Representing the last point of the contour of the potential height of the strip.
6. The automatic identifying method of a south rest slot according to claim 1, wherein the step S9 is specifically:
determining the distance between the north and south nodesI.e. if the length is less than 100km, if so, there is no south branch slot; otherwise, curve fitting is carried out on the south branch groove according to each node of the south branch groove, and the position of the south branch groove is determined according to the fitting result, so that the identification of the south branch groove is completed.
7. The automatic identification method of a south-most slot of claim 6, wherein the south-most and north-most node distancesThe expression of (2) is as follows:
wherein , and />Respectively representing the north-most nodesxAndycoordinates of-> and />Respectively representing the south-most nodesxAndycoordinates.
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