A method for calculating frontal slope during sandstorm weather

Abstract

The present invention provides a method for calculating the front slope in a sandstorm weather process, belonging to the field of meteorological technology. The present invention takes a point on the front, a point in the warm zone and a point in the cold and warm air before and after the front as analysis points; respectively calculates the horizontal pressure gradient difference on both sides of the front, the relative humidity of the air in the warm zone of the front, the actual water vapor pressure value of the air in the warm zone before the front, the density of the air in the warm zone before the front, the density of the clean dry cold air in the cold zone behind the front, and the air density in the cold zone behind the front; according to the density of the air in the cold zone behind the front and the density of the air in the warm zone before the front and the density difference of the air in the cold zone behind the front and the air in the warm zone before the front per unit volume, and according to the horizontal pressure gradient difference on both sides of the front, the front slope of the analysis point is obtained. The present invention solves the problem that the front slope cannot be correctly described in the sandstorm process analysis in the existing meteorological business by analyzing the front slope through the Margulis front slope calculation method.

Description

Technical Field

[0001] The invention belongs to the field of meteorological technology, and in particular relates to a method for calculating the front slope during sandstorm weather. Background Art

[0002] A large area of ​​air with relatively uniform horizontal distribution of meteorological elements (such as temperature and humidity) is called an air mass. In the same air mass, meteorological elements are roughly the same in different places, and weather phenomena are basically similar. Meteorological elements in the boundary area of ​​different air masses change significantly, and the gradient increases. The weather map shows that the contour lines of various elements are relatively dense. This narrow transition zone between air masses is called a front. The front on the ground is located in front of the cold high pressure, such as Figure 1 As shown, Figure 1 In the figure, the solid lines are isobars, the thick solid lines are fronts, G represents the high pressure center formed by cold air, and D represents the low pressure center formed by warm air. Figure 2 As shown, Figure 2 In the chart, 850hPa and 700hPa are high-altitude isobaric surfaces. From the ground to the high altitude, the front can generally be simply regarded as a plane, called the front.

[0003] On one side of the front is a cold air mass, and on the other side is a warm air mass. The cold air mass sinks due to its high density and high air pressure, and is a high-pressure area. On the other side of the front, the warm air mass has a high temperature and rises due to its low air density, and is a low-pressure area. The heavier cold air mass extends below the warm air mass in a wedge shape, and lifts the lighter warm air mass to the top of the cold air mass. Therefore, the interface between the cold and warm air masses is tilted, with the cold air below and the warm air above. Because the cold air has a high density and is heavier, and the warm air has a low density, the cold air expands toward the warm air, and pushes the warm air forward under the action of atmospheric circulation, that is, the cold air moves toward the warm air.

[0004] Because of the intersection of cold and warm air near the front, in my country's mid- and high-latitude regions, only near the front will important disastrous weather occur. In weather forecasting, frontal analysis plays a very important role, and the correct analysis of its intensity is related to the success or failure of meteorological disaster forecasting. So far, there is no frontal slope calculation method suitable for sandstorm weather processes. The frontal slope is an important indicator to characterize the intensity of the front. According to the characteristics of sandstorm weather processes, the research and development of a suitable frontal slope calculation method is of great significance for studying the characteristics of sandstorm weather, forecasting and warning, and ensuring public safety. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for calculating the frontal slope during sandstorm weather, which solves the problem that the sandstorm weather process analysis in the existing meteorological business still uses the Margulis frontal slope calculation method to analyze the frontal slope, which has obvious deficiencies and cannot correctly describe the front during the sandstorm process. The present invention realizes the analysis of the frontal slope during the sandstorm weather process, can better reflect the actual slope of the front during the sandstorm weather process, and provide more accurate data for the analysis and forecast of the sandstorm weather process.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] This scheme provides a method for calculating the front slope during sandstorm weather, including the following steps:

[0008] S1. Reading sea level pressure grid point data, and obtaining the sea level pressure field and the front position according to the sea level pressure grid point data;

[0009] S2. Take a point Q on the front as the analysis point, and the position with the largest pressure gradient adjacent to it, and take a point N in the warm area and a point L in the cold area in the cold and warm air before and after the front;

[0010] S3. Read the temperature T at point N N , dew point T dN And the sea level pressure value P N , read the temperature T at point L L and sea level pressure P L And the dust particle density value ρd is obtained by substituting the PM10 concentration at that time in the air quality monitoring;

[0011] S4, according to the distance Δx between point Q and points N and L L , Δx N , and the sea level pressure value P N and P L , calculate the horizontal pressure gradient difference on both sides of the front;

[0012] S5. Determine the temperature T at point N N Is it less than or equal to 0°C? If so, the relative humidity U of the air in the warm zone of the front is calculated according to the parameters when freezing occurs, and the process goes to step S6; otherwise, the relative humidity U of the air in the warm zone before the front is calculated according to the parameters when not freezing occurs, and the process goes to step S6;

[0013] S6. Calculate the saturated water vapor pressure value e at point N in the warm area before the front s , and according to the relative humidity U and actual water vapor pressure e of the air in the warm area before the front a Substitute the saturated water vapor pressure value e sCalculate the actual water vapor pressure value e of the air at point N in the warm area before the front a ;

[0014] S7, according to the actual water vapor pressure value of the air at point N in the warm area before the front a 、T at point N N and sea level pressure P N , the density of the air in the warm zone before the front is calculated using the moist air state equation N ;

[0015] S8, according to the temperature T at point L L and sea level pressure P L , the density ρ0 of the clean dry cold air in the cold zone behind the front is calculated using the dry air state equation;

[0016] S9, take the unit volume of dry cold air behind the front, and according to the density ρ0 of clean dry cold air in the cold area behind the front and the density value of dust particles ρ d , calculate the air density ρ in the cold area behind the front L ;

[0017] S10, according to the air density ρ in the cold zone behind the front L and the density of the warm air in front of the front ρ N , calculate the density difference between the air in the cold area behind the front and the air in the warm area in front of the front per unit volume, and calculate the front slope at point Q based on the horizontal pressure gradient difference on both sides of the front, thus completing the calculation of the front slope during sandstorm weather.

[0018] The beneficial effect of the present invention is that the present invention provides a method for calculating the front slope during sandstorm weather, the method comprising: taking a point Q on the front, a point N in the warm zone, and a point L in the cold zone as analysis points on the front and in the cold and warm air before and after the front; respectively calculating the horizontal pressure gradient difference on both sides of the front, the relative humidity U of the air in the warm zone of the front, and the actual water vapor pressure value e of the air at point N in the warm zone before the front; a , the density of the warm air in front of the front ρ N , the density of the air in the cold zone behind the front ρ0, the density of the air in the cold zone behind the front ρ L ; According to the air density ρ in the cold zone behind the front L and the density of the warm air in front of the front ρ N, calculate the density difference between the air in the cold area behind the front and the air in the warm area in front of the front per unit volume, and calculate the front slope at point Q according to the horizontal pressure gradient difference on both sides of the front. The present invention solves the problem that the front slope is still analyzed by the Margulis front slope calculation method in the analysis of sandstorm weather processes in existing meteorological services, which has obvious deficiencies and cannot correctly describe the front in the sandstorm process. The present invention realizes the analysis of the front slope in the sandstorm weather process, can better reflect the real slope of the front in the sandstorm weather process, and provide more accurate data for the analysis and forecast of the sandstorm weather process.

[0019] Furthermore, the expression of the horizontal pressure gradient difference on both sides of the front in step S4 is as follows:

[0020]

[0021]

[0022] Among them, P L represents the sea level pressure at point L, P N Indicates the sea level pressure value at point N, P Q represents the sea level pressure at point Q, Δx L represents the distance between point Q and point L, Δx N represents the distance between point Q and point N, Indicates the sea level pressure P at point L L The rate of change along the x direction, Indicates the sea level pressure P at point N N The rate of change along the x direction, where the x direction is the direction from the cold front to the cold center.

[0023] The beneficial effect of the above further solution is that the present invention obtains the horizontal pressure gradient difference on both sides of the front by calculation, which provides a prerequisite for the subsequent calculation of the front slope.

[0024] Furthermore, in step S5, the relative humidity U of the air in the warm zone in front of the center front is expressed as follows:

[0025]

[0026] Among them, A, B, and C represent constant parameters when ice and non-ice form. The parameters when ice form are: A=22.46, B=272.62, C=0.44, and the parameters when non-ice form are: A=17.62, B=243.12, C=0.5.

[0027] The beneficial effect of the above further scheme is that the present invention obtains the relative humidity U of the warm zone N point before the front to further calculate the actual water vapor pressure e before the front a Be prepared.

[0028] Furthermore, the saturated water vapor pressure value e at the warm zone N point in front of the center in step S6 is s The expression is as follows:

[0029]

[0030] The beneficial effect of the above further solution is that the present invention obtains the saturated water vapor pressure value e at the warm zone N in front of the front by calculating s , in order to further calculate the actual water vapor pressure e before the front a Be prepared.

[0031] Furthermore, in step S7, the density of the warm air in front of the center is N The expression is as follows:

[0032]

[0033] Among them, R d Represents the dry air specific gas constant.

[0034] The beneficial effect of the above further solution is that: the present invention obtains the air density ρ at the warm zone N in front of the front N , in preparation for calculating the density difference per unit volume between the cold air behind the front and the warm air in front of the front.

[0035] Furthermore, the density ρ0 of the clean dry cold air in the cold zone behind the front in step S8 is expressed as follows:

[0036]

[0037] Among them, R d Represents the dry air specific gas constant.

[0038] The beneficial effect of the above further scheme is that the present invention prepares for calculating the air density in the cold zone behind the front by obtaining the density ρ0 of the clean dry cold air in the cold zone behind the front.

[0039] Furthermore, in step S9, the air density of the cold zone behind the front is L The expression is as follows:

[0040] ρ L =ρ0+ρ d

[0041] The beneficial effect of the above further solution is that: the present invention obtains the air density ρ in the cold zone behind the front L , in preparation for calculating the density difference per unit volume between the cold air behind the front and the warm air in front of the front.

[0042] Furthermore, the density difference between the air in the cold area behind the front and the air in the warm area before the front per unit volume in step S10 is expressed as follows:

[0043] ρ L -ρ N =ρ0+ρ d -ρ N

[0044] The beneficial effect of the above further solution is that the present invention prepares for calculating the front slope by obtaining the density difference between the cold and warm air before and after the front.

[0045] Furthermore, the expression of the front slope at point Q in step S10 is as follows:

[0046]

[0047] Among them, tanα represents the front slope at point Q, g represents the gravitational acceleration constant, Indicates the sea level pressure P at point L L The rate of change along the x direction, Indicates the sea level pressure P at point N N The rate of change along the x direction, where the x direction is the direction from the cold front to the cold center.

[0048] The beneficial effect of the above further scheme is that the present invention provides more accurate data for the analysis and forecast of sandstorm weather processes by obtaining the front slope at point Q. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the ground front in the background technology.

[0050] Figure 2 Schematic diagram of the spatial structure of the front surface in the background technology.

[0051] Figure 3 Schematic diagram of dry and wet air at the same temperature and pressure in this embodiment.

[0052] Figure 4 1 is a comparison chart of the slope of the strong cold front in northern China (1.145°) and the slope of the sandstorm weather front (30°, 50°) in this embodiment.

[0053] Figure 5 This is a typical severe sandstorm weather process diagram in this embodiment.

[0054] Figure 6 Schematic diagram of the front slope model in this embodiment.

[0055] Figure 7 The figure is a flow chart of the method of the present invention.

[0056] Figure 8 Schematic diagram of the sea level pressure field in this embodiment.

[0057] Fig. 9 This is a schematic diagram of the ground situation at 20:00 on March 14 in this embodiment. DETAILED DESCRIPTION

[0058] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0059] Example

[0060] In this embodiment, the degree of inclination of the front is called the front slope, which is a key and important indicator for characterizing the strength of the front. When the physical properties of the air masses on both sides of the front are not much different, there is no front and the slope is 0. The greater the difference in density between the two sides of the front, the greater the front slope, indicating that the front is stronger.

[0061] The slope can be expressed by the angle between the front and the ground plane and its tangent function. In meteorology, the commonly used method for calculating the slope of the Margulies front is:

[0062]

[0063] Among them, α is the angle between the front and the horizontal plane, is the geostrophic parameter, which is related to latitude It is related to the angular velocity of the earth's rotation Ω, g is the acceleration of gravity, ΔT is the temperature difference between the cold and warm air masses on both sides of the front, T m is the average temperature on both sides of the front, ΔV g It is the difference between the geostrophic wind components parallel to the front line in the cold and warm air masses on both sides of the front.

[0064] In this embodiment, the geostrophic wind error is analyzed: g It is the horizontal uniform linear motion of air, which only occurs in the high-altitude free atmosphere. Its basic characteristics are: the resultant force of the external forces is zero, that is, in the horizontal direction, the Coriolis force and the horizontal pressure gradient force are balanced, there is no acceleration, and the air movement is parallel to the isobars.

[0065] In this embodiment, the geostrophic wind V gThere are huge deficiencies in its application to fronts. First, in the near-surface layer where the front is active, the complex surface produces significant friction on the atmosphere, so the friction of the near-surface atmosphere is very prominent and cannot be ignored. The atmosphere is not only affected by the pressure gradient force and the geostrophic force, but also by friction, and thus cannot meet the prerequisites for geostrophic winds. Secondly, the air pressure changes rapidly due to the combined effects of various meteorological elements. For example, after a strong cold front, the air pressure change can reach more than 7hPa in 3 hours, that is, the pressure gradient force changes very rapidly; but the geostrophic force takes a long time to gradually adjust and adapt. In this process, the pressure gradient force and the geostrophic force cannot achieve balance, resulting in the absence of geostrophic winds near the ground front. Therefore, the Margulis calculation method for calculating the frontal slope using geostrophic winds is not applicable.

[0066] In this embodiment, water vapor difference analysis shows that under natural conditions, air often contains water vapor, and the water vapor content in air with a higher temperature is much higher than that in air with a lower temperature. The Margulis formula does not consider this issue. Under the same pressure and temperature, any gas with the same volume contains the same number of molecules. The partial pressure of water vapor in the atmosphere is called the water vapor pressure e.

[0067] According to the ideal gas humid air state equation, the density of air containing water vapor is:

[0068]

[0069] Among them, ρ N is the density of warm and humid air; P N is the air pressure in the warm zone; e a is the actual water vapor pressure; R d is the dry air specific gas constant; T N is the temperature of warm and humid air. It can be seen that at the same temperature and pressure, when the water vapor pressure e in the air increases, the air density ρ decreases.

[0070] In this embodiment, from a physical point of view, when the water vapor pressure in the air is a When the total pressure is increased, if the total pressure remains unchanged, the partial pressure of dry air (P N -e a ) must decrease. When the volume and temperature are the same, the partial pressure of the gas is proportional to its molecular number, that is, when the number of water vapor molecules in the air increases, the temperature and pressure remain unchanged. To keep the number of air molecules equal in a certain volume, the number of dry air molecules must decrease. The relative molecular weight of water vapor (18.016) is smaller than the molecular weight of dry air (28.966). Therefore, at the same pressure and temperature, the density of wet air is smaller than that of dry air. The more water vapor it contains, the smaller the total molecular weight per unit volume, and the smaller the density. Figure 3 As shown, water vapor molecules are lighter than dry air molecules. Figure 3In the figure, the left picture is dry air and the right picture is humid air. In the figure, P is the air pressure, T is the absolute temperature, and V is the gas volume.

[0071] In this embodiment, regarding the analysis of dust particles, large-scale systematic sandstorms occur in the winter half of the year and are the product of a violent outbreak of strong cold air. In sandstorms, the density of cold and warm air on both sides of the front differs significantly. On the cold air side, the heavy, dense and strong invading cold air rolls up the surface dust, thus containing a large number of dust particles, whose density is higher than that of clean air. At the same time, on the warm air side, the higher temperature is conducive to the evaporation of water, and the water vapor content in the atmosphere is also higher. The Margulis front slope calculation method (1) does not take these issues into account, so it will produce a large error. According to the Margulis front slope calculation method and confirmed by weather observations, for general weather, the front slope in southern my country is about 1 / 200 to 1 / 500, corresponding to an angle of 0.283° to 0.115°; the front slope in the north is about 1 / 50 to 1 / 200, corresponding to an angle of 1.145° to 0.283°. That is, when the front of China advances 50 to 200 kilometers, or even 500 kilometers, its height extends 1 kilometer from the ground. In general, using the Margulis formula to calculate, in general weather processes, even the front slope of a strong cold front is very small, with a maximum of less than 1.2°. Figure 4 As shown, Figure 4 The X axis is the horizontal distance on the ground plane (in km), and the Z axis is the vertical height (in km). From a human perspective, in normal weather, even the strongest cold front cannot directly perceive this extremely small slope. However, during sandstorms, it can be found that the front slope is extremely large, and often an accompanying dust "wall" can be observed when the front advances. A rough visual inspection shows that the slope can often reach 30° to 50°, that is, 1 / 2 to 6 / 5. Figure 5 The photos of some typical severe sandstorm weather processes show that the front slope can reach 40°~70° or even higher, which is 40~60 times the slope of the conventional strong cold front. The difference with the calculation result of the original calculation method is extremely huge, indicating that the Margulies front slope calculation method cannot correctly describe the front in the sandstorm process, such as Figure 5 shown.

[0072] In summary, the Margulies front slope calculation method cannot accurately reflect the front slope during sandstorm weather, and it is necessary to explore a front slope calculation method suitable for sandstorm weather processes.

[0073] From the above analysis, we can know that:

[0074] First, due to the strong friction on the ground during dust storms, and the pressure gradient geostrophic force often cannot be balanced, the geostrophic wind cannot be used for calculations;

[0075] Secondly, dust storms mostly occur in the winter half of the year, when the temperature difference between cold and warm air is huge, and the effect of temperature on the water vapor content in cold and warm air of different properties needs to be considered;

[0076] Both, sand and dust are produced by the invasion of cold air, so the sand and dust content in the cold air behind the front is extremely high, while the warm air basically does not contain sand and dust, so the density difference must be considered. On this basis, a specific calculation method for the sandstorm weather front is proposed.

[0077] In this embodiment, a basic analysis is performed on the front slope calculation method. During the sandstorm weather, strong cold air invades to form a strong cold front. For the convenience of calculation, a suitable coordinate system is required, with the extension direction of the cold front as the Y axis, the direction from the cold front to the center of the cold air as the X axis, and the vertical direction from the surface upward as the Z axis, so the front diagram is obtained, as shown in the figure below: Figure 6 As shown, the angle between the front and the positive direction of the X-axis is α, which is the front slope.

[0078] The front is regarded as a zero-order discontinuity surface of density. When analyzing the calculation method of the front slope, the dynamic boundary conditions of the material surface should be met. The air pressure close to both sides of the front is equal and the air pressure change is equal, then:

[0079] P L =P N (3)

[0080] Right now:

[0081] dP L =dP N (4)

[0082] Among them, P L is the cold air pressure close to the front, P N is the pressure of warm air close to the front, dP L , dP N are the corresponding changes in air pressure.

[0083] At a fixed moment, the pressure changes of cold and warm air are expanded in space, and we can get:

[0084]

[0085] Subtract the two equations, and from equation (4) dP L =dP N We can get:

[0086]

[0087] Since the coordinate Y axis is parallel to the front, the front slope only appears in the X direction, so only the two-dimensional XZ plane is needed, and the items in the Y direction are no longer considered. The front slope is:

[0088]

[0089] According to meteorological principles, when sandstorms occur in the winter half of the year, the vertical pressure gradient force and gravity of the atmosphere are balanced. So for the denominator, according to the statics equation:

[0090]

[0091] Substituting into (5) we can get:

[0092]

[0093] Among them, the molecule and are the horizontal pressure gradients in the cold and warm air masses on both sides of the front, respectively; ρ L and ρ N are the densities of the cold and warm air masses on both sides of the front respectively; g is the gravitational acceleration constant.

[0094] In this embodiment, the factors affecting the front slope during the dust storm are analyzed.

[0095] (1) Analysis of water vapor effects

[0096] The dust storm is caused by the invasion of strong cold air, so compared with the summer process, there is strong cold air behind the front, and the temperature on this side is significantly lower. From the saturated water vapor pressure equation, we can know that the relationship between the water vapor content in the atmosphere and the temperature is:

[0097]

[0098] Among them, e s is the saturated water vapor pressure; T N is the temperature of warm air. It means that the higher the temperature, the higher the water vapor content in the atmosphere; conversely, the lower the temperature, the lower the water vapor content.

[0099] It can be seen that the cold air that causes the dust storm has very low water vapor content due to the low temperature. In addition, from the analysis of the water vapor source and transmission path, the water content of the air mass is very low in the winter half of the year. Even if there is a little water vapor, it will be continuously consumed on the world's largest continent before reaching China. Therefore, in the dust storm, it can be considered that the cold air side of the front of the dust storm basically does not contain water vapor and is dry cold air.

[0100] As for the warm air, because of its higher temperature, it is obviously rich in water vapor and is warm and humid air. Therefore, its density equation can be obtained from the humid air state equation:

[0101]

[0102] Among them, ρ N is the density of warm and humid air; P N is the sea level pressure of warm air; e a is the actual water vapor pressure; R d is the dry air specific gas constant; T N is the temperature of warm and humid air. The relative humidity calculation equation can be obtained:

[0103]

[0104] Where U is relative humidity; T dN is the dew point of air in warm area; A, B and C represent the constant parameters when freezing and non-freezing occur.

[0105] (2) Analysis of the effects of sand and dust particles

[0106] When the front passes, the huge density difference between the cold and warm air causes a strong pressure difference, forming a huge pressure gradient force. On the one hand, it pushes the front forward at high speed, and on the other hand, it causes strong winds at the front to blow up the surface dust, eventually forming sandstorm weather. Because the cold air is behind the front, the dust will fall into the cold air that invades later, so the air quality of the cold air is equal to the sum of the clean air quality and the dust particle quality.

[0107] Ignoring the dust, we only analyze the clean dry cold air. Substituting the gas state equation P = ρRT into the air pressure and temperature observed after the front, we get the density of the clean dry cold air ρ0:

[0108]

[0109] Among them, P L is the dry cold air pressure; T L It is the dry cold air temperature.

[0110] In actual dust weather, the dry and cold air behind the front is not clean, but contains a mass of M per unit volume. d Dust particles, so the cold air behind the front should be a mixture of clean, dry and cold air and dust.

[0111] It is known that the density of standard atmosphere is 1.27 kg / m 3 , and the density of dust particles is about 2000 times higher than that of air. Therefore, when considering the comprehensive density of this mixed atmosphere, the volume occupied by dust particles is too small to be ignored, so the actual density of dry cold air mixed with dust per unit volume is ρ L , is the sum of the density of clean dry cold air per unit volume and the density of the dust particles contained therein:

[0112] ρ L =ρ0+ρ d (14)

[0113] Among them, ρ L is the density of dry cold air per unit volume, ρ0 is the density of clean dry cold air per unit volume, ρ d is the density of dust particles per unit volume.

[0114] In the warm air, because it is before the front, the wind is weak, so there is no dust. Compared with the cold air behind the front, it can be considered that the dust particles do not significantly affect its mass.

[0115] Therefore, in the denominator of calculation method (7):

[0116] ρ L -ρ N =ρ0+ρ d -ρ N (15)

[0117] Therefore, the calculation method for the frontal slope in sandstorm weather is:

[0118]

[0119] Among them, the dust content per unit volume in cold air is ρ d Substitute the PM10 concentration at that time from air quality monitoring.

[0120] like Figure 7 As shown, the present invention provides a method for calculating the front slope during sandstorm weather, and the implementation method is as follows:

[0121] S1. Reading sea level pressure grid point data, and obtaining the sea level pressure field and the front position according to the sea level pressure grid point data;

[0122] In this embodiment, the sea level pressure grid point data is read according to the first type of MICAPS data, and the sea level pressure field and the front position are obtained according to the number of sea level pressure grid points, such as Figure 8 As shown, Figure 8 This is a schematic diagram of the air pressure from 70 degrees east longitude to 100 degrees east longitude and from 35 degrees north latitude to 50 degrees north latitude. Figure 8 In the figure, the solid lines are isobars, the solid lines with cold front symbols (triangles) are ground fronts, D represents the ground low pressure center, and G represents the ground high pressure center.

[0123] S2. Take a point Q on the front as the analysis point, and the position with the largest pressure gradient adjacent to it, and take a point N in the warm area and a point L in the cold area in the cold and warm air before and after the front;

[0124] In this embodiment, a point Q is taken on the front as the analysis point, and the sea level pressure is P Q, the unit is Pa; at the position where the pressure gradient is the largest adjacent to it, there is a point N in the warm area and a point L in the cold area in the cold and warm air before and after the front.

[0125] S3. Read the temperature T at point N N , dew point T dN And the sea level pressure value P N , read the temperature T at point L L and sea level pressure P L And the dust particle density value ρd is obtained by substituting the PM10 concentration at that time in the air quality monitoring;

[0126] In this embodiment, the temperature T at point N is read according to the first type of MICAPS data. N and dew point T dN , unit is ℃; sea level pressure P N , unit is hPa.

[0127] In this embodiment, the temperature T at point L is read according to the first type of MICAPS data. L , unit is ℃; Sea level pressure P L , in Pa; according to the concentration of PM10 in air monitoring at that time, the dust particle density value ρ is obtained d , unit is μg / m 3 . μg / m 3 Divide by 10 9 Convert to kg / m 3 , participate in the operation.

[0128] S4, according to the distance Δx between point Q and points N and L L , Δx N , and the sea level pressure value P N and P L , calculate the horizontal pressure gradient difference on both sides of the front;

[0129] In this embodiment, for the distance Δx L and Δx N , the latitude and longitude of the analysis point are obtained from the MICAPS Category 14 data, and the distance between two points on the sphere is calculated using the Haversine spherical distance calculation formula, in meters. The spherical distance calculation method is shown in formula (27).

[0130] The difference method is used to calculate the numerator of formula (9), that is:

[0131]

[0132] The horizontal pressure gradient difference on both sides of the front is calculated separately and The unit is Pa / m. Then:

[0133]

[0134] Among them, P L represents the sea level pressure at point L, P N Indicates the sea level pressure value at point N, P Q represents the sea level pressure at point Q, Δx L represents the distance between point Q and point L, Δx N represents the distance between point Q and point N, Indicates the sea level pressure P at point L L The rate of change along the x direction, Indicates the sea level pressure P at point N N The rate of change along the x direction, where the x direction is the direction from the cold front to the cold center.

[0135] S5. Determine the temperature T at point N N Is it less than or equal to 0°C? If so, the relative humidity U of the air in the warm zone of the front is calculated according to the parameters when freezing occurs, and the process goes to step S6; otherwise, the relative humidity U of the air in the warm zone before the front is calculated according to the parameters when not freezing occurs, and the process goes to step S6;

[0136] In this embodiment, it is determined whether the temperature at point N is less than or equal to 0°C by:

[0137] T N ≤0 (19)

[0138] If (19) is true, then according to the relative humidity calculation method, the parameters when ice is formed are: A = 22.46, B = 272.62, C = 0.44; otherwise, the parameters when no ice is formed are: A = 17.62, B ​​= 243.12, C = 0.5; Substitute the temperature T into formula (13) N 、T dN , P N Right now:

[0139]

[0140] Calculate the relative humidity U of the air in the warm area before the front.

[0141] S6. Calculate the saturated water vapor pressure value e at point N in the warm area before the front s , and according to the relative humidity U and actual water vapor pressure e of the air in the warm area before the front a Substitute the saturated water vapor pressure value e s Calculate the actual water vapor pressure value e of the air at point N in the warm area before the front a ;

[0142] In this embodiment, according to the saturated water vapor pressure calculation method of formula (10), substitute T N ,have:

[0143]

[0144] Calculate the saturated water vapor pressure value e at point N s , unit is Pa.

[0145] In this embodiment, according to formula (12), relative humidity U and actual water vapor pressure e a Substitute the saturated water vapor pressure value e s ,Right now:

[0146]

[0147] Calculate the actual water vapor pressure value e at point N a , unit is Pa.

[0148] S7, according to the actual water vapor pressure value of the air at point N in the warm area before the front a 、T at point N N and sea level pressure P N , the density of the air in the warm zone before the front is calculated using the moist air state equation N ;

[0149] In this embodiment, according to the wet air state equation (11), substitute T N , P N 、e a ,have:

[0150]

[0151] Calculate the density of the air in the warm zone before the front N , unit is kg / m 3 .

[0152] S8, according to the temperature T at point L L and sea level pressure P L , the density ρ0 of the clean dry cold air in the cold zone behind the front is calculated using the dry air state equation;

[0153] In this embodiment, according to the dry air state equation of formula (14), substitute T L , P L .have:

[0154]

[0155] The density of the air in the cold zone behind the front is calculated as ρ0, in kg / m 3 .

[0156] S9. Take the unit volume of dry cold air behind the front, and calculate the air density ρ in the cold area behind the front according to the density ρ0 of the clean dry cold air in the cold area behind the front and the density value of dust particles ρd. L ;

[0157] In this embodiment, according to formula (14), the unit volume of dry cold air behind the front is substituted into ρ0, ρ d .have:

[0158] ρ L =ρ0+ρ d (25)

[0159] The density of the air in the cold zone behind the front is calculated as follows: L , unit is kg / m 3 .

[0160] S10, according to the air density ρ in the cold zone behind the front L and the density of the warm air in front of the front ρ N , calculate the density difference between the air in the cold area behind the front and the air in the warm area in front of the front per unit volume, and calculate the front slope at point Q based on the horizontal pressure gradient difference on both sides of the front, thus completing the calculation of the front slope during sandstorm weather.

[0161] In this embodiment, according to formula (15), substitute ρ N .have:

[0162] ρ L -ρ N =ρ0+ρ d -ρ N (26)

[0163] The density difference between the cold air behind the front and the warm air in front of the front per unit volume is calculated.

[0164] According to the calculation method of the front slope during sandstorm weather in formula (16), the pressure gradient difference on both sides of the front and the air density difference on both sides of the front and the gravity acceleration constant g are substituted, and 9.81N / kg is taken.

[0165]

[0166] The front slope tanα at point Q is calculated, where tanα represents the front slope at point Q, and g represents the gravitational acceleration constant. Indicates the sea level pressure P at point L L The rate of change along the x direction, Indicates the sea level pressure P at point N N The rate of change along the x direction, where the x direction is the direction from the cold front to the cold center.

[0167] In this embodiment, the meteorological observation data involved in the present invention are stored in the MICAPS (Meteorological Information Comprehensive Analysis and Process System) format. This is my country's meteorological information comprehensive analysis and processing system, which is matched with satellite communications and meteorological databases. It is a weather forecast human-computer interaction work platform commonly used in many industries across the country. MICAPS supports multiple data formats, among which the first type is ground full-factor data. The air pressure, air temperature, dew point temperature, etc. required by the present invention are stored in this type of data; the fourth type of data is grid data, which is mainly used to analyze weather situation data such as ground pressure contours; the fourteenth type of data saves the metadata of the edited graphics, which is automatically generated when the graphics editing results are saved to determine the specific location of the front.

[0168] In this embodiment, for a sandstorm weather process on March 14, 2021, the observation data at 20:00 are selected, such as Fig. 9 As shown, Fig. 9 It is a schematic diagram of the pressure field from 70 degrees east longitude to 130 degrees east longitude and 30 degrees north latitude to 50 degrees north latitude. In the figure, the solid line is the isobar, the solid line with the cold front symbol (triangle) is the ground front, G represents the ground high pressure center, and D represents the ground low pressure center. Q1-Q5 analysis points were selected respectively, and the calculation method of the front slope of sandstorm weather was used for calculation, as shown in Table 1, Table 2 and Table 3 respectively, where Table 1 is the horizontal pressure gradient difference on both sides of the front at different analysis points, Table 2 is the density of warm and humid air in front of the front at different analysis points, and Table 3 is the density of dry and cold air behind the front at different analysis points and the front slope.

[0169] Table 1

[0170]

[0171] Table 2

[0172]

[0173] Table 3

[0174]

[0175] In this embodiment, the frontal slope tanα of each analysis point is obtained to be 1 / 58 to 1 / 9, that is, 0.975° to 6.43°. Compared with the frontal slope of the strong cold front in northern China, which is 1 / 50 to 1 / 200, it can reach 5-22 times the frontal slope in northern China. In comparison, the frontal slope calculation method can better reflect the true slope of the front during sandstorm weather, and provide more accurate data for the analysis and forecast of sandstorm weather.

[0176] The MICAPS data file format in the present invention is described below.

[0177] 1First type of data format

[0178] 1.1 File Header

[0179] The file header of the first type of data is:

[0180] diamond 1 data description (string) year month day hour total number of sites (all integers)

[0181] 1.2 Data

[0182] The first type of data is stored as follows:

[0183] Area station number (long integer) Longitude Latitude Altitude (both floating point numbers) Station level (integer) Total cloud cover Wind direction Wind speed Sea level pressure (or station pressure) 3-hour pressure change Past weather 1 Past weather 2 6-hour precipitation Low cloud shape Low cloud cover Low cloud high Dew point Visibility Current weather temperature Medium cloud shape High cloud shape sign 1 sign 2 (both integers) 24-hour temperature change 24-hour pressure change

[0184] 1.3 Other Notes

[0185] This type of data is used for standard ground mapping. When the value is missing, it is indicated by 9999. The station level indicates the zoom level of the station, that is, this station is mapped only when the graph is zoomed to this level. When the mark 1 is 1 and the mark 2 is 2, it means that there will be 24 hours of temperature and pressure changes. Otherwise, it means that there will be no 24 hours of temperature and pressure changes.

[0186] 2 The fourth type of data grid

[0187] 2.1 File Header

[0188] The file header of the fourth type of data is:

[0189] diamond 4 data description (string) year month day time time level (all integers) longitude grid interval latitude grid interval start longitude end longitude start latitude end latitude (all floating point numbers) latitude grid points number longitude grid points (all integers) contour line interval contour line start value end value smoothing coefficient bold line value (all floating point numbers)

[0190] 2.2 Data

[0191] The fourth type of data is placed in the latitude direction first and then the longitude direction (for a rectangular coordinate grid, the X direction is first and then the Y direction), and all of them are floating point numbers.

[0192] 2.3 Other Notes

[0193] This type of data is used to draw contour lines of grid data. The grid can be a latitude and longitude grid or a rectangular coordinate grid.

[0194] When using rectangular grid data: 1) Change the contour line end value to -1 (for rectangular coordinates in Lambert projection) or -2 (for rectangular coordinates in Mercator projection) or -3 (for rectangular coordinates in Northern Hemisphere projection). 2) Change the grid longitude interval and latitude interval to the longitude and latitude of the last point in the first row of the grid data. 3) Change the starting longitude and starting latitude to the longitude and latitude of the first point in the first row of the grid data. 4) Change the ending longitude and ending latitude to the longitude and latitude of the last point in the last row of the grid data.

[0195] The fourth type of data file can be used directly to fill in grid point values. The file header can specify the mapping method. The specification method is: 1) Change the bold line value to -1, indicating that contour lines are drawn and the map is filled at the same time; 2) Change it to -2 to indicate that only the map is filled without drawing contour lines.

[0196] 3. Data format of category 14

[0197] 3.1 File Header

[0198] The file header of the fourteenth category of data is:

[0199] diamond 14 data description (string) year month day time validity (all integers)

[0200] 3.2 Data

[0201] The storage method of the fourteenth category of data is:

[0202] LINES: Number of lines, line width, number of points, XY Z......, number of labels, XY Z......

[0203] LINES_SYMBOL: Number of lines, coded line width, points, NoLabel, 0

[0204] SYMBOLS: number of encoded XYZ wind direction angles or strings...

[0205] CLOSED_CONTOURS: Number of line widths Number of points XY Z......Number of labels XY Z......

[0206] STATION_SITUATION: Station number attributes......

[0207] WEATHER_REGION: Number of weather regions Weather code for the first weather region Number of points on the outer line Longitude of the first point Latitude of the first point 0.0 Longitude of the second point Latitude of the second point 0.0 ... Weather code for the second weather region Number of points on the outer line Longitude of the first point Latitude of the first point 0.0 Longitude of the second point Latitude of the second point 0.0 ...

[0208] 3.3 Other Notes

[0209] This type of data is automatically generated when saving the graphic editing results and can be used to generate the final forecast product.

[0210] LINES_SYMBOL represents weather system lines such as trough lines and cold fronts, and its codes are: 1-trough line, 2-cold front, 3-warm front, 4-stationary front, 5-occluded front, 38-frost line, 39-high temperature line.

[0211] The weather codes for weather zones are: 1-rain zone, 2-snow zone, 4-thunderstorm zone, 8-fog zone, 16-strong wind zone, 32-sandstorm zone

[0212] The weather symbol codes are: 26-light rain, 47-moderate rain, 55-heavy rain, 64-rainstorm, 25-showers, 23-light snow, 22-moderate snow, 21-heavy snow, 66-blizzard, 65-snow showers, 32-thunderstorm, 31-hail, 27-light rime, 28-freezing rain, 24-sleet, 29-light fog, 30-fog, 50-clear sky, 51-cloudy, 52-overcast, 42-tornado, 37-typhoon, 44-frost, 43-calm wind, 40-34 wind, 36-45 wind, 33-56 wind, 41-67 wind, 34-78 wind, 35-89 wind, 101-910 wind, 102-1011 wind, 103-1112 wind, 60-high center, 61-low center, 62-warm center, 63-cold center, 48-text notes.

[0213] In this embodiment, regarding the calculation method of spherical distance, if the longitude and latitude coordinates of any two points on the earth (lon1, lat1) and (lon2, lat2) are known, the distance between the two points can be calculated using the Haversine formula: convert the angles of the longitude and latitude coordinates into radians (rlon1, rlat1), (rlon2, rlat2). Use the following formula:

[0214]

[0215] Among them, S is the distance between two points on the sphere, in meters; a is the difference in latitude between the two points, i.e., a=rlat1-rlat2, in degrees; b is the difference in longitude between the two points, i.e., b=rlon1-rlon2, in degrees; r is the radius of the earth, which is 6.371×103 km。

Claims

1. A method for calculating the frontal slope during sandstorm weather, characterized in that: The following steps are involved: S1. Reading sea level pressure grid point data, and obtaining the sea level pressure field and the front position according to the sea level pressure grid point data; S2. Take a point Q on the front as the analysis point, and the position with the largest pressure gradient adjacent to it, and take a point N in the warm area and a point L in the cold area in the cold and warm air before and after the front; S3. Read the temperature T at point N N , dew point T dN And the sea level pressure value P N , read the temperature T at point L L and sea level pressure P L And the dust particle density value ρd is obtained by substituting the PM10 concentration at that time in the air quality monitoring; S4, according to the distance Δx between point Q and points N and L L , Δx N , and the sea level pressure value P N and P L , calculate the horizontal pressure gradient difference on both sides of the front; S5. Determine the temperature T at point N N Is it less than or equal to 0°C? If so, the relative humidity U of the air in the warm zone of the front is calculated according to the parameters when freezing occurs, and the process goes to step S6; otherwise, the relative humidity U of the air in the warm zone before the front is calculated according to the parameters when not freezing occurs, and the process goes to step S6; S6. Calculate the saturated water vapor pressure value e at point N in the warm area before the front s , and according to the relative humidity U and actual water vapor pressure e of the air in the warm area before the front a Substitute the saturated water vapor pressure value e s Calculate the actual water vapor pressure value e of the air at point N in the warm area before the front a ; S7, according to the actual water vapor pressure value of the air at point N in the warm area before the front a 、T at point N N and sea level pressure P N , the density of the air in the warm area before the front is calculated using the moist air state equation N ; S8, according to the temperature T at point L L and sea level pressure P L , the density ρ0 of the clean dry cold air in the cold zone behind the front is calculated using the dry air state equation; S9, take the unit volume of dry cold air behind the front, and according to the density ρ0 of clean dry cold air in the cold area behind the front and the density value of sand and dust particles ρ d , calculate the air density ρ in the cold area behind the front L ; S10, according to the air density ρ in the cold zone behind the front L and the density of the warm air in front of the front ρ N , calculate the density difference between the air in the cold area behind the front and the air in the warm area in front of the front per unit volume, and calculate the front slope at point Q based on the horizontal pressure gradient difference on both sides of the front, thus completing the calculation of the front slope during sandstorm weather.

2. The method for calculating the frontal slope during sandstorm weather according to claim 1, characterized in that: The expression of the horizontal pressure gradient difference on both sides of the front in step S4 is as follows: Among them, P L represents the sea level pressure at point L, P N Indicates the sea level pressure value at point N, P Q represents the sea level pressure at point Q, Δx L represents the distance between point Q and point L, Δx N represents the distance between point Q and point N, Indicates the sea level pressure P at point L L The rate of change along the x direction, Indicates the sea level pressure P at point N N The rate of change along the x direction, where the x direction is the direction from the cold front to the cold center.

3. The method for calculating the front slope during sandstorm weather according to claim 1, characterized in that: The relative humidity U of the air in the warm zone in front of the center front in step S5 is expressed as follows: Among them, A, B, and C represent constant parameters when ice and non-ice form. The constant parameters when ice form are: A=22.46, B=272.62, C=0.44, and the parameters when non-ice form are: A=17.62, B=243.12, C=0.

5.

4. The method for calculating the front slope during sandstorm weather according to claim 1, characterized in that: The saturated water vapor pressure value e of the warm zone N point in front of the center in step S6 s The expression is as follows: 。 5. The method for calculating the frontal slope during sandstorm weather according to claim 1, characterized in that: The density of the warm air in front of the center in step S7 is ρ N The expression is as follows: Among them, R d Represents the dry air specific gas constant.

6. The method for calculating the frontal slope during sandstorm weather according to claim 1, characterized in that: The density ρ0 of the clean dry cold air in the cold zone behind the front in step S8 is expressed as follows: Among them, R d Represents the dry air specific gas constant.

7. The method for calculating the front slope during sandstorm weather according to claim 1, characterized in that: In step S9, the air density of the cold zone behind the front is L The expression is as follows: r L =ρ0+ρ d 。 8. The method for calculating the front slope during sandstorm weather according to claim 1, characterized in that: The expression for the density difference between the air in the cold area behind the front and the air in the warm area before the front per unit volume in step S10 is as follows: r L -r N =ρ0+ρ d -r N 。 9. The method for calculating the frontal slope during sandstorm weather according to claim 1, characterized in that: The expression of the front slope of point Q in step S10 is as follows: Among them, tanα represents the front slope at point Q, g represents the gravitational acceleration constant, Indicates the sea level pressure P at point L L The rate of change along the x direction, Indicates the sea level pressure P at point N N The rate of change along the x direction, where the x direction is the direction from the cold front to the cold center.

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