Near space meteorological data measurement method based on expansion falling ball

Abstract

The invention provides a near space meteorological data measurement method based on an expansion falling ball, and relates to the technical field of data measurement, and the method comprises the steps: S1, obtaining the initial position point data of a falling ball under a station center coordinate system, and carrying out the preprocessing of the initial position point data, and obtaining the standard position point data; s2, fitting the standard position point data to obtain initial fitting position point data, and obtaining falling ball speed data based on the initial fitting position point data; s3, a vortex street period is obtained based on the falling ball speed data; s4, the vortex street period is judged, and the final fitting time length is determined; and S5, obtaining final fitting position point data, and obtaining wind speed data, wind direction data, air pressure data and temperature data. According to the invention, sideslip deviation generated by a vortex street of airflow at the rear side of a falling ball is weakened, and the quality of meteorological data is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of data measurement, and particularly to a method for measuring near-space meteorological data based on an expanding falling ball. Background Art

[0002] The expanding falling ball technology is a method for measuring near-space meteorological elements with intuitive method and low cost. According to the principle of mechanical equilibrium, the atmospheric density, wind speed, and wind direction are analyzed by resolving the spatio-temporal coordinates of the falling ball, and then the air pressure and temperature are obtained by using the ideal gas state equation.

[0003] The existing method for obtaining meteorological data by the falling ball method is to release a radiosonde balloon from a high altitude, record its spatio-temporal coordinates, analyze the atmospheric density, wind speed, and wind direction, and then obtain the air pressure and temperature by using the ideal gas state equation. However, the influence of the von Kármán vortex street phenomenon is often ignored in this method. The von Kármán vortex street phenomenon refers to the vortices alternately generated on both sides of an object when a fluid flows around a non-streamlined object. These vortices will cause the non-uniformity of the flow field around the ball, thus causing velocity measurement errors and trajectory deviations. Specifically, the lateral force generated by the von Kármán vortex street will cause the trajectory of the ball to deviate, leading to the judgment of wind speed and wind direction. The von Kármán vortex street will reduce the signal-to-noise ratio of the data and affect the reliability and accuracy of the data. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for measuring near-space meteorological data based on an expanding falling ball, which weakens the side-slip deviation generated by the von Kármán vortex street of the airflow behind the falling ball.

[0005] A method for measuring near-space meteorological data based on an expanding falling ball, comprising the following steps:

[0006] S1. Obtain the initial position point data of the falling ball in the station-centered coordinate system, and preprocess the initial position point data to obtain standard position point data;

[0007] S2. Obtain the initial fitting number of points based on the initial fitting time length and the sampling frequency; use the least squares method to fit the standard position point data to obtain the initial fitting position point data, and obtain the falling ball velocity data based on the initial fitting position point data;

[0008] S3. Obtain the von Kármán vortex street period based on the falling ball velocity data:

[0009] ;

[0010] Wherein: is the diameter of the falling ball; is the initial falling ball velocity; , is the initial X-axis fitting coordinate, obtained based on the initial X-axis fitting coordinate point data; is the initial Y-axis fitting coordinate, obtained based on the initial Y-axis fitting coordinate point data; is the initial Z-axis fitting coordinate, obtained based on the initial Z-axis fitting coordinate point data; represents the derivation; is the vortex cycle; is the Reynolds number;

[0011] S4. Determine the vortex cycle and determine the final fitting time length. , then As the final fitting time length; if , then As the final fitting time length, is the initial fitting time length, n is a positive integer greater than or equal to 2;

[0012] S5. Obtain a final number of fitting points based on the final fitting time length and the sampling frequency, fit the standard position point data based on the final number of fitting points to obtain the final fitting position point data, and obtain wind speed data, wind direction data, air pressure data, and temperature data based on the final fitting position point data.

[0013] Preferably, in S1, the standard position point data includes standard X-axis coordinate point data, standard Y-axis coordinate point data and standard Z-axis coordinate point data; the origin O of the station center coordinate system is the intersection of the horizontal rotation axis and the vertical rotation axis of the observation instrument, the X-axis points to due north, the Y-axis points to due east, and the Z-axis passes through the origin and is perpendicular to the XOY plane and points to the zenith.

[0014] Preferably, in S2, the initial fitting position point data includes initial X-axis fitting coordinate point data, initial Y-axis fitting coordinate point data and initial Z-axis fitting coordinate point data, and the final fitting position point data in S5 includes final X-axis fitting coordinate point data, final Y-axis fitting coordinate point data and final Z-axis fitting coordinate point data.

[0015] Preferably, S1 includes:

[0016] S11, obtaining the initial position point data of the falling ball in the station center coordinate system and performing interpolation processing to obtain the initial standard position point data;

[0017] S12, obtaining a correction fitting time length according to the initial standard Z-axis coordinate point data, obtaining a correction fitting point number based on the correction fitting time length and the sampling frequency, and obtaining initial fitting coordinate point data after fitting;

[0018] S13. Based on the initial fitting coordinate point data, the 3σ method is used to remove abnormal values ​​in the initial fitting coordinate point data and then interpolation processing is performed to obtain standard position point data.

[0019] Preferably, the expressions for the initial fitting time length and the initial number of fitting points in S2 are as follows:

[0020] ;

[0021] ;

[0022] Wherein, is the resolution of the height where the falling ball is located, is the theoretical average falling speed of the falling ball at the height, is the initial fitting time length, is the initial number of fitting points, is the sampling frequency, means rounding up to the nearest odd number.

[0023] Preferably, in S5, obtaining wind speed data, wind direction data, air pressure data, and temperature data from the final fitting position point data includes the following steps:

[0024] S51. Obtain X-axis velocity data, X-axis acceleration data, Y-axis velocity data, Y-axis acceleration data, Z-axis velocity data, and Z-axis acceleration data from the final fitting position point data;

[0025] S52. Obtain atmospheric density data, X-axis wind speed data, and Y-axis wind speed data based on S51, and calculate the judgment coefficient;

[0026] S53. Obtain wind speed data and wind direction data based on the X-axis wind speed data and the Y-axis wind speed data;

[0027] S54. Obtain air pressure data based on the atmospheric density data, and obtain temperature data based on the air pressure data and the atmospheric density data.

[0028] Preferably, the expressions for the atmospheric density data, the X-axis wind speed data, and the Y-axis wind speed data in S52 are as follows:

[0029] ;

[0030] In the formula, is the atmospheric density data, is the X-axis wind speed data, is the Y-axis wind speed data, is the Z-axis wind speed data, , is the average radius of the earth, m is the mass of the falling ball, is the gravitational acceleration at zero altitude, is the altitude of the origin of the topocentric coordinate system, is the Z-axis acceleration, is the X-axis velocity, is the Y-axis velocity, is the Z-axis speed, is the X-axis acceleration, is the Y-axis acceleration, is the X-axis angular velocity, is the Y-axis angular velocity, is the Z-axis angular velocity, is the air resistance coefficient, is the cross-sectional area of the falling ball, is the volume of the falling ball, x is the final X-axis fitting coordinate, obtained from the final X-axis fitting coordinate point data, and y is the final Y-axis fitting coordinate, obtained from the final Y-axis fitting coordinate point data.

[0031] Preferably, the judgment coefficient in S52 has the expression:

[0032] ;

[0033] In the formula, is the judgment coefficient, z is the final Z-axis fitting coordinate, is the atmospheric density corresponding to the final Z-axis fitting coordinate;

[0034] Judge the judgment coefficient. When ≤ ≤ , return to S1. When or , execute S53, is the distance traveled by the Z-axis speed corresponding to the final Z-axis fitting coordinate in 1 s.

[0035] Preferably, the wind speed data expression in S53 is:

[0036] ;

[0037] The wind direction data expression is:

[0038] ;

[0039] In the formula, represents the wind speed data, G represents the wind direction data, is the X-axis wind speed data, is the Y-axis wind speed data.

[0040] Preferably, the barometric pressure data and temperature data expressions in S54 are respectively:

[0041] ;

[0042] ;

[0043] In the formula, is the barometric data at an altitude of ; is the barometric data at the origin of the local coordinate system; is the atmospheric density data; is the acceleration of gravity at the origin of the local coordinate system; is the altitude at the origin of the local coordinate system; is the altitude at the i-th falling ball position; is the atmospheric density data at an altitude of ; is the atmospheric density data at the origin of the local coordinate system; is the mean radius of the Earth; , is the sea-level acceleration of gravity at the location of the local origin; is the final Z-axis fitting coordinate at the i-th falling ball position; is the calibrated value of the Earth's radius at sea level at the location of the local origin; is the standard acceleration of gravity; is the temperature data at an altitude of ; is the specific gas constant for dry air.

[0044] The effects of the present invention are as follows:

[0045] Based on the method for measuring near-space meteorological data using an expanding falling ball, the present invention obtains the vortex street period, regards a data segment of one period as a whole, fits the data within one period to extract the main trend, filters out the high-frequency fluctuations caused by the vortex street, thereby improving the accuracy and reliability of data processing, reducing the influence brought by the vortex street, effectively reducing the influence of the vortex street on speed measurement and trajectory deviation, and improving the quality of meteorological data.

[0046] Based on the method for measuring near-space meteorological data using an expanding falling ball, the present invention adds data validity checking. By comparing the actual falling speed corresponding to the coordinates of the inflection point with the theoretical average falling speed, it is possible to preliminarily determine whether the sphere has burst or collapsed, thereby preliminarily obtaining the validity of the data and avoiding subsequent calculation processes caused by huge defects in the data. Further, by introducing the judgment coefficient , the final determination of whether the sphere has burst or collapsed is obtained, thereby actually obtaining the validity of the data. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a flowchart of the method for measuring near-space meteorological data using an expanding falling ball according to the present invention;

[0048] Figure 2 is a schematic diagram of the drag coefficient of the ROBIN ball. DETAILED DESCRIPTION

[0049] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0050] like Figure 1 As shown, the present invention provides a near-space meteorological data measurement method based on an expansion falling ball, which comprises:

[0051] S1. Obtain the initial position point data of the falling ball in the station center coordinate system, and preprocess the initial position point data to obtain the standard position point data. The standard position point data includes standard X-axis coordinate point data, standard Y-axis coordinate point data, and standard Z-axis coordinate point data. The origin O of the station center coordinate system is the intersection of the horizontal rotation axis and the vertical rotation axis of the observation instrument. The X axis points to the north, the Y axis points to the east, and the Z axis passes through the origin and is perpendicular to the XOY plane and points to the zenith.

[0052] Specifically, S1 includes:

[0053] S11, obtaining the initial position point data of the falling ball in the station center coordinate system and performing interpolation processing to obtain the initial standard position point data.

[0054] The initial position point data includes initial X-axis coordinate point data, initial Y-axis coordinate point data, and initial Z-axis coordinate point data.

[0055] Interpolation processing is performed on the missing data in the initial position point data to obtain interpolation data; the interpolation data includes X-axis coordinate point interpolation data, Y-axis coordinate point interpolation data and Z-axis coordinate point interpolation data.

[0056] After removing the bit error data in the interpolation data, interpolation processing is performed to obtain initial standard position point data; the initial standard position point data includes initial standard X-axis coordinate point data, initial standard Y-axis coordinate point data and initial standard Z-axis coordinate point data.

[0057] The sounding code output by the observation instrument will perform check code calculation on the sounding meteorological data bytes and output a check code field. When this field is 1, it means that a byte has changed during the transmission process and interference has occurred during the sending process, resulting in inconsistency between the actual received data and the sent data. For this set of data, the method is to eliminate it and then interpolate and fill in the points.

[0058] For example, the 9th to 24th bytes of the sounding code are the sounding data including time, longitude, latitude and altitude. The check code will accumulate these bytes and generate the check code through CRC-16. Output to the end of the sounding code. This method can further judge the validity of the data when the sounding instrument outputs data normally, but when it is interfered with in the receiving environment or during transmission.

[0059] S12. Obtain the calibration fitting time length based on the initial standard Z-axis coordinate point data, obtain the calibration fitting point number based on the calibration fitting time length and the sampling frequency, and obtain the initial fitting coordinate point data after fitting.

[0060] Based on the calibration fitting point number, fit the initial standard X-axis coordinate point data, the initial standard Y-axis coordinate point data, and the initial standard Z-axis coordinate point data to obtain the initial fitting coordinate point data, namely the initial X-axis fitting coordinate point data, the initial Y-axis fitting coordinate point data, and the initial Z-axis fitting coordinate point data.

[0061] S13. Based on the initial X-axis fitting coordinate point data, the initial Y-axis fitting coordinate point data, and the initial Z-axis fitting coordinate point data, use the 3σ method to perform interpolation after removing the outliers in the initial fitting coordinate point data to obtain the standard position point data, namely the standard X-axis coordinate point data, the standard Y-axis coordinate point data, and the standard Z-axis coordinate point data.

[0062] The expression of the 3σ method is:

[0063] ;

[0064] In the formula: is the standard deviation, n is the calibration fitting point number, is the i-th initial standard X-axis coordinate point among the n initial standard X-axis coordinate points, is the value after fitting. When <3 and >-3 = otherwise = .

[0065] Preferably, after S11, it further includes:

[0066] Obtain the coordinates of the inflection point of the falling ball and the Z-axis falling speed data based on the initial Z-axis coordinate point data. The inflection point of the falling ball is the point where the Z-axis acceleration of the falling ball is zero.

[0067] When the Z-axis coordinate corresponding to the Z-axis falling speed is greater than or equal to the coordinate of the inflection point, judge the Z-axis falling speed. When the difference between the Z-axis falling speed and the theoretical average falling speed corresponding to the Z-axis coordinate is greater than the first set threshold, discard the initial position point data and return to S11. When the difference between the Z-axis falling speed and the theoretical average falling speed corresponding to the Z-axis coordinate is less than or equal to the first set threshold, execute S12.

[0068] When the Z-axis coordinate corresponding to the falling speed of the Z-axis is less than the coordinate of the inflection point, the falling speed of the Z-axis is judged. When the difference between the falling speed of the Z-axis and the theoretical average falling speed corresponding to the Z-axis coordinate is greater than the second set threshold, the data of the initial position point is discarded and returned to S11. When the difference between the falling speed of the Z-axis and the theoretical average falling speed corresponding to the Z-axis coordinate is less than or equal to the second set threshold, S12 is executed; the first set threshold is greater than the second set threshold.

[0069] S2. Obtain the initial fitting number of points based on the initial fitting time length and the sampling frequency; use the least squares method to fit the standard position point data to obtain the initial fitting position point data, and obtain the falling ball speed data based on the initial fitting position point data.

[0070] According to the standard Z-axis coordinate point data, obtain the initial fitting time length, and obtain the initial fitting number of points based on the initial fitting time length and the sampling frequency.

[0071] Preferably, the expression of the initial fitting time length is:

[0072] ;

[0073] In the formula: is the resolution of the height where the falling ball is located, is the theoretical average falling speed of the height where the falling ball is located, is the initial fitting time length.

[0074] The expression of the initial fitting number of points is:

[0075] ;

[0076] In the formula: is the initial fitting number of points, is the sampling frequency, means rounding up to the nearest odd number.

[0077] Based on the initial fitting number of points, use the least squares method to fit the standard X-axis coordinate point data, the standard Y-axis coordinate point data, and the standard Z-axis coordinate point data to obtain the initial fitting position point data, that is, the initial X-axis fitting coordinate point data, the initial Y-axis fitting coordinate point data, and the initial Z-axis fitting coordinate point data.

[0078] Obtain the falling ball speed data based on the initial X-axis fitting coordinate point data, the initial Y-axis fitting coordinate point data, and the initial Z-axis fitting coordinate point data.

[0079] S3. Obtain the vortex street period based on the falling ball speed data. The expression is:

[0080] ;

[0081] In the formula: is the diameter of the falling ball, is the initial falling ball velocity, , is the initial X-axis fitting coordinate, obtained based on the initial X-axis fitting coordinate point data, is the initial Y-axis fitting coordinate, obtained based on the initial Y-axis fitting coordinate point data, is the initial Z-axis fitting coordinate, obtained based on the initial Z-axis fitting coordinate point data, represents taking the derivative, is the vortex street period, is the Reynolds number, when or there is no vortex street.

[0082] S4. Judge the vortex street period to determine the final fitting time length. If , then take as the final fitting time length; if , then take as the final fitting time length, is the initial fitting time length, and n is a positive integer greater than or equal to 2.

[0083] S5. Obtain the final fitting number of points based on the final fitting time length and the sampling frequency, and perform fitting on the standard position point data, namely the standard X-axis coordinate point data, the standard Y-axis coordinate point data, and the standard Z-axis coordinate point data, based on the final fitting number of points to obtain the final fitting position point data. The final fitting position point data is the final X-axis fitting coordinate point data, the final Y-axis fitting coordinate point data, and the final Z-axis fitting coordinate point data. In a specific embodiment, the fitting process is as follows:

[0084] First, obtain the final fitting number of points based on the final fitting time length and the sampling frequency. Then, perform fitting on the standard position point data, namely the standard X-axis coordinate point data, the standard Y-axis coordinate point data, and the standard Z-axis coordinate point data, based on the final fitting number of points.

[0085] During the fitting process, first perform smoothing processing on the standard X-axis coordinate point data, the standard Y-axis coordinate point data, and the standard Z-axis coordinate point data respectively to obtain the smoothed data of the standard X-axis coordinate point data, the standard Y-axis coordinate point data, and the standard Z-axis coordinate point data. Then, perform fitting on the smoothed data of the standard X-axis coordinate point data and the standard Y-axis coordinate point data based on the final fitting number of points to obtain the final X-axis fitting coordinate point data and the final Y-axis fitting coordinate point data.

[0086] When fitting the standard Z-axis coordinate point data, based on the final number of fitted points, the least squares method is used to fit the standard Z-axis coordinate point data to obtain the preliminary final Z-axis fitted coordinate point data. After obtaining the preliminary final Z-axis fitted coordinate point data, the preliminary final Z-axis fitted coordinate point data is judged. If the difference between the preliminary final Z-axis fitted coordinate point data and the smoothed data of the standard Z-axis coordinate point data is greater than the set threshold, the obtained final Z-axis fitted coordinate point data is discarded and the standard Z-axis coordinate point data is returned for moving average smoothing processing again. If the difference between the final Z-axis fitted coordinate point data and the smoothed data of the standard Z-axis coordinate point data is less than or equal to the set threshold, the final Z-axis fitted coordinate point data is used as the final Z-axis fitted coordinate point data.

[0087] After that, wind speed data, wind direction data, air pressure data, and temperature data are obtained according to the final fitted position point data. The specific steps are as follows:

[0088] S51. Obtain X-axis velocity data, X-axis acceleration data, Y-axis velocity data, Y-axis acceleration data, Z-axis velocity data, and Z-axis acceleration data according to the final fitted position point data.

[0089] X-axis velocity data and X-axis acceleration data are obtained according to the final X-axis fitted coordinate point data, Y-axis velocity data and Y-axis acceleration data are obtained based on the final Y-axis fitted coordinate point data, and Z-axis velocity data and Z-axis acceleration data are obtained based on the final Z-axis fitted coordinate point data.

[0090] Specifically, the first derivative of the final X-axis fitted coordinate point data is taken to obtain the X-axis velocity data, and the first derivative is taken after the cubic term fitting of the X-axis velocity data to obtain the X-axis acceleration data.

[0091] The first derivative of the final Y-axis fitted coordinate point data is taken to obtain the Y-axis velocity data, and the first derivative is taken after the cubic term fitting of the Y-axis velocity data to obtain the Y-axis acceleration data.

[0092] The first derivative of the final Z-axis fitted coordinate point data is taken to obtain the Z-axis velocity data, and the first derivative is taken after the cubic term fitting of the Z-axis velocity data to obtain the Z-axis acceleration data.

[0093] S52. Based on S51, obtain atmospheric density data, X-axis wind speed data, and Y-axis wind speed data, and calculate the judgment coefficient.

[0094] Atmospheric density data, X-axis wind speed data, and Y-axis wind speed data are obtained based on the X-axis velocity data, X-axis acceleration data, Y-axis velocity data, Y-axis acceleration data, Z-axis velocity data, and Z-axis acceleration data. The expression is:

[0095] ;

[0096] In the formula: is the atmospheric density data, is the X-axis wind speed data, is the Y-axis wind speed data, is the Z-axis wind speed data, , is the average radius of the Earth, m is the mass of the falling ball, is the gravitational acceleration at zero altitude, is the altitude of the origin of the station-centered coordinate system, is the Z-axis acceleration, is the X-axis velocity, is the Y-axis velocity, is the Z-axis velocity, is the X-axis acceleration, is the Y-axis acceleration, is the X-axis angular velocity, is the Y-axis angular velocity, is the Z-axis angular velocity, is the air resistance coefficient, is the cross-sectional area of the falling ball, is the volume of the falling ball, x is the final X-axis fitting coordinate, obtained from the final X-axis fitting coordinate point data, y is the final Y-axis fitting coordinate, obtained from the final Y-axis fitting coordinate point data, and the resistance coefficient is a key parameter for falling ball detection. Currently, the mainly available one is Figure 2 the resistance curve of the ROBIN ball shown in the figure. When the sphere falls into a lower altitude and the falling ball speed becomes subsonic, its resistance coefficient has a good compliance with Figure 2 the subsonic section data shown in the figure. The change of the resistance coefficient in the transonic section is relatively complex. In the low-altitude section below 2.5M, the resistance coefficient is calculated using .

[0097] Calculate the judgment coefficient based on the atmospheric density data and the final Z-axis fitting coordinate point data. The expression is:

[0098] ;

[0099] In the formula, is the judgment coefficient, z is the final Z-axis fitting coordinate, is the atmospheric density corresponding to the final Z-axis fitting coordinate;

[0100] Judge the judgment coefficient. When ≤ ≤ , return to S1. When or , execute S53, The distance traveled by the Z-axis velocity corresponding to the final Z-axis fitting coordinate in 1 s.

[0101] S53. Obtain wind speed data and wind direction data based on the X-axis wind speed data and the Y-axis wind speed data.

[0102] The expression of the wind speed data is:

[0103] 。

[0104] The expression of the wind direction data is:

[0105] 。

[0106] In the formula: represents the wind speed data, G represents the wind direction data, is the X-axis wind speed data, is the Y-axis wind speed data.

[0107] Since the X-axis of the topocentric coordinate system points due north, the Y-axis points due east, and the Z-axis passes through the origin and is perpendicular to the XOY plane and points to the zenith, the X-axis wind speed is the meridional wind speed, the Y-axis wind speed is the zonal wind speed, the Z-axis wind speed is the vertical wind speed, and W is the synthesized wind speed data.

[0108] S54. Obtain the air pressure data based on the atmospheric density data, and obtain the temperature data based on the air pressure data and the atmospheric density data. The specific expressions of the air pressure data and the temperature data are shown as follows.

[0109] The expression of the air pressure data is:

[0110] 。

[0111] In the formula: is the air pressure data at the altitude of , is the air pressure data at the origin of the topocentric coordinate system, is the atmospheric density data, is the gravitational acceleration at the origin of the topocentric coordinate system, is the altitude at the origin of the topocentric coordinate system, is the altitude of the i-th falling ball position, obtained according to the final Z-axis fitting coordinate point data, is the atmospheric density data at the altitude of , is the atmospheric density data at the origin of the topocentric coordinate system, is the average radius of the Earth, , is the sea-level gravitational acceleration at the location of the topocenter, is the final Z-axis fitting coordinate of the i-th falling ball position, obtained from the final Z-axis fitting coordinate point data, is the calibrated value of the Earth's radius at sea level where the station center is located, is the standard acceleration of gravity.

[0112] The temperature data expression is:

[0113] .

[0114] In the formula: is the temperature data at an altitude of , is the gas constant of dry air.

[0115] The above embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for measuring near-space meteorological data based on an expanding falling ball, characterized in that, It includes: S1, obtaining the initial position point data of the falling ball in the station center coordinate system, and preprocessing the initial position point data to obtain standard position point data; S2. Obtaining the initial fitting point number based on the initial fitting time length and the sampling frequency; fitting the standard position point data using the least square method to obtain the initial fitting position point data, and obtaining the falling ball velocity data based on the initial fitting position point data; S3. Obtain vortex cycle based on falling ball velocity data: ； Wherein: is the diameter of the falling ball; is the initial falling ball velocity; , is the initial X-axis fitting coordinate, obtained based on the initial X-axis fitting coordinate point data; is the initial Y-axis fitting coordinate, obtained based on the initial Y-axis fitting coordinate point data; is the initial Z-axis fitting coordinate, obtained based on the initial Z-axis fitting coordinate point data; represents taking the derivative; is the vortex street period; is the Reynolds number; S4. Judge the vortex street period to determine the final fitting time length. If , then take as the final fitting time length; if , then take as the final fitting time length, is the initial fitting time length, and n is a positive integer greater than or equal to 2; S5. Obtain a final number of fitting points based on the final fitting time length and the sampling frequency, fit the standard position point data based on the final number of fitting points to obtain the final fitting position point data, and obtain wind speed data, wind direction data, air pressure data, and temperature data based on the final fitting position point data.

2. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 1, wherein In S1, the standard position point data include standard X-axis coordinate point data, standard Y-axis coordinate point data and standard Z-axis coordinate point data; the origin O of the station center coordinate system is the intersection of the horizontal rotation axis and the vertical rotation axis of the observation instrument, the X-axis points to due north, the Y-axis points to due east, and the Z-axis passes through the origin and is perpendicular to the XOY plane and points to the zenith.

3. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 2, wherein In S2, the initial fitting position point data includes initial X-axis fitting coordinate point data, initial Y-axis fitting coordinate point data and initial Z-axis fitting coordinate point data, and the final fitting position point data in S5 includes final X-axis fitting coordinate point data, final Y-axis fitting coordinate point data and final Z-axis fitting coordinate point data.

4. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 1, wherein S1 includes: S11, obtaining the initial position point data of the falling ball in the station center coordinate system and performing interpolation processing to obtain the initial standard position point data; S12, obtaining a correction fitting time length according to the initial standard Z-axis coordinate point data, obtaining a correction fitting point number based on the correction fitting time length and the sampling frequency, and obtaining initial fitting coordinate point data after fitting; S13. Based on the initial fitting coordinate point data, the 3σ method is used to remove abnormal values ​​in the initial fitting coordinate point data and then interpolation processing is performed to obtain standard position point data.

5. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 1, characterized in that, The expressions for the initial fitting time length and the initial fitting points in S2 are: ； ； Among them, is the resolution of the height where the falling ball is located, is the theoretical average falling speed of the height where the falling ball is located, is the initial fitting time length, is the initial number of fitting points, is the sampling frequency, means rounding up to the nearest odd number.

6. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 3, wherein S5 obtains wind speed data, wind direction data, air pressure data and temperature data according to the final fitting position point data, including the following steps: S51, obtaining X-axis velocity data, X-axis acceleration data, Y-axis velocity data, Y-axis acceleration data, Z-axis velocity data and Z-axis acceleration data according to the final fitting position point data; S52, based on S51, obtain the atmospheric density data, the X-axis wind speed data and the Y-axis wind speed data, and calculate the judgment coefficient; S53, obtaining wind speed data and wind direction data based on the X-axis wind speed data and the Y-axis wind speed data; S54. Obtain air pressure data based on the air density data, and obtain temperature data based on the air pressure data and the air density data.

7. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 6, wherein The expressions of atmospheric density data, X-axis wind speed data and Y-axis wind speed data in S52 are: ； In the formula, is the atmospheric density data, is the X-axis wind speed data, is the Y-axis wind speed data, is the Z-axis wind speed data, , is the average radius of the Earth, m is the mass of the falling ball, is the gravitational acceleration at zero altitude, is the altitude of the origin of the topocentric coordinate system, is the Z-axis acceleration, is the X-axis velocity, is the Y-axis velocity, is the Z-axis velocity, is the X-axis acceleration, is the Y-axis acceleration, is the X-axis angular velocity, is the Y-axis angular velocity, is the Z-axis angular velocity, is the air resistance coefficient, is the cross-sectional area of the falling ball, is the volume of the falling ball, x is the final X-axis fitting coordinate, obtained from the final X-axis fitting coordinate point data, y is the final Y-axis fitting coordinate, obtained from the final Y-axis fitting coordinate point data.

8. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 7, wherein Judgment coefficient in S52 The expression is: ； In the formula, is the judgment coefficient, z is the final Z-axis fitting coordinate, is the atmospheric density corresponding to the final Z-axis fitting coordinate; Judge the judgment coefficient. When ≤ ≤ , return to S1. When or , execute S53. is the distance moved by the Z-axis speed corresponding to the final Z-axis fitting coordinate in 1 s.

9. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 8, characterized in that The wind speed data expression in S53 is: ； The wind direction data expression is: ； In the formula, represents wind speed data, and G represents wind direction data. is the wind speed data on the X-axis. is the wind speed data on the Y-axis.

10. The method for measuring near-space meteorological data based on an expanding falling ball according to claim 9, wherein The expressions for pressure data and temperature data in S54 are: ； ； In the formula, is the barometric data at an altitude of ; is the barometric data at the origin of the station-centered coordinate system; is the atmospheric density data; is the acceleration due to gravity at the origin of the station-centered coordinate system; is the altitude at the origin of the station-centered coordinate system; is the altitude of the i-th falling ball position; is the atmospheric density data at an altitude of ; is the atmospheric density data at the origin of the station-centered coordinate system; is the mean radius of the Earth; , is the acceleration due to gravity at sea level at the location of the station center; is the final Z-axis fitting coordinate of the i-th falling ball position; is the calibrated value of the Earth radius at sea level at the location of the station center; is the standard acceleration due to gravity; is the temperature data at an altitude of ; is the specific gas constant of dry air.

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