A Method for Evaluating Atmospheric Wind Field Errors in Meteor Radar

Abstract

This invention discloses a method for evaluating atmospheric wind field errors using meteor radar, comprising the following steps: Step 1, selecting meteor echoes from two meteor radars; Step 2, reading the number of meteors at each altitude from both meteor radars; Step 3, retrieving wind speeds from both meteor radars at each altitude; Step 4, calculating the correlation coefficients of the wind speed retrieved from both meteor radars at each altitude and analyzing their relationship with the observed number of meteors; Step 5, obtaining the relative systematic error of the wind speed retrieved from both meteor radars at each altitude; Step 6, obtaining the random error of the wind speed retrieved from both meteor radars at each altitude. The meteor radar atmospheric wind field error evaluation method disclosed in this invention can preliminarily obtain the error of the wind field retrieved by meteor radar, providing essential data error information for accurate understanding of the near-space environment and research on data assimilation and forecasting technologies.

Description

Technical Field

[0001] This invention belongs to the field of error analysis of detection data from near-space exploration equipment, and specifically relates to a method for evaluating atmospheric wind field errors of meteor radar in this field. Background Technology

[0002] Meteor radar is an important tool for detecting near-space atmosphere. It obtains the line-of-sight drift velocity of a single meteor by observing the Doppler shift of the incident wave and the reflected echo of the meteor's trail. Then, it uses the least squares method to fit the line-of-sight drift velocities of all meteors within a certain time-altitude window to obtain the average wind speed within that window. However, due to the lack of direct contact observation methods in near-space, it is impossible to assess the wind speed observation error of meteor radar, and the accuracy of wind speed measurements remains unclear. While the few existing detection methods (mid-frequency radar, lidar, FPI, etc.) can provide atmospheric wind field detection, differences in detection principles, target medium properties, and spatiotemporal variations lead to uncertainties in comparative analysis between different devices. Using two independent meteor radar systems operating simultaneously at the same site, with the same detection principle and target, allows for a preliminary determination of wind speed errors through comparative analysis. Summary of the Invention

[0003] This invention overcomes the technical problem that the wind speed error of meteor radar cannot be obtained due to the indeterminate differences in comparative analysis between different observation devices, and provides a method for evaluating atmospheric wind field error of meteor radar.

[0004] The present invention adopts the following technical solution:

[0005] An improved method for evaluating atmospheric wind field errors in meteor radar includes the following steps:

[0006] Step 1, Meteor echo selection from two meteor radars:

[0007] Read the echo zenith angle from the data of the two meteor radars, and remove the echoes with a zenith angle greater than 60 degrees from both meteor radars, keeping the echoes with a zenith angle less than 60 degrees.

[0008] Step 2: Read the number of meteors at each altitude from both meteor radars:

[0009] Import the data files from the two meteor radars using MATLAB software;

[0010] Read the values ​​of the number variable at each height level from the two files into num. met,i , j With num stmet,i,j Of the two variables, the number of meteors at each altitude of the two meteor radars are num respectively. met,i,j With numstmet,i,j , i represents each altitude, j represents the j-th observation by the two meteor radars;

[0011] Step 3: The two meteor radars retrieve wind speeds at various altitudes.

[0012] High-frequency phase difference between transmitted and received echoes Find the derivative to obtain the Doppler frequency shift f. d , λ represents the radar's operating wavelength;

[0013] Calculate the radial velocity V of each meteor. r ,

[0014] Select all meteors and their radial velocities within a time-height window with a time span of 1 hour and an altitude range of 2 km;

[0015] Using the least squares method, the radial velocities of all meteors within the selected time-height window are fitted to obtain the wind speed value V within that time-height window. When the value is minimized, V is obtained, where N is the number of meteors within the time-height window;

[0016] Step 4: Calculate the correlation coefficient of wind speed at various altitudes using the two meteor radars and analyze its relationship with the observed number of meteors:

[0017] Calculate the correlation coefficients of zonal wind speeds retrieved from two meteor radars at various altitudes.

[0018]

[0019] In the above formula, This is a one-dimensional vector composed of all observations of zonal wind speed retrieved by the 37.5MHz meteor radar at various altitudes. This is a one-dimensional vector composed of all observations of zonal wind speed retrieved by the 53.1MHz meteor radar at various altitudes.

[0020] Calculate the correlation coefficients of meridional wind speeds retrieved from the two meteor radars at various altitudes.

[0021]

[0022] In the above formula, This is a one-dimensional vector composed of all observations of meridional wind speed retrieved by the 37.5MHz meteor radar at various altitudes. This is a one-dimensional vector composed of all observations of meridional wind speed retrieved by the 53.1MHz meteor radar at various altitudes.

[0023] Analyze the number of meteors (num) at different altitudes from the two meteor radars. met,i,j ,numstmet,i,j Correlation coefficients with their inversion of latitude and longitude wind speeds at various altitudes The relationship was investigated, and it was found that the fewer meteors observed, the higher the uncorrelation between the wind fields of the two radars.

[0024] Step 5: The two meteor radars retrieve the relative systematic error of the wind speed at each altitude.

[0025] Calculate the relative systematic error δu of the zonal wind speed inversion by the two meteor radars at various altitudes. sys,i :

[0026]

[0027] Calculate the relative systematic error δv of the meridional wind speed retrieved by the two meteor radars at various altitudes. sys,i :

[0028]

[0029] Step 6: The random error of wind speed inversion at each altitude is obtained by the two meteor radars:

[0030] Calculate the average zonal wind speed obtained from the j-th observation by the two meteor radars at various altitudes.

[0031]

[0032] Calculate the standard deviation δu of the zonal wind speed retrieved from the j-th observation at each altitude using two meteor radars. ran,i,j :

[0033]

[0034] Calculate the random error δu of zonal wind speed inversion at various altitudes using two meteor radars. ran,i :

[0035]

[0036] In the above formula, m represents the total number of observations by the two meteor radars;

[0037] Calculate the average meridional wind speed obtained from the j-th observation by the two meteor radars at various altitudes.

[0038]

[0039] Calculate the standard deviation δv of the meridional wind speed retrieved from the j-th observation by the two meteor radars at various altitudes. ran,i,j :

[0040]

[0041] Calculate the random error δv of meridional wind speed inversion at various altitudes using two meteor radars. ran,i :

[0042]

[0043] The beneficial effects of this invention are:

[0044] The meteor radar atmospheric wind field error assessment method disclosed in this invention can initially obtain the error of the meteor radar inverted wind field, providing necessary data error information for accurate understanding of the near-space environment and research on data assimilation and forecasting technology. Attached Figure Description

[0045] Figure 1 This is a flowchart illustrating the method of the present invention;

[0046] Figure 2 This is a time series of meteor counts observed by two meteor radars at 37.5MHz and 53.1MHz from November 1, 2013 to December 31, 2014.

[0047] Figure 3(a) shows the zonal wind speed retrieved by the two meteor radars at various altitudes;

[0048] Figure 3(b) shows the meridional wind speed retrieved by the two meteor radars at various altitudes;

[0049] Figure 4 These are the correlation coefficients of latitudinal and meridional wind speeds retrieved by two meteor radars at various altitudes;

[0050] Figure 5 It consists of two meteor radars observing the number of meteors at various altitudes. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] Example 1: This example discloses a method for evaluating atmospheric wind field errors in meteor radar, such as... Figure 1 As shown, it includes the following steps:

[0053] Step 1, Meteor echo selection from two meteor radars:

[0054] Read the echo zenith angle from the data of the two meteor radars, and remove the echoes with a zenith angle greater than 60 degrees from both meteor radars, keeping the echoes with a zenith angle less than 60 degrees.

[0055] Step 2: Read the number of meteors at each altitude from both meteor radars:

[0056] Import data files from two meteor radars using MATLAB software; in this example, MATLAB software is used to read two files named met_wind_hour.mat and stmet_wind_hour.mat.

[0057] Read the values ​​of the number variable at each height level from the two files into num. met,i,j With num stmet,i,j Of the two variables, the number of meteors at each altitude of the two meteor radars are num respectively. met,i,j With num stmet,i,j , i represents each altitude, j represents the j-th observation by the two meteor radars;

[0058] Step 3: The two meteor radars retrieve wind speeds at various altitudes.

[0059] Read the parameters needed for wind speed inversion from both meteor radars. Using the read parameters, invert the wind speed from each of the two meteor radars:

[0060] High-frequency phase difference between transmitted and received echoes Find the derivative to obtain the Doppler frequency shift f. d , λ represents the radar's operating wavelength;

[0061] Calculate the radial velocity V of each meteor. r ,

[0062] Select all meteors and their radial velocities within a time-height window with a time span of 1 hour and an altitude range of 2 km;

[0063] Using the least squares method, the radial velocities of all meteors within the selected time-height window are fitted to obtain the wind speed value V within that time-height window. When the value is minimized, V is obtained, where N is the number of meteors within the time-height window;

[0064] Step 4: Calculate the correlation coefficient of wind speed at various altitudes using the two meteor radars and analyze its relationship with the observed number of meteors:

[0065] Calculate the correlation coefficients of zonal wind speeds retrieved from two meteor radars at various altitudes.

[0066]

[0067] In the above formula, This is a one-dimensional vector composed of all observations of zonal wind speed retrieved by the 37.5MHz meteor radar at various altitudes. This is a one-dimensional vector composed of all observations of zonal wind speed retrieved by the 53.1MHz meteor radar at various altitudes.

[0068] Calculate the correlation coefficients of meridional wind speeds retrieved from the two meteor radars at various altitudes.

[0069]

[0070] In the above formula, This is a one-dimensional vector composed of all observations of meridional wind speed retrieved by the 37.5MHz meteor radar at various altitudes. This is a one-dimensional vector composed of all observations of meridional wind speed retrieved by the 53.1MHz meteor radar at various altitudes.

[0071] Analyze the number of meteors (num) at different altitudes from the two meteor radars. met,i,j ,num stmet,i,j Correlation coefficients with their inversion of latitude and longitude wind speeds at various altitudes The relationship between the observed meteors was investigated, and it was found that the fewer meteors observed, the higher the correlation between the wind fields of the two radars; therefore, the number of observed meteors is a major factor causing errors in meteor radar systems.

[0072] Step 5: The two meteor radars retrieve the relative systematic error of the wind speed at each altitude.

[0073] Calculate the relative systematic error δu of the zonal wind speed inversion by the two meteor radars at various altitudes. sys,i :

[0074]

[0075] Calculate the relative systematic error δv of the meridional wind speed retrieved by the two meteor radars at various altitudes. sys,i :

[0076]

[0077] Step 6: The random error of wind speed inversion at each altitude is obtained by the two meteor radars:

[0078] Calculate the average zonal wind speed obtained from the j-th observation by the two meteor radars at various altitudes.

[0079]

[0080] Calculate the standard deviation δu of the zonal wind speed retrieved from the j-th observation at each altitude using two meteor radars. ran,i,j :

[0081]

[0082] Calculate the random error δu of zonal wind speed inversion at various altitudes using two meteor radars. ran,i :

[0083]

[0084] Calculate the average meridional wind speed obtained from the j-th observation by the two meteor radars at various altitudes.

[0085]

[0086] Calculate the standard deviation δv of the meridional wind speed retrieved from the j-th observation by the two meteor radars at various altitudes. ran,i,j :

[0087]

[0088] Calculate the random error δv of meridional wind speed inversion at various altitudes using two meteor radars. ran,i :

[0089]

[0090] In summary, step 1 selects meteor echoes, which are used in step 2 to read the number of meteors and step 3 to retrieve wind speed. Step 2 obtains the number of meteors observed by the two meteor radars at each altitude, which is used in step 4 to analyze the correlation coefficient between the number of meteors observed by the two meteor radars and the retrieved wind speed. Step 3 obtains the wind speed retrieved by the two meteor radars at each altitude, which is used in step 4 to calculate the correlation coefficient between the wind speed retrieved by the two meteor radars at each altitude; this is also used in step 6 to obtain the random error of the wind speed retrieved by the two meteor radars at each altitude. Step 4 obtains the correlation coefficient of the wind speed retrieved by the two meteor radars at each altitude and analyzes its relationship with the observed number of meteors, which is used in step 5 to obtain the relative systematic error of the wind speed retrieved by the two meteor radars at each altitude. Step 5 obtains the relative systematic error of the wind speed retrieved by the two meteor radars at each altitude. Step 6 obtains the random error of the wind speed retrieved by the two meteor radars at each altitude.

[0091] The following example illustrates this embodiment in detail:

[0092] Using observational data from two meteor radars at the same site over approximately one year, from November 1, 2013 to December 31, 2014, the echo zenith angles from the two meteor radars were read according to step 1 of this embodiment. Echoes with zenith angles greater than 60 degrees were removed from both meteor radars, retaining those less than 60 degrees. Step 2 was then used to read the meteor counts at various altitudes from both meteor radars. First, two files named met_wind_hour.mat and stmet_wind_hour.mat were read using MATLAB software. Then, the number variable values ​​at 21 altitude levels in each file were read, representing the meteor counts. After processing, the estimated meteor count for atmospheric wind field was approximately 100–3000 per hour. The results are shown in [see figure]. Figure 2 Following step 3, the two meteor radars retrieved wind speeds at various altitudes, and the retrieved latitudinal and meridional results are shown in Figures 3(a) and 3(b), respectively. Following step 4, the correlation coefficients of the wind speed retrievals from the two meteor radars at various altitudes were calculated, and the results are shown in... Figure 4 The relationship between the observed meteor count and the observed meteor count was analyzed, revealing that the fewer meteors observed ( Figure 5 The higher the wind field uncorrelation between the two radars, the better. Figure 4 Therefore, the number of observed meteors is a major factor causing system errors in meteor radar systems. Following step 5, the relative system errors of the latitude and longitude wind speeds retrieved from the two meteor radars at various altitudes were calculated, and the results are shown in the table below:

[0093]

[0094] Following step 6, the random errors in retrieving latitudinal and longitudinal wind speeds at various altitudes from the two meteor radars were calculated, and the results are shown in the table below:

[0095]

Claims

1. A method for evaluating atmospheric wind field error in meteor radar, characterized in that, Includes the following steps: Step 1, Meteor echo selection from two meteor radars: Read the echo zenith angle from the data of the two meteor radars, and remove echoes with zenith angles greater than 60 degrees from both meteor radars, keeping echoes with zenith angles less than 60 degrees. Step 2: Read the number of meteors at each altitude from both meteor radars: Import the data files from the two meteor radars using MATLAB software; Read the values ​​of the number variable at each height level from the two files into num. met,i,j With num stmet,i,j Among the two variables, the number of meteors at each altitude of the two meteor radars are num respectively. met,i,j With num stmet,i,j , i represents each altitude, j represents the j-th observation by the two meteor radars; Step 3: The two meteor radars retrieve wind speeds at various altitudes. High-frequency phase difference between transmitted and received echoes Find the derivative to obtain the Doppler frequency shift f. d , λ represents the radar's operating wavelength; Calculate the radial velocity V of each meteor. r , Select all meteors and their radial velocities within a time-height window with a time span of 1 hour and an altitude range of 2 km; Using the least squares method, the radial velocities of all meteors within the selected time-height window are fitted to obtain the wind speed value V within that time-height window. When the value is minimized, V is obtained, where N is the number of meteors within the time-height window; Step 4: Calculate the correlation coefficient of wind speed at various altitudes using the two meteor radars and analyze its relationship with the observed number of meteors: Calculate the correlation coefficients of zonal wind speeds retrieved from two meteor radars at various altitudes. In the above formula, This is a one-dimensional vector composed of all observations of zonal wind speed retrieved by the 37.5MHz meteor radar at various altitudes. This is a one-dimensional vector composed of all observations of zonal wind speed retrieved by the 53.1MHz meteor radar at various altitudes. Calculate the correlation coefficients of meridional wind speeds retrieved from the two meteor radars at various altitudes. In the above formula, This is a one-dimensional vector composed of all observations of meridional wind speed retrieved by the 37.5MHz meteor radar at various altitudes. This is a one-dimensional vector composed of all observations of meridional wind speed retrieved by the 53.1MHz meteor radar at various altitudes. Analyze the number of meteors (num) at different altitudes from the two meteor radars. met,i,j ,num stmet,i,j Correlation coefficients with their inversion of latitude and longitude wind speeds at various altitudes The relationship was found to be such that the fewer meteors observed, the higher the uncorrelation between the wind fields of the two radars; Step 5: The two meteor radars retrieve the relative systematic error of the wind speed at each altitude. Calculate the relative systematic error δu of the zonal wind speed inversion by the two meteor radars at various altitudes. sys,i : Calculate the relative systematic error δv of the meridional wind speed retrieved by the two meteor radars at various altitudes. sys,i : Step 6: The random error of wind speed inversion at each altitude is obtained by the two meteor radars: Calculate the average zonal wind speed obtained from the j-th observation by the two meteor radars at various altitudes. Calculate the standard deviation δu of the zonal wind speed retrieved from the j-th observation at each altitude by the two meteor radars. ran,i,j : Calculate the random error δu of zonal wind speed inversion at various altitudes using two meteor radars. ran,i : In the above formula, m represents the total number of observations by the two meteor radars; Calculate the average meridional wind speed obtained from the j-th observation by the two meteor radars at various altitudes. Calculate the standard deviation δv of the meridional wind speed retrieved from the j-th observation by the two meteor radars at various altitudes. ran,i,j : Calculate the random error δv of meridional wind speed inversion at various altitudes using two meteor radars. ran,i :

Images