Wind shear factor calculation method based on one-dimensional wind speed measurement

Abstract

The invention relates to a wind shear factor calculation method based on one-dimensional wind speed measurement, and the method comprises the following specific wind speed estimation steps after preprocessing: 1, obtaining the distribution of the radial speed of meteorological echoes scanned by all horizontal azimuth angles of a radar along with the distance through a frequency domain analysis algorithm; 2, according to the radial wind speed distribution, the horizontal plane coordinates of the center position of wind shear are obtained; 3, calculating the distance from each effective range gate on the expected flight path of the airplane to the wind shear center; and 4, calculating the vertical wind speed on the expected flight path of the airplane by using a corrected vertical wind speed calculation method based on the axial symmetry non-rotation field approximation of the wind shear wind field and the non-fluid static pressure model of the near-surface wind field. The nonlinear wind speed model estimation of the vertical wind speed of the central area of the wind shear wind field is provided, the calculation amount of the calculation model is small, the method does not depend on preset parameters, and compared with a traditional method, errors are small.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radar signal processing, and in particular to a wind shear factor calculation method based on one-dimensional wind speed measurement. BACKGROUND

[0002] Low-level wind shear refers to the sudden change of wind direction and speed within a short distance at the same height or different heights near the ground. Low-level wind shear has the characteristics of short change time, small range and large intensity, and is the most serious weather hazard in the take-off and landing stages. When an aircraft is exposed to wind shear of sufficient intensity and duration, it may crash due to loss of airspeed or flight altitude. An aircraft is considered to be in danger when the wind shear reduces the energy state of the aircraft at a rate faster than the engine thrust can compensate. The aviation industry usually uses a dimensionless wind shear F factor to measure the degree of wind shear danger: where, is the horizontal wind speed, is the acceleration of gravity, is the vertical wind speed, is the airspeed of the aircraft.

[0003] Doppler radar or Doppler sonar is a commonly used means to detect low-level wind shear. The basic principle is to measure the wind speed along the direction of the emitted detection energy through Doppler shift, and thus to calculate the wind speed change along the radial direction. Usually, the Doppler radar is configured to emit horizontally. Due to the limitations of the Doppler speed measurement principle, the vertical speed cannot be directly measured. A commonly used solution is to use a vertical wind model to estimate the vertical component from the horizontal wind measurement. First, the microburst core is determined by analyzing the linear correlation coefficient of the radial wind speed profile, and then the vertical wind speed gradient is determined using the mass continuity equation , and finally the vertical wind is calculated using the linear model or the empirical model of the vertical wind speed at the height .

[0004] Since the vertical wind speed gradient of the real wind shear changes with height, the accuracy of the linear model is poor. On the other hand, the empirical model usually relies on a three-dimensional parameterized model of the wind shear wind field, and the model parameters are pre-set, depending on the assumption of the initial environment that produces the wind shear, so the generalization for different wind shear scenarios is poor. SUMMARY

[0005] To solve the technical problems of poor accuracy of existing wind shear vertical wind linear prediction model and poor generalization of empirical model relying on pre-set parameters, the present application provides a wind shear factor calculation method based on one-dimensional wind speed measurement.

[0006] The specific content of the application is as follows: a wind shear factor calculation method based on one-dimensional wind speed measurement, after pretreatment is completed, wind speed estimation is carried out through the following steps:

[0007] Step 1: using a frequency domain analysis algorithm, the radial velocity distribution of the radar each horizontal azimuth scanning meteorological echo with distance is obtained;

[0008] Step 2: according to the radial wind speed distribution, the horizontal plane coordinate of the center position of the wind shear is obtained;

[0009] Step 3: the distance from each effective distance gate on the expected flight path of the aircraft to the center of the wind shear is calculated;

[0010] Step 4: based on the axisymmetric irrotational field approximation of the wind shear wind field and the non-hydrostatic pressure model of the near-surface wind field, the vertical wind speed calculation method is used to calculate the vertical wind speed on the expected flight path of the aircraft;

[0011] Step 5: according to the horizontal and vertical wind speed information on the expected flight path of the aircraft, the wind shear danger factor on the flight path of the aircraft is calculated.

[0012] Further, the pretreatment of the radar echo data includes: after receiving the IQ signal, the frequency domain correction is carried out according to the aircraft attitude and speed information, the data is pretreated according to the spectrum width information, and the noise area is removed.

[0013] Further, the method for calculating the horizontal plane coordinate of the center position of the wind shear in step 2 is as follows: according to the radar scanning system parameters, the beam azimuth angle of the radar is , the corresponding radial wind speed is zero, and the distance is , the corresponding radial wind speed along the radial distance gradient is , and the position of the wind shear center in the polar coordinate system is The maximum beam azimuth angle ( ).

[0014] Further, step 3 includes: selecting the speed information and speed spectrum width information in the expected flight path direction of the aircraft, carrying out noise suppression and data quality control through the speed spectrum width information to select the distance gate of the wind shear region, and calculating the distance R from the flight path direction to the wind shear center for any distance gate.

[0015] Further, step 4 includes: selecting the speed information and speed spectrum width information in the direction, carrying out noise suppression and data quality control through the speed spectrum width information to select the distance gate of the wind shear region; according to the speed measurement result in the direction, the wind shear region is divided into a downburst core area and an edge area, and the vertical wind speed of the downburst core area is calculated.

[0016] Further, the judgment basis of the downburst core area is that the radial wind speed distribution of the core area is described as wherein is the distance from the wind shear center, is the change rate of the speed in the direction with the distance, and the subscript indicates the corresponding height of the wind field from the ground; for any distance gate on the expected flight path of the aircraft, the distance from the wind shear center axis is calculated , and the same calculation method is used to obtain ; the linear correlation coefficient of the adjacent N distance gates is calculated, and the value range is [-1, +1], if the value is greater than 0.9, it is judged to be the core area, and the core area radius is recorded as D(z), .

[0017] Further, according to the continuity equation under the cylindrical coordinate system, it is assumed that the wind shear flow field has no tangential component, and there is , in the wind shear core area, there is , in the edge area, the term is ignored, that is ; for the vertical wind speed linear model of the wind shear , it is assumed that the dynamic pressure starts to be generated at , and decreases linearly with height, in the downburst core area, if the vertical wind speed gradient at the height is known, then for any height , there is , wherein , , the vertical wind speed gradient is integrated to obtain the vertical wind speed estimation of the downburst core area , wherein .

[0018] Further, the value range of t is less than 0.99.

[0019] The application is based on the axisymmetric irrotational field approximation of wind shear, and a nonlinear wind speed model estimation of the vertical wind speed of the center area of the wind shear wind field is proposed from the fluid continuity equation and the non-fluid static pressure model of the near-ground wind field. The calculation model has small operation amount, does not depend on preset parameters, and has small error compared with the traditional method. BRIEF DESCRIPTION OF DRAWINGS

[0020] The application will be further illustrated below in combination with the drawings.

[0021] Figure 1 It is a module schematic diagram of the wind shear factor calculation method based on one-dimensional wind speed measurement of the application;

[0022] Figure 2Fig. 1 is a schematic diagram of the relationship between the three-directional wind speed and reflectivity with distance for the TASS dataset wind shear;

[0023] Figure 3 Fig. 4 is a schematic diagram of the radial wind speed and core region of the wind shear center direction spectrum width;

[0024] Figure 4 Fig. 5 is a calculation result of the wind shear risk factor, wherein the red line is the total F factor, and the dark blue line is the vertical direction F factor proportional to the vertical wind speed. DETAILED DESCRIPTION

[0025] In combination Figures 1-4 , the present application provides a wind shear factor calculation method based on one-dimensional wind speed measurement, which comprises radar echo scanning, IQ data sampling, aircraft attitude speed compensation, radial wind speed calculation, determination of the wind shear center position, calculation of the expected flight path horizontal wind speed and core region, dynamic model correction, and F factor calculation. After IQ data sampling, the radial wind speed is calculated by combining spectrum width estimation, data pre-quality control, and aircraft attitude speed compensation results. The specific steps are as follows:

[0026] Without loss of generality, the radar adopts a single horizontal scanning scheme, and follows the commonly used radar echo processing strategy. After receiving the IQ signal, the frequency domain is corrected according to the aircraft attitude, speed, and other information, the data is preprocessed according to the spectrum width and other information, and the noise area is removed. After the preprocessing is completed, the specific wind speed estimation steps are as follows:

[0027] Step 1: Use the frequency domain analysis algorithm to obtain the distribution of the radial velocity of the radar each horizontal azimuth scanning meteorological echo with distance;

[0028] Step 2: According to the radial wind speed distribution, the horizontal plane coordinates of the center position of the wind shear are obtained; according to the radar scanning system parameters, the beam azimuth angle of the radar is , the distance corresponding to the radial wind speed of zero is , and the gradient of the radial wind speed along the radial distance is , then the position of the wind shear center in the polar coordinate system is .

[0029] Step 3: Calculate the distance from each effective distance gate on the expected flight path of the aircraft to the wind shear center; select the speed information and speed spectrum width information in the expected flight path direction of the aircraft, and perform noise suppression and data quality control through the speed spectrum width information to select the distance gate in the wind shear region. For any distance gate, calculate the distance R between the flight path direction and the distance to the wind shear center .

[0030] ​Step 4: Based on the axisymmetric irrotational field approximation of the wind shear field and the non-hydrostatic pressure model of the near-ground wind field, the vertical wind speed on the expected flight path of the aircraft is calculated using a modified vertical wind speed calculation method.

[0031] Firstly, the speed information and speed spectrum width information in the direction are selected, and the noise suppression and data quality control are performed through the speed spectrum width information to select the distance gate of the wind shear region. According to the speed information in the direction, the wind shear region is divided into a core area and an edge area of the downburst. The judgment basis is that according to the anti's' type characteristic radial wind speed distribution of the wind shear shown in FIG. 1, the radial wind speed distribution of the core area is described as wherein Figure 3 is the distance from the center of the wind shear, is the change rate of the speed in the direction with the distance, which does not change with the , and the subscript indicates the corresponding height of the wind field from the ground. For any distance gate on the expected flight path of the aircraft, the distance from the axis of the wind shear center is calculated as and the same calculation method is used to obtain .

[0032] The judgment basis for whether it is a core area is that the linear correlation coefficient (value range [-1, +1]) of the adjacent N distance gates is calculated, and if the value is greater than 0.9, it is judged to be a core area. The core area radius is denoted as D(z). Since in the practical scene of the airborne radar, the height , there is .

[0033] To solve the vertical wind speed, firstly, according to the continuity equation in the cylindrical coordinate system, and assuming that the wind shear flow field has no tangential component, there is . In the core area of the wind shear, there is . While in the edge area, the term can be ignored, that is, .

[0034] In the traditional linear model of the vertical wind speed of the wind shear, . This model will underestimate the vertical wind speed of the downburst core area when the aircraft flight path is high from the ground. This is because the downburst will be squeezed by the ground when it sinks to the near-ground, and a non-hydrostatic dynamic pressure is formed in the vertical direction, so that along the vertical direction appears a trend of being stronger closer to the ground. In the linear model approximation, the vertical dynamic pressure of the near-ground downburst along the axis of the wind shear center can be expressed as . The above formula actually limits the scale of the ground generated squeezing dynamic pressure, that is, ​​​Therefore, as a first-order correction to the linear model, it is reasonable to assume that Dynamic pressure begins to be generated when the height decreases, and increases linearly with the height. Vertical wind speed gradient , then for any height , have ,in The above formula already implies the condition Finally, the vertical wind speed gradient is integrated to obtain the vertical wind speed estimate for the downburst core area. ,in Typically, the core area of ​​wind shear, D, is greater than 1 km, and the aircraft's wind shear warning threshold altitude, z, is approximately 370 meters. Therefore, this correction is reasonable. In practice, to prevent t from exceeding 1, t can be limited to less than a certain threshold, such as 0.99.

[0035] The parameters of a specific example of this application are shown in Table 1.

[0036] Table 1 Example model parameters

[0037] Flight height Z (m) Core radius D (m) Correction factor t F-factor error (unmodified) F-factor error (after correction) 372 1500 0.5 +36% -3%

[0038] Step 5: Calculate the wind shear risk factor on the aircraft's flight path based on the horizontal and vertical wind speed information on the aircraft's expected flight path.

[0039] Figure 4 The F-factor calculation results for the linear model and the modified model proposed in this paper are compared when applied to an axisymmetric, irrotational wind field in the US standard wind shear dataset, TASS. It can be seen that due to the consideration of dynamic pressure correction, the vertical wind speed correction of the present invention is significantly improved compared to the linear model. It should be noted that the derivation of the present invention is based on an axisymmetric, irrotational wind shear flow field. In actual observations, this approximation is generally applicable to most strong convective or cumulonimbus-type wind shear.

[0040] The present invention uses an airborne Doppler radar, transmits a radar waveform toward a possible wind shear hazard area ahead of the route, and analyzes the radar echo IQ data to obtain a wind speed estimate in the transmitting direction. After obtaining the distribution of wind speed in the wind field in that direction with distance, based on the axisymmetric irrotational field approximation of the wind shear wind field, and starting from the fluid continuity equation and the non-hydrostatic pressure model of the near-ground wind field, a nonlinear wind speed model is proposed to estimate the vertical wind speed in the central area of ​​the wind shear wind field. Compared with the existing nonlinear wind speed model, the calculation model is simple to implement and does not rely on preset parameters. Due to the consideration of dynamic pressure correction, the correction of vertical wind speed by the present invention is greatly improved compared with the linear model. The present invention has the characteristics of simple implementation, small amount of calculation, high speed, and high parameter estimation accuracy.

[0041] In the foregoing description, numerous specific details are set forth to provide a thorough understanding of the present application. However, there are cases in which well-known structures, circuits and processes have not been described in detail, or have been described only briefly, in order to avoid unnecessarily obscuring the present application. Furthermore, the foregoing description is not intended to limit the present application to the particular embodiments described. Instead, unless otherwise specified, any combination of the disclosed features and / or methods are included within the scope of the present application. The present application includes any modifications or variations of the method and system described above that are within the scope of the present application, which is limited only by the claims.

Claims

1. A method for calculating a wind shear factor based on one-dimensional wind speed measurements, characterized by: After the pre-processing is completed, the wind speed estimation is performed by the following steps: Step 1: using a frequency domain analysis algorithm, the distribution of the radial velocity of the weather echo of each azimuthal scanning of the radar with respect to the distance is obtained; Step 2: according to the radial wind speed distribution, the horizontal plane coordinate of the center position of the wind shear is obtained; Step 3: the distance from each effective distance gate on the expected flight path of the aircraft to the center of the wind shear is calculated; Step 4: based on the axisymmetric irrotational field approximation of the wind shear wind field and the non-hydrostatic pressure model of the near-ground wind field, the vertical wind speed on the expected flight path of the aircraft is calculated using a modified vertical wind speed calculation method; Step 5: according to the horizontal and vertical wind speed information on the expected flight path of the aircraft, the wind shear danger factor on the flight path of the aircraft is calculated.

2. The method for calculating a wind shear factor based on one-dimensional wind speed measurement according to claim 1, characterized in that: The pre-processing of the radar echo data includes: after receiving the IQ signal, the frequency domain correction is performed according to the aircraft attitude and speed information, the data is pre-processed according to the spectrum width information, and the noise area is removed.

3. The method of calculating a wind shear factor based on one-dimensional wind speed measurements according to claim 1, characterized in that: The method for calculating the horizontal plane coordinates of the center position of the wind shear in step 2 is as follows: according to the radar scanning system parameters, let the beam azimuth angle of the radar be , the distance corresponding to the radial wind speed of zero is , the gradient of the radial distance corresponding to the radial wind speed is , and the position of the wind shear center in the polar coordinate system is The maximum beam azimuth angle (θmax) is .

4. The method of calculating a wind shear factor based on one-dimensional wind speed measurements according to claim 3, characterized in that: Step 3 includes: selecting the speed information and the speed spectrum width information in the direction of the expected flight path of the aircraft, performing noise suppression and data quality control through the speed spectrum width information to select the distance gate of the wind shear region, and for any distance gate, calculating the distance R from the flight path direction to the center of the wind shear.

5. The method of calculating a wind shear factor based on one-dimensional wind speed measurements according to claim 3, characterized in that: Step 4 includes: selecting velocity information and velocity spectrum width information in the direction, and performing noise suppression and data quality control by the velocity spectrum width information to select a distance gate of the wind shear region; according to the velocity measurement results in the direction, dividing the wind shear region into a downburst core region and an edge region, and calculating the vertical wind speed of the downburst core region.

6. The method of calculating a wind shear factor based on one-dimensional wind speed measurements according to claim 5, characterized in that: The judgment basis for the core area of the downburst is to describe the radial wind speed distribution of the core area as wherein is the distance from the wind shear center, is the rate of change of the speed in this direction with the distance, and the subscript indicates the corresponding height of the wind field from the ground; for any distance gate on the expected flight path of the aircraft, the distance from the wind shear center axis is calculated and the same calculation method is used to obtain ; the linear correlation coefficient of the adjacent N distance gates is calculated, the value range is [-1, +1], if the value is greater than 0.9, it is judged as the core area, and the core area radius is recorded as D(z), .

7. The method of calculating a wind shear factor based on one-dimensional wind speed measurements according to claim 6, characterized in that: According to the continuity equation in the cylindrical coordinate system, assuming that the wind shear flow field has no tangential component, we have , in the core area of ​​wind shear, there are , in the marginal area, ignore Item, that is ; For the linear model of wind shear vertical wind speed , assuming that Dynamic pressure begins to be generated when the height decreases, and increases linearly with the height decrease. In the core area of ​​the downburst, if the height is known, Vertical wind speed gradient , then for any height , have ,in , , integrating the vertical wind speed gradient, we can estimate the vertical wind speed in the core area of ​​the downburst ,in .

8. The method of calculating a wind shear factor based on one-dimensional wind speed measurements according to claim 7, characterized in that: The value range of t is less than 0.99.

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