CN116819534A - Shore-based ultrahigh frequency radar wind speed inversion method and system - Google Patents
Shore-based ultrahigh frequency radar wind speed inversion method and system Download PDFInfo
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Abstract
The invention discloses a shore-based ultra-high frequency radar wind speed inversion method and system, which are characterized in that firstly, a wind speed measurement time sequence value measured by a wind speed measuring instrument is obtained, a Bragg spectral peak width is calculated by finding a radar echo Doppler spectrum corresponding to the wind speed measurement value, then a wind direction corresponding to the wind speed measurement value is obtained, parameters of a wind speed inversion model are solved by using a least square method according to the obtained wind speed, bragg spectral peak width and wind direction time sequence, and finally the Bragg spectral peak width and wind direction are obtained according to a radar echo Doppler spectrum for wind speed inversion and are substituted into the wind speed inversion model to obtain the wind speed. The invention provides a relation model of Bragg spectrum peak width and wind speed and wind direction, and obtains model parameters by means of a small amount of standard wind speed, bragg spectrum peak width and wind direction data, thereby realizing rapid and real-time wind speed inversion, expanding the application range of offshore ultra-high frequency radar ocean remote sensing, and being beneficial to improving the offshore area wind speed monitoring capability.
Description
Technical Field
The invention belongs to the technical field of marine environment radar monitoring, and particularly relates to a shore-based ultrahigh frequency radar wind speed inversion method and system.
Background
Offshore wind speed measurements are critical to various applications such as weather forecast, marine navigation, offshore energy production, coastal engineering, and the like. Wind is a key factor in determining weather and sea conditions in coastal areas, and in order to ensure the safety of ocean activities and infrastructure, wind speed and wind direction must be accurately measured. Moreover, wind energy production is increasingly gaining attention as a renewable energy source, and understanding the dynamics of offshore wind patterns is beneficial for optimizing the performance of wind turbines and reducing the cost of energy production, so offshore wind speed measurements are essential for selecting and designing offshore wind farms.
The existing instruments for measuring the near-shore wind speed comprise anemometers, laser radars, spaceborne synthetic aperture radars, spaceborne scatterometers, X-band radars, high-frequency ground wave radars and the like. Anemometers are typically mounted on buoys or vessels that can only provide measurements at a fixed location or on a single track, and cannot obtain spatially varying conditions of wind speed over a large area. Furthermore, anemometers require regular calibration and maintenance to ensure accurate measurements, but in offshore environments this is a great challenge, as the instrument is often exposed to harsh conditions such as salt water sprays, high winds and high waves. The laser radar can provide high-resolution real-time wind speed measurement, but the measurement range is limited to hundreds of meters, and the measurement accuracy is easily affected by atmospheric conditions such as fog, rain, haze and the like. Space coverage of the satellite-borne instrument is large, but time continuity of wind speed measurement in a specific area is poor because the satellite-borne instrument cannot stay for a long time. The X-band radar can perform large-area, high-resolution and real-time wind speed measurement, but is easily interfered by weather factors. The high-frequency ground wave radar has the advantages of large-scale, all-weather, real-time, continuous measurement, less maintenance and the like, but has limited spatial resolution, often has a close-range blind area of several kilometers in an offshore area, and is easy to be interfered by other radio waves.
Compared with the high-frequency ground wave radar, the shore-based ultrahigh-frequency radar has the advantages of all weather, real-time and continuous measurement, less maintenance and the like. And the ultra-high frequency radar has higher working frequency, so that the spatial resolution is higher, the detection range is more concentrated in the offshore area, and the radio wave interference of the working frequency band is less. In addition, the ultra-high frequency radar is more sensitive to small changes of sea waves, so that higher measurement accuracy is facilitated.
At present, the shore-based ultra-high frequency radar is mainly applied to river flow rate detection and is mainly applied to sea clutter observation in the field of ocean perception. The conventional shore-based ultra-high frequency radar wind direction measurement method comprises a method for inverting wind direction according to the power ratio (Bragg Peak Power Ratio, BPPR for short) of a positive frequency first-order Bragg peak to a negative frequency first-order Bragg peak on an echo Doppler spectrum and a method for inverting wind direction according to a corrected echo Doppler spectrum centroid (Modified Doppler Spectrum Centroid, MDSC for short). However, no publication exists for Guan Anji ultra-high frequency radar wind speed measurement method.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a shore-based ultrahigh frequency radar wind speed inversion method and a system, so that the shore-based ultrahigh frequency radar can be applied to offshore area wind speed measurement, and the potential advantages of the shore-based ultrahigh frequency radar in offshore marine environment monitoring can be exerted.
In order to achieve the purpose, the technical scheme provided by the invention is a shore-based ultrahigh frequency radar wind speed inversion method, which comprises the following steps:
step 1, selecting a time sequence of wind speed measurement actually measured by a wind speed measuring instrument in a radar coverage area to construct a time sequence of standard wind speed;
step 2, calculating a time sequence of Bragg spectrum peak width according to the radar echo Doppler spectrum of the place corresponding to the standard wind speed time sequence in the step 1;
step 2.1, finding the standard wind speed U at the moment t in the step 1 0 For the echo Doppler spectrum of the unit, searching a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies, wherein the positive and negative frequency first-order Bragg peaks are peaks with maximum power on positive and negative frequency half shafts of the Doppler spectrum respectively; if both Bragg peaks can be found, comparing the powers of the two Bragg peaks, and recording the frequency of the Bragg peak with higher power as omega BH0 (t); if only a positive frequency first order Bragg peak can be found or only a negative frequency first order Bragg peak can be found, the frequency of the Bragg peak is marked as omega BH0 (t)；
Step 2.2, at ω BH0 Searching for a spectral peak with the nearest power exceeding a set threshold value on the left side of (t), and taking the corresponding frequency as the left boundary omega of the Bragg peak BHL0 (t); at omega BH0 Searching for a spectral peak with the nearest power exceeding a set threshold on the right side of (t), and taking the corresponding frequency as the right side of the Bragg peakBoundary omega BHR0 (t)；
Step 2.3, using a Gaussian function to calculate the left boundary ω obtained in step 2.2 BHL0 (t) and right boundary ω BHR0 The Doppler spectrum fit between (t), namely:
wherein G (·) represents the echo Doppler spectrum, ω represents the angular frequency, a 0 、b 0 、c 0 、d 0 A constant determined by fitting is needed;
step 2.4, the constant c obtained in step 2.3 0 The value of (2) is taken as the Bragg spectrum peak width W of the moment t 0 (t)；
Step 3, obtaining a wind direction time sequence corresponding to the time sequence of the standard wind speed;
step 4, inputting the values of the standard wind speed time sequence, the Bragg spectrum peak width time sequence and the wind direction time sequence obtained in the step 1-step 3 into a wind speed inversion model, and solving parameters of the wind speed inversion model by using a least square method;
step 5, calculating the width of a Bragg spectrum peak according to the radar echo Doppler spectrum for wind speed inversion;
step 5.1, searching positive frequency first-order Bragg peaks and negative frequency first-order Bragg peaks near positive and negative standard Bragg frequencies of a radar echo Doppler spectrum for wind speed inversion; if both Bragg peaks can be found, comparing the powers of the two Bragg peaks, and recording the frequency of the Bragg peak with higher power as omega BH The method comprises the steps of carrying out a first treatment on the surface of the If only a positive frequency first order Bragg peak can be found or only a negative frequency first order Bragg peak can be found, the frequency of the Bragg peak is marked as omega BH ；
Step 5.2, at ω BH Searching for a spectral peak with the nearest power exceeding a preset threshold value at the left side of the Bragg peak, and taking the corresponding frequency as the left boundary omega of the Bragg peak BHL The method comprises the steps of carrying out a first treatment on the surface of the At omega BH Searching for a spectral peak with the nearest power exceeding a preset threshold value on the right side of the Bragg peak, and taking the corresponding frequency as the right boundary omega of the Bragg peak BHR ；
Step 5.3, using a Gaussian function on the left boundary ω BHL And right boundary omega BHR Doppler spectrum fitting between, namely:
wherein G (·) represents the echo Doppler spectrum, ω represents the angular frequency, and a, b, c, d is a constant that needs to be determined by fitting;
step 5.4, taking the value of the constant C obtained in the step 5.3 as the width W of the Bragg spectrum peak;
step 6, calculating to obtain wind direction according to radar echo Doppler spectrum for wind speed inversion;
and 7, substituting the Bragg spectrum peak width obtained in the step 5 and the wind direction obtained in the step 6 into a wind speed inversion model, and calculating to obtain the wind speed.
The specific method for searching the first-order Bragg peak with positive frequency and negative frequency in the step 2.1 is as follows:
(1) respectively defining the frequency ranges of a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies according to the maximum flow velocity value of the detected sea area;
(2) searching spectral peaks with power and prominence exceeding set threshold in the frequency range of the positive frequency first-order Bragg peak, and recording the frequency value as omega P1 ，ω P2 ，ω P3 … …; the same method is adopted to obtain the spectral peak frequency value omega in the frequency range of the negative frequency first-order Bragg peak N1 ，ω N2 ，ω N3 ，……；
(3) Selecting one spectrum peak to form spectrum peak pair from two frequency ranges, calculating its frequency difference, recording as omega P1 -ω N1 ，ω P1 -ω N2 ，ω P2 -ω N1 ，ω P2 -ω N2 … …; discarding the pair of spectral peaks if the frequency difference exceeds a set threshold; if the number of the finally obtained spectral peak pairs is not zero, the spectral peak pair with the largest average power is selected from the obtained spectral peak pairs,the corresponding spectral peaks are positive frequency first-order Bragg peak and negative frequency first-order Bragg peak; if the number of the finally obtained spectrum peak pairs is zero, the positive frequency first-order Bragg peak and the negative frequency first-order Bragg peak of the Doppler spectrum cannot be found; if the number of the spectrum peaks searched in the distribution range of the first-order Bragg peak of the positive frequency is not zero, taking the spectrum peak with the largest power as the first-order Bragg peak of the positive frequency, and considering that the first-order Bragg peak of the negative frequency of the Doppler spectrum cannot be found; if the number of the spectral peaks which are searched in the distribution range of the first-order Bragg peak with the negative frequency is not zero, the spectral peak with the largest power is taken as the first-order Bragg peak with the negative frequency, and the first-order Bragg peak with the positive frequency of the Doppler spectrum cannot be found.
In step 3, a time sequence Φ of wind direction is constructed by using wind direction measurement values measured by the anemometers at the same time and the same place in the radar coverage area 0 (t) or inverting the value of the Doppler spectrum BPPR of the radar echo of the place corresponding to the standard wind speed time sequence to obtain phi 0 (t) or inverting according to the echo Doppler spectrum centroid MDSC value of the place corresponding to the corrected standard wind speed time sequence to obtain phi 0 (t)。
The specific calculation process for obtaining the wind speed value by inversion of the echo Doppler spectrum centroid MDSC value of the place corresponding to the corrected standard wind speed time sequence is as follows:
if two first order Bragg peaks are found, the MDSC is calculated according to the following equation:
wherein M represents MDSC value, G (·) represents echo Doppler spectrum, ω represents angular frequency, ω P Angular frequency, ω representing positive frequency first order Bragg peak N Angular frequency, ω representing negative frequency first order Bragg peak B Representing the echo angular frequency of the bragg resonant ocean wave.
If only the positive frequency first order Bragg peak is found, the MDSC is calculated according to the following equation:
wherein M represents MDSC, G (& gt) represents echo Doppler spectrum, omega represents angular frequency, omega P Angular frequency, ω representing positive frequency first order Bragg peak B Representing the echo angular frequency of the bragg resonant ocean wave.
If only negative frequency first order Bragg peaks are found, the MDSC is calculated according to the following equation:
wherein M represents MDSC, G (& gt) represents echo Doppler spectrum, omega represents angular frequency, omega N Angular frequency, ω representing negative frequency first order Bragg peak B Representing the echo angular frequency of the bragg resonant ocean wave.
When a wave direction spread function of cosine form is selected, the obtained M value is substituted into formula (5) to obtain θ w And will theta w Is taken as the wind direction value phi at the moment t 0 (t), namely:
where S is a parameter of a direction expansion function, θ r Indicating the direction of the radar beam.
In addition, the wind speed inversion model in the step 4 has two forms, and the standard wind speed time sequence U obtained in the steps 1 to 3 is obtained 0 (t), bragg peak width time series W 0 (t) wind direction time series Φ 0 The value of (t) is substituted into the following two model formulas, and the parameters of the two models are obtained by solving the two model formulas through a least square algorithm.
Model 1:
model 2:
in which W is 0 (t) is the Bragg peak width at time t, U 0 (t) is the standard wind speed at the moment t, phi 0 (t) wind direction at time t, θ r Is the direction of the radar beam, (e 1 ，g 1 ，h 1 ) And (e) 2 ，f 2 ，g 2 ，h 2 ) And the model parameters to be solved are.
And in the step 6, the wind direction Φ is obtained according to the inversion of the radar echo Doppler spectrum BPPR value for wind speed inversion, or the Φ is obtained according to the inversion of the radar echo Doppler spectrum MDSC value for wind speed inversion.
In the step 7, the wind speed U can be obtained by substituting the bragg peak width W obtained in the step 5 and the wind direction Φ obtained in the step 6 into any one of the following two models;
model 1:
model 2:
wherein W is the width of Bragg spectrum peak, U is wind speed, phi is wind direction, theta r Is the direction of the radar beam, (e 1 ，g 1 ，h 1 ) And (e) 2 ，f 2 ，g 2 ，h 2 ) Is a model parameter.
The invention also provides a shore-based ultra-high frequency radar wind speed inversion system which is used for realizing the shore-based ultra-high frequency radar wind speed inversion method.
And, including processor and memory, the memory is used for storing the program instruction, and the processor is used for calling the program instruction in the memory and carrying out a shore-based ultra-high frequency radar wind speed inversion method as above.
Or comprises a readable storage medium, wherein the readable storage medium is stored with a computer program, and the computer program realizes the shore-based ultra-high frequency radar wind speed inversion method when being executed.
Compared with the prior art, the invention has the following advantages:
1) The invention provides a relation model of Bragg spectral peak width, wind speed and wind direction, and obtains model parameters by means of a small amount of standard wind speed, bragg spectral peak width and wind direction data, thereby realizing rapid and real-time wind speed inversion;
2) The method solves the problem of lack of a method suitable for the shore-based ultrahigh frequency radar wind speed inversion, expands the application range of the shore-based ultrahigh frequency radar ocean remote sensing, and is beneficial to improving the offshore area wind speed monitoring capability.
Drawings
FIG. 1 is a flow chart of a method of an embodiment of the present invention.
FIG. 2 is a graph of the results of a comparison of a shore-based ultra-high frequency radar for wind speed inversion and a buoy-mounted anemometer for wind speed measurement using the method of the present invention, wherein graph (a) and graph (c) are the changes over time of the measured wind speed values of the shore-based ultra-high frequency radar and the buoy-mounted anemometer at the same location, respectively, the abscissa is the date, the ordinate is the wind speed, the solid curve is the radar measurement, the dashed curve is the buoy measurement, graph (b) and graph (d) are the radar-to-buoy measured wind speed value scatter plot, the abscissa is the buoy measurement, the ordinate is the radar measurement wind speed, the shade represents the wind direction and the radar radial direction angle, graph (a) and graph (b) are the results obtained using model 1 formula, and graph (c) and graph (d) are the results obtained using model 2 formula.
Detailed Description
The invention provides a shore-based ultrahigh frequency radar wind speed inversion method and a shore-based ultrahigh frequency radar wind speed inversion system, and the technical scheme of the invention is further described below with reference to drawings and embodiments.
Example 1
As shown in FIG. 1, the invention provides a shore-based ultra-high frequency radar wind speed inversion method, which comprises the following steps:
step 1, selecting a time sequence of wind speed measurement actually measured by a wind speed measuring instrument in a radar coverage area to construct a time sequence of standard wind speed.
The embodiment selects wind speed measurement values of the anemometer in the radar coverage area at a plurality of time points to construct a standard wind speed time sequence. When data is selected, the wind speed at the corresponding moment of the data needs to be considered to cover the required wind speed measuring range, such as 0-20 m/s, and the wind direction at the corresponding moment can cover the wider wind direction measuring range, such as 0-360 degrees.
And 2, calculating to obtain the time sequence of the Bragg spectrum peak width according to the radar echo Doppler spectrum of the place corresponding to the standard wind speed time sequence in the step 1.
Step 2.1, finding the standard wind speed U at the moment t in the step 1 0 And (t) a distance azimuth element of a corresponding place, searching a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies of the radar echo Doppler spectrum of the unit, wherein the positive and negative frequency first-order Bragg peaks are peaks with maximum power on positive and negative frequency half shafts of the Doppler spectrum respectively. If both Bragg peaks can be found, comparing the powers of the two Bragg peaks, and recording the frequency of the Bragg peak with higher power as omega BH0 (t); if only a positive frequency first order Bragg peak can be found or only a negative frequency first order Bragg peak can be found, the frequency of the Bragg peak is marked as omega BH0 (t)。
The specific method for searching the first-order Bragg peak of the positive frequency and the negative frequency is as follows:
(1) and respectively defining the frequency ranges of the positive frequency first-order Bragg peak and the negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies according to the maximum flow velocity value of the detected sea area.
(2) Searching spectral peaks with power and prominence exceeding set threshold in the frequency range of the positive frequency first-order Bragg peak, and recording the frequency value as omega P1 ，ω P2 ，ω P3 … …. The same procedure was adopted to carry out the method,obtaining a spectral peak frequency value omega in a negative frequency first-order Bragg peak frequency range N1 ，ω N2 ，ω N3 ，……。
(3) Selecting one spectrum peak to form spectrum peak pair from two frequency ranges, calculating its frequency difference, recording as omega P1 -ω N1 ，ω P1 -ω N2 ，ω P2 -ω N1 ，ω P2 -ω N2 … …. If the frequency difference exceeds the set threshold, the spectral peak pair is discarded, and the frequency difference threshold is set to 2.5 omega B ，ω B Representing the echo angular frequency of the bragg resonant ocean wave. If the number of the finally obtained spectral peak pairs is not zero, the spectral peak pair with the largest average power is selected from the obtained spectral peak pairs, and the corresponding spectral peak is used as a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak. If the number of the finally obtained spectrum peak pairs is zero, the positive frequency first-order Bragg peak and the negative frequency first-order Bragg peak of the Doppler spectrum cannot be found. If the number of the spectral peaks which are searched in the distribution range of the first-order Bragg peak with the positive frequency is not zero, the spectral peak with the largest power is taken as the first-order Bragg peak with the positive frequency, and the first-order Bragg peak with the negative frequency of the Doppler spectrum cannot be found. If the number of the spectral peaks which are searched in the distribution range of the first-order Bragg peak with the negative frequency is not zero, the spectral peak with the largest power is taken as the first-order Bragg peak with the negative frequency, and the first-order Bragg peak with the positive frequency of the Doppler spectrum cannot be found.
Step 2.2, at ω BH0 Searching for a spectral peak with the nearest power exceeding a set threshold value on the left side of (t), and taking the corresponding frequency as the left boundary omega of the Bragg peak BHL0 (t); at omega BH0 Searching for a spectral peak with the nearest power exceeding a set threshold on the right side of (t), and taking the corresponding frequency as the right boundary omega of the Bragg peak BHR0 (t)。
Step 2.3, using a Gaussian function to calculate the left boundary ω obtained in step 2.2 BHL0 (t) and right boundary ω BHR0 The Doppler spectrum fit between (t), namely:
wherein G (·) represents the echo Doppler spectrum, ω represents the angular frequency, a 0 、b 0 、c 0 、d 0 For constants that need to be determined by fitting.
Step 2.4, the constant c obtained in step 2.3 0 The value of (2) is taken as the Bragg spectrum peak width W of the moment t 0 (t)。
And step 3, obtaining a wind direction time sequence corresponding to the time sequence of the standard wind speed.
Construction of a wind direction time sequence Φ using wind direction measurements from a co-time and co-location anemometer within a radar coverage area 0 (t) or inverting the value of the Doppler spectrum BPPR of the radar echo of the place corresponding to the standard wind speed time sequence to obtain phi 0 (t) or inverting according to the echo Doppler spectrum centroid MDSC value of the place corresponding to the corrected standard wind speed time sequence to obtain phi 0 (t)。
In this embodiment, the wind speed value is obtained by inversion of the echo doppler spectrum centroid MDSC value of the location corresponding to the corrected standard wind speed time sequence, and the specific calculation process is as follows:
if two first order Bragg peaks are found, the MDSC is calculated according to the following equation:
wherein M represents MDSC value, G (·) represents echo Doppler spectrum, ω represents angular frequency, ω P Angular frequency, ω representing positive frequency first order Bragg peak N Angular frequency, ω representing negative frequency first order Bragg peak B Representing the echo angular frequency of the bragg resonant ocean wave.
If only the positive frequency first order Bragg peak is found, the MDSC is calculated according to the following equation:
wherein M represents MDSC, G (& gt) represents echo Doppler spectrum, omega represents angular frequency, omega P Angular frequency, ω representing positive frequency first order Bragg peak B Representing the echo angular frequency of the bragg resonant ocean wave.
If only negative frequency first order Bragg peaks are found, the MDSC is calculated according to the following equation:
wherein M represents MDSC, G (& gt) represents echo Doppler spectrum, omega represents angular frequency, omega N Angular frequency, ω representing negative frequency first order Bragg peak B Representing the echo angular frequency of the bragg resonant ocean wave.
If a wave direction spread function of cosine form is selected, the value of M is substituted into the following equation to find θ w And will theta w Is taken as the wind direction value phi at the moment t 0 (t), namely:
where S is a parameter of a direction expansion function, θ r Indicating the direction of the radar beam.
In specific implementation, other wave direction expansion functions can be selected to solve theta according to the needs w For example, the hyperbolic secant form of the expansion function proposed by Donelan, the gaussian form of the direction expansion function proposed by Apel, the unified propagation model proposed by Elfouhaily, and the like.
And 4, inputting the values of the standard wind speed time sequence, the Bragg spectrum peak width time sequence and the wind direction time sequence obtained in the steps 1-3 into a wind speed inversion model, and solving parameters of the wind speed inversion model by using a least square method.
Considering that the wavelength of electromagnetic waves emitted by the ultra-high frequency radar is far smaller than the dominant wavelength of waves, describing sea roughness by adopting a double-scale model, calculating an echo Doppler spectrum function formula of the shore-based ultra-high frequency radar based on the double-scale model, further establishing a relation between the echo Doppler spectrum and the wave spectrum, wherein the wave spectrum can be expressed as the product of a non-directional wave altitude spectrum and a wave direction function, in order to obtain an analytical expression, the non-directional wave altitude spectrum is approximately expressed as a PM saturated wave spectrum, and the main wave direction of waves is assumed to be consistent with the wind direction, so that the wave spectrum can be expressed as a function of wind speed and wind direction, and then establishing a relation model of Doppler spectrum width, wind speed and wind direction according to the echo Doppler spectrum function as follows:
model 1:
in which W is 0 (t) is the Bragg peak width at time t, U 0 (t) is the standard wind speed at the moment t, phi 0 (t) wind direction at time t, θ r Is the direction of the radar beam, (e 1 ，g 1 ，h 1 ) And the model parameters to be solved are.
Optimizing the model 1 based on the measured data to obtain:
model 2:
in which W is 0 (t) is the Bragg peak width at time t, U 0 (t) is the standard wind speed at the moment t, phi 0 (t) wind direction at time t, θ r Is the direction of the radar beam, (e 2 ，f 2 ，g 2 ，h 2 ) And the model parameters to be solved are.
Substituting the values of the standard wind speed time sequence, the Bragg spectrum peak width time sequence and the wind direction time sequence obtained in the step 1-step 3 into a wind speed inversion model in the formula (6) or the formula (7), and solving by using a least square algorithm to obtain parameters of the two models.
And 5, calculating the Bragg spectrum peak width according to the radar echo Doppler spectrum for wind speed inversion.
And 5.1, searching a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies of the echo Doppler spectrum. If both Bragg peaks can be found, comparing the powers of the two Bragg peaks, and recording the frequency of the Bragg peak with higher power as omega BH The method comprises the steps of carrying out a first treatment on the surface of the If only a positive frequency first order Bragg peak can be found or only a negative frequency first order Bragg peak can be found, the frequency of the Bragg peak is marked as omega BH 。
Step 5.2, at ω BH Searching for a spectral peak with the nearest power exceeding a preset threshold value at the left side of the Bragg peak, and taking the corresponding frequency as the left boundary omega of the Bragg peak BHL The method comprises the steps of carrying out a first treatment on the surface of the At omega BH Searching for a spectral peak with the nearest power exceeding a preset threshold value on the right side of the Bragg peak, and taking the corresponding frequency as the right boundary omega of the Bragg peak BHR 。
Step 5.3, using a Gaussian function on the left boundary ω BHL And right boundary omega BHR Doppler spectrum fitting between, namely:
where G (·) represents the echo Doppler spectrum, ω represents the angular frequency, and a, b, c, d is a constant that needs to be determined by fitting.
And 5.4, taking the value of the constant C obtained in the step 5.3 as the Bragg spectrum peak width W.
And 6, calculating the wind direction according to the radar echo Doppler spectrum for wind speed inversion.
The wind direction phi is obtained according to the inversion of the radar echo Doppler spectrum BPPR value for wind speed inversion, or the phi is obtained according to the inversion of the radar echo Doppler spectrum MDSC value for wind speed inversion.
And 7, substituting the Bragg spectrum peak width obtained in the step 5 and the wind direction obtained in the step 6 into a wind speed inversion model, and calculating to obtain the wind speed.
Substituting the Bragg spectral peak width W obtained in the step 5 and the wind direction phi obtained in the step 6 into any one of the following two models to obtain the wind speed U.
Model 1:
model 2:
wherein W is the width of Bragg spectrum peak, U is the standard wind speed, theta r Is the direction of the radar beam, Φ is the wind direction, (e) 1 ，g 1 ，h 1 ) And (e) 2 ，f 2 ，g 2 ，h 2 ) Is a model parameter.
Comparative experiments
Figure 2 shows a comparative experiment performed in fowls in the fowls yellow peninsula 10 months 2015. The graph (a) and the graph (c) are respectively the change of the measured value of the shore-based ultrahigh frequency radar and the anemometer mounted on the buoy at the same place along with time, the abscissa is the date, the ordinate is the wind speed, the solid line curve is the radar measurement result, and the dotted line curve is the buoy measurement result. The graphs (b) and (d) are scatter diagrams, the abscissa is the wind speed measured by the buoy, the ordinate is the wind speed measured by the radar, and the color shade represents the included angle between the wind direction and the radial direction of the radar. Fig. (a) and (b) are results obtained using the model 1 formula, and fig. (c) and (d) are results obtained using the model 2 formula. From figures (a) and (b) it can be seen that model 1 has an inversion result that is relatively close to the wind speed measurement of the buoy at wind speeds less than 7.5 m/s. From figures (c) and (d), it can be seen that the inversion results of model 2 are better consistent with the wind speed measurements of the buoy throughout the experimental stage. The mean square error of the wind speed measurement of the model 1 during the experiment is calculated to be 3m/s, and the mean square error of the wind speed measurement of the model 2 is calculated to be 1m/s. Experimental results show that the wind speed inversion method provided by the invention is suitable for the shore-based ultra-high frequency radar, effectively expands the application range of the shore-based ultra-high frequency radar for ocean remote sensing, and is beneficial to improving the wind speed monitoring capability of offshore areas.
Example two
Based on the same inventive concept, the invention also provides a shore-based ultra-high frequency radar wind speed inversion system, which comprises a processor and a memory, wherein the memory is used for storing program instructions, and the processor is used for calling the program instructions in the memory to execute the shore-based ultra-high frequency radar wind speed inversion method.
Example III
Based on the same inventive concept, the invention also provides a shore-based ultra-high frequency radar wind speed inversion system, which comprises a readable storage medium, wherein a computer program is stored on the readable storage medium, and the shore-based ultra-high frequency radar wind speed inversion system method is realized when the computer program is executed.
The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.
Claims (10)
1. The shore-based ultrahigh frequency radar wind speed inversion method is characterized by comprising the following steps of:
step 1, selecting a time sequence of wind speed measurement actually measured by a wind speed measuring instrument in a radar coverage area to construct a time sequence of standard wind speed;
step 2, calculating a time sequence of Bragg spectrum peak width according to the radar echo Doppler spectrum of the place corresponding to the standard wind speed time sequence in the step 1;
step 3, obtaining a wind direction time sequence corresponding to the time sequence of the standard wind speed;
step 4, inputting the values of the standard wind speed time sequence, the Bragg spectrum peak width time sequence and the wind direction time sequence obtained in the step 1-step 3 into a wind speed inversion model, and solving parameters of the wind speed inversion model by using a least square method;
step 5, calculating the width of a Bragg spectrum peak according to the radar echo Doppler spectrum for wind speed inversion;
step 6, calculating to obtain wind direction according to radar echo Doppler spectrum for wind speed inversion;
and 7, substituting the Bragg spectrum peak width obtained in the step 5 and the wind direction obtained in the step 6 into a wind speed inversion model, and calculating to obtain the wind speed.
2. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 1, wherein: step 2 comprises the following steps:
step 2.1, finding the standard wind speed U at the moment t in the step 1 0 For the echo Doppler spectrum of the unit, searching a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies, wherein the positive and negative frequency first-order Bragg peaks are peaks with maximum power on positive and negative frequency half shafts of the Doppler spectrum respectively; if both Bragg peaks can be found, comparing the powers of the two Bragg peaks, and recording the frequency of the Bragg peak with higher power as omega BH0 (t); if only a positive frequency first order Bragg peak can be found or only a negative frequency first order Bragg peak can be found, the frequency of the Bragg peak is marked as omega BH0 (t)；
Step 2.2, at ω BH0 Searching for a spectral peak with the nearest power exceeding a set threshold value on the left side of (t), and taking the corresponding frequency as the left boundary omega of the Bragg peak BHL0 (t); at omega BH0 Searching for a spectral peak with the nearest power exceeding a set threshold on the right side of (t), and taking the corresponding frequency as the right boundary omega of the Bragg peak BHR0 (t)；
Step 2.3, using a Gaussian function to calculate the left boundary ω obtained in step 2.2 BHL0 (t) and right boundary ω BHR0 The Doppler spectrum fit between (t), namely:
wherein G (·) represents the echo Doppler spectrum, ω represents the angular frequency, a 0 、b 0 、c 0 、d 0 A constant determined by fitting is needed;
step 2.4, the constant c obtained in step 2.3 0 The value of (2) is taken as the Bragg spectrum peak width W of the moment t 0 (t)。
3. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 2, wherein: the specific method for searching the first-order Bragg peak with positive frequency and negative frequency in the step 2.1 is as follows:
(1) respectively defining the frequency ranges of a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak near the positive and negative standard Bragg frequencies according to the maximum flow velocity value of the detected sea area;
(2) searching spectral peaks with power and prominence exceeding set threshold in the frequency range of the positive frequency first-order Bragg peak, and recording the frequency value as omega P1 ，ω P2 ，ω P3 … …; the same method is adopted to obtain the spectral peak frequency value omega in the frequency range of the negative frequency first-order Bragg peak N1 ，ω N2 ，ω N3 ，……；
(3) Selecting one spectrum peak to form spectrum peak pair from two frequency ranges, calculating its frequency difference, recording as omega P1 -ω N1 ，ω P1 -ω N2 ，ω P2 -ω N1 ，ω P2 -ω N2 … …; discarding the pair of spectral peaks if the frequency difference exceeds a set threshold; if the number of the finally obtained spectral peak pairs is not zero, selecting the spectral peak pair with the maximum average power from the obtained spectral peak pairs, wherein the corresponding spectral peak is used as a positive frequency first-order Bragg peak and a negative frequency first-order Bragg peak; if the number of the finally obtained spectrum peak pairs is zero, the positive frequency first-order Bragg peak and the negative frequency first-order Bragg peak of the Doppler spectrum cannot be found; if the number of the spectrum peaks searched in the distribution range of the first-order Bragg peak of the positive frequency is not zero, taking the spectrum peak with the largest power as the first-order Bragg peak of the positive frequency, and considering that the first-order Bragg peak of the negative frequency of the Doppler spectrum cannot be found; if the number of the spectrum peaks searched in the distribution range of the negative frequency first-order Bragg peak is not zero, the spectrum peak with the largest power is taken as the negative frequency first-order Bragg peak, and the spectrum peak is considered to be unable to find the multiple peaksThe positive frequency first order bragg peak of the pler spectrum.
4. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 1, wherein: step 3, constructing a wind direction time sequence phi by using wind direction measurement values measured by the anemometers at the same time and the same place in the radar coverage area 0 (t) or inverting the value of the Doppler spectrum BPPR of the radar echo of the place corresponding to the standard wind speed time sequence to obtain phi 0 (t) or inverting according to the echo Doppler spectrum centroid MDSC value of the place corresponding to the corrected standard wind speed time sequence to obtain phi 0 (t)；
The specific calculation process for obtaining the wind speed value by inversion of the echo Doppler spectrum centroid MDSC value of the place corresponding to the corrected standard wind speed time sequence is as follows:
if two first order Bragg peaks are found, the MDSC is calculated according to the following equation:
wherein M represents MDSC value, G (·) represents echo Doppler spectrum, ω represents angular frequency, ω P Angular frequency, ω representing positive frequency first order Bragg peak N Angular frequency, ω representing negative frequency first order Bragg peak B The echo angular frequency of the Bragg resonance sea wave is represented;
if only the positive frequency first order Bragg peak is found, the MDSC is calculated according to the following equation:
wherein M represents MDSC, G (& gt) represents echo Doppler spectrum, omega represents angular frequency, omega P Angular frequency, ω representing positive frequency first order Bragg peak B The echo angular frequency of the Bragg resonance sea wave is represented;
if only negative frequency first order Bragg peaks are found, the MDSC is calculated according to the following equation:
wherein M represents MDSC, G (& gt) represents echo Doppler spectrum, omega represents angular frequency, omega N Angular frequency, ω representing negative frequency first order Bragg peak B The echo angular frequency of the Bragg resonance sea wave is represented;
when a wave direction spread function of cosine form is selected, the obtained M value is substituted into formula (5) to obtain θ w And will theta w Is taken as the wind direction value phi at the moment t 0 (t), namely:
where S is a parameter of a direction expansion function, θ r Indicating the direction of the radar beam.
5. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 1, wherein: in the step 4, the wind speed inversion model has two forms, and the standard wind speed time sequence U obtained in the steps 1 to 3 is obtained 0 (t), bragg peak width time series W 0 (t) wind direction time series Φ 0 Substituting the value of (t) into the following two model formulas, and solving to obtain parameters of the two models by using a least square algorithm;
model 1:
model 2:
in which W is 0 (t) is the time tBragg spectral peak width, U 0 (t) is the standard wind speed at the moment t, phi 0 (t) wind direction at time t, θ r Is the direction of the radar beam, (e 1 ，g 1 ，h 1 ) And (e) 2 ，f 2 ，g 2 ，h 2 ) And the model parameters to be solved are.
6. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 1, wherein: step 5 comprises the following steps:
step 5.1, searching positive frequency first-order Bragg peaks and negative frequency first-order Bragg peaks near positive and negative standard Bragg frequencies of a radar echo Doppler spectrum for wind speed inversion; if both Bragg peaks can be found, comparing the powers of the two Bragg peaks, and recording the frequency of the Bragg peak with higher power as omega BH The method comprises the steps of carrying out a first treatment on the surface of the If only a positive frequency first order Bragg peak can be found or only a negative frequency first order Bragg peak can be found, the frequency of the Bragg peak is marked as omega BH ；
Step 5.2, at ω BH Searching for a spectral peak with the nearest power exceeding a preset threshold value at the left side of the Bragg peak, and taking the corresponding frequency as the left boundary omega of the Bragg peak BHL The method comprises the steps of carrying out a first treatment on the surface of the At omega BH Searching for a spectral peak with the nearest power exceeding a preset threshold value on the right side of the Bragg peak, and taking the corresponding frequency as the right boundary omega of the Bragg peak BHR ；
Step 5.3, using a Gaussian function on the left boundary ω BHL And right boundary omega BHR Doppler spectrum fitting between, namely:
wherein G (·) represents the echo Doppler spectrum, ω represents the angular frequency, and a, b, c, d is a constant that needs to be determined by fitting;
and 5.4, taking the value of the constant C obtained in the step 5.3 as the Bragg spectrum peak width W.
7. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 1, wherein: in the step 6, the wind direction phi is obtained according to the inversion of the radar echo Doppler spectrum BPPR value used for wind speed inversion, or the phi is obtained according to the inversion of the radar echo Doppler spectrum MDSC value used for wind speed inversion.
8. A shore-based ultra-high frequency radar wind speed inversion method as defined in claim 1, wherein: in the step 7, substituting the Bragg spectrum peak width W obtained in the step 5 and the wind direction phi obtained in the step 6 into any one of the following two models, so as to obtain the wind speed U;
model 1:
model 2:
wherein W is the width of Bragg spectrum peak, U is wind speed, phi is wind direction, theta r Is the direction of the radar beam, (e 1 ，g 1 ，h 1 ) And (e) 2 ，f 2 ，g 2 ，h 2 ) Is a model parameter.
9. A shore-based ultra-high frequency radar wind speed inversion system, comprising a processor and a memory, wherein the memory is used for storing program instructions, and the processor is used for calling the program instructions in the memory to execute a shore-based ultra-high frequency radar wind speed inversion method according to any one of claims 1-8.
10. A shore-based ultra-high frequency radar wind speed inversion system, comprising a readable storage medium, wherein the readable storage medium has a computer program stored thereon, which when executed, implements a shore-based ultra-high frequency radar wind speed inversion method according to any one of claims 1-8.
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