JP2014215237A - Meteorological observation deice, meteorological observation program and meteorological observation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a meteorological observation device, a meteorological observation program and a meteorological observation method that enable accuracy of a meteorological observation to be improved.SOLUTION: The meteorological observation device includes: a reception part that receives a scattered radio wave of a beam of radio wave emitted in a plurality of directions toward atmosphere; a generation part that generates reception data in a frequency domain from the reception data in a time domain obtained by use of the reception part; a flying object determination part that determines whether or not a scattered component caused by a flying object is included in the scattered radio wave on the basis of reception data in at least one of the time domain and the frequency domain; an exclusion processing part that performs exclusion processing of the reception data including the scattered component caused by the flying object according to the determination result of the flying object determination part; and a decision part that decides whether to utilize the exclusion processing to be performed by the exclusion processing part on the basis of commonality among pieces of the reception data in the frequency domain with respect to the beam of radio wave different in the direction.

Description

  The present invention relates to a meteorological observation apparatus for observing wind speed or direction, a meteorological observation program and a meteorological observation method for realizing the meteorological observation apparatus.

  A wind profiler emits radio waves (also called beams) from the ground toward the sky, receives the scattering of radio waves caused by wind turbulence (fluctuation in the refractive index of the air), etc. Measure the wind direction. Since the radio waves scattered in the atmosphere change according to the wind flow, the wind speed and direction can be estimated by processing the received signal using the Doppler effect to obtain the Doppler spectrum (non- Patent Document 1).

Wind profiler observation work at the Japan Meteorological Agency, Yoshio Kato, Toshihiro Abo, Kenji Kobayashi, Yasushi Izumikawa, Masahito Ishihara, Weather, 50, 2003, 891-907

  The signal received by the wind profiler from the atmosphere (atmospheric echo) is very weak, whereas the signal received from flying objects such as birds (migratory birds), insects, or aircraft (referred to as bird echoes or flying object echoes) Is relatively strong and may affect wind measurements. For this reason, when obtaining the Doppler spectrum, the observation accuracy is improved by performing a bird echo removal process for removing a spectrum showing a large signal intensity that is considered to be caused by a bird echo.

  On the other hand, when precipitation occurs, the precipitation particles become scatterers, and the signal received from the precipitation particles (referred to as precipitation echoes) is relatively strong like the bird echoes. It was difficult to distinguish whether it was due to the body or due to precipitation particles. For this reason, for example, if a spectrum that is not caused by a bird echo is erroneously removed due to a bird echo, the observation accuracy may be lowered.

  The present invention has been made in view of such circumstances, and provides a meteorological observation apparatus capable of improving the accuracy of meteorological observation, a meteorological observation program and a meteorological observation method for realizing the meteorological observation apparatus. With the goal.

  A meteorological observation apparatus according to a first aspect of the present invention is a receiver that receives scattered radio waves of radio waves emitted in a plurality of directions toward the atmosphere, and frequency domain reception data obtained using the receiver. A generation unit that generates reception data, a flying object determination unit that determines whether or not a scattered component due to a flying object is included in the scattered radio wave based on at least one of reception data in a time domain and a frequency domain, and the flight In accordance with the determination result of the body determination unit, the elimination processing unit that performs the exclusion process of the reception data including the scattered component due to the flying object, and the removal based on the commonality between the reception data in the frequency domain with respect to radio waves having different directions And a determination unit that determines whether to use the exclusion process by the processing unit.

  In a weather observation apparatus according to a second aspect based on the first aspect, the determination unit further performs the removal processing based on a phase rotation amount between a phase having the maximum amplitude in the reception data in the frequency domain and a previous phase value. Decide whether to use the exclusion process by department.

  The meteorological observation apparatus according to a third aspect of the present invention is the meteorological observation device according to the first or second aspect, wherein the determination unit further performs an exclusion process by the removal processing unit based on continuity between the received data in the frequency domain for different altitudes. Decide whether to use.

  The meteorological observation device according to a fourth aspect of the present invention is the meteorological observation device according to any one of the first to third aspects, wherein the flying object determination unit is configured such that the amplitude of the received data in the frequency domain or the maximum value of the power of the received data is a threshold value. In the case of exceeding the scattering wave, it is determined that a scattered component by the flying object is included in the scattered radio wave.

  The meteorological observation device according to a fifth aspect of the present invention is the meteorological observation device according to any one of the first to third aspects, wherein the flying object determining unit is configured to perform the above operation when the integrated value of the power of the received data in the frequency domain exceeds a threshold It is determined that the scattered component by the flying object is included in the scattered radio wave.

  The meteorological observation device according to a sixth aspect of the present invention is the meteorological observation device according to any one of the first to third aspects, wherein the flying object determination unit is configured such that when the maximum absolute value of the received data in the time domain exceeds a threshold value, It is determined that a scattered component by the flying object is included in the scattered radio wave.

  The meteorological observation apparatus according to a seventh aspect of the present invention is the meteorological observation device according to any one of the first to third aspects, wherein the flying object determination unit has a difference value obtained by subtracting a minimum value from a maximum value of the reception data in the time domain. In the case of exceeding the scattering wave, it is determined that a scattered component by the flying object is included in the scattered radio wave.

  A meteorological observation device according to an eighth aspect of the present invention is a receiver that receives scattered radio waves of a radio beam emitted toward the atmosphere, and generates frequency domain received data from time domain received data obtained using the receiver. A generating unit, a flying object determining unit that determines whether or not a scattered component due to the flying object is included in the scattered radio wave based on at least one received data in the time domain and the frequency domain, and the flying object determining unit According to the determination result, based on the exclusion processing unit that performs the exclusion process of the reception data including the scattering component by the flying object, and the phase rotation amount of the phase having the maximum amplitude in the reception data in the frequency domain and the previous phase value And a determination unit that determines whether to use the exclusion process by the removal processing unit.

  A meteorological observation program according to a ninth aspect causes a computer to function as the meteorological observation apparatus according to any one of the first to eighth aspects.

  According to a tenth aspect of the present invention, there is provided a meteorological observation method comprising: a step of receiving scattered radio waves of a radio beam emitted in a plurality of directions toward the atmosphere; and reception of a frequency domain from time domain received data obtained through the receiving step. A step of generating data, and a step of determining whether or not to use a reception data exclusion process including a scattered component due to a flying object, based on the commonality between the reception data in the frequency domain for radio beams having different directions. Including.

  In the first to seventh inventions, the ninth invention, and the tenth invention, the receiving unit receives radio waves scattered in the atmosphere by a beam emitted toward the atmosphere for each of a plurality of beam directions. The plurality of beam directions can be, for example, five directions including a zenith direction and an east-west-north-north direction inclined by a predetermined angle (for example, 14 degrees) from the zenith. For example, the beam can be sequentially emitted in a plurality of beam directions from an antenna installed horizontally near the ground. The beam is emitted as intermittent pulses and receives radio waves scattered while not being emitted.

  The generation unit converts and generates time domain reception data obtained using the reception unit into frequency domain reception data. For the transformation / generation, for example, complex FFT (fast Fourier transformation) may be used, or wavelet transformation may be used. Further, the altitude at which the radio wave is scattered can be obtained from the time difference between the beam emission time and the reception time of the scattered radio wave. The observation altitude can be determined as a required altitude from about 100 m to about 10 km, for example.

  The determination unit determines whether or not to use the exclusion process by the removal processing unit based on the commonality between the reception data in the frequency domain for radio beams having different directions. For example, precipitation particles fall in a substantially vertical direction according to a vertical downward direction or a horizontal wind in a relatively wide range in the atmosphere. The beam pattern of a directional antenna used in a wind profiler or the like is composed of a main lobe that is strong in the main axis direction and side lobes that leak in the other direction. For example, in the case of a wind profiler that oscillates a radio wave beam only at the approximate zenith with a zenith angle of about 14 degrees, scattering from precipitation particles falling in a substantially vertical direction over a relatively wide range is mainly performed regardless of the beam direction. There is a commonality between different beam directions, for example, the same level of scattering intensity can be obtained at the same altitude in any beam direction. On the other hand, flying objects such as a flock of birds are present at a relatively low altitude and in a relatively narrow area, and move in a substantially horizontal direction. Therefore, although a bird echo is captured in one specific beam direction, a bird echo cannot be captured in another beam direction, and there is a bird echo at an altitude of 100 m in one beam direction. , 300 m, etc., there is no commonality between different beams. By using these characteristics, it is possible to distinguish the reception data caused by the flying object and the reception data caused by the precipitation particles, and the observation accuracy such as the wind speed and the wind direction can be improved.

  In the second invention, the determination unit further determines whether or not to use the exclusion processing by the removal processing unit based on the phase rotation amount between the phase having the maximum amplitude in the received data in the frequency domain and the previous phase value. decide. The amplitude A in the received data in the frequency domain is represented by the square root of (I × I + R × R), ie, amplitude A = √ (I × I + R × R), where R is the real part of the complex number and I is the imaginary part. The maximum value is Amax. The phase represents the phase value α at Amax, where R is the real part of the complex number and I is the tangent part of the complex number, that is, the arc tangent of (I / R), that is, phase α = arctan (I / R). Further, the phase rotation amount Δα can be expressed by a difference between the current phase value α and the previous phase value α2, that is, Δα = α−α2. In deciding whether to use reception data exclusion processing that includes scattered components due to flying objects, for example, Δα is compared with the upper and lower thresholds, and those that are higher than the lower threshold and lower than the upper threshold are regarded as precipitation echoes, and are removed. It is also possible to determine not to use the exclusion process by the unit, and it is also possible to determine the difference from the previous phase rotation amount Δα2 = α2−α3, that is, the change amount of the phase rotation amount by comparing with a threshold value.

  In the third invention, the determination unit determines whether to use the exclusion process by the removal processing unit based on the continuity between the received data in the frequency domain for different altitudes. For example, since precipitation particles exist over an altitude of several kilometers, they have continuity in the altitude direction, such that the same scattering intensity can be obtained over an altitude of several kilometers. On the other hand, since flying objects such as flocks do not exist at altitudes of several kilometers, using these characteristics, the received data caused by flying objects and received data caused by precipitation particles are distinguished. Observation accuracy such as wind speed and direction can be improved.

  In the fourth aspect of the invention, the flying object determining unit may include a scattered component of the flying object included in the scattered radio wave when the amplitude of the received data in the frequency domain or the maximum value of the power of the received data exceeds a threshold value. judge. The amplitude A in the received data in the frequency domain is represented by the square root of (I × I + R × R), ie, amplitude A = √ (I × I + R × R), where R is the real part of the complex number and I is the imaginary part. And the power P can be expressed by its square, that is, P = (I × I + R × R). The maximum value of these amplitude values or power values is obtained. For example, if the maximum value is equal to or greater than a threshold value, it can be determined that the flying object echo is included.

  In the fifth invention, the flying object determination unit determines that the scattered radio wave includes a scattered component by the flying object when the integrated value of the power of the received data in the frequency domain exceeds a threshold value. The power P in the frequency domain received data can be expressed as P = (I × I + R × R) where R is the real part of the complex number and I is the imaginary part. The integrated value Psum of the power can be expressed by integrating the power P at all frequency points or at a plurality of frequency points around the maximum value of the power P, that is, Psum = ΣP. For example, if the integral value of the power is greater than or equal to the threshold value, it can be determined that the flying object echo is included.

  In the sixth aspect of the invention, the flying object determining unit determines that the scattered component by the flying object is included in the scattered radio wave when the maximum absolute value of the reception data in the time domain exceeds the threshold value. The received data in the time domain can be expressed by positive and negative voltage values. That is, the flying object determination unit determines that the flying object scattered signal is included when the peak voltage (maximum value of the absolute value of the voltage) of the reception data in the time domain exceeds a predetermined threshold, and the peak of the reception data When the voltage (the maximum absolute value of the voltage) is equal to or less than a predetermined threshold, it can be determined that the flying object scattering signal is not included. Since only the voltage peak value is scanned to determine whether or not the predetermined threshold value is exceeded, the process for determining whether or not the flying object scattering signal is included can be lightened and the determination process is required. The processing time can be quickly obtained by shortening the time.

  In the seventh invention, the flying object determination unit includes a scattered component due to the flying object when the difference value obtained by subtracting the minimum value from the maximum value of the reception data in the time domain exceeds the threshold value. Is determined. The received data in the time domain can be expressed by positive and negative voltage values. That is, the flying object determination unit determines that the flying object scattering signal is included when the peak voltage difference (the difference between the maximum value and the minimum value of the voltage) of the reception data in the time domain exceeds a predetermined threshold. When the peak voltage difference of data (difference between the maximum value and the minimum value of the voltage) is not more than a predetermined threshold value, it can be determined that the flying object scattering signal is not included. Since only the voltage peak value is scanned to determine whether or not the predetermined threshold value is exceeded, the process for determining whether or not the flying object scattering signal is included can be lightened and the determination process is required. The processing time can be quickly obtained by shortening the time.

  In the eighth invention, the receiving unit receives the radio wave scattered in the atmosphere by the beam emitted toward the atmosphere for each of a plurality of beam directions. The plurality of beam directions can be, for example, five directions including a zenith direction and an east-west-north-north direction inclined by a predetermined angle (for example, 14 degrees) from the zenith. For example, the beam can be sequentially emitted in a plurality of beam directions from an antenna installed horizontally near the ground. The beam is emitted as intermittent pulses and receives radio waves scattered while not being emitted.

  The generation unit converts and generates time domain reception data obtained using the reception unit into frequency domain reception data. For the transformation / generation, for example, complex FFT (fast Fourier transformation) may be used, or wavelet transformation may be used. Further, the altitude at which the radio wave is scattered can be obtained from the time difference between the beam emission time and the reception time of the scattered radio wave. The observation altitude can be determined as a required altitude from about 100 m to about 10 km, for example.

  The determination unit determines whether to use the exclusion process by the removal processing unit based on the phase rotation amount between the phase having the maximum amplitude in the reception data in the frequency domain and the previous phase value. The amplitude A in the received data in the frequency domain is represented by the square root of (I × I + R × R), ie, amplitude A = √ (I × I + R × R), where R is the real part of the complex number and I is the imaginary part. The maximum value is Amax. The phase represents the phase value α at Amax, where R is the real part of the complex number and I is the tangent part of the complex number, that is, the arc tangent of (I / R), that is, phase α = arctan (I / R). Further, the phase rotation amount Δα can be expressed by a difference between the current phase value α and the previous phase value α2, that is, Δα = α−α2. In deciding whether to use the received data exclusion process that includes the scattering component by the flying object, for example, Δα is compared with the upper and lower threshold values, and those that are above the lower threshold value and below the upper threshold value are regarded as precipitation echoes. Can be determined not to be used, and the difference from the previous phase rotation amount Δα2 = α2−α3, that is, the amount of change in the phase rotation amount can be compared with a threshold value.

  According to the present invention, it is possible to improve the accuracy of weather observation.

It is a block diagram which shows an example of a structure of the weather observation apparatus of this Embodiment. It is a schematic diagram which shows an example of a structure of an antenna apparatus. It is explanatory drawing which shows an example of the pulse signal which a transmission / reception apparatus sends out It is a schematic diagram which shows a mode that the beam emitted from the antenna apparatus is scattered in air | atmosphere. It is explanatory drawing which shows an example of reception data. It is explanatory drawing which shows an example of a Doppler spectrum. It is a schematic diagram which shows an example of the mode of the emitted beam. It is explanatory drawing which shows an example of the peak value of the Doppler spectrum for every beam direction. It is explanatory drawing which shows an example of the bird echo removal process according to the precipitation determination result. It is explanatory drawing which shows an example of the Doppler spectrum after incoherent integration. It is explanatory drawing which shows an example of a display of a Doppler spectrum. It is explanatory drawing which shows the other example of a display of a Doppler spectrum. It is explanatory drawing which shows an example which displayed the arrow vector of the wind vector. It is a flowchart which shows an example of the process sequence of a weather observation apparatus. It is a flowchart which shows an example of the process sequence of a weather observation apparatus.

(Embodiment 1)
Hereinafter, a weather observation apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of the weather observation apparatus 100 according to the present embodiment. As shown in FIG. 1, the weather observation apparatus 100 includes an antenna apparatus 10, a transmission / reception apparatus 20, a signal processing apparatus 30, a data processing apparatus 40 that provides a user interface for the signal processing apparatus 30, and the like. The weather observation apparatus 100 is a so-called wind profiler radar, which is a pulse Doppler radar having a center frequency of about 1.3 GHz.

  FIG. 2 is a schematic diagram showing an example of the configuration of the antenna apparatus 10. The antenna device 10 has, for example, an active phased array antenna. The opening area of the antenna is, for example, about 1 square meter to 20 square meters, and beam scanning (beam direction) has five directions, ie, the zenith direction and the east, west, north, and south directions having a predetermined zenith angle (for example, 14 degrees). Note that the plurality of directions (also referred to as beam directions) refer to at least two directions, for example, among the zenith direction and the five directions of the east, west, south, and north directions inclined at a predetermined angle (eg, 14 degrees) from the zenith.

  The transmitting / receiving device 20 transmits a pulse signal having a predetermined pulse width at a predetermined repetition period. The predetermined pulse width can be, for example, about 0.6 μs to 4 μs. The predetermined repetition period can be set to, for example, about 50 μs to 200 μs. In the present embodiment, the repetition period is described as 100 μs.

  FIG. 3 is an explanatory diagram illustrating an example of a pulse signal transmitted by the transmission / reception device 20. As shown in FIG. 3, the transmission / reception device 20 repeats pulse transmission with a predetermined pulse width at a repetition period T1 (100 μs) a predetermined number of times (for example, 64 times) that is the number of times of coherent integration. These are repeated for the number of FFT points (for example, 128 times). That is, the transmission / reception apparatus 20 transmits 64 × 128 pulses for one beam direction (beam scanning).

  The transmission / reception device 20 has a function as a reception unit, and is scattered in the atmosphere after the pulse signal 1 shown in FIG. 3 is emitted as a beam until the second pulse signal 2 is transmitted. Receive the received radio wave.

  FIG. 4 is a schematic diagram showing how the beam emitted from the antenna apparatus 10 is scattered in the atmosphere. The beam emitted in a predetermined direction is scattered by fluctuation of the refractive index of air in the atmosphere, and the scattered radio wave is received by the antenna apparatus 10. Assuming that the beam launch time is 0 and the reception times of scattered radio waves are t1, t2, and t3, it can be understood at which altitude in the atmosphere the radio waves received at each time are scattered. That is, the observation altitude of the received data can be calculated based on the emission time of the emitted beam and the reception time of the scattered radio wave. The observation altitude is calculated by the signal processing device 30. Further, as the observation altitude, for example, a required altitude from about 100 m to about 10 km can be determined.

  The signal processing device 30 includes a CPU 31 that controls the entire device, a signal processing unit 32, a determination unit 33, a flying object determination unit 34, and the like.

  The signal processing unit 32 has an AD converter, a DA converter, a coherent integration function, a fast Fourier transform function, an incoherent integration function, and the like.

  The signal processing device 30 acquires reception data obtained by receiving the scattered radio waves with the antenna device 10. The received data is time-series data indicating the intensity of radio waves scattered at the altitude for each observation altitude.

  FIG. 5 is an explanatory diagram showing an example of received data. In FIG. 5, the horizontal axis indicates time, and the vertical axis indicates voltage. As described above, the transmission / reception device 20 repeatedly transmits a pulse having a predetermined pulse width at a repetition period T1 (for example, 100 μs) for a predetermined number of times (for example, 64 times) that is the number of times of coherent integration. By repeating these for the number of FFT points (for example, 128 times), the received data becomes time-series data indicating 128 voltage values.

  FIG. 5 is a plot of 128 I-phase time-series data and Q-phase time-series data delayed by 90 degrees from the I-phase. The example of FIG. 5 shows received data whose beam direction is the zenith direction and whose observation altitude is h1, for example. That is, the same data as in FIG. 5 is obtained for other observation altitudes in the zenith direction, and similarly for each observation altitude in other beam directions.

  When the time-series data as illustrated in FIG. 5 is one reception data, the signal processing unit 32 integrates (coherent integration) the reception data for 64 pieces, for example. Increase the noise ratio (S / N ratio). Note that coherent integration corresponds to adding each received data while storing phase information of 64 pieces of received data.

  The flying object determination unit 34 determines whether or not the received data includes a flying object scattering signal in accordance with whether or not the peak value of the received data exceeds a predetermined range. As illustrated in FIG. 5, the reception data is time-series data indicating the intensity of radio waves scattered at a predetermined altitude, and each data can be represented by, for example, positive and negative voltage values. Note that whether or not the flying object scatter signal is included in the received data can be determined using the time domain received data and can also be determined using the frequency domain spectrum.

  Signals received from the atmosphere (atmospheric echoes) are very weak, whereas signals received from flying objects such as flocks of birds (migratory birds), insects, or aircraft (referred to as bird echoes or flying object echoes) There is a tendency to be strong.

  That is, the flying object determining unit 34 determines that the flying data is included in the received data when the peak voltage of the received data (the maximum value of the absolute value of the voltage) exceeds a predetermined threshold value. When the peak voltage (the maximum absolute value of the voltage) is less than or equal to a predetermined threshold value, it is determined that the flying object scattering signal is not included in the received data.

  The flying object determination unit 34 turns on the flag with the flying object scattering signal in association with the reception data determined to include the flying object scattering signal. Note that all the flags are turned off in advance before the flying object determination. That is, as a result of the flying object determination, the flag is turned on only for the flying object. In addition to the method of turning on the flag, an appropriate method can be used to distinguish the presence / absence of the flying object scattering signal.

  As described above, it is only necessary to scan the peak value of the voltage of the received data and determine whether or not the predetermined threshold is exceeded. Therefore, the process of determining whether or not the flying data is included in the received data is performed. In addition to reducing the weight, the time required for the determination process can be shortened, and the processing result can be obtained quickly. That is, in the case of a method for determining a flying object echo according to whether or not the power of time-series received data is equal to or higher than a predetermined power threshold, it is necessary to calculate the power of the received data. The processing for discriminating is heavy, the processing time is long, and the determination result cannot be obtained quickly. For this reason, it is necessary to take measures such as reducing the number of observation points. However, in this embodiment, such a problem can be solved.

  The signal processing unit 32 has a function as a removal processing unit, and performs a process of excluding received data including a scattered component by the flying object according to the determination result of the flying object determining unit 34.

  The signal processing unit 32 has a function as a generation unit. The received data as illustrated in FIG. 5 is converted into a spectrum (for example, Doppler spectrum) for each beam direction by orthogonal transformation such as Fourier transformation or other transformation operations. Generate. The orthogonal transform is, for example, complex FFT (fast Fourier transform) or wavelet transform, and performs time / frequency transform.

  FIG. 6 is an explanatory diagram showing an example of a Doppler spectrum. In FIG. 6, the horizontal axis represents the Doppler frequency, and the vertical axis represents the spectrum intensity. In the example of FIG. 6, the Doppler frequency is shown in the range of −10 Hz to 10 Hz, but is not limited to this. As shown in FIG. 6, the Doppler spectrum shows the distribution of spectrum intensity with respect to the Doppler frequency, which is the frequency difference between the frequency of the emitted beam caused by the Doppler effect and the frequency of the received radio wave.

  The example of FIG. 6 shows, for example, a Doppler spectrum in which the beam direction is the zenith direction and the observation altitude is h1. That is, the same data as in FIG. 6 is obtained for other observation altitudes in the zenith direction, and similarly for each observation altitude in other beam directions.

  The signal processing unit 32 generates a Doppler spectrum as illustrated in FIG. 6 for each of the five beam directions including the zenith direction and the east, west, south, and north directions over about 2 seconds. Then, the signal processing unit 32 repeats the same process 30 times over about 1 minute. That is, the Doppler spectrum illustrated in FIG. 6 is generated 30 times for each of the five beam directions of the zenith direction and the east, west, south, and north directions. Note that the number of generations is not limited to 30.

  Next, a method for determining whether or not to use received data removal processing including scattered components by the flying object will be described. The determination unit 33 determines whether to use the exclusion processing by the signal processing unit 32 (removal processing unit) based on the commonality between the reception data in the frequency domain for radio beams with different directions.

  FIG. 7 is a schematic diagram showing an example of the state of the emitted beam. For simplicity, FIG. 7A illustrates a zenith beam in the zenith direction, and FIG. 7B illustrates an east beam in the east direction. Precipitating particles fall in a substantially wide range in the atmosphere in a vertically downward direction or a substantially vertical direction in response to horizontal wind. The beam pattern of a directional antenna used in a wind profiler or the like is composed of a main lobe that is strong in the main axis direction and side lobes that leak in the other direction. For example, in the case of a wind profiler that oscillates a radio wave beam only at the approximate zenith with a zenith angle of about 14 degrees, scattering from precipitation particles falling in a substantially vertical direction over a relatively wide range is mainly performed regardless of the beam direction. There is a commonality between different beam directions, for example, the same level of scattering intensity can be obtained at the same altitude in any beam direction.

  On the other hand, flying objects such as a flock of birds are present at a relatively low altitude and in a relatively narrow area, and move in a substantially horizontal direction. Therefore, although a bird echo is captured in one specific beam direction, a bird echo cannot be captured in another beam direction, and there is a bird echo at an altitude of 100 m in one beam direction. , 300 m, etc., there is no commonality between different beams. By using these characteristics, it is possible to distinguish the reception data caused by the flying object and the reception data caused by the precipitation particles, and the observation accuracy such as the wind speed and the wind direction can be improved.

  That is, the determination unit 33 uses the exclusion process by the signal processing unit 32, assuming that the scattered radio wave includes a scattering component due to precipitation particles when the reception data in the frequency domain for radio waves with different directions are common. Decide not to. On the other hand, the determination unit 33 uses the exclusion process by the signal processing unit 32, assuming that the scattered radio wave includes a scattered component due to the flying object when the reception data in the frequency domain for radio waves with different directions is not common. Then decide.

  Next, a method for determining the presence or absence of commonality will be described. The determination unit 33 calculates a difference value between the peak values of the Doppler spectrum for each beam direction. When the plurality of beam directions are the five directions of the zenith direction and the east, west, north, and south directions, the difference value may be any two of the five directions, or may be the three directions, the four directions, or all the directions.

  FIG. 8 is an explanatory diagram showing an example of the peak value of the Doppler spectrum for each beam direction. As shown in FIG. 8, it is assumed that there are five beam directions, ie, zenith, east, west, south, and north, and the Doppler spectrum peak values in the respective beam directions are Pz, Pe, Pw, Ps, and Pn. When the calculated difference value is equal to or less than the predetermined difference threshold value Pth, the determination unit 33 determines that the precipitation scattering signal is included as having commonality. For example, if | Pz−Pe | <Pth, it can be determined that there is commonality. In addition, in order to improve the accuracy of the determination of the presence / absence of commonality, the determination is made not only by the commonality between any two beam directions but also by whether or not the difference value between the five directions is equal to or less than a predetermined difference threshold value Pth. It is preferable to do this. As described above, the presence or absence of precipitation can be determined with a simple configuration in which the peak values of Doppler spectra in different beam directions are compared with each other.

  Next, the relationship between the precipitation determination result and the flying object determination result will be described. When the signal processing unit 32 determines that the flying object scatter signal is included in the received data in the flying object determination unit 34 and the determination unit 33 determines that the precipitation scatter signal is not included, the reception processing unit 32 receives the reception signal. Exclude the data and generate a Doppler spectrum. That is, if the received data peak voltage (maximum absolute value of the voltage) exceeds a predetermined threshold and it is determined that the flying data scatter signal is included in the received data, the precipitation scatter signal is included. If it is determined that the scattered data contained in the received data is not caused by precipitation particles, but is caused by a flying object, the received data is excluded (for example, bird echo removal processing) To generate a Doppler spectrum.

  FIG. 9 is an explanatory diagram showing an example of a bird echo removal process according to the precipitation determination result. FIG. 9 illustrates, for example, the case where the beam direction is the zenith direction and the altitude is h1. As shown in FIG. 9, it is assumed that there are 30 received data “1”, “2”,..., “30” divided in time during time T2 (for example, 1 minute). One reception data includes 128 time-series data for each of the I-phase and Q-phase illustrated in FIG.

  The Doppler spectra “1”, “2”,... “30” are generated by performing a complex FFT on the received data “1”, “2”,.

  As shown in FIG. 9, when the peak voltage (maximum value of the absolute value of the voltage) of the fourth received data “4” exceeds a predetermined threshold value, a flying object scattering signal is included in the received data. Assume that you have determined. That is, it is determined that the received data “4” includes a bird echo.

  In this case, when the determination unit 33 determines that the precipitation scattering signal is not included, that is, when it is determined that there is no precipitation echo, the Doppler spectrum obtained by performing the complex FFT on the fourth received data “4”. A smoothed Doppler spectrum is generated by performing incoherent integration using the remaining 29 Doppler spectra excluding “4”. Thereby, flying object scattering signals such as bird echoes can be reliably removed, and wind speed, wind direction, etc. can be observed with high accuracy.

  On the other hand, when the signal processing unit 32 determines that the flying object scatter signal is included in the received data and determines that the precipitation scattered signal is included, the signal processor 32 does not exclude the received data and does not exclude the received data. Is generated. That is, if it is determined that the received data includes a flying object scattering signal on the assumption that the peak voltage of the received data (the maximum absolute value of the voltage) exceeds a predetermined threshold, the precipitation scattering signal is included. If it is determined that the scattered data included in the received data is due to precipitation particles and not due to flying objects, the received data is not excluded (for example, bird echo) A Doppler spectrum is generated without performing a removal process.

  That is, when the determination unit 33 determines that the precipitation scattering signal is included, that is, when it is determined that there is a precipitation echo, the Doppler spectrum “4” obtained by performing the complex FFT on the fourth received data “4”. A smoothed Doppler spectrum is generated by incoherent integration using 30 Doppler spectra without excluding "4". Thereby, it is possible to prevent the received data from being erroneously removed as the flying object scattering signal, and it is possible to observe the wind speed, the wind direction, and the like with high accuracy.

  FIG. 10 is an explanatory diagram showing an example of a Doppler spectrum after incoherent integration. In FIG. 10, the horizontal axis represents the Doppler frequency, and the vertical axis represents the spectrum intensity. In the example of FIG. 10, the Doppler frequency is shown in the range of −10 Hz to 10 Hz, but is not limited to this. The example of FIG. 10 shows, for example, a Doppler spectrum in which the beam direction is the zenith direction and the observation altitude is h1. That is, the same data as in FIG. 10 is obtained for other observation altitudes in the zenith direction, and similarly for each observation altitude in other beam directions.

  In addition, the flying object determination unit 34 can determine whether or not a flying object scattering signal is included for each beam direction. For example, a different or the same threshold value is set for each beam direction, and the flying object determination unit 34 sets the peak voltage (the maximum absolute value of the voltage) of the reception data to a predetermined threshold value for each different beam direction. When it exceeds, it is determined that the flying object scatter signal is included in the received data, and when the peak voltage of the received data (the maximum value of the absolute value of the voltage) is equal to or lower than a predetermined threshold, the flying object scatter signal is included in the received data. It is determined that it is not included. Thereby, it is possible to determine whether the flying object scattering signal is mixed for each different beam direction, and the accuracy of weather observation can be improved.

  In addition, the flying object determination unit 34 can determine whether or not a flying object scattering signal is included for each altitude. For example, a different or the same threshold value is set for each altitude, and the flying object determination unit 34 has a peak voltage (maximum absolute value of voltage) of received data that exceeds a predetermined threshold value for each different altitude. When it is determined that the flying data is included in the received data and the peak voltage of the received data (the maximum absolute value of the voltage) is equal to or lower than a predetermined threshold, the flying data is included in the received data. Judge that it is not. Thereby, it is possible to determine whether the flying object scattering signal is mixed for each different altitude, and it is possible to improve the accuracy of weather observation.

  Note that the presence or absence of a bird echo or the like may be determined based on whether or not the maximum value of the absolute value of the received data voltage exceeds the threshold in all beam directions and all altitudes.

  FIG. 11 is an explanatory diagram showing an example of display of a Doppler spectrum. In the example of FIG. 11, for the sake of simplicity, a display example of a Doppler spectrum in which the beam direction is east and west is shown. However, a display example of the Doppler spectrum illustrated in FIG. The direction can be determined. In FIG. 11, the horizontal axis indicates the Doppler frequency, and the vertical axis indicates the altitude. In addition, the intensity of the spectrum is expressed in contour lines by the difference in color or the difference in shading. In the example of FIG. 11, the spectrum intensity is shown in five steps for simplicity, but in actuality, it can be displayed in more steps or continuously.

  In the example of FIG. 11, in the Doppler spectrum in which the beam direction is east, the Doppler frequency at the place where the spectrum intensity at the altitude indicated by the broken line is the highest is approximately −50 Hz. When the wavelength of the radio wave is λ, the moving speed of the wind (turbulent flow) is V, and the Doppler frequency is f, there is a relationship of V = λ × f / 2, and the wind speed is approximately −5.5 m / s. For example, if it is defined as a direction away when the Doppler frequency is negative, it can be determined that the east direction is away.

  On the other hand, in the Doppler spectrum in which the beam direction is west, the Doppler frequency at the highest spectral intensity at the altitude indicated by the broken line is approximately 50 Hz, and the wind speed is approximately 5.5 m / s. For example, if it is defined as a direction to go away when the Doppler frequency is negative, it can be determined that the west direction is approaching. As a result, it can be seen that at the altitude indicated by the broken line, it approaches from the west and moves away from the east, that is, west wind. The wind speed is understood to be (5.5-(− 5.5)) / 2Sin (14) ≈22.7 m / s, assuming that the beam tilt angle, that is, the zenith angle is 14 degrees, for example.

  FIG. 12 is an explanatory diagram showing another example of displaying a Doppler spectrum. In the example of FIG. 12, for the sake of simplicity, a display example of the Doppler spectrum with the beam direction being the zenith is shown, but the display example of the Doppler spectrum illustrated in FIG. Can be sought. In FIG. 12, the horizontal axis indicates the Doppler frequency, and the vertical axis indicates the altitude. In addition, the intensity of the spectrum is expressed in contour lines by the difference in color or the difference in shading. In the example of FIG. 12, the spectrum intensity is shown in five steps for simplicity, but actually, it can be displayed in more steps or continuously.

  FIG. 12A shows a Doppler spectrum when the bird echo removal process is not performed in the case of fine weather. As shown in FIG. 12A, it is possible to confirm an area where the band-like spectrum intensity is large in a wide range of Doppler frequency at a relatively low altitude. This is presumably because, in the case of a flock of birds, the variation in Doppler frequency increases due to fluctuations in the scattering state of radio waves due to variations in bird flight and flapping.

  On the other hand, as a result of the determination by the flying object determination unit 34 of the present embodiment, when the bird echo removal process is performed, as shown in FIG. 12B, the band-like spectrum intensity seen in a wide range of Doppler frequencies is large. The area can be removed, and a highly accurate Doppler spectrum can be obtained.

  FIG. 13 is an explanatory diagram showing an example in which the wind vector is displayed as an arrow. In FIG. 13, the horizontal axis indicates time, for example, the elapsed state of 4 hours. In FIG. 13, the upper side indicates north, the lower side indicates south, the right side indicates east, and the left side indicates west. Arrow feathers indicate the direction and strength of the wind.

  As shown in FIG. 13A, when the bird echo removal process is not performed, it can be seen that there is a disturbance in the wind direction in the portion surrounded by a circle in the figure. On the other hand, as shown in FIG. 13B, when the bird echo removal process is performed, the turbulence in the wind direction is removed.

  Next, the operation of the weather observation apparatus 100 of the present embodiment will be described. 14 and 15 are flowcharts showing an example of the processing procedure of the weather observation apparatus 100. The processing illustrated in FIGS. 14 and 15 is mainly processing in the signal processing device 30, and for the sake of convenience, the subject of the processing will be described as the CPU 31.

  The CPU 31 sets the beam direction (S11), and emits the beam in the set beam direction (S12). The CPU 31 receives the scattered radio wave (S13) and extracts time-series data of received data at a predetermined altitude (S14). Here, the time series data to be extracted is illustrated in FIG.

  The CPU 31 coherently integrates a plurality of pieces (for example, 64 pieces) of received data to increase the signal-to-noise ratio (S / N ratio) of the received data (S15). The CPU 31 acquires time series data (received data) for the number of FFT points (for example, 128 points) (S16). The CPU 31 determines whether or not there is a bird echo in the received data (S17). If there is a bird echo (YES in S17), the flag of the received data determined to have a bird echo (with flying object scattering signal) Flag) is turned on (S18). If there is no bird echo (NO in S17), the CPU 31 performs the process of step S19 described later without performing the process of step S18.

  The CPU 31 determines whether or not the process has been performed a predetermined number of times (for example, 30 times) (S19), and if it is not the predetermined number of times (NO in S19), the process after step S14 is continued. If it is the predetermined number of times (YES in S19), the CPU 31 performs a complex FFT process on each of the predetermined number of received data (S20).

  The CPU 31 determines whether or not the processing has been completed for all the beam directions (S21). If the processing has not been completed for all the beam directions (NO in S21), the beam direction is switched (S22). Repeat the process.

  When all the beam directions are completed (YES in S21), the CPU 31 determines whether there is a precipitation echo (S23). If there is a precipitation echo (YES in S23), all the flags turned on in step S18 are turned off (S24). When there is no precipitation echo (NO in S23), the CPU 31 performs the process of step S25 described later without performing the process of step S24.

  The CPU 31 excludes the Doppler spectrum corresponding to the reception data in which the flag (the flag with the flying object scattering signal) is turned on from the Doppler spectrum generated by the complex FFT in Step S20, and corresponds to the reception data with the flag off. Incoherent integration is performed using only the Doppler spectrum (S25), a smoothed Doppler spectrum is generated (S26), and the process ends.

  The signal processing apparatus 30 described above can also be realized using a general-purpose computer including a CPU, a RAM, and the like. That is, as shown in FIGS. 14 and 15, a computer program that defines each processing procedure is recorded on a recording medium, the recording medium is loaded into a RAM provided in the computer, and the computer program is executed by the CPU. Thus, the processing performed by the signal processing device 30 on the computer can be realized. 14 and 15 can be downloaded via a network such as the Internet instead of the recording medium.

  In the above-described embodiment, as illustrated in FIG. 9, when the received data “4” includes a bird echo, the Doppler spectrum corresponding to the received data “4” is excluded to perform incoherent integration. However, the present invention is not limited to this. For example, as illustrated in FIG. 9, when it is determined that the bird data is included in the reception data “4”, the Doppler corresponding to the reception data “3” and “5” before and after the reception data “4”. The spectrum may be excluded and incoherent integration may be performed. Immediately after a flock of birds enters or exits the beam irradiation area, the level difference between the bird echo and the required signal may be small, and the range to be removed in a time series should be widened. Thus, the influence of a flock of birds and the like can be reliably removed.

  In the first embodiment described above, the flying object determination unit 34 includes a scattered component due to the flying object when the difference value obtained by subtracting the minimum value from the maximum value of the reception data in the time domain exceeds the threshold value. You may make it determine with it. The received data in the time domain can be expressed by positive and negative voltage values. That is, the flying object determination unit 34 determines that the flying object scattering signal is included when the peak voltage difference (the difference between the maximum value and the minimum value of the voltage) of the reception data in the time domain exceeds a predetermined threshold value. When the peak voltage difference (the difference between the maximum value and the minimum value) of the received data is equal to or less than a predetermined threshold, it can be determined that the flying object scattering signal is not included. Since only the voltage peak value is scanned to determine whether or not the predetermined threshold value is exceeded, the process for determining whether or not the flying object scattering signal is included can be lightened and the determination process is required. The processing time can be quickly obtained by shortening the time.

(Embodiment 2)
In the first embodiment, the precipitation determination is performed based on the commonality of Doppler spectra between a plurality of beam directions. However, the present invention is not limited to this. In the second embodiment, the precipitation determination is performed only in one beam direction. Hereinafter, precipitation determination according to the second embodiment will be described. The beam direction may be either the zenith direction or the east, west, south, and north directions.

  The signal processing unit 32 performs Fourier transform on the received data obtained by reception to generate a Doppler spectrum a plurality of times. The Fourier transform is, for example, a complex FFT (fast Fourier transform) as in the first embodiment.

  The determination unit 33 determines whether to use the exclusion processing by the signal processing unit 32 (removal processing unit) based on the phase rotation amount between the phase having the maximum amplitude in the reception data in the frequency domain and the previous phase value. . The amplitude A in the received data in the frequency domain is represented by the square root of (I × I + R × R), ie, amplitude A = √ (I × I + R × R), where R is the real part of the complex number and I is the imaginary part. The maximum value is Amax. The phase represents the phase value α at Amax, where R is the real part of the complex number and I is the tangent part of the complex number, that is, the arc tangent of (I / R), that is, phase α = arctan (I / R). Further, the phase rotation amount Δα can be expressed by a difference between the current phase value α and the previous phase value α2, that is, Δα = α−α2. In deciding whether to use the received data exclusion process that includes the scattering component by the flying object, for example, Δα is compared with the upper and lower threshold values, and those that are above the lower threshold value and below the upper threshold value are regarded as precipitation echoes. Can be determined not to be used, and the difference from the previous phase rotation amount Δα2 = α2−α3, that is, the amount of change in the phase rotation amount can be compared with a threshold value.

(Embodiment 3)
In the third embodiment, an example in which precipitation determination is performed using a beam in the zenith direction will be described. The determination unit 33 determines whether to use the exclusion process by the signal processing unit 32 (removal processing unit) based on the continuity between the received data in the frequency domain for different altitudes. For example, since precipitation particles exist over an altitude of several kilometers, they have continuity in the altitude direction, such that the same scattering intensity can be obtained over an altitude of several kilometers. On the other hand, flying objects such as flocks of birds do not exist at altitudes of several kilometers, so by using these characteristics, received data caused by flying objects and received data caused by precipitation particles are distinguished. Observation accuracy such as wind speed and direction can be improved.

(Embodiment 4)
In the above-described embodiment, the flying object determination is performed according to whether or not the peak value of the voltage of the received data exceeds a predetermined range, but is not limited to this. For example, as a power value of the Doppler spectrum, when a value obtained by integrating the Doppler spectrum on the frequency axis exceeds a predetermined power threshold value, it may be determined that there is a bird echo. Alternatively, when the spectrum intensity of the Doppler spectrum exceeds a predetermined intensity threshold, it may be determined that there is a bird echo. Alternatively, it may be determined that there is a bird echo when the power of received data in a certain time range exceeds a predetermined power threshold.

  For example, the flying object determining unit 34 can determine that the scattered radio wave includes a scattered component due to the flying object when the amplitude of the received data in the frequency domain or the maximum value of the received data power exceeds a threshold value. . The amplitude A in the received data in the frequency domain is represented by the square root of (I × I + R × R), ie, amplitude A = √ (I × I + R × R), where R is the real part of the complex number and I is the imaginary part. And the power P can be expressed by its square, that is, P = (I × I + R × R). The maximum value of these amplitude values or power values is obtained. For example, if the maximum value is equal to or greater than a threshold value, it can be determined that the flying object echo is included.

  In addition, the flying object determination unit 34 can determine that the scattered radio wave includes a scattered component due to the flying object when the integral value of the power of the received data in the frequency domain exceeds a threshold value. The power P in the frequency domain received data can be expressed as P = (I × I + R × R) where R is the real part of the complex number and I is the imaginary part. The integrated value Psum of the power can be expressed by integrating the power P at all frequency points or at a plurality of frequency points around the maximum value of the power P, that is, Psum = ΣP. For example, if the integral value of the power is greater than or equal to the threshold value, it can be determined that the flying object echo is included.

  However, when using the total power of the Doppler spectrum or using the power of the received data, it takes time to calculate the power value, so the observed value cannot be calculated quickly, and the observation points are thinned out. Therefore, the above-described first to third embodiments are superior. Similarly, when using the spectral intensity of the Doppler spectrum, it is necessary to scan the Doppler spectrum along the frequency axis to search for the peak value, and the observed value cannot be calculated quickly, and the observation points are thinned out. Therefore, the above-described first to third embodiments are superior.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Antenna apparatus 20 Transmission / reception apparatus 30 Signal processing apparatus 31 CPU
32 signal processing unit 33 determination unit 34 flying object determination unit 40 data processing device

Claims (10)

A receiver for receiving scattered radio waves of radio waves emitted in multiple directions toward the atmosphere;
A generating unit that generates frequency domain received data from time domain received data obtained using the receiving unit;
A flying object determination unit that determines whether or not a scattered component by the flying object is included in the scattered radio wave based on at least one of the reception data in the time domain and the frequency domain;
According to the determination result of the flying object determining unit, an exclusion processing unit that performs an exclusion process of received data including a scattered component by the flying object;
A weather observation apparatus comprising: a determination unit that determines whether to use exclusion processing by the removal processing unit based on commonality between the reception data in the frequency domain for radio beams having different directions. The determination unit
The meteorological observation according to claim 1, further comprising: determining whether or not to use exclusion processing by the removal processing unit based on a phase rotation amount between a phase having a maximum amplitude in the received data in the frequency domain and a previous phase value. apparatus. The determination unit
The meteorological observation apparatus according to claim 1, further comprising: determining whether to use exclusion processing by the removal processing unit based on continuity between reception data in the frequency domain for different altitudes. The flying object determination unit
4. The method according to claim 1, wherein when the amplitude of the received data in the frequency domain or the maximum value of the power of the received data exceeds a threshold value, it is determined that a scattered component by the flying object is included in the scattered radio wave. The weather observation apparatus according to any one of the above. The flying object determination unit
4. The device according to claim 1, wherein when the integrated value of the power of the reception data in the frequency domain exceeds a threshold value, it is determined that a scattered component due to the flying object is included in the scattered radio wave. 5. Weather observation equipment. The flying object determination unit
4. The method according to claim 1, wherein when the maximum value of the absolute value of the reception data in the time domain exceeds a threshold value, it is determined that a scattered component by the flying object is included in the scattered radio wave. 5. The described weather observation apparatus. The flying object determination unit
4. The method according to claim 1, wherein when the difference value obtained by subtracting the minimum value from the maximum value of the reception data in the time domain exceeds a threshold value, it is determined that a scattered component due to the flying object is included in the scattered radio wave. The weather observation apparatus according to any one of the above. A receiver for receiving scattered radio waves of radio waves emitted toward the atmosphere;
A generating unit that generates frequency domain received data from time domain received data obtained using the receiving unit;
A flying object determination unit that determines whether or not a scattered component by the flying object is included in the scattered radio wave based on at least one of the reception data in the time domain and the frequency domain;
In accordance with the determination result of the flying object determination unit, an exclusion processing unit that performs an exclusion process of received data including a scattered component by the flying object;
A weather observation apparatus comprising: a determination unit that determines whether or not to use exclusion processing by the removal processing unit based on a phase rotation amount between a phase having a maximum amplitude in the reception data in the frequency domain and a previous phase value.   A weather observation program for causing a computer to function as the weather observation apparatus according to any one of claims 1 to 8. Receiving scattered radio waves of radio beams launched in multiple directions toward the atmosphere;
Generating frequency domain received data from time domain received data obtained through the receiving step;
Determining whether or not to use reception data exclusion processing including a scattered component by a flying object based on commonality between reception data in the frequency domain with respect to radio beams having different directions.

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