JP5214562B2 - Meteorological radar system and its precipitation intensity calculation method and program - Google Patents

Description

  The present invention relates to a weather radar system that contributes to weather disaster prevention, such as rainfall calculation in dams, rivers, roads, sewer management, etc., using multi-parameter radar (also known as dual polarization Doppler radar), and in particular, for calculating precipitation intensity. The present invention relates to a technique for improving resolution and accuracy.

In a conventional weather radar system, precipitation intensity is calculated using a method based on one of the observation parameters of phase difference between specific polarizations (K _DP ), radar reflection factor (Z), and differential radar reflection factor (Z _DR ). It was broken. Moreover, precipitation intensity calculation was performed by switching three methods according to the strength of the expected precipitation intensity or the clutter level (see Non-Patent Document 1).

However, the phase resolution between specific polarizations (K _DP ) has a large distance resolution, and the radar reflection factor (Z) maintains the relative relationship between the strength of precipitation, but the absolute accuracy is low, the radar reflection factor ( Z) and differential radar reflectivity factor (Z _DR ) have problems such as poor accuracy when the radio wave is attenuated due to rainfall.

V.N.Bringi and V.Chandrasekar, POLARIMETRIC DOPPLER WEATHER RADAR, CAMBRIDGE UNIVERSITY PRESS, p.517, 2001. “Radar Remote Sensing of Weather and Atmosphere” by Fukao and Hamazu, Kyoto University Academic Press, published in March 2005

As described above, in the conventional weather radar system, precipitation intensity is measured by a method based on one of the observation parameters among the phase difference between specific polarizations (K _DP ), the radar reflection factor (Z), and the differential radar reflection factor (Z _DR ). Calculations were made, and precipitation intensity was calculated by switching between the three methods depending on the strength of the expected precipitation intensity or the clutter level. However, each observation parameter has its advantages and disadvantages and is accurate. There was a problem that results could not be obtained stably.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a weather radar system, a precipitation intensity calculation method, and a program for calculating the precipitation intensity with high resolution and high accuracy.

  The meteorological radar system and its precipitation intensity calculating method and program according to the present invention employ the following means in order to achieve the above object.

In the first aspect, a horizontally-polarized wave and a vertically-polarized radar wave are transmitted simultaneously, and a reflected wave is received. A signal processing device for calculating received power, and a radar reflection factor (Z _H ) for horizontally polarized waves with a first spatial resolution based on the beam width and pulse width of the radar wave based on the received power for each polarization, and means and said horizontal radar reflectivity factor of polarization (Z _H) and differential radar reflection based on radar reflectivity factor (Z _V) of the vertically polarized wave to calculate the radar reflectivity factor of vertical polarization (Z _V) Based on the means for calculating the factor (Z _DR ) and the phase difference between the polarizations of the received power (φ _DP ), the phase difference between the polarizations (K _DP ) is calculated with a second spatial resolution lower than the first spatial resolution. And means for each second spatial resolution region based on the phase difference between the specific polarizations (K _DP ). The relationship between the means for calculating the average precipitation intensity (R _ave [mm / h]) and the radar reflection factor (Z _H ) of the horizontally polarized wave and the precipitation intensity (R [mm / h]) is as follows: When represented
Z _H = B × R ^β (B and β are constants)
Means for calculating a first constant (B) based on the differential radar device reflection factor (Z _DR ), the first constant (B), the average precipitation intensity (R _ave [mm / h]), and the horizontal Means for estimating the second constant (β) included in the relational expression based on the radar reflection factor (Z _H ) of the polarization; the first constant (B); the second constant (β); Means for calculating the precipitation intensity (R [mm / h]) of the first spatial resolution based on the relational expression based on the radar reflection factor (Z _H ) of the horizontally polarized wave.

A second aspect further includes means for removing a high frequency component of the inter-polarization phase difference (φ _DP ) in the first aspect.

In a third aspect, in the first or second aspect, the attenuation with respect to the distance between the radar reflection factor (Z _H ) of the horizontally polarized wave and the radar reflection factor (Z _V ) of the vertically polarized wave is calculated between the polarizations. A means for correcting using the phase difference (φ _DP ) is further provided.

A fourth aspect further comprises means for smoothing the precipitation intensity (R (K _DP ) [mm / h]) in the azimuth direction and the distance direction in any one of the first to third aspects. is there.

  According to the present invention, it is possible to provide a weather radar system capable of calculating precipitation intensity with high resolution and high accuracy, and a precipitation intensity calculation method and program thereof.

1 is a block configuration diagram showing an embodiment of a weather radar system according to the present invention. The block block diagram which shows the other structural example of the weather radar system which concerns on this invention. The processing system figure which shows the flow of a process of the data converter of the weather radar system shown in FIG. FIG. 4 is a waveform diagram for explaining the low-pass filter processing shown in FIG. 3. The figure which shows the detail of the 2nd constant estimation process shown in FIG. The figure which shows the detail of the smoothing process shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings, the same symbols indicate the same or corresponding parts.

  FIG. 1 is a block diagram showing a configuration of a weather radar system using a multi-parameter radar as an embodiment of the present invention. This system includes an antenna device (antenna) 11, a transmission device (horizontal polarization) 12, a reception device (horizontal polarization) 13, a transmission device (vertical polarization) 14, a reception device (vertical polarization) 15, and a frequency conversion device. (Vertically polarized wave) 16, a signal processing device 17, a monitoring control device 18, a data conversion device 19, a data display device 20, a data storage device 21, a data communication device 22, a remote monitoring control device 23, and a remote display device 24. .

  Here, as shown in FIG. 2, the transmission device 12 may be configured to share the horizontal polarization and the vertical polarization. A configuration in which the frequency converter 16 can be separated, for example, is further conceivable in both FIG. 1 and FIG.

  In the above configuration, when a monitoring control signal from the remote monitoring control device 23 is sent to the signal processing device 17 through the monitoring control device 18, digital data of a seed signal stored therein is generated in the signal processing device 17. After the D / A conversion, the signals are transmitted to the frequency conversion device 16 as horizontal polarization and vertical polarization transmission IF signals, and are up-converted to RF signals, respectively.

  The horizontally-polarized and vertically-polarized transmission RF signals obtained by the frequency converter 16 are amplified by the transmitters 12 and 14 to transmission power that can be observed over a long distance. The amplified two waves of horizontal polarization and vertical polarization are simultaneously sent from the antenna device 11 to the space.

  Both the horizontally polarized waves and the reflected waves caused by the vertically polarized waves from the precipitation in the space are captured by the antenna device 11 for each of the horizontally polarized waves and the vertically polarized waves, respectively, and received by the receiving devices 13 and 15, respectively. After being converted into an IF signal at 16, both are sent to the signal processing device 17.

  The signal processing device 17 performs A / D conversion on the received IF signal of horizontal polarization / vertical polarization sent to the horizontal polarization / vertical polarization, performs I / Q detection, and then receives received power (horizontal polarization, Vertical polarization), a function of calculating a phase difference between polarizations between a horizontal polarization and a vertical polarization, a cross-correlation between polarizations, and a Doppler velocity.

The data converter 19 calculates a plurality of observation parameters such as a relative polarization phase difference (K _DP ), a radar reflection factor (Z), and a differential radar reflection factor (Z _DR ) from the received power obtained by the signal processing device 17. The precipitation intensity (R) is calculated using these observation parameters. Specific processing contents will be described later.

  The data display device 20 displays the data analyzed by the data conversion device 19. The data storage device 21 stores the data analyzed by the data conversion device 19. The data communication device 22 takes communication means outside the radar site and transfers the data analyzed by the data conversion device 19. The remote display device 24 displays or analyzes the data transferred from the radar site. The remote monitoring control device 23 can monitor the radar system in the same manner as the monitoring control device 18.

In the weather radar system having the above configuration, the precipitation intensity calculating method according to the present invention will be described with reference to FIG.
FIG. 3 is a processing system diagram showing the flow of processing of the precipitation intensity calculation method used in the data converter 19 of the weather radar system. In FIG. 3, the normal calculation method is based on “Radar Remote Sensing of Weather and Atmosphere (Fukao et al.)” Of Non-Patent Document 2.

In the radar reflection factor calculation processing 101, based on the radar equation, a horizontal polarization radar reflection factor (Z _H ) is calculated from the horizontal polarization reception power (Pr _H ), and the vertical polarization reception power (Pr _V ). The radar reflection factor (Z _V ) of vertical polarization is calculated from The resolution of the radar reflection factors (Z _H , Z _V ) corresponds to the horizontal beam width in the azimuth direction and the pulse width in the distance direction. The resolution of this radar reflection factor (Z _H , Z _V ) is called high resolution (first spatial resolution).

In the low-pass filter process 102, the phase difference (φ _DP ) between the polarizations is filtered in the distance direction using a low-pass filter such as IIR or FIR. For the phase difference between polarizations (φ _DP ), in order to remove as high frequency components as possible, a large average number of hits in the azimuth direction is taken. As a result, by taking a certain number of radar hits in the azimuth direction, data is generated with a beam width greater than or equal to the horizontal beam width. Further, since a high-frequency component exists in the distance direction, if the specific polarization phase difference (K _DP ), which is the distance derivative of the polarization phase difference (φ _DP ), is calculated as it is, the data includes a lot of noise components. For this reason, the low-pass filter processing 111 removes the high-frequency component in the distance direction of the inter-polarization phase difference (φ _DP ). This is shown in FIG. In FIG. 4, (a) shows the pre-filter processing, (b) shows the post-filter processing, the horizontal axis indicates the distance (r), and the vertical axis indicates the inter-polarization phase difference (φ _DP ). .

In the attenuation correction process 103, the radar attenuation factor (Z _H ) is estimated from the phase difference (φ _DP ) between the polarizations of the horizontally polarized waves and the vertically polarized waves up to the region, and is corrected. Specifically, the radar reflectivity factor (Z _H ) after correction is obtained by the following equation. Α is a constant. If the radar reflection factor at the point r before correction is Z _H (r) ′,
10log ₁₀ Z _H (r) = ₁₀ log ₁₀ Z _H (r) ´−α (φ _DP (r) −φ _DP (0))
And can be calculated. Further, the value after the filter processing in the low-pass filter processing 102 may be used for the inter-polarization phase difference (φ _DP ).

In the specific polarization phase difference calculation process 104 calculates the ratio polarizations retardation (K _DP) by a distance differential polarization phase difference (phi _DP). The relative polarization phase difference (K _DP ) corresponding to the total rainfall between the two points is expressed as φ _DP (r ₁ ), φ _DP (r ₂ ) after passing through the filters at two points r1 and r2 in the distance direction. ), It can be calculated by the following equation.
K _DP = {φ _DP (r ₂ ) −φ _DP (r ₁ )} / {2 (r ₂ −r ₁ )}
Here, the low-resolution (second spatial resolution) is calculated from the phase difference between the polarizations (K _DP ) at the azimuth angle Θ [deg] and the distance L [m]. As shown in FIG. 4B, when removing the high-frequency component of the inter-polarization phase difference (φ _DP ), the resolution in the distance direction decreases, so the distance between the two points r1 and r2 (L = r2− Set r1) to the resolution in the distance direction after passing through the low-pass filter. The magnitude of L depends on the resolution of the low-pass filter. Further, the resolution of the azimuth angle Θ depends on the number of hits necessary for calculating φ _DP .

In the average precipitation intensity calculation process 105, the average precipitation intensity (R _ave ) for each low resolution area is calculated from the low-resolution phase difference between specific polarizations (K _DP ). Specifically, it is calculated by the following formula. Note that f is a transmission frequency [GHz] and b2 is a constant (for example, 0.85).
R _ave = 129 × (K _DP / f) ^b2
In the radar reflection factor calculation processing 106, the differential radar apparatus reflection factor (Z _DR ) defined by the ratio of the horizontally polarized radar reflection factor (Z _H ) and the vertically polarized radar reflection factor (Z _V ) is reduced to a low resolution. Calculate with The low-resolution differential radar apparatus reflection factor (Z _DR ) is, for example, a value obtained by averaging the attenuation-corrected radar reflection factors (Z _H , Z _V ) calculated in the high resolution in the low resolution region, or low The value near the center in the resolution region is adopted and obtained.

The first constant calculator 107 calculates a constant B (first constant) that constitutes a relational expression between the radar reflection factor (Z _H ) of the horizontally polarized wave and the precipitation intensity (R). The following formula 1 is known for calculating precipitation intensity (R) using the radar reflection factor (Z _H ) of horizontal polarization. B and β are constants and are determined according to the type of rain.

Z _H = B × R ^β (Formula 1)
Here, the constant B is determined by the following method using the differential radar apparatus reflection factor (Z _DR ) calculated by the differential radar reflection factor calculation processing 106.

The constant B is represented by, for example, the following formulas 2 and 3 by empirically obtained constants a and b. Based on Equation 2 or Equation 3, the constant B can be obtained from the low-resolution differential radar apparatus reflection factor (Z _DR ).
B = a x Z _DR (Formula 2)
B = a × Z _DR + b (Formula 3)
Further, in the above method, a constraint condition may be set such that it is within ± 10% compared to B of adjacent low resolution meshes.

The second constant estimation unit 108 estimates a constant β constituting a relational expression between the horizontally polarized radar reflection factor (Z _H ) and the precipitation intensity (R).
Here, the radar reflection factor (Z) is calculated as high resolution at an azimuth angle θ [deg] and a distance l [m]. The relationship between high resolution and low resolution is considered as follows.
Θ = m × θ
L = n × l
Therefore, as shown in FIG. 5, when mesh numbers i = 1 to m in the azimuth direction with high resolution and mesh numbers j = 1 to n in the distance direction are used, the above equation 1 is converted as follows.
Z _H (i, j) = B × R (i, j) ^β (Formula 4)
From Equation 2 above,
R (i, j) = (Z _H (i, j) / B) ^-β (Formula 5)
Here, assuming that the total precipitation in the region of azimuth angle Θ [deg] and distance L [m] is the same for both low and high resolution,

Holds.

  Here, β is analytically estimated from the above equations 4 and 6. In calculating β, smoothing processing may be performed under a constraint condition such as determining within a value of ± 10% of β in the adjacent low resolution region.

In the precipitation intensity calculation process 109, the low resolution B calculated in the first constant calculation process 107, the low resolution β estimated in the second constant estimation process 108, and the attenuation correction process 103 are corrected. Based on Equation 3 above, high-resolution R (i, j) is calculated using the horizontally polarized radar reflection factor (Z _H (i, j)).

  In the smoothing processing 110, data smoothing processing is performed in the azimuth direction and the distance direction to obtain data having no joint step. As the smoothing method, for example, the following two methods are used.

(First smoothing method)
As shown in FIG. 6, the first smoothing method arranges four different low resolution meshes shifted in the distance direction and the azimuth direction with respect to the high resolution mesh. In the specific polarization phase difference calculation process 104, the low resolution meshes of the four patterns, by calculating each ratio polarization phase difference (K _DP), a high resolution for the specific polarization phase difference of four patterns (K _DP) Precipitation intensity (R (K _DP )) can be calculated. Then, in the smoothing processing 110, smoothing is performed by adopting values near the center of each low-resolution mesh, as shown in FIG. 6, from four patterns of high-resolution precipitation intensity (R (i, j)). Precipitation intensity ((R (i, j)) can be obtained, or a weighted average may be taken for meshes that overlap in four patterns.

(Second smoothing method)
The second smoothing technique, the ratio polarizations phase difference calculation process 104, when calculating the ratio polarization phase difference of a low resolution (K _DP), relative polarization phase difference of adjacent low resolution mesh (K _DP) This is a method of providing constraint conditions so as not to have a difference greater than a certain level. For example, it is determined within ± 10% of the value of phase difference between specific polarizations (K _DP ) of other surrounding mesh regions.

As described above, in this embodiment, the average precipitation intensity (R _ave ) obtained from the phase difference between specific polarizations (K _DP ) having a low spatial resolution but high correlation with precipitation intensity, and the spatial resolution Although the correlation with the absolute value of precipitation intensity is low, the radar reflection factor (Z _H , Z _V ) and the differential radar reflection factor (Z _DR ), which are relative values near the point, are obtained. The constant B constituting the relational expression between (Z _H ) and precipitation intensity (R) is calculated from the differential radar reflection factor (Z _DR ), and the constant β of the relational expression is calculated from the average precipitation intensity (R _ave ). It is estimated and the high-resolution precipitation intensity ((R (i, j))) is calculated using this relational expression. Therefore, according to the above precipitation intensity calculation method, it is possible to calculate precipitation intensity with high spatial resolution and high accuracy.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, according to the present invention, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 11 ... Antenna apparatus (antenna), 12 ... Transmission apparatus (horizontal polarization), 13 ... Reception apparatus (horizontal polarization), 14 ... Transmission apparatus (vertical polarization), 15 ... Reception apparatus (vertical polarization), 16 ... Frequency conversion device (horizontal polarization), 17 ... signal processing device, 18 ... monitoring control device, 19 ... data conversion device, 20 ... data display device, 21 ... data storage device, 22 ... data communication device, 23 ... remote monitoring control Device ... 24 Remote display device 101 ... Radar reflection factor calculation processing 102 ... Low pass filter 103 ... Attenuation correction processing 104 ... Relative polarization phase difference calculation processing 105 ... Average precipitation intensity calculation processing 106 ... Differential radar reflection Factor calculation processing, 107: first constant calculation processing, 108: second constant estimation processing, 109: precipitation intensity calculation processing, 110: smoothing processing.

Claims (12)

A transmission / reception device that simultaneously transmits horizontally polarized waves and vertically polarized radar waves, and receives the reflected waves;
A signal processing device that performs dual polarization observation from the received signal of the transmitting / receiving device and calculates received power for each polarization; and
Based on the received power for each polarization, with a first spatial resolution based on the beam width and pulse width of the radar wave, the radar reflection factor for horizontal polarization (Z _H ) and the radar reflection factor for vertical polarization (Z _V )
Means for calculating a differential radar device reflection factor (Z _DR ) based on the horizontal polarization radar reflection factor (Z _H ) and the vertical polarization radar reflection factor (Z _V );
Means for calculating a phase difference (K _DP ) between specific polarizations with a second spatial resolution lower than the first spatial resolution based on the phase difference between polarizations (φ _DP ) of the received power;
Means for calculating an average precipitation intensity (R _ave [mm / h]) for each second spatial resolution region based on the phase difference between specific polarizations (K _DP );
When the relationship between the radar reflection factor (Z _H ) of the horizontally polarized wave and the precipitation intensity (R [mm / h]) is expressed by the following relational expression:
Z _H = B × R ^β (B and β are constants)
Means for calculating a first constant (B) based on the differential radar device reflection factor (Z _DR );
Based on the first constant (B), the average precipitation intensity (R _ave [mm / h]), and the radar reflection factor (Z _H ) of the horizontally polarized wave, the second constant (β )
Based on the relational expression based on the first constant (B), the second constant (β), and the radar reflection factor (Z _H ) of the horizontally polarized wave, the precipitation intensity (R [ means for calculating mm / h]). The weather radar system according to claim 1, further comprising means for removing a high-frequency component of the inter-polarization phase difference (φ _DP ). And means for correcting the attenuation with respect to the distance between the horizontally polarized radar reflection factor (Z _H ) and the vertically polarized radar reflection factor (Z _V ) using the phase difference between the polarizations (φ _DP ). The weather radar system according to claim 1 or 2, wherein The weather radar system according to any one of claims 1 to 3, further comprising means for smoothing the precipitation intensity (R (K _DP ) [mm / h]) in the azimuth direction and the distance direction. A transmitter / receiver that transmits horizontal and vertically polarized radar waves simultaneously and receives the reflected waves, and a signal that calculates the received power for each polarization by performing dual polarization observation from the received signal of the transmitter / receiver A method used in a weather radar system comprising a processing device,
Based on the received power for each polarization, with a first spatial resolution based on the beam width and pulse width of the radar wave, the radar reflection factor for horizontal polarization (Z _H ) and the radar reflection factor for vertical polarization (Z _V )
Calculating a differential radar apparatus reflection factor (Z _DR ) based on the horizontal polarization radar reflection factor (Z _H ) and the vertical polarization radar reflection factor (Z _V );
Calculating the phase difference between specific polarizations (K _DP ) with a second spatial resolution lower than the first spatial resolution based on the phase difference between polarizations of the received power (φ _DP );
A process of calculating an average precipitation intensity (R _ave [mm / h]) for each second spatial resolution region based on the phase difference between specific polarizations (K _DP );
When the relationship between the radar reflection factor (Z _H ) of the horizontally polarized wave and the precipitation intensity (R [mm / h]) is expressed by the following relational expression:
Z _H = B × R ^β (B and β are constants)
Calculating a first constant (B) based on the differential radar device reflection factor (Z _DR );
Based on the first constant (B), the average precipitation intensity (R _ave [mm / h]), and the radar reflection factor (Z _H ) of the horizontally polarized wave, the second constant (β )
Based on the relational expression based on the first constant (B), the second constant (β), and the radar reflection factor (Z _H ) of the horizontally polarized wave, the precipitation intensity (R [ mm / h]), and a method for calculating precipitation intensity. 6. The precipitation intensity calculating method according to claim 5, further comprising a step of removing a high-frequency component of the inter-polarization phase difference (φ _DP ). A step of correcting the attenuation with respect to the distance between the radar reflection factor (Z _H ) of the horizontal polarization and the radar reflection factor (Z _V ) of the vertical polarization using the phase difference (φ _DP ) between the polarizations; The precipitation intensity calculation method according to claim 5, wherein the precipitation intensity is calculated.   The precipitation intensity calculation method according to claim 5, further comprising a step of smoothing the precipitation intensity (R [mm / h]) in an azimuth direction and a distance direction. A transmitter / receiver that transmits horizontal and vertically polarized radar waves simultaneously and receives the reflected waves, and a signal that calculates the received power for each polarization by performing dual polarization observation from the received signal of the transmitter / receiver A computer for controlling a weather radar system including a processing device;
Based on the received power for each polarization, with a first spatial resolution based on the beam width and pulse width of the radar wave, the radar reflection factor for horizontal polarization (Z _H ) and the radar reflection factor for vertical polarization (Z _V )
A process of calculating a differential radar apparatus reflection factor (Z _DR ) based on the horizontal polarization radar reflection factor (Z _H ) and the vertical polarization radar reflection factor (Z _V );
A process of calculating a specific inter-polarization phase difference (K _DP ) with a second spatial resolution lower than the first spatial resolution based on the inter-polarization phase difference (φ _DP ) of the received power;
A process for calculating an average precipitation intensity (R _ave [mm / h]) for each of the second spatial resolution regions based on the phase difference between specific polarizations (K _DP );
When the relationship between the radar reflection factor (Z _H ) of the horizontally polarized wave and the precipitation intensity (R [mm / h]) is expressed by the following relational expression:
Z _H = B × R ^β (B and β are constants)
A process of calculating a first constant (B) based on the differential radar device reflection factor (Z _DR );
Based on the first constant (B), the average precipitation intensity (R _ave [mm / h]), and the radar reflection factor (Z _H ) of the horizontally polarized wave, the second constant (β )
Based on the relational expression based on the first constant (B), the second constant (β), and the radar reflection factor (Z _H ) of the horizontally polarized wave, the precipitation intensity (R [ mm / h]) is calculated, and a precipitation intensity calculation program is executed. The precipitation intensity calculation program according to claim 9, further comprising a process of removing a high-frequency component of the inter-polarization phase difference (φ _DP ). And further comprising a process of correcting the attenuation with respect to the distance between the horizontally polarized radar reflection factor (Z _H ) and the vertically polarized radar reflection factor (Z _V ) using the phase difference between the polarizations (φ _DP ). The precipitation intensity calculation program according to claim 9 or 10, wherein: The precipitation intensity calculation program according to any one of claims 9 to 11, further comprising a process of smoothing the precipitation intensity (R (K _DP ) [mm / h]) in an azimuth direction and a distance direction. .

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