JP2005345212A - Simulation device for performing cloud observation by cloud observation radar device and its method, and cloud observation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simulation device for performing cloud observation by a cloud observation radar device and its method, and a cloud observation device; to more accurately find the falling velocity of cloud waterdrops by simulation, and to aliasing-correct actual cloud observation data. <P>SOLUTION: This cloud observation radar device, being a Doppler radar device, is equipped with: a pulse generation means for reception pulses which are generated from transmission pulses reflected by cloud waterdrops, the transmission pulses being transmitted from the radar device mounted on an artificial satellite; an average Doppler velocity calculation means for calculating an average Doppler velocity of waterdrops based on temporally continuing pulse pairs with respect to the transmission pulses of a time series, with the pulse generation means generating the transmission pulses as the sum of reflection vectors of respective waterdrops including errors in phase owing to the positions of a plurality of waterdrops existing in an observation area and errors in visual axis direction angle of a transmission beam; and an aliasing-correction means for aliasing-correcting the Doppler velocity. This device is further equipped with a means for finding a relation between the number of pair samples and the standard deviation of average cloud waterdrop falling velocities. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a simulation apparatus and method for observing the falling speed of cloud water droplets with a cloud observation radar apparatus, and a cloud capable of accurately determining the falling speed of cloud water drops based on observation data of a cloud observation radar apparatus mounted on an artificial satellite. It relates to observation equipment.

  Cloud observation with artificial satellites can accurately observe the distribution of clouds in the earth's atmosphere and is important for predicting the weather on the earth.

  A conventional cloud profiling radar device (Cloud Profiling Radar) is designed to observe only backscattering from the cloud of radar pulses in the line of sight, and the cloud is regarded as stationary. In this case, dynamic information such as the falling speed of cloud water droplets could not be obtained (see Non-Patent Document 1).

  The present invention does not observe the reflection of radar pulses as if the clouds were stationary as in a conventional cloud observation radar device, but measures the Doppler velocity caused by the reflection of radar pulses on falling water droplets. Thus, a cloud observation radar simulation device and a cloud observation device capable of observing the fall of cloud water droplets are provided. In the following description, the cloud observation radar apparatus uses the W-band of an artificial satellite, and the frequency (f) of the radar pulse is 94.05 GHz.

  FIG. 1 shows a system of a cloud observation radar apparatus of the present invention. FIG. 1A is a principle explanatory view. The cloud observation radar device is mounted on the artificial satellite 1, outputs a radar pulse in the line-of-sight direction, and receives a reflection signal from the cloud 2. Since the water droplet of the cloud 2 has a velocity component that falls downward, the frequency of the reflected pulse causes a Doppler shift according to the falling velocity of the cloud water droplet. In the artificial satellite 1, the cloud observation radar device obtains the frequency shift of the transmission wave and the reception wave, and obtains the Doppler velocity generated by the drop velocity of the water drop of the cloud 2. The artificial satellite 1 transmits observation data including the calculated Doppler velocity of the cloud 2 to the ground station (see FIG. 1C).

In the following description, it is assumed that the orbit of the artificial satellite 1 has an altitude of 450 km. The satellite velocity (V _sat ) is 7.6 km. The observation direction is the line-of-sight direction for measuring the vertical drop speed of cloud water droplets.

FIG. 1B shows radar pulses of the cloud observation radar device. The frequency f (for example, 94.05 GHz) and the wavelength are λ. The dynamic range (V _dyn ) of the Doppler velocity can be calculated as ± λ / 4T _s . The dynamic range (V _dyn ) represents a Doppler speed that does not cause aliasing (described later). In the following description, the pulse repetition frequency (PRF) is about 5.9 kHz (Ts = 170 μsec). In this case, V _dyn is ± 4.69 m / s.

  FIG. 1C shows the configuration of the cloud observation radar device mounted on the artificial satellite 1. In FIG. 1C, reference numeral 1 denotes an artificial satellite. Reference numeral 10 denotes a cloud observation radar device. 11 is an oscillation circuit, 11 'is a radar pulse generation circuit, 12 is a transmission / reception circuit, 13 is a mixing circuit, 14 is a reception circuit, 14' is a Doppler velocity data generation device, and 15 is a transmission circuit. 21 is a radar antenna. Reference numeral 31 denotes a transmission antenna which transmits the observation data of the artificial satellite to the ground. 32 is a ground station, and 33 is a receiving antenna of the ground station.

  In the configuration of FIG. 1C, in the cloud observation radar apparatus 10, the oscillation circuit 11 oscillates a signal having a radar transmission frequency, and the radar pulse generation circuit 11 'generates a radar pulse. The transmission / reception circuit 12 outputs a radar pulse signal. The radar antenna 21 outputs a transmission pulse 22 in the line-of-sight direction. The transmission pulse 22 is reflected by the water droplets of the cloud 2 to become a reception pulse (reflection pulse) 23 and is received by the radar antenna 21. The received pulse undergoes a Doppler shift in frequency due to the falling speed of the cloud water drop. The received pulse is sent to the receiving circuit 14 via the transmission / reception circuit 12 and further sent to the mixing circuit 13. The mixing circuit 13 obtains a frequency difference between the transmission pulse and the reception pulse of the oscillation circuit 11 and obtains a frequency shift generated in the reception pulse. The Doppler speed data generator 14 'generates Doppler speed data. The transmission circuit 15 generates a transmission signal including the Doppler velocity and transmits it to the ground station 32 via the transmission antenna 31.

The ground station 32 receives the observation data of the cloud observation radar device 10 transmitted from the artificial satellite 1 by the receiving antenna 33. Observation data is stored in a storage device by computer processing, and further data analysis is performed by a computer.
F. K. Li, E .; Im, S, L. Durden, and R.D. Girad, “Cloud Profiling Radar (CPR) for the CloudSat mission”, Proc. 2000 Int. Geosci. Remote Sensing Symp. , Pp. 2821-2823, 2000. A. S. Frisch, C.I. W. Fairall, and J.M. B. Snoder, “Measurement of strutous crowd and drizzle parameter in ASEX with a Ka-band Doppler radar and a microwave radiator,” J. Snoder. Atmos. Sci. , Vol. 52, pp. 2788-2799, 1995. A. J. et al. Heimsfield, L.M. M.M. Miloschich, and A.M. Slingo, “An observational and theoretical study of high supercooled altocumulus,” J. et al. Atmos. Sci. , Vol. 48, pp. 923-945, 1991. E. E. Gossard, J. et al. B. Snider, E .; E. Clothiaux, B.H. Martiner, J.M. S. Gibson, R.A. A. Kropfli, and A.M. S. Frisch, “The potential of 8-mm radars for remote sensing sensing drop size distributions,” J. Am. Atmos. Oceanic Technol. vol. 14, pp. 76-87, 1997.

FIG. 2 is an explanatory diagram of a problem to be solved by the invention. When the attitude of the artificial satellite 1 is tilted, the direction of the radar beam deviates from the line-of-sight direction. Let that angle be γ. The vertical observation of cloud water drops is disturbed due to the angle γ. The error of the Doppler velocity based on the gaze direction angle error caused by the inclination of the attitude of the artificial satellite can be calculated by V _sat · sin γ. There are positive and negative errors depending on the direction of the angle γ. In the case of V _sat = 7.6 km and V _dyn = 4.69 m / sec, if γ is larger than 0.035 °, V _sat · sin γ becomes larger than V _dyn = 4.69 m or −V _dyn (− 4.69 m) (absolute value is greater than V _dyn ), resulting in Doppler velocity _aliasing . Therefore, in order to avoid aliasing, the satellite must satisfy −0.035 ≦ γ ≦ 0.035 (see FIG. 6). However, it is very difficult to maintain the attitude accuracy of satellites at this level, which is impossible in reality. For this reason, when cloud observation is performed using a cloud observation radar mounted on an artificial satellite, it is necessary to correct the Doppler velocity aliasing.

Further, in the measurement of the average Doppler velocity <v>, the average measurement accuracy of the Doppler velocity <v> as pulse-pair number N _a averaging is large is improved. However, since the satellite is moved while measuring the cloud water droplets falling speed, horizontal distance resolution by increasing the N _a (distance resolution) increases. Therefore, it is necessary to find the optimal N _a in consideration of measurement accuracy and horizontal resolution.

  An object of the present invention is to provide a simulation device capable of simulating cloud observation by a cloud observation radar device under various conditions in the conditions of an artificial satellite and a cloud water drop model. It is another object of the present invention to provide a simulation apparatus and method capable of obtaining the standard deviation of the average cloud water drop falling speed obtained by the simulation based on the number of pulse pairs for calculating the average Doppler effect.

  It is another object of the present invention to provide a simulation apparatus that can easily correct the Doppler velocity aliasing correction including an error in the line-of-sight direction.

  It is another object of the present invention to provide a cloud observation apparatus that can easily correct Doppler velocity aliasing correction including a gaze direction angle error γ.

(I) Error analysis of Doppler velocity The average Doppler velocity (<v>) can be calculated from pulse pair processing as follows.

ここに，λは雲観測レーダ装置の波長であり，Ｎ_a は平均のためのパルスペア数である。Ｐ_i は雲のある決められた領域でのｉ番目の受信信号であり，Ｐ^* はＰの共役複素数である。＜ｖ＞のブラケットは平均値であることを示す。もし，Ｎ_a が無限大であれば，＜ｖ＞は誤差なしに測定される。実際，Ｎ_a は有限であり，どのように観測しても，＜ｖ＞は常に誤差をもつ。

Here, lambda is the wavelength of the cloud observation radar, N _a is the pulse-pair number for the average. P _i is the i-th received signal in a certain area with clouds, and P ^* is a conjugate complex number of P. <V> brackets indicate average values. If _Na is infinite, <v> is measured without error. In fact, N _a is finite, even how observed, with <v> is always error.

The present invention, the relationship between the standard deviation of the pulse pair number and Doppler velocity for the average Doppler velocity can be easily obtained, to provide a simulation apparatus that can determine the appropriate N _a.

The basic concept of the simulation method of the present invention is as follows. First, radar pulses are generated by simulation. N _a +1 received signals are generated. From these signals, <v> _Na is calculated by equation (1). Subscripts N _a in <v> _Na means that calculated from N _a number of pulse pairs by average <v> _Na. <V> _Na always has an error because it is measured experimentally by averaging. <V> error of _Na is form clumps N _s a set of N _a number of pulse pairs of <v> _Na, the standard deviation based on N _s number of data <v> _Na in each pulse pair group It can be evaluated by taking.

If there is no correlation between each pulse pair, the Doppler speed cannot be calculated from the pulse pair processing. The pulse P _i can be calculated by taking the vector sum of the backscatter vectors of each cloud droplet of the radar pulse. Correlation pulse P _{i + 1} subsequent to the pulse P _i and pulse P _i can be represented by the phase shift at the cloud water droplets caused by water drops motion cloud between T _s in the simulation. A signal composed of mutually correlated received signals observed by a cloud observation radar device from an artificial satellite can be generated by computer simulation using this cloud water drop model.
(Ii) Cloud water droplet size distribution
A drop size distribution is required in a cloud drop model, which can be generated using random numbers. The cloud water droplet size can be calculated as a lognormal distribution (see Non-Patent Document 2). The lognormal distribution (N (X)) of cloud water droplet size is

ここに，Ｘは，雲水滴の直径Ｄμｍの対数であり，Ｘ₀ はＸの平均値であり，σ_X はＸの標準偏差であり，そしてＮ_t は単位体積（ｃｍ^-3）あたりの全雲水滴数である。対数正規分布により雲水滴サイズを計算するために，Ｘ₀ ，σ_X ，およびＮ_t が実験により求められている必要がある。Ｈｅｙｍｓｆｉｅｌｄ等は高度７３００ｍから７４２０ｍの範囲の関数として雲水滴サイズ分布を測定した（非特許文献３参照）。本シミュレーションではＨｅｙｍｓｆｉｅｌｄの実験データを使用して，雲水滴サイズ分布を計算した。本発明において，Ｎ_t ＝１３６および高度７３６０ｍでのσ_X ＝０．４０１を例として使用した。図３はこの条件で雲水滴サイズ分布を示す。

Where X is the logarithm of the diameter D μm of the cloud droplet, X ₀ is the average value of _X , σ _X is the standard deviation of X, and N _t is the total per unit volume (cm ⁻³ ). It is the number of cloud water drops. In order to calculate the cloud water droplet size by the lognormal distribution, X ₀ , σ _X , and N _t need to be obtained by experiments. Heimsfield et al. Measured cloud droplet size distribution as a function of altitudes ranging from 7300 m to 7420 m (see Non-Patent Document 3). In this simulation, the water droplet size distribution was calculated using Heymsfield experimental data. In the present invention, N _t = 136 and σ _X = 0.401 at an altitude of 7360 m were used as examples. FIG. 3 shows the cloud droplet size distribution under these conditions.

Rayleigh scattering occurs when the wavelength of the electromagnetic wave irradiated to the cloud droplet is smaller than the diameter of the droplet. The reflection coefficient Z (mm ⁶ / m ³ ) at that time can be expressed by the following equation (3) using the cloud water droplet distribution.

ここに，１０^-3・１０^X の項はｍｍ単位での雲水滴の直径を表し，Ｄ_min およびＤ_max は雲水滴の最大および最小の直径であり，それぞれ０．１および１００．０μｍであると推定できる。この場合，Ｚは−１２．４ｄＢＺである。

Here, the term 10 ⁻³ · 10 ^X represents the diameter of the cloud droplet in mm, and D _min and D _max are the maximum and minimum diameter of the cloud droplet, which are 0.1 and 100.0 μm, respectively. Can be estimated. In this case, Z is -12.4 dBZ.

The terminal drop velocity V _t (m / sec) of the cloud water droplet in the static atmosphere can be expressed as a function of the diameter D (μm) of the cloud water droplet as follows (see Non-Patent Document 4).

V _t (D) = a ₁ · D · (1.0−exp (−a ₂ · D)), (4)
Here, a ₁ and a ₂ are constants, that is, 4.0 × 10 ³ and 1.2 × 10 ⁴ , respectively. FIG. 4 shows the relationship between cloud water drop diameter and terminal drop velocity.

The average Doppler velocity is actually obtained by the above-described equation (1) for calculating the pulse pair, but theoretically, the average cloud water droplet drop velocity (V _DOP ) can be calculated by the following equation.

ドップラー効果の周波数の幅（標準偏差σ_DOP ）は，以下の式で計算できる。

The frequency range of the Doppler effect (standard deviation σ _DOP ) can be calculated using the following formula.

ここに，Ｖ_DOP2（Ｖ_DOP の二乗）は，

Where V _DOP2 (V _DOP squared) is

この場合，＜Ｖ_DOP ＞は０．２ｍ／ｓ，＜σ_DOP ＞は０．０６２ｍ／ｓである。ブラケットは平均値を意味する。

In this case, <V _DOP > is 0.2 m / s and <σ _DOP > is 0.062 m / s. A bracket means an average value.

(Iii) Cloud Observation Simulation Device Using a Cloud Observation Radar Device Mounted on an Artificial Satellite FIG. 5A is a diagram showing that a cloud observation radar device mounted on an artificial satellite performs cloud observation in the line of sight. FIG. 5A shows the relationship between the transmission beam of the cloud observation radar device and the cloud observation region. FIG. 5B shows the observation region, the radar beam angle is 2θ (θ = 0.05 °), and the distance resolution is 500 m. The length of the bidirectional arrow in FIG. 5B represents the distance resolution and is 500 m. The distance resolution is determined by the radar pulse width. The observation point is point A, and the altitude is 7360 m. The distance resolution in the horizontal direction is 10 km (pulse integration is performed to calculate the average Doppler velocity) in a trade-off between the resolution in the horizontal direction and the observation accuracy of observing the average Doppler velocity with the radar pulse having a transmission pulse interval T _s = 170 μsec. The distance between the satellites in between).

FIG. 5 (c) shows that the i-th transmission pulse is a cloud water drop 1 (α _1, β ₁ ), 2 (α _2, β ₂ ), 3 (α _3, β ₃ ),... J (α _{j ,} β _j ),... are reflected to reflect reflected pulses A _1i (α _1, β ₁ ) _, A _2i (α _2, β ₂ ) _, A _3i (α _3, β ₃ ),. A _ji (α _j, β _j ),... Is generated, and the vector sum of each reflected pulse is the received pulse P _i .

It was generated by simulation so that normally 10 ¹⁰ cloud water droplets were randomly arranged in the range of the volume of the truncated cone centering on the position A at an altitude of 7360 m in FIG. This numerical value of cloud water droplets is smaller than the number of cloud water droplets actually present in the region of the truncated cone in FIG. However, since 10 ¹⁰ cloud water drops are statistically large in number, they can be used in the simulation. Arranging the above-mentioned cloud droplets at random means that each generated cloud droplet has a random initial phase in the range of 0 ° to 360 °. The pulse P _i is calculated as the vector sum of the backscatter from each cloud drop. The pulse P _{i + 1} can be obtained by simulation by shifting the phase of each cloud water drop, assuming that the pulse P _{i + 1} is generated by the cloud water drop and the satellite movement for T _s seconds. In the present invention, the vertical movement of the atmosphere is not handled. As described with reference to FIG. 2, when there is a gaze direction angle error of the angle γ in the radar beam direction, the phase shift (Δφ _j ) of the j-th cloud water droplet can be expressed by the following equation.

ここに，Ｖ_tjはｊ番目の雲水滴の終端落下速度であり，α_j は−θからθの範囲にあるｊ番目の雲水滴の視線方向からの角度である。β_j は０から３６０°の範囲にあるｊ番目の雲水滴の衛星移動方向からの角度である（図５参照）。λは，レーダ波長でｃｍである。雲水滴での後方散乱信号のベクトル和は，各信号ベクトルの実部をｘ軸とし，虚部をｙ軸で表し，信号の振幅はベクトルの長さであらわし，位相ダイアグラムにより求めることができる。各ベクトルの位相は式（７）のΔφで決められる。その際，レーダアンテナのアンテナパターンの分布をビーム中央を中心にしたガウス分布（ｅｘｐ（−２．７８θ_j ² ／θ² ））であるとして，粒子毎に重み付けをしてそれぞれの粒子での反射ベクトルＡ_jiを求め，ベクトル和をとるようにした。ノイズの影響はベクトル和にノイズ信号を加えることにより考慮する。本シミュレーションではノイズレベルは−２０．０ｄＢとして計算した。

Here, V _tj is the terminal drop speed of the j-th cloud water droplet, and α _j is the angle from the line-of-sight direction of the j-th cloud water droplet in the range of −θ to θ. β _j is an angle from the satellite moving direction of the j-th cloud drop in the range of 0 to 360 ° (see FIG. 5). λ is cm at the radar wavelength. The vector sum of the backscattered signals in the cloud water droplets can be obtained from the phase diagram, where the real part of each signal vector is represented by the x axis and the imaginary part is represented by the y axis, and the signal amplitude is represented by the length of the vector. The phase of each vector is determined by Δφ in equation (7). At this time, assuming that the distribution of the antenna pattern of the radar antenna is a Gaussian distribution (exp (−2.78θ _j ² / θ ² )) centered on the center of the beam, the reflection is performed on each particle by weighting each particle. The vector A _ji was obtained and the vector sum was taken. The effect of noise is taken into account by adding a noise signal to the vector sum. In this simulation, the noise level was calculated as -20.0 dB.

(Iv) Aliasing Correction FIG. 6 shows the relationship between the gaze direction angle error γ and the average Doppler velocity <v>. Positive γ represents that the target is approaching, and negative γ represents that the target is moving away. In the simulation, γ is −0.1 °, −0.08 °, −0.06 °, −0.04 °, −0.02 °, 0.0 °, 0.02 °, 0.04 °, and 0. Performed at 0.06 °, 0.08 ° and 0.1 °. The plots (black circles and white circles in the figure) are average Doppler velocities <v> obtained by the equation (1) in the simulation, and are calculated from pulse pairs of N _a = 10 ¹⁰ . The solid line is the velocity component in the line-of-sight direction of the artificial satellite, and is obtained by calculation as V _sat · sin γ. The thick solid line indicates the range where Doppler velocity aliasing does not occur (equal to the dynamic range), and the thin solid line indicates the area where aliasing occurs. The black circle plot is in an area where no aliasing occurs. The white circle plot is for the area where aliasing occurred.

Aliasing can be corrected with reference to γ as follows. _Aliasing occurs when the absolute value of the line-of-sight direction component of the artificial satellite becomes larger than V _dyn = λ / 4T _s . Therefore, in the gaze direction angle error γ, the gaze direction angle error γ _a causing aliasing is obtained by V _sat · sin γ _a = V _dyn . In this case, since V _dyn = 4.69 m / s and V _sat = 7.6 km / s, γ _a = 0.035 °.

Therefore, in the case of FIG. 6, if γ is larger than 0.035 °, the aliasing correction Doppler speed <v _c > is obtained as <v _c > = 2V _dyn + <v> (V _dyn > 0). When γ is smaller than −0.035 °, the aliasing corrected average Doppler velocity <v _c > is obtained as <v _c > = − 2 V _dyn + <v> (V _dyn > 0).

FIG. 7 shows the relationship between δ, the aliasing corrected average Doppler velocity <v _c >, and the gaze direction angle error γ. The solid line is the line-of-sight component of the Doppler velocity of the satellite velocity V _sat and is obtained as V _sat · sin γ. Corresponding to γ = 0, V _sat · sin γ = 0. The thick solid line is in the γ range where no aliasing occurs, and the thin solid line is in the γ range where aliasing occurs. The white circle plot represents an aliasing corrected version of the plot of FIG. The black circle plot does not perform aliasing correction, and is the same as the black circle plot in FIG. The dotted line is a line connecting the plots. A thick dotted line is a region where aliasing does not occur, and a thin dotted line is a region where aliasing occurs.

There is a slight difference between the solid and dotted lines. This difference is the cloud water drop falling speed V _DOP (cloud water drop Doppler speed). Brackets represent average. Therefore, <V _DOP > in FIG. 7 represents the average drop speed of cloud water droplets. In FIG. 7, <V _DOP > = − 0.2 m / s, and <V _DOP > = <v _c > −V _sat.・ Calculated as sin γ.

As described in section (i), an amount and a pulse pair number N _a using the average cloud water droplets falling velocity _{(<V DOP> meas) (} meas is measured to obtain the average Doppler velocity <v> the error including relationships that by indicating that have (the same applies hereinafter)) can be determined by examining whether the average cloud falling speed how changes by changing the N _a.

FIG. 8 shows the relationship between the number of pulse pairs and the standard deviation of the average cloud droplet drop speed (<V _DOP > _meas ), and is obtained using γ as a parameter. The line-of-sight angle error γ = 0.0 ° is the curves (1) and (2) indicated by the solid line, the curve (1) is when noise is not taken into account, and the curve (2) is when noise is taken into account. Shows the case. Except curves (1) and (2), the number of pulse pairs and average cloud drop drops at γ = ± 0.02 °, ± 0.04 °, ± 0.06 °, ± 0.08 ° and ± 0.1 ° The relationship of the standard deviation of speed is shown. The relationship to γ is indicated by a solid line, a long dotted line, a long point-point-long point-point line, a dotted line, and a long point-point-point-point line (in FIG. 8, there are overlapping graphs). . Differences due to positive and negative values of γ are small and overlap in Fig. 8 (Note that the applicant submitted Fig. 8 in which the difference in curves due to positive and negative values of γ is color-coded in blue and red on the property submission form. To do).

The spread (σ _sat ) of the frequency spectrum of the Doppler effect caused by satellite movement can be approximated by the following equation.

σ _sat ≒ 0.3sin (2θ) ・ V _sat (8)
From this equation (8), σ _sat ≈4 m / s is obtained. The standard deviation indicated by the solid curve (2) at N _a = 1 is determined by two factors (σ _DOP and σ _sat ). σ _DOP (0.062 m / s) is much smaller than σ _sat . For this reason, σ _DOP is ignored, and the standard deviation is 4 m / s as a value obtained from Equation (8). Since this value substantially matches the result of FIG. 8 obtained by simulation, it is shown that the simulation is correct.

In the graph of the number of pulse pairs and the standard deviation of <V _DOP > _meas shown in FIG. 8, when the relationship between γ = 0.0 ° (solid curve (1) in FIG. 8) and other cases is seen, it is Divided. One is group A, which is close to γ = 0.0 ° (solid curve (1) in FIG. 8). Group A is γ = ± 0.02 °, ± 0.06 °, ± 0.08 °. The other is group B, in which the standard deviation of <V _DOP > _meas is far from the standard deviation at γ = 0.0 °. Group B has γ = ± 0.04 ° and ± 0.1 °.

γ = ± 0.04 ° is in the aliasing region (see FIG. 7), and it is close to the boundary that causes aliasing. Aliasing correction is determined based on whether γ is larger or smaller than γ _a , and therefore it is conceivable that those near the boundary of aliasing include those that should not be subjected to aliasing correction. Therefore, it is estimated that γ = ± 0.04 ° has a large standard deviation. The same applies to γ = ± 0.1 °. In this case, it is considered that this is due to the fact that it is close to the next aliasing point (the line-of-sight component of the satellite velocity is ± 2 · V _dyn ). In such a case, the standard deviation of <V _DOP > _meas becomes large.

In group A, γ = ± 0.02 °, ± 0.06 °, and ± 0.08 ° are away from the aliasing point γ _a . In this case, the aliasing effect can be correctly corrected by referring to γ. As shown in FIG. 8, in these cases, the relationship between the standard deviation of <V _DOP> m _eas and pulse pair number is almost the same as the standard deviation of γ = 0.0 °.

As described above, in order to set the target measurement accuracy of the average cloud water drop falling speed <V _DOP > to 1 m / s or less, the satellite moving distance L for obtaining the average Doppler speed <v> is set to 10 km. The maximum pulse pair number N _amax can be calculated by N _a = L / (T _s · V _sat ). Since L = 10 km, T _a = 170 μsec, and V _sat = 7.6 km / sec, the maximum number of pulse pairs N _amax ≈8000. As shown in FIG. 8, when _{N a = 8000, <V DOP} > meas of gamma = 0.0 For ° and Group A is about 0.4 m / s, less than the target measurement accuracy.

Since the cloud water droplet size distribution and the static atmosphere used in the present invention are assumed, the average cloud water droplet drop speed <V _DOP > is small. The Doppler speed against the rain is also an object of the present invention. The vertical motion of the atmosphere can be greater than 1 m / s. From these facts, the target accuracy (1 m / s or less) will be appropriate. As shown in FIG. 8, in the group B with N _a = 8000, the standard deviation of <V _DOP > _meas is about 1.3 m / s, which is larger than the target accuracy. Such a large standard deviation is caused by misjudging the correction of the aliasing effect. Therefore, this simulation also shows that it is necessary to consider the error of <V _DOP > _{meas in} the _aliasing correction when it is close to the aliasing point.

  According to the present invention, a computer simulation of a cloud observation radar device can be easily and accurately performed according to a cloud model such as a particle diameter distribution of cloud water droplets, a condition such as an inclination of an artificial satellite, and the like. In the simulation, the standard deviation for each number of pulse pairs used for calculating the average Doppler velocity can be easily obtained for the average cloud water droplet velocity obtained by the aliasing correction. Therefore, it is possible to easily evaluate the obtained cloud water drop falling speed.

Furthermore, the present invention makes it possible to automatically correct the Doppler velocity aliasing correction with reference to γ. If the aliasing corrected average Doppler velocity <v _c > is far from the aliasing point, the standard deviation of <V _DOP > _meas is almost the same as when γ = 0. In this case, the simulation shows that aliasing can be corrected well. If the aliasing correction average Doppler velocity <v _c > is close to the aliasing point, the standard deviation of <V _DOP > _meas becomes large. In this case, the simulation shows that it is necessary to consider the error of <V _DOP > _meas .

  In addition, the simulation apparatus as described above can be applied to data processing of observation data of a cloud observation radar apparatus mounted on an actual artificial satellite, and aliasing due to a gaze direction angle error included in the observation data. Automatic correction can be determined and corrected automatically. Therefore, the cloud observation apparatus of the present invention can easily obtain an accurate cloud water drop falling speed in cloud observation.

  FIG. 9 is a diagram showing a system configuration of a simulation apparatus for observing clouds with a Doppler radar apparatus mounted on the artificial satellite of the present invention. In FIG. 9, reference numeral 41 denotes a CPU. Reference numeral 42 denotes an internal memory of the computer. Reference numeral 43 denotes a simulation program holding device 1, which is a storage device of a computer, and is an optical storage device such as an internal magnetic storage device, a semiconductor memory device, an external magnetic storage device, or a CDROM, and is a cloud observation radar mounted on an artificial satellite. It holds computer programs necessary for simulation of cloud observation by the device. Reference numeral 44 denotes a simulation program holding device 2, which is an external storage device such as a magnetic storage device or a CDROM, and holds a calculation program for obtaining various parameters necessary for simulation of the cloud observation radar.

  Reference numeral 45 denotes an interface, which is an interface of the external storage device 46, the input device 47, and the output device 48. Reference numeral 46 denotes an external storage device, which is a magnetic storage device, an optical storage device, or the like that holds simulation results and the like. An input device 47 is an input device such as a keyboard and a mouse. An output device 48 is a printer, a display, or the like.

  Reference numeral 50 denotes a simulation program holding device 3, which is a storage device of a computer, and is an optical storage device such as an internal magnetic storage device, a semiconductor memory device, an external magnetic storage device, or a CDROM, which is necessary for simulation of cloud observation radar. Holds the program.

In the simulation program holding device 1 (43), 51 is a pulse P _i generation program, and generates a pulse P _i required for the simulation. An average Doppler speed calculation program 52 is a program for calculating an average Doppler speed <v> according to equation (1). 53 is an aliasing correction program for correcting aliasing of observation data. 54 is an average cloud water drop dropping speed calculation program for calculating an average cloud water drop falling speed <V _DOP >. 155 'is a dynamic range calculation program for calculating the dynamic range of the cloud observation radar device. 180 ′ is a distance resolution calculation program.

In the simulation program holding device 2 (44), 61 is a cloud water droplet size distribution calculation program, which calculates a cloud water droplet distribution N (X) according to the equation (2). A cloud reflection coefficient calculation program 62 is a program for calculating the reflection coefficient Z of the radar pulse in the cloud water droplets according to the equation (3). 63 is a terminal velocity calculation program for calculating the cloud water droplet termination velocity V _t (D) according to the equation (4). 66 is a cloud water droplet phase calculation program for calculating the particle phase Δφ _j according to the equation (7). 159 'is a maximum pulse-pair number computation program, and requests the maximum value N _amax of pulse pair number N _a for calculating the average Doppler velocity <v>.

In the simulation program holding apparatus 3 (50), reference numeral 64 denotes a <σ _DOP > calculation program, which is a program for calculating the Doppler frequency spread. _{Reference numeral} 65 denotes a <V _DOP2 > calculation program that calculates <V _DOP2 > (average of V _DOP squares). 1511 is a program for automatically generating the number of pulse pairs, and is a program for automatically generating the number of pulse pairs for calculating the average Doppler velocity <v>. A pulse pair generation program 1521 automatically generates a number of pulse pairs corresponding to the number of pulse pairs automatically generated by the pulse pair number automatic generation program 1511. Reference numeral 1531 denotes a standard deviation calculation program for calculating the standard deviation of the average cloud water drop dropping speed.

FIG. 10 is a diagram for explaining the operation of the means for generating, in the simulation apparatus of the present invention, a pulse P _i that is transmitted from the cloud observation radar and reflected by the cloud water droplets and observed by the cloud observation radar. is there.

Reference numeral 71 denotes simulation data holding means A, which is a memory of a computer and holds the cloud droplet size distribution N (X), cloud reflection coefficient Z, cloud droplet drop velocity V _t (D), cloud droplet phase Δφ _{j and the} like. To do. Reference numeral 171 denotes a cloud water droplet size distribution N (X) which is generated by the cloud water droplet size distribution generation means 161. Reference numeral 172 denotes a cloud reflection coefficient Z that is held, and is generated by the cloud reflection coefficient calculation means 162. Reference numeral 173 denotes a cloud water droplet end velocity V _t (D), which is generated by the cloud water droplet end velocity calculation means 163. Reference numeral 174 denotes a cloud water droplet phase Δφ _j which is generated by the cloud water droplet phase calculation means 166.

Reference numeral 72 denotes a reflection pulse holding means for each particle, which holds a reflection pulse vector for each particle, and is a memory of a computer. Reference numeral 76 denotes a vector of the reflected pulse at each generated particle, which has the magnitude and phase of the vector. 73 is a pulse P _i retaining means is a memory of a computer, the pulse P _i generation means pulse velocity vector generated by 151 (the size, phase) is to hold the. 75 is a vector of generated pulses P _i .

Reference numeral 151 denotes pulse P _i generation means for generating a reflection pulse A _ji reflected from each cloud droplet by the i-th incident pulse, and the i-th vector sum of the reflection pulses A _ji generated by backscattering of each cloud droplet. The pulse P _i is generated by adding the sum for each pulse. Reference numeral 1520 denotes a reflected pulse generating means for each particle. Reference numeral 1530 denotes a vector sum calculation means for calculating the sum of Doppler velocity vectors generated by reflection at each particle by the i-th input pulse.

Reference numeral 161 denotes cloud water droplet size distribution generation means for obtaining the size distribution of the cloud water droplets, and calculates the equation (2). Reference numeral 162 denotes cloud reflection coefficient calculation means for calculating the reflection coefficient Z of the radar pulse from the cloud water droplets according to the equation (3). Reference numeral 163 denotes cloud water droplet end velocity calculating means for calculating the cloud water droplet end velocity V _t (D) according to equation (4). Reference numeral 166 denotes cloud water drop phase calculation means for calculating each cloud water drop cloud phase Δφ _j using equation (7). 159 is a maximum pulse-pair number calculating means, the maximum value of the pulse pair number N _a for calculating the average Doppler velocity <v> a are those calculated by _{N max = L / V sat ·} T s.

Pulse P _i generation means 151, cloud water droplet size distribution generation unit 161, cloud reflection coefficient computing unit 162, cloud water droplet terminal velocity calculating unit 163, cloud water droplet phase calculation unit 166, the maximum pulse-pair number calculating unit 159, respectively, of FIG. 9 pulse P _i generation program 51 in the system configuration structure, cloud water droplet size distribution calculation program 61, cloud reflection coefficient calculation program 62, the terminal velocity calculation program 63, by respectively CPU41 cloud water droplet phase calculation program 66 and the maximum pulse-pair calculation program 159 ' It is what is done.

A line-of-sight distance resolution calculation unit 180 calculates the line-of-sight distance resolution Δ _R based on the pulse width _TW and the radar pulse propagation velocity c. The distance resolution calculation means 180 is composed of a distance resolution calculation program 180 ′ and a CPU shown in FIG.

Reference numeral 91 denotes a simulation data holding means B, which is a memory of a computer. The wavelength λ of the radar pulse of the cloud observation radar, the pulse interval T _s , the maximum number of pulse pairs N _amax , the distance resolution Δ _R , the numerical value of the cloud water drop model, the satellite It holds the speed V _sat , the line-of-sight angle error γ, the satellite moving distance L for obtaining a predetermined distance resolution in the horizontal direction, the pulse width Tw, and the like. An input device 47 is used to input various numerical values. A 48-output device that outputs simulation results and the like.

The operation of the configuration of FIG. 10 will be described. The input device 47 is used to input the radar pulse wavelength λ, the pulse interval T _s , the satellite velocity V _sat , the cloud altitude to be observed, the cloud water drop model value, and the like. The data is held in the simulation data holding means B91.

The cloud water droplet size distribution generating unit 161 obtains the cloud water droplet size distribution N (X) according to the equation (2), and holds the cloud water droplet size distribution N (X) in the simulation data holding unit A71 ((X ₀ , σ _X )). Is decided beforehand). The cloud reflection coefficient calculating means 162 calculates the cloud reflection coefficient Z by the expression (3) based on the cloud water droplet size distribution N (X) and the maximum and minimum size of the cloud water droplets, and holds them in the simulation data holding means A71. . The cloud water drop terminal velocity calculating means 163 obtains the relationship between the cloud water droplet diameter size D and the terminal velocity based on the cloud water droplet terminal velocity V _t (D) in the equation (4), and the simulation data holding means A71 sends the cloud water droplet diameter size D and Holds the relationship of terminal speed. The cloud water droplet phase calculating means 166 calculates the cloud water droplet phase Δφ _j using the equation (7) and holds it in the simulation data holding means 71.

In the pulse P _i generating means 151, the reflection pulse generating means 1520 for each particle is determined by the cloud water droplet size distribution N (X), the cloud reflection coefficient Z, the cloud water droplet end velocity V _t (D), and the cloud water droplet phase Δφ _j. The back scattered vector A _ji generated by the reflection of the j th particle by the j th transmission pulse is obtained for each cloud water drop, and the reflected pulse vector A _ji obtained for each cloud water drop is held in the reflected pulse holding means 72. To do. Further, the vector sum calculation means 1530 calculates the sum of the Doppler velocity vectors A _ji of each particle generated for each i-th transmission pulse for each A _ji for each _i , and generates the Doppler velocity vector of the pulse P _i . It is held in the pulse _Pi holding means 73.

Maximum pulse pair number calculating means 159, the maximum value of the pulse pair number N _a for calculating the average Doppler velocity <v> was calculated by _{N amax = L / V sat ·} T s, it is held in the simulation data holding means B91. Note that L is the satellite moving distance and determines the horizontal distance resolution, and is determined in advance, and is determined by the pulse P _i and the pulse P _{i + 1} generated while the artificial satellite moves the distance L. Calculate the average Doppler speed. The line-of-sight distance resolution calculation means 180 obtains the distance resolution from the radar pulse width T _W and the propagation speed c of the radar pulse by the distance resolution Δ _R = T _W · c / 2 and holds it in the simulation data holding means B (91). .

  FIG. 11 shows a configuration for obtaining the cloud water droplet velocity of the present invention. In FIG. 11, the pulse pair number automatic generation means 190, the average Doppler velocity calculation means 152, the dynamic range calculation means 155, the aliasing correction means 153, and the average cloud water droplet drop speed calculation means 160 are respectively the pulse pair number automatic generation program in FIG. 1511, an average Doppler velocity calculation program 52, a dynamic range calculation program 155 ′, an aliasing correction program 53, an average cloud water droplet drop velocity calculation program 54, and a CPU. A calculation program corresponding to the satellite Doppler velocity component calculation means 156 is not shown in FIG.

Reference numeral 91 denotes simulation data holding means B. Reference numeral 92 denotes simulation data holding means C, which is a memory and has an average Doppler velocity <v>, an aliasing angle γ _a , a dynamic range V _dyn , an aliasing corrected average Doppler velocity <v _c >, a satellite Doppler velocity component (V _sat · sinγ), and average cloud water drop falling speed <V _DOP > is maintained. 73 pulses P _i retaining means der. 75 is a data vector for each pulse P _i.

152 is a mean Doppler velocity calculation means extracts the pulse pairs of pulses P _i and the pulse P _{i + 1} from the pulse P _i holding means 73, by N _a number of pulse pair (1) the average Doppler velocity calculated according to equation The obtained average Doppler velocity <v> is held in the simulation data holding means C (92) together with the line-of-sight direction angle error.

Reference numeral 155 denotes dynamic range calculation means for inputting the wavelength λ of the radar pulse and the pulse interval T _s from the simulation data holding means B (91), and obtaining the dynamic range by V _dyn = ± λ / 4T _s . Reference numeral 156 denotes satellite Doppler velocity component calculation means for calculating the satellite Doppler velocity component V _sat · sin γ. Reference numeral 153 denotes aliasing correction means for performing aliasing correction according to the aliasing angle γ _a and the average Doppler velocity <v>. 157 is an aliasing angle calculating means, and requests gamma _a by _{V dyn = V sat · sinγ a} . Reference numeral 158 denotes aliasing correction calculation means for performing _aliasing correction of the Doppler velocity of cloud water droplets by <v _c > = 2V _dyn + <v> or <v _c > = − 2 V _dyn + <v>. . Reference numeral 160 denotes an average cloud water drop falling speed calculation means, and V _{sat according to} the average Doppler velocity <v _c > of the cloud water droplets obtained by correcting the average cloud water drop falling velocity <V _DOP > with the satellite Doppler velocity component V _sat · γ and _aliasing. -It is obtained by γ- <v _c >.

The operation of the configuration of FIG. 11 will be described. The average Doppler velocity calculation means 152 receives the wavelength λ of the radar pulse and the pulse interval T _s from the simulation data holding means B (91). Further, _a pulse pair of N _a Doppler velocity vectors P _i and P _{i + 1} is obtained from the pulse P _i holding means 73, and the average Doppler velocity <v> is calculated according to the equation (1). <V> of the calculation result is held in the simulation data holding means C (92).

The dynamic range calculation means 155 inputs the wavelength λ of the radar pulse and the pulse interval T _s from the simulation holding means B (91), and obtains the dynamic range by V _dyn = ± λ / 4T _s . The obtained dynamic range V _dyn is held in the simulation data holding means C (92). The satellite Doppler velocity component calculation means 156 receives the satellite velocity V _sat and the satellite gaze direction angle error γ from the simulation data holding means B (91), calculates the satellite Doppler velocity component from V _sat · sin γ, and stores the simulation data holding means. C (92).

In aliasing correction unit 153, gamma _a calculation means obtains the dynamic range V _dyn from the simulation data holding means _{B (91), V dyn =} V a _sat · sin [gamma] becomes _a gamma _a calculated, simulated data holding means C ( 92). The aliasing correction calculation means 158 inputs V _dyn , γ _a , <v> from the simulation data holding means C (92), and γ is larger than or smaller than γ _a (| γ _a |> | γ |). In some cases, aliasing correction is performed by <v _c > = 2V _dyn + <v> or −2V _dyn + <v>, and the obtained <v _c > is held in the simulation data holding means C (92).

The average cloud water drop falling speed calculating means 160 receives the averaged Doppler speed <v _c > corrected by aliasing and the satellite Doppler speed component V _sat · sin γ held in the simulation data holding means C (92), and the average cloud water drop falling is calculated. The speed <V _DOP > is obtained by the calculation formula of <V _DOP > = V _sat · sin γ− <v _c > and is held in the simulation data holding means C (92).

The output device 48 displays the average Doppler speed <v>, the aliasing corrected average Doppler speed <v _c >, V _dyn , γ _a, etc., based on each data held in the simulation holding means C (92). , Output the graph to a printer.

  In addition, the numerical values held in the simulation data holding means A, the simulation data holding means B, etc. are output to a display, a printer or the like as necessary.

FIG. 12 shows a configuration for calculating the standard deviation of the present invention. Figure 12 is a construction for obtaining the standard deviation by N _a average cloud water droplets falling speed of the present invention <V _DOP>. The simulation apparatus of the present invention can determine how the average Doppler velocity changes by changing the number of pulse pairs for obtaining the average Doppler velocity, and can obtain the standard deviation at each number of pulse pairs. γ, V _sat , V _dyn , λ, T _s, etc. are determined. Γ _a , V _sat · sin γ, γ _{a and the} like are calculated in advance. For example, consider a case where the average cloud drop speed is obtained by 10 pulses (N _a = 1). From time-series pulses P _i (i = 1 to N) (N is a large integer), first, i = 1, and 10 consecutive pulse pairs (P ₁ , P ₂ ), (P ₂ , P ₃ ) , (P ₃ , P ₄ ),... (P ₁₀ , P ₁₁ ) are extracted. The average Doppler velocity <v> is calculated and held by this pulse pair. Also, the aliasing averaged Doppler speed <v _c > is obtained and taken into account in consideration of γ. Further, the average cloud water drop falling speed <V _DOP > _meas is obtained and held. Since the meaning of <V _DOP> of _meas "meas" is error is included in the average cloud water droplets falling speed obtained Te finite number of pulse pair number, the it is intended to mean a (described later). Next, assuming that i = 11, (P ₁₁ , P ₂₃ ), (P ₁₂ , P ₁₃ ), (P ₁₃ , P ₁₄ ),... (P ₂₀ , P ₂₁ ) are extracted in the same manner as above. Calculate and hold the average cloud water drop falling speed <V _DOP > _meas . Such 10 generates a large number of pulse pairs to (N _S group), an average cloud water droplets falling speed <V _{DOP> meas} calculated for each pulse pair group holds. As such retained as the N _S mean standard deviation of the mean Doppler velocity and standard deviation were calculated was determined by the number 10 pulse pairs to the cloud water droplets fall velocity <V _DOP> of the obtained. Similar processes seek each cloud average fall velocity <V _DOP> in N _{a meas} standard deviation of up while changing the N _a to N _amax (e.g. N _a = 1 to N _amax), holds.

In FIG. 12, the pulse pair number automatic generation means 190 generates N _a smaller than the maximum number of pulse pairs N _amax held in the simulation data holding means B (91) and holds it in the N _a holding means 95 (usually, N _a The initial value of 1 is 1). Pulse selection means 191 extracts from the data pulses P _i of time-series, N _a number of successive pulses P _i to P _i + n a (n = N _a) on the basis of the N _a. The pulse selecting means 191 obtains the N _s group from the pulse group of the set of N _a continuous pulses. As N _s, a predetermined large numerical value is input by the input device 47 and held in the N _s holding means 99.

Request <V _{DOP> meas} in <V _{DOP> meas} calculating unit 1522 by P _i and P _{i + 1} of the N _a number of pairs in each group. First, <v> is obtained by the average Doppler velocity calculation means 152. Next, aliasing correction is performed by the aliasing correction means 153. Further, <V _DOP > _meas is calculated by the average cloud drop speed calculation means 160. <V _{DOP> meas} in N _a determined is maintained at <V _{DOP> meas} holding means 200. The above processing is repeated for each pel spare group, <V _DOP > _meas is obtained for each pulse pair group, and each <V _DOP > _meas is held in the <V _DOP > _meas holding means 200. The standard deviation calculation means A (192) _obtains the standard deviation of the obtained <V _DOP > _meas of the N _s group, and repeats the above processing held in the simulation data holding means D (93) while changing N _a , N A large number of <V _DOP > _meas up to _amax is obtained, and each standard deviation SD is obtained and held in the simulation data holding means D (93). The relationship between the standard deviation SD and N _a thus determined is output to the output device 48.

FIG. 12 shows a configuration for obtaining the standard deviation (<σ _DOP >) of the Doppler frequency spread. The standard deviation calculation means B (193) for obtaining the standard deviation <σ _DOP > of the Doppler frequency spread is based on the estimated maximum diameter D _max , minimum diameter D _min and particle distribution N (X) of the cloud water droplet size. The average cloud water drop falling speed <V _DOP > is obtained by calculation according to equation (5). Further, the average of the squares of V _DOP <V _DOP2 > is calculated according to the expression after the expression (6). Further, the standard deviation calculation means B (193) calculates the standard deviation <σ _DOP > by the equation (6). The obtained standard deviation <σ _DOP > is held in the standard deviation holding means 199. 212 is a <σ _sat > calculating means for calculating the spread <σ _sat > of the Doppler spectrum generated by the movement of the satellite according to the equation (8). The calculated <σ _sat > is held in the standard deviation holding means 199 and outputted to the output device 48.

FIG. 13 is a flowchart of the pulse _Pi calculation means of the present invention. As shown in FIG. 13, first, the cloud water droplet size distribution N (X) is obtained by calculation according to equation (2) and held in the storage means (S1). At this time, σ _X and X ₀ are estimated based on past observation data. The cloud end water drop end velocity V _t (D) is calculated according to the equation (4) and held in the storage means (S2). In accordance with the cloud water drop model, the phase shift of the cloud water drop is calculated according to the equation (7) and stored in the storage means (S3). The radar reflection coefficient Z is calculated according to equation (3) and stored in the storage means (S4). The reflection pulse A _ji (α _j , β _j ) at the j-th particle with respect to the i-th radar transmission signal is obtained and held in the storage means for each particle (S5). The vector sum of the reflection vectors from each particle is calculated and stored in the storage means (S6). It is determined whether all particles have been obtained. If not, j is updated (j = j + 1) (S7, S8). The processes of S5 and S6 are repeated with the updated j. If A _ji is obtained for all j with respect to the i-th incident pulse in S8, a vector sum of backscattering in the cloud water droplet is obtained in S10, and a pulse _Pi is generated and held. In S11, it is determined whether sought pulse P _i for all incident pulses, and updates the i in S13 if not determined and repeated in S5 after processing. If the pulse P _i has been obtained for all i in S8, the process ends.

FIG. 14 is a flowchart of the Doppler velocity calculation means of the present invention. An initial value of i (i = 1) is set (S0). The wavelength λ of the radar pulse is input (S1). The pulse interval T _s is input (S2). Enter the number of pulse pairs N _a for calculating the average Doppler velocity. (S3). The pulse pair P _i and P _{I + 1} are input (S4). The average Doppler speed <v> is calculated according to the equation (1) (S5). The calculated average Doppler speed <v> is held in the storage area (S6). It is determined whether or not N _a pulse pairs have been calculated. If N _a has not been calculated, i = i + 1 is set, and the processing from S4 is repeated (S7, S8). When N _a number of the pulse pairs to calculate the average Doppler velocity <v>, and outputs the average Doppler velocity <v> (S9).

FIG. 15 is a flowchart of the dynamic range calculation means. The pulse interval T _s is input (S1). The pulse wavelength λ is input (S2). The dynamic range V _dyn = ± λ / 4T _s is calculated (S4). The calculated dynamic range V _dyn is held in the storage area (S4). The dynamic range V _dyn is output as necessary (S5).

FIG. 16 is a flowchart of the aliasing correction means of the present invention. The dynamic range V _dyn and the satellite gaze direction angle error γ are input (S1). V _dyn = determined by calculating the aliasing angle gamma _a to be _{± V sat · sinγ a (S2} ). Whether γ> γ _a or γ <−γ _{a is} determined (S3). If γ> γ _a or γ <−γ _a is not satisfied, the aliasing corrected average Doppler velocity <v _c > = <v> is set (S4). The aliasing correction average Doppler speed <v _c > is held in the storage area (S5). The aliasing corrected average Doppler speed <v _c > is output (S6). If γ> γ _{a in} the determination of S3, <v _c > = 2V _dyn + <v> is set (S7). If the determination in gamma <-gamma _a of _{S3 <v c> = - 2V} dyn + Request <v> (S7). The obtained <v _c > is held in the storage area (S5). The held aliasing correction average Doppler speed <v _c > is output (S6).

FIG. 17 is a flowchart of the cloud water droplet velocity calculation means. The aliasing corrected average Doppler speed <v _c > is input (S1). The line-of-sight component V _sat · sin γ of the satellite Doppler velocity is calculated and stored in the storage area (S2). Average cloud water drop falling speed <V _DOP > = <v _c > −V _sat · sin γ is calculated (S 3). The average cloud water drop dropping speed <V _DOP > is held in the storage area (S4). The average cloud falling speed <V _DOP > is output (S5).

FIG. 18 is a flowchart for calculating the standard deviation according to the number of sample pairs of the Doppler average speed of the present invention. The number of pulse pairs N _a = 1 and i = 1 is set as an initial value (S0). The pulse pair P _i , P _{i + 1} is input (S1). Mean average by the Doppler velocity <v> and to calculate the aliasing corrected aliasing compensation average Doppler velocity <v _c> and satellite Doppler velocity component V _sat · sin [gamma], to calculate the V _sat · sinγ- <v> Cloud water drop falling speed <V _DOP > _meas is obtained (S2). The average cloud water drop falling speed <V _DOP > _meas is maintained (S3). It is determined whether N _a pulse pairs have been obtained (S4, S5). If N _a pulse pairs are not obtained, i = i + 1 is set and the processes after S1 are repeated (S5). It is determined whether N _s average cloud water drop falling speed <V _DOP > _meas has been obtained (S7, S8). If N _s average cloud water droplet drop speeds have not been obtained, i is set to i = i + 1 in S9, and the processing after S1 is repeated.

S7, it is determined in S8, When Motoma' is N _s number of average cloud water droplets falling speed <V _{DOP> meas,} based on calculating the standard deviation SD of the N _s number of <V _{DOP> meas} in S10 (S10) . The obtained standard deviation SD is held in the storage area (S11). N _a is determined whether Motoma' the standard deviation of the cloud water droplets falling speed of N _amax (S12). If N _amax has not been obtained, N _a = N _a +1 is set in S13, i = 1 is set in S14, and the processes after S1 are repeated.

When it has been obtained up to N _a = N _amax at S12, the process ends and outputs the standard deviation from the N _a = 1 to N _a = N _amax.

FIG. 19 shows a configuration of a satellite-borne cloud observation radar apparatus that generates observation data to be processed by the cloud observation apparatus of the present invention. In FIG. 19, 1 is an artificial satellite. Reference numeral 10 denotes a cloud observation radar device. Reference numeral 11 denotes an oscillation circuit. 11 ′ is a radar pulse generation circuit, and 12 is a transmission and reception circuit. Reference numeral 13 denotes a mixing circuit. Reference numeral 14 denotes a receiving circuit. Reference numeral 15 denotes an output circuit. Reference numeral 300 denotes observation data holding means A, which comprises a microprocessor and storage means. Reference numeral 301 denotes an input interface. Reference numeral 152 denotes an average Doppler speed calculation means for calculating an average Doppler speed <v> from the pulse pairs P _i and P _{i + 1} having the number of pulse pairs N _a . Reference numeral 302 denotes time data generation means for generating observation time data. A transmission data creation device 310 generates transmission data such as an average Doppler velocity <v> by cloud observation transmitted to the ground, a gaze direction angle error in the beam direction of the cloud observation radar, and an observation time. Reference numeral 314 denotes observation data holding means which holds data observed by the cloud observation radar apparatus 10 and holds the observed Doppler frequency. Reference numeral 315 denotes transmission data holding means 315 for holding transmission data transmitted from the satellite to the ground station together with time information.

320 denotes various data holding means for holding numerical values such as the pulse interval T _s necessary for calculating the average Doppler velocity and the number of pulses N _a (or integration time) added to obtain the average. Reference numeral 330 denotes γ data generation means for generating transmission data of a gaze direction angle error γ in the radar beam direction. An output interface 350 outputs transmission data to the transmission device. Reference numeral 360 denotes a time device, which is a timer for obtaining satellite time. Reference numeral 361 denotes a γ detection device that detects a gaze direction angle error γ of a radar beam observed by cloud radar. Reference numeral 369 denotes a transmission device. Reference numeral 370 denotes an input circuit. Reference numeral 371 denotes a modulation circuit that modulates a signal in order to transmit transmission data to the ground. Reference numeral 372 denotes a transmission circuit.

  The operation of the configuration of FIG. 19 will be described. In the cloud observation radar apparatus 10, the oscillation circuit 11 oscillates a signal having a transmission pulse frequency, and the radar pulse generation circuit 11 ′ generates a radar transmission pulse. The transmission / reception circuit 12 outputs a radar pulse in the direction of the line of sight toward the target (cloud) by the radar antenna. The radar pulse reflected from the target (cloud) is received by the radar antenna and sent to the wave receiving circuit 14 via the transmission / reception circuit 12. The mixing circuit 13 obtains the Doppler frequency by the difference between the frequency of the signal of the oscillation circuit (frequency of the transmission pulse) and the frequency of reception (frequency of the radar pulse reflected by the cloud water droplets) input via the wave receiving circuit 14. The Doppler frequency is transmitted from the output circuit 15 to the observation data generating means 300.

  In the observation data generation means 300, the average Doppler velocity calculation means 152 generates an average Doppler velocity <v> based on the Doppler frequencies of a plurality of received signals observed by the cloud observation radar device 10. On the other hand, the time device 360 generates the time of the satellite, and the time signal is sent to the time data generating means 302 via the input interface 301 to generate time data. In the transmission data generation means, average Doppler velocity <v> and observation time data are generated and held. Also, the gaze direction angle error of the satellite radar antenna is detected by the γ detection device 361 and input to the γ data generation means 330 via the input interface 301. In transmission data creation means 310, data of γ and time are generated and held. The transmission data is input to the modulation circuit of the transmission device 370 via the output interface 350, modulated, and transmitted as satellite transmission data from the transmission circuit 372 to the ground via the transmission antenna.

  FIG. 20A shows the configuration of the cloud observation apparatus of the ground station of the present invention. In FIG. 20A, 401 is a receiving device. Reference numeral 403 denotes a demodulation circuit. Reference numeral 404 denotes an output circuit. In the data processing device 400, reference numeral 413 denotes an input interface. Reference numeral 420 denotes observation data holding means for holding observation data transmitted from a satellite and received. Reference numeral 451 denotes an aliasing correction unit having the same configuration as the aliasing correction unit 153 of FIG. Reference numeral 452 denotes an aliasing angle calculation unit having the same configuration as the aliasing angle calculation unit 157 of FIG. Reference numeral 453 denotes aliasing correction calculation means, which has the same configuration as the aliasing correction calculation means 158 of FIG. Reference numeral 455 denotes an average cloud water drop falling speed calculating means having the same configuration as the average cloud water drop falling speed calculating means 160 of FIG.

Reference numeral 460 denotes satellite Doppler velocity calculation means, which has the same configuration as the satellite Doppler velocity component calculation means 156 in FIG. 11, and calculates satellite Doppler velocity components from V _sat · sin γ from the satellite velocity V _sat and the gaze direction angle error γ. . Reference numeral 462 denotes a dynamic range calculation unit having the same configuration as the dynamic range calculation unit 155 of FIG. Reference numeral 470 denotes various parameter holding means, which include parameters such as satellite velocity V _sat , radar pulse pulse interval T _s , radar beam gaze direction angle error λ, and the like necessary for calculating average Doppler velocity, satellite Doppler velocity, and the like. It is to hold. Reference numeral 480 denotes a calculation result holding unit. Reference numeral 481 denotes an output interface.

FIG. 20B shows the structure of data held by the calculation result holding unit 480. Time when the average Doppler velocity was observed, gaze direction angle error γ, satellite Doppler velocity component (V _sat · sin γ), dynamic range (V _dyn ), average Doppler velocity (<v>), aliasing corrected average Doppler velocity < v _c >, cloud water drop falling speed <V _DOP >.

  The operation of the configuration shown in FIG. A transmission signal from the artificial satellite is received by the reception circuit 402 via the reception antenna. The received signal is modulated by the demodulation circuit 403 and output from the output circuit 404. The signal output from the output circuit 404 is stored in the observation data holding unit 420 via the input interface. The stored data includes observation time, average Doppler velocity <v>, and gaze direction angle error γ.

The dynamic range calculation means 462 calculates the dynamic range from the radar pulse length λ and the pulse interval T _{s according} to V _dyn = ± λ / 4T _s . Aliasing correction unit 451 compares the cloud observation data gamma and gamma _a (previously obtained in advance by calculation as V _dyn = V _sat · sinγ _a to become gamma _a), to determine the presence or absence of aliasing, if necessary Aliasing correction is performed on <v> obtained as observation data. Since this method is the same as the method described in the description of FIG. 11, detailed description thereof is omitted. The average cloud water drop falling speed calculating means 455 calculates the cloud water drop falling speed <V _DOP > based on the satellite Doppler velocity component and the average Doppler velocity corrected for _aliasing (this calculation method is the same as the method described in FIG. 16). ). Each calculation result is held in the calculation result holding means 480. The calculation result held in the calculation result holding means 480 is output to the output device 485.

  The flowchart of the aliasing correction unit 451 is the same as the flowchart of the aliasing correction unit in FIG. The flowchart of the average cloud water drop falling speed calculating means 455 is the same as the flowchart of the cloud water drop falling speed calculating means of FIG. The flowchart of the dynamic range calculation unit 462 is the same as the flowchart of the dynamic range calculation unit of FIG.

FIG. 21 shows the system configuration of the cloud observation apparatus for the ground station of the present invention. In FIG. 21, 401 is a receiving device. Reference numeral 400 denotes a data processing apparatus, which is a computer. Reference numeral 410 denotes a CPU. Reference numeral 411 denotes a memory. Reference numeral 4121 denotes various data holding means, which is a storage device that holds various programs necessary for processing cloud observation data. Reference numeral 420 denotes observation data holding means, which is a storage device. Reference numeral 430 denotes an interface, which is an external storage device. Reference numeral 484 denotes an input device. Reference numeral 485 denotes an output device.
Reference numeral 440 denotes program storage means for holding various programs. 441 is a satellite Doppler velocity calculation program. Reference numeral 442 denotes an aliasing correction program. Reference numeral 443 denotes a cloud water drop falling speed calculation program. Reference numeral 412 denotes various program holding means for holding various programs necessary for data processing.

  In the configuration of FIG. 21, each program, CPU 410, and memory 411 constitute each means shown in FIG. Since the flowchart is the same as the flowchart of each means corresponding to each program, description thereof will be omitted.

  According to the computer simulation apparatus for a cloud observation radar of the present invention, the Doppler velocity aliasing correction can be easily corrected with reference to γ. In addition, regarding the average cloud water droplet velocity obtained by the aliasing correction, the standard deviation for each number of pulse pairs used for calculating the average Doppler velocity can be easily obtained. Therefore, it is possible to easily evaluate the obtained cloud water drop falling speed. Further, the Doppler simulation apparatus of the present invention can perform simulation of Doppler radar for observing clouds under various observation conditions. In addition, the standard deviation of the observation results can be obtained in various cases, and the observation results can be easily evaluated. Therefore, the simulation device of the present invention is useful in the development of a cloud observation radar device.

  The cloud observation apparatus of the present invention calculates the dynamic range and aliasing angle based on the satellite speed, radar wavelength, pulse interval, etc. of the satellite, and compares it with the gaze direction angle error contained in the satellite observation data. Automatically corrects the average Doppler velocity of cloud water drops. Therefore, it is possible to easily find the exact drop speed of cloud water droplets from the observation data of the satellite.

It is a principle explanatory view of cloud observation by the cloud observation radar device of the present invention. It is explanatory drawing of the subject which this invention tends to solve. It is a figure which shows the example of the cloud water droplet size distribution used by this invention. It is a figure which shows the example of the relationship between the diameter of the cloud water droplet used by this invention, and the terminal drop speed of a cloud water droplet. It is explanatory drawing of the production _| generation method of the pulse Pi of this invention. It is a figure which shows the relationship between the gaze direction angle error of this invention, and an average Doppler velocity. It is a figure which shows the relationship between the gaze direction angle error of this invention, and the average Doppler speed which carried out the aliasing correction | amendment. It is a figure which shows the example of the relationship between the number of pulse pairs calculated | required with the simulation apparatus of this invention, and the standard deviation of a cloud water droplet fall speed. It is a figure which shows the example of a structure of the simulation system which observes a cloud by the Doppler radar mounted in the artificial satellite of this invention. It is a figure which shows the structure of the pulse _Pi production _| generation means of this invention. It is a figure which shows the structure for calculating | requiring the cloud water droplet velocity of this invention. It is a figure which shows the structure for calculating the standard deviation of this invention. It is a figure which shows the flowchart of the pulse _Pi calculation means of this invention. It is a figure which shows the flowchart of the average Doppler speed calculation means of this invention. It is a figure which shows the flowchart of the dynamic range calculation means of this invention. FIG. It is a figure which shows the flowchart of the aliasing correction | amendment means of this invention. It is a figure which shows the flowchart of the cloud water droplet fall speed calculation means of this invention. It is a figure which shows the flowchart of the standard deviation calculation means of the average cloud water droplet falling speed of this invention. It is a figure which shows the structure of the satellite observation cloud observation radar apparatus which produces | generates the observation data processed with the cloud observation apparatus of this invention. It is a figure which shows the cloud observation apparatus of the ground station of this invention. It is a figure which shows the system configuration | structure of the cloud observation apparatus of the ground station of this invention.

Explanation of symbols

47: input device 48: output device 71: simulation data holding means A
72: Reflected pulse holding means for each particle 73: Pulse _Pi holding means 91: Simulation data holding means B
151: Pulse P _i generation means 1520: reflections of each particle pulse generating means 1530: vector sum calculation means 159: maximum pulse-pair number calculating means 161: cloud water droplet distribution generation unit 162: Cloud reflection coefficient computing means 163: Cloud terminal velocity calculating means 166: Cloud water drop phase calculation means 171: Cloud water drop size distribution 172: Cloud reflection coefficient 173: Cloud water drop terminal velocity 174: Cloud water drop phase 180: Distance resolution calculation means in the line-of-sight direction

Claims (6)

In a simulation device for simulating observation by cloud observation radar device with computer and storage means,
The cloud observation radar device is a Doppler radar device, and pulse generation means for generating a reception pulse generated when a transmission pulse transmitted from a cloud observation radar device mounted on an artificial satellite is reflected by a cloud water droplet;
Storage means for holding the pulses generated by the pulse generation means,
The pulse generating means generates a transmission pulse as a sum of a phase based on the positions of a plurality of water droplets in the observation region and a reflection vector of each water droplet including a gaze direction angle error of the radar pulse of the transmission pulse, Storage means for holding a gaze direction angle error;
An average Doppler speed calculating means for calculating an average Doppler speed of water droplets based on a pair of temporally continuous pulses in the transmission pulse in time series, and a storage means for holding the average Doppler speed;
Calculate the aliasing angle that causes aliasing based on the dynamic range of the cloud observation radar system, compare the aliasing angle with the gaze direction angle error of the radar beam, and respond according to the relationship between the aliasing angle and the gaze direction angle error Aliasing correction means for correcting aliasing of the average Doppler speed;
A cloud observation radar apparatus simulation apparatus comprising storage means for holding the dynamic range and the aliasing angle. The average Doppler velocity is <v>, the aliasing corrected average Doppler velocity is <v _c >, the gaze direction angle error is γ, the cloud observation radar dynamic range is V _dyn (V _dyn ≧ 0), and the aliasing angle is γ _a When (γ _a ≧ 0),
If the magnitude of γ and γ _a is γ _a ≦ γ ≦ γ _a , the aliasing correction means assumes that no aliasing correction is performed, sets <v _c > = <v>, and γ <−γ _a or γ > If γ _a <v _c> = (for _{γ> γ a) 2V dyn +} <v>, or _{<v c> = - 2V dyn} + <v> (γ < case-gamma _a) by aliasing correction The cloud observation radar apparatus simulation apparatus according to claim 1, wherein an average Doppler velocity is obtained. When the moving speed of the satellite is V _sat , a means for calculating the gaze direction angle component V _sat · sin γ of the satellite speed, a storage means for holding the gaze direction angle error component,
Mean cloud water drop fall calculating means for calculating average cloud water drop fall speed <V _DOP > by <V _DOP > = V _sat · sin γ− <v _c >, and memory holding average cloud water drop fall speed <V _DOP > Means,
Means for generating N _s pulse pairs of N _a P _i and P _{i + 1} , and pulse pair groups P _i and P _{i + 1} are different for each pulse pair group, and each pulse pair group of N _s Average cloud water drop falling speed is calculated and stored in the storage means for each time, standard deviation creating means for obtaining the standard deviation of the N _s average cloud water drop falling speed <V _DOP >, and storage means for holding the standard deviation And
3. The average cloud water drop falling speed <V _DOP > can be evaluated by calculating the average cloud water drop falling speed at _a different Na, obtaining the standard deviation, and holding it in a storage means. The cloud observation radar apparatus simulation apparatus according to 1. In a simulation method for simulating observation data observed by a cloud observation radar device using a computer and storage means,
The cloud observation radar device is a Doppler radar device, and a received pulse generated when a transmission pulse transmitted from a cloud observation radar device mounted on an artificial satellite is reflected by a cloud water droplet is a position of a plurality of water droplets in the observation region. Is generated as the sum of the reflection vector of each water drop including the phase error angle of the radar beam of the transmission pulse and the phase of the transmission pulse, and the received pulse and the angle error of the visual axis direction are held in the storage means,
Calculating an average Doppler velocity based on time-sequential pulse pairs in the time-series pulse data;
The aliasing angle that causes aliasing is calculated based on the dynamic range of the cloud observation radar device, the aliasing angle is compared with the gaze direction angle error of the radar beam, and the relationship between the aliasing angle and the gaze direction angle error is calculated. A simulation method of a cloud observation radar device that corrects aliasing of the average Doppler velocity accordingly. When the moving speed of the satellite is V _sat , the gaze direction angle component V _sat · sin γ of the satellite speed is calculated, and the gaze direction angle error component is held in the storage means,
The average cloud water drop falling speed <V _DOP > is calculated by <V _DOP > = V _sat · sin γ− <v _c >, and the average cloud water drop falling speed <V _DOP > is held in the storage means.
N _a number of the P _i and pulse-pair group P _{i + 1} and N _s number generator, pulse-pair group P _i and P _{i + 1} for each pulse pair group are different, for each pulse pair group of the N _s The average cloud water drop falling speed is calculated and held in the memory means, the standard deviation of the N _s average cloud water drop falling speed <V _DOP > is obtained, and the standard deviation is held in the memory means,
5. The average cloud water drop falling speed <V _DOP > can be evaluated by calculating the average cloud water drop falling speed at _a different Na, obtaining the standard deviation, and holding it in a storage means. Simulation method for cloud observation radar equipment. In the cloud observation device that processes the observation data of the cloud observation radar device mounted on the artificial satellite,
Means for receiving the average Doppler velocity <v> of cloud water droplets sent from the satellite and the gaze direction angle error γ of the observation radar beam, storage means for holding the observation data,
Aliasing correction means for correcting aliasing of the received average Doppler speed;
Cloud observation comprising cloud water drop drop speed calculating means for calculating an average cloud water drop fall speed by calculating a difference between the average Doppler speed corrected for aliasing and a Doppler speed component in the gaze direction of the satellite apparatus.

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