Method, device and system for measuring cloud structure

Abstract

To provide a method and a device for measuring two-dimensional distribution and / or three-dimensional distribution (i.e., cloud structure) of cloud automatically and highly accurately by scanning the whole sky or a part thereof by using infrared laser beam.SOLUTION: Provided is a method for measuring a cloud structure. The method includes: a signal processing step of obtaining scattered light intensity of a plurality of measurement regions along an emission direction of laser beam by using a plurality of scattered light data obtained from scattered light of laser beam emitted to the atmosphere; a cloud evaluating step of evaluating whether or not each of the plurality of scattered light data is scattered light data from cloud particles on the basis of the obtained scattered light intensity; and a cloud structure determining step of determining a cloud structure on the basis of scattered light data in which the data has been evaluated as scattered light data from cloud particles by the cloud evaluating step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to meteorological observation technology, and more specifically, to technology for automatically measuring cloud structures such as cloud height and distribution using infrared laser light. [Background technology]

[0002] Cloud distribution around an airport, such as cloud base height and cloud cover, is an essential observation factor for safe flight operations, since it determines the range that aircraft taking off and landing can see. Conventionally, devices for measuring cloud base height have been installed around the runway, but these devices can only measure the cloud base height directly above the device, and the determination of cloud base height and cloud cover relies on visual observation.

[0003] The technologies described in Patent Documents 1 to 3 have been proposed as technologies for measuring cloud base height and cloud amount. Patent Document 1 proposes a device for determining cloud amount using a ceilometer that measures cloud base height. This device determines a cloud base height candidate from a cloud base height determined based on the reflected light of a laser beam emitted vertically upward multiple times, determines a cloud layer candidate from the multiple cloud base height candidates, and determines the cloud amount from the cloud base height data and the cloud layer candidate. In other words, this device estimates the cloud amount directly above the device, and is not capable of measuring the cloud base height and cloud amount at any position.

[0004] Patent Document 2 proposes a device that measures the distribution of cloud base heights from cloud images. This device reads out the azimuth and zenith angles of clouds from images taken by two wide-angle cameras facing the zenith, and calculates the cloud base height distribution based on these angles and the positions of the wide-angle cameras. The technology in Patent Document 2 uses image data, and although it can grasp the presence or absence of clouds in the image, it has problems such as being unable to obtain distance information and being unable to perform measurements at night.

[0005] Patent Document 3 also proposes a device for measuring cloud height over the entire sky. This device obtains multiple cloud base heights using local cloud height values ​​obtained from a small number of cloud height measuring devices and the relative heights of multiple cloud bases estimated based on image data of the entire sky. The technology of Patent Document 3 requires the use of multiple cloud height measuring devices and uses image data, so like Patent Document 2, although it can grasp the presence or absence of clouds in the image, it has problems such as being unable to obtain distance information and being unable to perform measurements at night. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-309309 A [Patent Document 2] JP 2019-060754 A [Patent Document 3] Patent Publication No. 2022-013152 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above-mentioned problems with the prior art, the present invention aims to provide a method and apparatus for automatically and accurately measuring the surface and / or three-dimensional distribution of clouds (i.e., cloud structure) by scanning the entire sky or part of it with infrared laser light. [Means for solving the problem]

[0008] The present invention provides a method for measuring cloud structure, which includes a signal processing step of determining scattered light intensities in a plurality of measurement regions along a direction of transmission of a laser beam using a plurality of scattered light data obtained from scattered light of a laser beam transmitted toward the atmosphere, a cloud determination step of determining whether each of the plurality of scattered light data is scattered light data from cloud particles based on the determined scattered light intensities, and a cloud structure determination step of determining a cloud structure based on the scattered light data determined to be scattered light data from cloud particles by the cloud determination step.

[0009] In another aspect, the present invention provides an apparatus for measuring cloud structure, comprising: a light transmitting unit for transmitting a laser beam toward the atmosphere, a light receiving unit for receiving scattered light of the transmitted laser beam, a signal processing unit for determining scattered light intensities of a plurality of measurement regions along the transmission direction of the laser beam using a plurality of scattered light data obtained from the received scattered light, and a cloud determination / structure determination unit for determining whether each of the plurality of scattered light data is scattered light data from cloud particles based on the determined scattered light intensities, and for determining the structure of the cloud based on the scattered light data determined to be scattered light data from cloud particles.

[0010] In yet another aspect, the present invention provides a computer program including program instructions for causing a computer to execute a method for measuring a cloud structure. Furthermore, the present invention provides a cloud structure measurement system for measuring a cloud structure, comprising an optical transceiver that transmits laser light toward the atmosphere and receives scattered light, and a computer that receives data from the optical transceiver and performs the method for measuring a cloud structure. Furthermore, the present invention provides a computer that includes a storage device storing a computer program including program instructions for causing a computer to execute the method for measuring a cloud structure, and a processor, and is configured to determine a cloud structure by communicating with a Doppler lidar device that transmits laser light toward the atmosphere and receives scattered light. Effect of the Invention

[0011] According to the present invention, the measurement of cloud structure, such as cloud base height, and the height, number, thickness and density of cloud layers, is automated and databased in real time, making it possible to quickly provide accurate information to aircraft, etc. Also, according to the present invention, the measurement of cloud structure and wind can be performed simultaneously, improving the measurement efficiency. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram outlining a method for measuring cloud structure according to an embodiment of the present invention. [Diagram 2] 1 is a block diagram showing the configuration of a cloud structure measurement system for measuring cloud structure according to one embodiment of the present invention. [Figure 3A] 1 is a flowchart showing processing performed by a cloud structure measurement system according to one embodiment of the present invention. [Figure 3B] 13 is a flowchart showing processing performed by a cloud structure measurement system according to another embodiment of the present invention. [Figure 4] 4A and 4B are schematic diagrams showing a method for measuring the structure of cloud layers according to one embodiment of the present invention, where FIG. 4A shows the concept of measuring the cloud height and number of layers, and FIG. 4B shows the concept of measuring the thickness and density of the cloud layer. [Diagram 5] FIG. 2 is a schematic diagram showing an example of a three-dimensional map representing the three-dimensional structure of clouds and a two-dimensional map representing the altitude of the cloud base according to an embodiment of the present invention. [Figure 6] 1 shows an example of a measurement of scattered light intensity and the measurement object that each echo represents, according to one embodiment of the present invention. [Figure 7] 13 shows an example of measurements when laser light is emitted at different elevation angles according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Overview of the cloud structure measurement system) FIG. 1 shows an overview of a method for measuring the cloud structure of the entire sky or a part thereof according to an embodiment of the present invention. This method can be realized, for example, by using a Doppler lidar device known to those skilled in the art. In the present invention, a transmission light such as an infrared laser light is sent toward the atmosphere in a range of 0 to 360 degrees in the horizontal direction and 0 to 180 degrees in the vertical direction, and scattered light of the sent laser light scattered by cloud particles or particles other than cloud particles (aerosols floating in the atmosphere) or both is acquired. The acquired scattered light signal is divided into a plurality of measurement ranges according to the distance along the direction of sending the laser light, and is converted into scattered light intensity in frequency space through instantaneous Fourier transform for each measurement range. The intensity of the peak frequency obtained from the spectrum of each measurement range is set as the scattered light intensity of each measurement range. It is determined whether the scattered light corresponding to the obtained scattered light intensity is scattered light from cloud particles or scattered light from other particles (aerosols) based on the difference in scattered light intensity and spectrum shape.

[0014] According to the present invention, the distribution and altitude of cloud bases can be automatically measured. According to the present invention, the altitude, number, thickness and density of multiple cloud layers can also be measured simultaneously up to a desired altitude by appropriately adjusting the transmission intensity of the laser light. From the data of the cloud base or cloud layers or both measured in this way, three-dimensional structure data of clouds can be automatically obtained. It is also possible to visualize the three-dimensional structure by mapping the three-dimensional structure data on a two-dimensional map or a three-dimensional map. According to the present invention, wind information can be obtained in a space where there are no clouds, and cloud information can be obtained in a space where clouds are present.

[0015] According to the present invention, scattered light data can be acquired in the range of 0 to 360 degrees horizontally and 0 to 180 degrees vertically, making it possible to automatically measure the approach path to an airport runway, the three-dimensional structure of clouds above each runway, a heliport or drone port, and sudden changes in wind such as wind shear.

[0016] As used herein, the scattered light intensity (also referred to as the scattering intensity or echo) is the intensity (in dB) of the scattered light that returns to the measurement system after the emitted laser light hits aerosols, cloud particles, etc. and is reflected. The spectral intensity is the intensity for each frequency of the scattered light that returns to the measurement system. The spectral shape is the shape of a graph in which the spectral intensity is arranged in order of frequency. The measurement range is each of a number of measurement regions that are separated according to the distance along the direction of emission of the laser light (also referred to as the line of sight direction).

[0017] FIG. 2 shows the configuration of a cloud structure measurement system 1 for measuring cloud structure according to one embodiment of the present invention.

[0018] The cloud structure measurement system 1 (hereinafter simply referred to as the system 1) comprises an optical transmitter / receiver 2 and a cloud structure measurement device 3. The optical transmitter / receiver 2 has an optical transmitter 21 that transmits laser light toward the atmosphere, and an optical receiver 22 that receives scattered light scattered by cloud particles or aerosols. The cloud structure measurement device 3 has a control / signal processor 31, a cloud judgment / structure determination unit 32, a wind calculator 33, and a wind / cloud information display unit 34.

[0019] The system 1 can be realized by using a Doppler lidar device well known to those skilled in the art. For example, a typical Doppler lidar device has an optical transmitter and receiver that transmits and receives laser light, and the system 1 can be realized by incorporating the components constituting the cloud structure measurement device, namely, the control and signal processing unit 31, the cloud judgment and structure determination unit 32, the wind calculation unit 33, and the wind and cloud information display unit 34, into the Doppler lidar device. Alternatively, the system 1 can be realized by providing a device that transmits and receives laser light and a cloud structure measurement device that receives a signal of the received scattered light and determines the cloud structure as separate devices.

[0020] The cloud structure measuring device 3 can be realized by using a general-purpose computer capable of communication, and more specifically, by hardware having a processing device which is a control unit such as a CPU (processor), a storage device and storage medium capable of storing a computer program including program instructions for causing a computer to execute the method for measuring a cloud structure according to the present invention and other programs, and a communication device with the outside. The storage device can be a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), an SSD (Slid State Drive), etc. The functions of each part of the cloud structure measuring device 3 can be realized, for example, by the CPU reading out the program and program instructions from the ROM, and reading and writing to the RAM to execute processing.

[0021] The above computer programs and other programs may be provided by being read from, for example, a USB (Universal Serial Bus) memory or an externally connected HDD, SSD, etc., which are examples of external storage media, or by being downloaded from another computer via a network. Furthermore, the functions of each part of the cloud structure measuring device 3 are not limited to being provided in one computer, and all or part of the functions of each part may be distributed and provided in one or more computers, and the same functions may be realized by communicating with each other via a medium such as the Internet.

[0022] (Details of the cloud structure measurement system's functions) <Optical transmitter / receiver> The optical transmitter / receiver 2 has an optical transmitter 21 that transmits laser light toward the atmosphere, and an optical receiver 22 that receives scattered light scattered by cloud particles or particles other than cloud particles. The optical transmitter 21 is not limited as long as it is configured to transmit laser light. For example, an optical transmitter / receiver employed in a well-known Doppler lidar device can be used as the optical transmitter 21. Such an optical transmitter / receiver can transmit laser light toward the atmosphere by rotating a horizontal rotating mirror in a range of 360 degrees and rotating a vertical rotating mirror in a range of 180 degrees, for example.

[0023] The direction in which the laser light is emitted can be set arbitrarily according to the atmospheric conditions, for example, in the azimuth angle range of 0 degrees to 360 degrees, the elevation angle range of 0 degrees to 180 degrees, and with the required angular resolution. Also, the laser light may be set to be emitted only in a specific direction, such as the direction of approach and takeoff of aircraft on a runway, to measure the cloud structure in that direction.

[0024] The optical receiver 22 is not limited as long as it is configured to receive scattered light that is returned after the laser light sent from the optical transmitter 21 is scattered by cloud particles or particles other than cloud particles. For example, an optical transmitter / receiver employed in a well-known Doppler lidar device can be configured to rotate so as to receive the returning scattered light. The optical transmitter / receiver 2 is preferably configured to perform analog / digital conversion (A / D conversion) of the received scattered light signal to generate scattered light data as a digital signal. The generated scattered light data is output to the cloud structure measurement device 3. Alternatively, an A / D converter may be provided in the cloud structure measurement device 3, and the scattered light signal received by the optical receiver 22 may be sent to the A / D converter of the cloud structure measurement device 3.

[0025] <Control and signal processing section> The control / signal processing unit 31 can include a control unit 31a and a signal processing unit 31b. The control unit 31a can control the operation of the entire system 1. Furthermore, the control unit 31a can control the azimuth angle and elevation angle of the optical transmitter 21 and the optical receiver 22 of the optical transmitter / receiver 2, and can provide information on the azimuth angle and elevation angle of the optical transmitter / receiver 2 to the wind information / cloud information display unit 34.

[0026] The signal processing unit 31b receives a plurality of scattered light data generated from the scattered light received by the light receiving unit 22, and can obtain the scattered light intensity from the plurality of scattered light data. The scattered light data received when the laser light is transmitted at a certain azimuth angle and elevation angle, and obtained for each of a plurality of measurement ranges according to the distance along the transmission direction of the laser light, is regarded as one scattered light data. When the laser light is transmitted over the entire sky, a plurality of scattered light data corresponding to different azimuth angles, elevation angles, and measurement ranges are obtained from the laser light transmitted at a plurality of azimuth angles and elevation angles. The number of azimuth angles and elevation angles at which the laser light is transmitted, and the number of measurement ranges can be appropriately set according to the resolution required for the application using the cloud structure finally obtained.

[0027] The signal processing unit 31b can obtain the scattered light intensity from the scattered light data. The signal processing unit 31b samples the acquired scattered light data at high speed, performs a real-time Fourier transform for each of the measurement ranges, and obtains the scattered light intensity in each of the measurement ranges. Specifically, for each of the measurement ranges, a power spectrum is obtained that represents the scattered light intensity as a function of frequency, and a normal distribution function is fitted to this power spectrum to obtain fitting parameters. Next, the scattered light intensity in that measurement range is determined based on the value of the peak frequency included in the fitting parameters.

[0028] In this embodiment, the fitting parameters include the values ​​of the peak frequency, the peak intensity, and the peak width. Then, a normal distribution function GAUSS(x) corresponding to the fitting parameters is defined as follows:

number

[0029] <Cloud judgment / structure determination section> The cloud determination / structure determination unit 32 determines whether the scattered light data is scattered light data from cloud particles based on the obtained scattered light intensity, and can determine the cloud structure based on the scattered light data determined to be scattered light data from cloud particles.

[0030] Based on the obtained scattered light intensity, it can be determined whether the light is scattered from cloud particles as follows.

[0031] (a) First embodiment of the judgment First, the scattered light intensity continuously obtained from the ground or its vicinity is due to scattered light from aerosols in the air, and therefore the scattered light data from which the scattered light intensities are obtained is determined to be not due to scattered light scattered by cloud particles (i.e., the scattered light intensity of aerosols in the air). Here, the threshold value for determining that the scattered light intensity of the scattered light data from cloud particles or the scattered light intensity of the scattered light data from particles other than cloud particles (aerosols) can be determined based on meteorological observation data at the measurement location or a preliminary investigation. For example, taking a past example observed by the applicant, when the background noise is -64 dB, scattered light intensity greater than that can be determined to be due to scattered light from cloud particles or particles other than cloud particles.

[0032] That is, when the cloud determination / structure determination unit 32 continuously obtains a scattered light intensity of, for example, -64 dB or more from the ground or its vicinity, it determines that the scattered light intensity is obtained from scattered light data from particles (aerosols) other than cloud particles. Also, when the scattered light intensity of -64 dB or more continuously obtained from the ground or its vicinity stops, the cloud determination / structure determination unit 32 determines that particles (aerosols) other than cloud particles no longer exist. The scattered light intensity from particles (aerosols) other than cloud particles obtained in this manner is transmitted to the wind calculation unit 33 described later, and the wind speed and wind direction are calculated based on the scattered light intensity.

[0033] Here, the concept of measuring the structure of cloud layers will be explained with reference to Figure 4. Figure 4(a) shows the concept of measuring the cloud height and number of layers, and Figure 4(b) shows the concept of measuring the thickness and density of the cloud layers. As shown in FIG. 4(a), the laser light A sent from the light sending unit 21 of the cloud structure measurement system 1 hits particles in the atmosphere and is scattered, and some of the scattered light returns to the light receiving unit 22 of the cloud structure measurement system 1. When the scattered light intensity equal to or greater than the threshold value is obtained again after the scattered light intensity equal to or greater than the threshold value obtained continuously from the ground or its vicinity is interrupted, the cloud judgment and structure determination unit 32 judges that the scattered light intensity is based on the scattered light from the cloud particles. The intensity of the scattered light A' obtained at this time can be judged to be based on the scattered light from the bottom of the cloud, that is, the cloud base. Also, as shown in FIG. 4(b), a plurality of measurement ranges in which the scattered light intensity equal to or greater than the threshold value is successively obtained are judged to be the measurement range corresponding to the position of the cloud, and when the scattered light intensity equal to or greater than the threshold value is not obtained next time, the measurement range immediately before that can be judged to be the range corresponding to the top of the cloud. The plurality of successive scattered light intensities obtained in this way are judged to be based on the scattered light from the first cloud layer.

[0034] 4(a), the altitude of the bottom of the cloud, i.e., the cloud base, can be calculated from the time from when laser light A is emitted from the cloud structure measurement system 1 until it returns as scattered light A'. When laser light A is emitted at a specified elevation angle, the altitude of the cloud base can be calculated using that angle and the distance from the light transmitter 21 to the cloud.

[0035] As shown in Figure 4(b), the thickness of the cloud layer can be calculated from the difference between the altitude of the measurement range (i.e., corresponding to the cloud base) when the scattered light intensity above the threshold is obtained again after the scattered light intensity above the threshold, which is continuously obtained from the ground or its vicinity, stops, and the altitude of the measurement range immediately before the measurement range where the scattered light intensity above the threshold stops being obtained. Also, the cloud density can be determined from the magnitude of each of the consecutive scattered light intensities above the threshold, and the greater the scattered light intensity, the denser the cloud is determined to be.

[0036] By adjusting the intensity of the laser light transmission, it is possible to measure cloud layers at a higher altitude than the first cloud layer. That is, by transmitting laser light with an intensity that can reach farther than the first cloud layer, the transmitted laser light A that is not scattered by the particles of the first cloud layer travels further as laser light B shown in FIG. 4(a), and a part of the scattered light B' scattered by the cloud particles returns to the light receiving unit 22 of the cloud structure measurement system 1. After the scattered light intensity continuously obtained by the first cloud layer is interrupted, the scattered light B' that again has a scattered light intensity equal to or greater than the threshold value can be determined to be scattered light from the measurement range corresponding to the bottom of the second cloud layer.

[0037] As in the case of the first cloud layer, the altitude of the bottom of the second cloud layer can be calculated from the time from when the laser light A is emitted until it returns as scattered light B'. When the laser light A is emitted at a predetermined elevation angle, the altitude of the bottom of the second cloud layer can be calculated using the angle and the distance from the light emitter 21 to the cloud. As in the case of the first cloud layer, the thickness of the second cloud layer can also be calculated from the difference between the altitude of the measurement range (i.e., corresponding to the bottom of the second cloud layer) when the scattered light intensity of the first cloud layer is continuously obtained and the scattered light intensity of the first cloud layer is again obtained after the threshold value is broken, and the altitude of the measurement range immediately before the measurement range where the subsequent continuous scattered light intensity of the second cloud layer is no longer obtained. In addition, the density of the cloud can be determined from the magnitude of each of the continuous scattered light intensities of the first cloud layer and the cloud is determined to be denser as the scattered light intensity is greater.

[0038] Similarly, by further adjusting the transmission intensity of the laser light, information on the Nth cloud layer located above the second cloud layer can be obtained. If the continuous scattered light intensity above the threshold is no longer obtained after the continuous scattered light intensity above the threshold is interrupted, it can be determined that no clouds exist above the cloud layer where the continuous scattered light intensity was obtained. As described above, among the scattered light data determined to be scattered light data from cloud particles, each of the multiple data sets consisting of multiple consecutive scattered light data is determined to be scattered light data from each of the multiple cloud layers (the first cloud layer to the Nth cloud layer).

[0039] (b) Embodiment 2 of the judgment The determination of whether or not a particle is a cloud particle in the above-mentioned embodiment 1 is performed based on the absolute value of the scattered light intensity in each measurement range, and whether or not continuous data of the scattered light intensity by aerosols or cloud particles is interrupted is used to determine whether or not there is a cloud. This method has the advantage that the determination is simple and the amount of calculation is small, so there is no need to use large calculation resources. On the other hand, this method may be difficult to determine whether or not there is a cloud when aerosols and clouds are continuous without interruption. This is particularly problematic when the difference in particle size between the two is small. When such weather conditions are expected, the following method can be used.

[0040] The judgment according to the second embodiment is made based on the difference in scattered light intensity between adjacent measurement ranges in the line of sight. Specifically, the cloud judgment and structure determination unit 32 compares the scattered light intensity between adjacent measurement ranges in the line of sight, starting from the ground or its vicinity, and judges that the scattered light data in a measurement range in which the scattered light intensity changes continuously with a value smaller than a predetermined difference is based on scattered light data from particles (aerosols) other than cloud particles. Next, when the scattered light intensity between adjacent measurement ranges becomes equal to or greater than a predetermined difference, the cloud judgment and structure determination unit 32 judges that a cloud starts from that measurement range. The predetermined difference can be determined based on meteorological observation data at the measurement location or a preliminary investigation. For example, taking a past example observed by the applicant, the difference in scattered light intensity between particles (aerosols) other than cloud particles and cloud particles can be set to 5 dB or more. The scattered light intensity due to the scattered light from particles (aerosols) other than cloud particles obtained in this way is transmitted to the wind calculation unit 33 described later, and the wind speed and wind direction are calculated based on the scattered light intensity.

[0041] The concept of measuring the structure of a cloud layer will be explained similarly with reference to Fig. 4(a). Laser light A emitted from the light transmitting unit 21 of the cloud structure measurement system 1 hits particles in the atmosphere and is scattered, and a part of the scattered light A' returns to the light receiving unit 22 of the cloud structure measurement system 1. If the difference in scattered light intensity between adjacent measurement ranges in the line of sight direction calculated using the returned scattered light A' is 5 dB or more, the cloud judgment and structure determination unit 32 judges that the scattered light intensity of the farther measurement range is based on scattered light from cloud particles (the beginning of the cloud). The intensity of the scattered light A' obtained at this time can be judged to be based on scattered light from the lowest part of the cloud, i.e., the cloud base.

[0042] Next, as shown in Fig. 4(b), a plurality of consecutive measurement ranges in which the difference in scattered light intensity between adjacent measurement ranges is less than 5 dB are determined to be the measurement range corresponding to the position of the cloud, and when the difference in scattered light intensity between adjacent measurement ranges becomes 5 dB or more, the cloud determination / structure determination unit 32 can determine that the closer of the two measurement ranges is the measurement range corresponding to the top of the cloud. The scattered light intensity thus obtained, which changes continuously with values ​​smaller than a predetermined value, is determined to be based on scattered light from the first cloud layer.

[0043] 4(a), the altitude of the bottom of the cloud, i.e., the cloud base, can be calculated from the time from when laser light A is emitted from the cloud structure measurement system 1 until it returns as scattered light A'. When laser light A is emitted at a specified elevation angle, the altitude of the cloud base can be calculated using that angle and the distance from the light transmitter 21 to the cloud.

[0044] As shown in Figure 4(b), the thickness of the cloud layer can be calculated from the difference between the altitude of the farther measurement range (i.e., corresponding to the cloud base) when the difference in scattered light intensity between adjacent measurement ranges becomes 5 dB or more, and the altitude of the closer measurement range when the difference in scattered light intensity between adjacent measurement ranges becomes smaller than 5 dB. Also, the density of the cloud can be determined from the magnitude of the scattered light intensity of the measurement range determined to be cloud particles, and the greater the scattered light intensity, the denser the cloud is determined to be.

[0045] By adjusting the transmission intensity of the laser light, it is possible to measure cloud layers at a higher altitude than the first cloud layer. That is, by transmitting the laser light with an intensity that can reach farther than the first cloud layer, the transmitted laser light A that is not scattered by the particles of the first cloud layer travels further as the laser light B shown in FIG. 4(a), and a part of the scattered light B' scattered by the cloud particles returns to the optical receiver 22 of the cloud structure measurement system 1. When a difference in scattered light intensity of 5 dB or more is obtained again farther than the first cloud layer, it can be determined that the scattered light B' in the farther measurement range corresponds to the bottom of the second cloud layer.

[0046] As in the case of the first cloud layer, the altitude of the bottom of the second cloud layer can be calculated from the time from when the laser light A is emitted until it returns as scattered light B'. When the laser light A is emitted at a predetermined elevation angle, the altitude of the bottom of the second cloud layer can be calculated using the angle and the distance from the light transmitter 21 to the cloud.

[0047] Furthermore, a plurality of consecutive measurement ranges in which the difference in scattered light intensity between adjacent measurement ranges is less than 5 dB is determined to be a measurement range corresponding to the position of a cloud, and when the difference in scattered light intensity between adjacent measurement ranges is then 5 dB or more, the cloud determination and structure determination unit 32 can determine that the closer of the two measurement ranges is the range corresponding to the top of the cloud. In this way, similar to the case of the first cloud layer, the scattered light intensity that changes continuously at a value smaller than a predetermined value is determined to be based on scattered light from the second cloud layer. The thickness and density of the second cloud layer can also be calculated in the same way as the case of the first cloud layer.

[0048] Similarly, by further adjusting the transmission intensity of the laser light, information on the Nth cloud layer located above the second cloud layer can be obtained. If the difference between adjacent measurement ranges at a position farther away than the Nth cloud layer is not 5 dB or more, it can be determined that there are no clouds above the Nth cloud layer. As described above, for scattered light data determined to be scattered light data from cloud particles, the scattered light intensities of adjacent measurement areas along the direction of laser light emission are compared, and each of the multiple data sets consisting of scattered light data for which the scattered light intensity changes continuously with values ​​smaller than a predetermined difference is determined to be scattered light data from each of the multiple cloud layers (the first cloud layer to the Nth cloud layer).

[0049] <Wind calculation department> The wind calculation unit 33 can calculate the wind direction and wind speed in a space without clouds based on the scattered light intensity from particles (aerosols) other than cloud particles. Specifically, the wind calculation unit 33 obtains a power spectrum that represents the scattered light intensity as a function of frequency for each of a plurality of measurement ranges, and performs fitting of a normal distribution function to this power spectrum to obtain fitting parameters. Next, the wind speed is calculated by obtaining the frequency difference between the peak frequency value included in the fitting parameter and a reference frequency that represents a wind speed of 0 m / s, and converting the frequency difference into a wind speed value. For example, a frequency difference of 1 MHz corresponds to 0.77 m / s, and the wind speed can be obtained from this relationship. This relationship can be obtained using the following formula. V=(L / 2)F Here, L is the wavelength of the laser light (m), F is the receiving bandwidth (Hz), and V is the wind speed in the line of sight (m / s).

[0050] <Wind information / cloud information display section> The wind information / cloud information display unit 34 can visually display cloud information and wind information by mapping the cloud structure and wind information obtained based on the scattered light intensity onto a two-dimensional map, a three-dimensional map, or both. FIG. 5 is a schematic diagram showing an example of a three-dimensional map representing the spatial structure of clouds and a two-dimensional map representing the altitude of the cloud base according to an embodiment of the present invention.

[0051] The three-dimensional map showing the three-dimensional structure of the cloud and the two-dimensional map showing the altitude of the cloud base can be created by a method well known to those skilled in the art. That is, as described above, the cloud judgment and structure determination unit 32 judges the altitude of the cloud base existing in a certain direction (certain azimuth angle and elevation angle) and the altitude, number, thickness and density of the cloud layers based on the scattered light intensity of the scattered light returned after the laser light transmitted in that direction is scattered by cloud particles. The wind information and cloud information display unit 34 maps the cloud information data of the whole sky or a part thereof obtained by transmitting the laser light in a plurality of directions (azimuth angle and elevation angle) into a three-dimensional space of the whole sky by a method well known to those skilled in the art. The data of the transmission direction (azimuth angle and elevation angle) of the laser light required for mapping can be provided to the wind information and cloud information display unit 34 from the control unit 31a.

[0052] Specifically, for three-dimensional grid points set in the space of the entire sky, 1 is mapped to grid points where clouds exist, and 0 is mapped to grid points where clouds do not exist. By mapping 1 or 0 to all grid points, a three-dimensional map of the cloud structure can be created. In addition, by projecting the lowest altitude position of each cloud layer in two dimensions in the cloud structure mapped in three dimensions, a two-dimensional map showing the position of the cloud base in the entire sky or a part of it can be created. If necessary, information on the altitude of the cloud base can be displayed on the two-dimensional map by changing the color or density of the cloud base depending on the altitude. If necessary, the number of grid points where 1 is mapped out of the number of all grid points can be calculated, and the percentage of the total cloud amount can be displayed on a scale of, for example, 10 levels.

[0053] (Processing flow chart of cloud structure measurement system) Figure 3 is a flow chart showing the processing performed by the system 1 described thus far. Figure 3A is a flow chart 300A corresponding to embodiment 1 for determining whether the returning scattered light is from a cloud particle, and Figure 3B is a flow chart 300B corresponding to embodiment 2 for determining whether the returning scattered light is from a cloud particle.

[0054] Starting with flowchart 300A, system 1 transmits laser light by optical transceiver 2 and receives scattered light that is returned after being scattered by cloud particles or particles other than cloud particles (aerosols) (sA301). The laser light can be transmitted in any direction by being controlled by control unit 31a in the range of 0 to 360 degrees horizontally and in the range of 0 to 180 degrees vertically at any angular resolution. The scattered light received by optical transceiver 2 is processed by control and signal processing unit 31 to determine the scattered light intensity.

[0055] The cloud determination and structure determination unit 32 determines that the scattered light intensity equal to or greater than the threshold value that is continuously obtained from the ground or its vicinity is the scattered light intensity due to particles other than cloud particles (sA302).When the scattered light intensity equal to or greater than the threshold value is obtained again after the continuously obtained scattered light intensity is interrupted (sA304), the cloud determination and structure determination unit 32 determines that the scattered light intensity is based on scattered light from cloud particles (first cloud echo) (sA305).

[0056] The cloud judgment / structure determination unit 32 judges that a plurality of measurement ranges in which the scattered light intensity is equal to or greater than the threshold value are consecutive measurement ranges corresponding to the position of the cloud, and when the scattered light intensity equal to or greater than the threshold value is not obtained next time, it can judge that the measurement range immediately before that is the range corresponding to the top of the cloud. The consecutive scattered light intensities thus obtained are judged to be based on scattered light from the first cloud layer. Based on the obtained scattered light intensity, the cloud base height, the thickness of the cloud layer and / or the cloud density can be calculated (sA305).

[0057] When the next scattered light intensity equal to or greater than the threshold is obtained (sA306), the cloud determination / structure determination unit 32 determines that the scattered light intensity is based on scattered light from cloud particles (second cloud echo). As in the case of the first cloud layer, a plurality of measurement ranges in which the scattered light intensity equal to or greater than the threshold is continuous are determined to be the measurement range corresponding to the position of the cloud (second cloud layer), and when the next scattered light intensity equal to or greater than the threshold is no longer obtained, the measurement range immediately before that can be determined to be the range corresponding to the top of the second cloud layer, and the cloud base height, cloud layer thickness, and / or cloud density can be obtained based on the continuous scattered light intensity obtained (sA307). The cloud determination / structure determination unit 32 repeats the above determination based on the scattered light intensity, and can determine the Nth cloud layer as necessary (sA308, sA309).

[0058] Based on the cloud structure data obtained as described above and the data on the laser light emission direction (azimuth angle and elevation angle) provided by the control unit 31a, the wind information / cloud information display unit 34 performs two-dimensional mapping (sA310) and / or three-dimensional mapping (sA311) that can visually display cloud information. The wind information / cloud information display unit 34 maps the cloud information data of the entire sky or a part of it into the two-dimensional space and / or three-dimensional space of the entire sky, and outputs it in any manner (for example, by displaying it on a monitor) (sA312).

[0059] Next, flowchart 300B will be described. Here, the same processes as those in flowchart 300A will be briefly described. The system 1 receives scattered light that has been scattered by cloud particles or particles other than cloud particles (aerosols) and returned (sB301).

[0060] The cloud determination / structure determination unit 32 compares the scattered light intensity between adjacent measurement ranges in sequence from the ground or its vicinity (sB302), and determines that the scattered light data in a measurement range where the scattered light intensity changes continuously at a value smaller than a predetermined difference (sB303) is obtained from scattered light from particles (aerosols) other than cloud particles (SB304). The cloud determination / structure determination unit 32 continues to compare the scattered light intensity between adjacent measurement ranges and determines whether the difference is equal to or greater than a predetermined value (sB305). If the difference is smaller than the predetermined value, it determines that the scattered light intensity is still from particles (aerosols) other than cloud particles (sB304).

[0061] The cloud determination / structure determination unit 32 continues to compare the scattered light intensity between adjacent measurement ranges, and if the difference is equal to or greater than a predetermined value, it determines that the scattered light intensity in that measurement range is based on scattered light from cloud particles (first cloud echo) (sB306). The cloud determination / structure determination unit 32 further continues to compare the scattered light intensity between adjacent measurement ranges, and determines whether the difference is equal to or greater than a predetermined value (sB307). If the difference is smaller than the predetermined value, it determines that the scattered light intensity is still from cloud particles (first cloud layer) (sB306).

[0062] If the difference between the scattered light intensities of adjacent measurement ranges becomes equal to or greater than a predetermined value as a result of continuing to compare the scattered light intensities between the adjacent measurement ranges, the cloud judgment and structure determination unit 32 can judge that the closer of the two measurement ranges where the difference appears corresponds to the top of the cloud, and can judge that the first cloud layer has been passed. Based on the obtained scattered light intensity, the cloud base height, the cloud layer thickness and / or the cloud density can be obtained (sB308). The cloud judgment and structure determination unit 32 can repeat the above judgment based on the scattered light intensity, and judge the Nth cloud layer as necessary (sB309, sA310).

[0063] Based on the cloud structure data and laser light transmission direction data obtained as described above, the wind information / cloud information display unit 34 performs two-dimensional mapping (sB311) and / or three-dimensional mapping (sB312) that can visually display cloud information, and outputs cloud information data for the entire sky or part of it (sB313).

[0064] (Example of scattered light intensity measurement) Below, examples of results obtained from measurement experiments conducted by the applicant of the present application will be shown. Fig. 6 shows an example of scattered light intensity measurement according to an embodiment of the present invention and the measurement target represented by each echo, which is an example of measurement when laser light is sent vertically upward. Fig. 6(a) to Fig. 6(d) show measurement images of scattered light intensity over time and schematic diagrams of the target represented by each image. In each case, the horizontal axis shows Doppler velocity (m / s) and the vertical axis shows altitude (km), and a scale bar of scattered light intensity is shown between the image and the schematic diagram.

[0065] In both measurement images, scattered light intensity is obtained continuously from the ground (altitude 0 km) to an altitude of approximately 0.7 km, and this continuous scattered light intensity is determined to be scattered light intensity (wind echo) caused by particles (aerosols) other than cloud particles based on the determination embodiment 1. In Fig. 6(a), scattered light intensity (cloud echo) is obtained in the range of altitudes from approximately 0.9 km to approximately 1.0 km and further in the range of altitudes from approximately 1.2 km to approximately 1.3 km, indicating the presence of cloud layers of approximately the same thickness in each range.

[0066] After a certain time has passed, as shown in Figure (b), continuous cloud echoes are obtained in the range of altitudes from about 1.0 km to about 1.5 km above the wind echo, and it can be seen that the two cloud layers at the time of Figure 6 (a) have changed to one thick cloud layer. Similarly, Figure 6 (c) shows that a thin cloud layer exists in the range of altitudes from about 0.9 km to about 1.0 km, and a thicker cloud layer exists in the range of altitudes from about 1.2 km to about 1.4 km. Furthermore, Figure 6 (d) shows that one cloud layer exists in the range of altitudes from about 1.2 km to about 1.4 km.

[0067] FIG. 7 shows an example of measurement when laser light is emitted with different elevation angles. FIG. 7(a) is a schematic diagram showing the state in which laser light is emitted horizontally over 360 degrees at each elevation angle and the scattered light intensity is measured, and FIG. 7(b) is a diagram showing the measurement results on a two-dimensional map of the entire sky. "EL" in the figure represents the elevation angle. In FIG. 7(a), the lines at each elevation angle represent the laser light, and the parts represented by thick lines exemplarily show the parts where scattered light intensity (wind echo) due to particles other than cloud particles (aerosols) is obtained. FIG. 7(b) shows the two-dimensional map and the scattered light intensity scale bar on the right side, which are measurement results obtained at one elevation angle, and the elevation angle increases from the left to the right.

[0068] In each two-dimensional map in Fig. 7(b), the center of the circle corresponds to the vertically upward direction of the light-transmitting part, the upper part corresponds to the north, the lower part corresponds to the south, the left part corresponds to the west, and the right part corresponds to the east. As shown in Fig. 7(b), this system can distinguish between the light intensity scattered by particles other than cloud particles (wind echo) and the light intensity scattered by cloud particles (cloud echo), and visualize the distribution of cloud bases.

[0069] A person skilled in the art will understand that, based on this description, it is possible to implement one embodiment of the invention described in the claims of this application, and that various modifications of the embodiment are possible within the technical scope of the invention described in the claims.

Claims

1. 1. A method for measuring cloud structure, comprising: a signal processing step of determining scattered light intensities in a plurality of measurement regions along a direction of transmission of the laser light using a plurality of scattered light data obtained from scattered light of the laser light transmitted to the atmosphere; a cloud determination step of determining whether each of the plurality of scattered light data is scattered light data from cloud particles based on the determined scattered light intensity; a cloud structure determination step for determining a cloud structure based on the scattered light data determined to be scattered light data from cloud particles in the cloud determination step; The method includes:

2. The cloud determination step includes: Among the obtained plurality of scattered light data, the scattered light data in which the scattered light intensity is continuously obtained from the ground or its vicinity is determined to be scattered light data from particles other than cloud particles; Determining that scattered light data that is not scattered light data from particles other than cloud particles is scattered light data from cloud particles The method of claim 1 , comprising:

3. The method according to claim 2 , wherein the cloud determination step includes determining that scattered light data that reappears after scattered light data from particles other than cloud particles has ceased is scattered light data from a cloud base.

4. The method of claim 2, wherein the cloud determination step includes determining that each of a plurality of data sets consisting of a plurality of consecutive scattered light data among the scattered light data determined to be scattered light data from cloud particles is scattered light data from each of a plurality of cloud layers.

5. The method of claim 4 , wherein the cloud structure determining step includes determining a thickness and density of each of the plurality of cloud layers based on scattered light data from each of the plurality of cloud layers.

6. The cloud determination step includes: For the multiple scattered light data obtained, the scattered light intensities of adjacent measurement areas are compared along the direction of laser light emission, starting from the ground or its vicinity, and scattered light data for which the scattered light intensity changes continuously with a value smaller than a predetermined difference is determined to be scattered light data from particles other than cloud particles; Determining that scattered light data that is not scattered light data from particles other than cloud particles is scattered light data from cloud particles The method of claim 1 , comprising:

7. 7. The method of claim 6, wherein the cloud determination step includes comparing the scattered light intensities of adjacent measurement areas along the direction of laser light transmission for scattered light data determined to be scattered light data from cloud particles, and determining that each of a plurality of data sets consisting of scattered light data in which the scattered light intensities vary continuously with values ​​smaller than a predetermined difference is scattered light data from each of a plurality of cloud layers.

8. The method according to claim 2 , further comprising a wind calculation step of determining wind information in a space where no clouds exist based on the scattered light intensity of the scattered light data determined to be scattered light data from particles other than cloud particles.

9. The method of claim 3 , wherein the cloud structure determining step includes determining a cloud base altitude based on scattered light data from the cloud base.

10. The method of claim 4 , wherein the cloud structure determining step includes determining a cloud layer structure based on scattered light data from each of the plurality of cloud layers.

11. A computer program for measuring cloud structure, comprising program instructions causing a computer to carry out the method according to any one of claims 1 to 10.

12. An apparatus for measuring cloud structure, comprising: a light transmitting unit that transmits laser light to the atmosphere; a light receiving unit for receiving scattered light of the emitted laser light; a signal processing unit that uses a plurality of scattered light data obtained from the received scattered light to determine scattered light intensities in a plurality of measurement regions along the direction of transmission of the laser light; a cloud determination and structure determination unit that determines whether each of the plurality of scattered light data is scattered light data from cloud particles based on the obtained scattered light intensity, and determines the structure of the cloud based on the scattered light data that is determined to be scattered light data from cloud particles; An apparatus comprising:

13. The cloud determination and structure determination unit includes: Among the multiple scattered light data obtained, scattered light data in which scattered light intensity is continuously obtained from the ground or its vicinity is determined to be scattered light data from particles other than cloud particles; The scattered light data that is not scattered light data from particles other than cloud particles is determined to be scattered light data from cloud particles.

13. The apparatus of claim 12.

14. The device according to claim 12, wherein the cloud determination / structure determination unit determines that scattered light data that reappears after scattered light data from particles other than cloud particles has ceased is scattered light data from a cloud base.

15. The device described in claim 12, wherein the cloud determination / structure determination unit determines that, among the scattered light data determined to be scattered light data from cloud particles, each of a plurality of data sets consisting of a plurality of consecutive scattered light data is scattered light data from each of a plurality of cloud layers.

16. The apparatus of claim 15 , wherein the cloud determination and structure determination unit determines a thickness and density of each of a plurality of cloud layers based on scattered light data from each of a plurality of cloud layers.

17. The cloud determination and structure determination unit includes: For the multiple scattered light data obtained, the scattered light intensities of adjacent measurement areas along the direction of laser light emission are compared in order from the ground or its vicinity, and scattered light data for which the scattered light intensity changes continuously with a value smaller than a predetermined difference is determined to be scattered light data from particles other than cloud particles; Scattered light data that is not scattered light data from particles other than cloud particles is determined to be scattered light data from cloud particles.

13. The apparatus of claim 12.

18. The cloud determination and structure determination unit compares the scattered light intensities of a plurality of measurement regions along the direction of laser light emission for the scattered light data determined to be scattered light data from cloud particles, and determines that each of a plurality of data sets consisting of scattered light data for which the scattered light intensity continuously changes with a value smaller than a predetermined difference is scattered light data from each of a plurality of cloud layers.

20. The apparatus of claim 17.

19. The device according to claim 12 , further comprising a wind calculation unit that calculates wind information in a space where no clouds exist based on the scattered light intensity of the scattered light data determined to be scattered light data from particles other than cloud particles.

20. The apparatus according to claim 14 , wherein the cloud determination and structure determination unit determines the altitude of the cloud base based on scattered light data from the cloud base.

21. The apparatus of claim 15 , wherein the cloud determination and structure determination unit determines the structure of a cloud layer based on scattered light data from each of a plurality of cloud layers.

22. A cloud structure measurement system for measuring cloud structure, comprising an optical transceiver unit that transmits laser light toward the atmosphere and receives scattered light, and a computer that receives data from the optical transceiver unit and performs the method described in any one of claims 1 to 10.

23. 12. A computer comprising a storage device having stored thereon the computer program of claim 11 and a processor, the computer being configured to determine cloud structure by communicating with a Doppler lidar device that transmits laser light into the atmosphere and receives scattered light.

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