RU2497159C2 - Method of determining height of cloud base - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: wide-panoramic automated scanning system is used to automatically determine areas with the highest contrast, from which the height of the cloud base is determined. A frame consisting of M×N cells is broken down into radiance layers. The height of the cloud base is determined from the speed of a fragment of the cloud field relative cells (cell speed of layers) and the height difference of layers, given on a standard model of the Earth.

EFFECT: automating the determination of the height of a cloud base from movement of its spatial structure of radiation in real time and broader functional capabilities of weather observations.

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Description

The invention relates to meteorology, to methods for determining the physical parameters of the atmosphere, and allows you to determine the height of the lower border of cloudiness (NGO).

A known method of determining the height of the lower boundary of the clouds by means of a meter [1], which consists in measuring the angular coordinates of the selected portion of the lower boundary of the cloud relative to two stationary matrix photodetectors having a regular pixel position structure and arranged so that their optical axes have known vertical and horizontal angles and lie in the same plane, and the viewing angles overlap at a certain height between them. The disadvantages of this method are the problem of selecting and identifying the same fragment of cloudiness, which is performed manually by the operator, the increased sensitivity of the system to errors in photodetectors, the relatively high cost of manufacturing and operating the meter, as well as a small viewing area.

Also known is the radar method for determining the height of an NGO using a spotlight [2], which sends short pulses and receives a reflected signal. Based on the delay time of the return signal, the height of the NGO is calculated. The disadvantages of this method is that for translucent clouds, the reflected signal will be attenuated, which will lead to a significant increase in the error of measurement of height. In addition, the measurement of NGOs is carried out only at a specific point.

The problem to which this invention is directed is to automate the process of determining the height of an NGO in real time and obtain the distribution of the height of an NGO in the scanning area of a radiometer in almost the entire hemisphere.

The technical result is the expansion of the functionality of meteorological observations by automating the determination of the height of the lower cloud boundary both day and night in real time by shifting its spatial structure of its own radiation.

Comparison of the proposed method with the prototype made it possible to establish compliance with its condition of "novelty." When comparing the proposed method with other well-known technical solutions did not reveal similar signs, which allows us to conclude that the condition "inventive step".

The method is illustrated by drawings. Figure 1 shows the geometry of the formation of two adjacent time frames on the intrinsic radiation of clouds in the projection onto the plane. The time interval between frames is t. Figure 2 shows the image of the converted neighboring frames in a Cartesian coordinate system. Figure 3 illustrates the definition of the projection of the velocity of a fragment of a cloud field.

The specified technical result during the implementation of the invention is achieved by means of a wide-panoramic automated scanning system [3], which performs continuous circular scanning in the range of the natural radiation of the cloud field by almucantarat for a time at which the spatial structure of the radiation of the cloud field remains unchanged. During this time, a series of values of the energy brightness, or the radiation temperature of the cloud field through each degree, or minutes of the arc are recorded, that is, the height of the NGO is determined, which is uniquely related to the radiation temperature. After the recording of data by line is completed, the angle of inclination of the scanning mirror changes, the cycle repeats and the next line is recorded. After a specified number of lines, the scanning mirror of the wide-panoramic automated scanning system returns to its original initial position, the cycle repeats and the next frame is recorded. The scanning system automatically determines the gaps in the clouds by two adjacent frames, in real time, as the most contrasting areas of the cloudy sky, which determine the height of the lower boundary of the clouds.

That is, a frame of a cloudy sky is formed from the matrix set recorded in the system memory (where N is the horizontal value and M is the vertical). Each of the N × M values represents a specific region - an image in the infrared region on the celestial sphere. Then, the program changes the shape of the matrix, for the transition from angular coordinates to Cartesian (figure 2).

Both frames are conventionally divided into 2 layers according to energy brightness. The lower layer, which corresponds to a higher radiation temperature, consists of elements with an energy brightness exceeding 0.9 · B _max , the upper layer includes elements with a lower radiation temperature (with brightness from 0.75 · B _max to 0.85 · B _max , where B _max is the threshold set in the system for the maximum value of the energy brightness of the frame).

For this pair of layers (lower / upper), the most contrasting portion limited by the frame is automatically determined (Fig. 2). By most contrasting is meant a section of a frame containing the largest number of cells of the corresponding layers. On frame b (FIG. 2), a fragment of the layer bounded by the frame is offset from its position on frame a (FIG. 2). The number of cells (n) onto which the layer has shifted during the registration of one frame (t) determines the cell velocity of the layer (ν).

$$\nu =\frac{n}{t}$$

It is defined by the horizontal and vertical components of the displacement of this fragment. The area in frame b (figure 2) is shifted in all possible vertical and horizontal directions from one cell to the maximum displacement d, which determines the maximum speed. The elements of frame b (FIG. 2) inside the offset region are subtracted from the corresponding elements of the marked region of frame a (FIG. 2). The resulting differences are summed modulo, forming a matrix F (a matrix of sums of absolute differences for all possible offsets).

$$F_{i\text{'}\text{'},j\text{'}\text{'}}={\displaystyle \sum _{i=i_{\mathrm{one}}}^{i_2}{\displaystyle \sum _{j=j_{\mathrm{one}}}^{j_2}\left|M_{i,j}-N_{i+i\text{'}\text{'},j+j\text{'}\text{'}}\right|}}$$

фрагмента. Зная временной интервал t между двумя соседними кадрами, определяются горизонтальные (υ) и вертикальные (u) составляющие ячейковой скорости:M _{i, j} , N _{i, j} - elements inside the limited area of the frame a and b (Fig. 2), respectively; i ', j' - all possible offsets from -d to + d; i ₁ , i ₂ - vertical boundaries of the region; j ₁ , j ₂ - horizontal area boundaries; The minimum matrix element corresponds to the most probable bias $$\left({i^{\prime }}_o,{j^{\prime }}_o\right)$$

fragment. Knowing the time interval t between two adjacent frames, the horizontal (υ) and vertical (u) components of the cell velocity are determined:

$$\upsilon =\frac{{i^{\prime }}_o}{t},$$

$$u=-\frac{{j^{\prime }}_o}{t}$$

The signs in front of the expressions are determined by the choice of direction of speed. Based on the found components, the total cell velocity of the layer is determined:

$$\nu =\sqrt{{\upsilon }^2+u^2}.$$

The angle α of the deviation of the vector of the total cell velocity ν from the horizontal is calculated as:

$$\alpha =a\sin \left(\frac{u}{\nu }\right),\upsilon >0$$

$$\alpha =\pi -a\sin \left(\frac{u}{\nu }\right),\upsilon <0$$

Since the direction of the motion vector of a fragment of the cloud layer usually does not coincide with the radial line connecting the fragment and the center of the frame (Fig. 3), it is necessary to know the projection of the total cell velocity on this line, which are calculated by the following formula:

v = ν cos (α-β),

where α is the angle of deviation of the velocity vector of the corresponding layer of the fragment, β is the angle of inclination of the radial line, which is determined by the coordinates of the center of the fragment.

The above calculations are performed for the upper and lower layers separately. As a result, the cell velocities of their projections v _{vertical ball} , v _{lower ball} are determined for the upper and lower layer.

For each layer, the average value of the energy brightness (radiation temperature) is determined. According to these average values, according to the standard model of the Earth’s atmosphere [4] (Fig. 2), the approximate heights of the upper (Ho _. ) And lower (Ho _. ) Layers and their height difference h are determined.

h = But _ver. -But _lower.

The height of the NGO is determined by the following formula:

H = hv v _ball / (v _{lower ball} -v _{ball v} ).

The conclusion of the last formula is illustrated by the following example.

Suppose a scanning radiometer detects two clouds moving at the same speed but at different heights H, H + h (or one cloud with a lower boundary H and an upper H + h). In figure 1, these clouds are depicted at different points in time, corresponding to i and i + 1 frames of the radiometer. Fragments of interest to us are depicted in the lower part of the figure. When comparing fragments of two frames of the radiometer, it is seen that the projection speeds (υ _ver and υ _lower ) of the upper and lower clouds are different.

Let the absolute speed of the upper cloud be v, and the time interval between two frames be t. Then KL = KH + v · t (Fig. 1). During time t, the projection of the upper cloud travels the distance CC ₁ = AC ₁ -AC. From the similarity of the triangles AOS and KOH it follows:

AC = KHH / (H + h)

From the similarity of the triangles AOS and KOH it follows:

AC ₁ = KL · H / (H + h) = (KH + v · t) · H / (H + h)

CC ₁ = AC ₁ -AC = (KH + v · t) · H / (H + h) -KH · H / (H + h) = v · t · H / (H + h)

H / (H + h) = const. Denote k = H / (H + h) and rewrite the equality:

AC ₁ = AC + kv

The last equation corresponds to the uniform motion of the cloud projection at a speed v · H / (H + h).

We denote the angle of SOA by α, and the angle of BOA by β. The length of the segment BB ₁ is equal to υ _bottom · t, and the length of the segment CC ₁ is equal to υ _ver · t. From geometry you can see:

BC = H · (tan α-tan β)

CD = htg α

BD = BC + CD = H · (tg α-tg β) + h · tg α

B ₁ C ₁ = H · (tg C ₁ OA-tg B ₁ OA)

tg C ₁ OA = AC ₁ / H = (AC + CC ₁ ) / H = (H · tg α + υ _ver · t) / N

tg B ₁ OA = AB ₁ / H = (AB + BB ₁ ) / H = (H · tg β + υ _lower · t) / Н

B ₁ C ₁ = H · tg α + υ _ver · tH · tg β-υ _lower · t

C ₁ D ₁ = htg C ₁ LD ₁

C ₁ LD ₁ = C ₁ OA

C ₁ D ₁ = h · tg C ₁ OA = h · tg α + h · υ _ver · t / H

B ₁ D ₁ = B ₁ C ₁ + C ₁ D ₁ = H · tg α + υ _ver · tH · tg β-υ _lower · t + h · tg α + h · υ _ver · t / H

The segments BD and B ₁ D ₁ are equal, whence:

H · (tg α-tg β) + h · tg α = H · tg α + υ _ver · tH · tg β-υ _lower · t + h · tg α + h · υ _ver · t / H

After conversion, the equation takes the form:

υ _lower · t-υ _ver · t = h · υ _ver · t / H

h · υ _ver / H = υ _lower -υ _ver

N = h · υ _ver / (υ _lower -υ _ver )

The projection speed (υ) is linearly related to the cell velocity (v _cell ):

υ = v _cells

where 1 is the cell size. From:

H = h · v _{vertical ball} · 1 / (v _{lower ball} · 1-v _{vertical ball} · 1) = h · v _{vertical ball} / (v _{lower ball} –v _{vertical ball} )

This method makes it possible to well approach the exact value of the height of the NGO, since the dependence of the height on the energy brightness in the region where the clouds can be can be considered linear. The error in determining the height (ξ) from the brightness is additive in nature, and when calculating the height difference of the layers, it will be compensated:

H = H _{nizh.ist LO} + ξ

H _ver = H _ver.ist + ξ

H = H _ver -H _lower = H _ver.ist + ξ-H _{lower.ist -ξ} = H _ver.ist -H _lower.ist

For a more accurate estimate of the height of the lower cloud cover using this method, there are several recommendations:

- Splitting the frame into an even greater number of energy layers (4, 5, etc.). At the same time, the total number of height estimates for each of them will increase, which means that the accuracy of determining NGOs will increase.

- Instead of two frames, you can use a larger number of pairs of adjacent frames. For each pair, the height of the lower cloud cover is calculated. Averaging these results will give an even more accurate estimate.

Used sources

1. RF patent No. 2321029, IPC G01W 1/00 for the invention "Method for determining the height, direction and speed of movement of the lower border of cloudiness".

2. Patent of the Russian Federation 2136016, IPC G01S 17/95, G01W 1/00, for the invention "Radar meter for measuring the height of the lower boundary of the clouds."

3. RF patent No. 2331853, IPC G01J 3/06 for the invention of "Cloud Form Recognition Device".

4. International standard atmosphere. Aviation: Encyclopedia. M .: Big Russian Encyclopedia. Editor-in-chief G.P. Svishchev. 1994.

Claims (1)

A method for determining the height of the lower cloud boundary at a time interval by which, by means of a wide-panoramic automated scanning system that scans in the range of the cloud field’s own radiation spectrum, the most low-temperature sections are determined in software, in which fragments of the cloud layers are sorted by radiation temperature, and the projection of the layers is determined their altitude difference and the height of the lower cloud cover.

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