RU2538028C1 - Method for multi-position determination of optical atmospheric characteristics - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: short light pulses are emitted into an inhomogeneous atmosphere and echo signals are received. The echo signals are corrected for the lidar geometric factor. The corrected signals are accumulated during a given period of time depending on the overall length of the investigated area. The light pulses are deflected in at least two points of the probing path in directions towards a common scattering volume. Optical thickness of the area enclosed between points where the pulses are deflected is taken into account in order to determine transparency of the atmosphere.

EFFECT: high accuracy of determination due to correct accounting for influencing factors.

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Description

The invention relates to the field of meteorology, and more specifically to methods for determining the characteristics of atmospheric pollution, and can be used, for example, to measure the transparency of the atmosphere by lidar systems in determining aerosol pollution of the air.

There is a method of optical sensing of a heterogeneous atmosphere [1], in which light pulses are sent to the atmosphere along intersecting sounding paths passing in noncollinear directions, echo signals are received, and atmospheric characteristics are determined by the power of the echo signals using calculation formulas.

This known method has low accuracy, since it is based on the assumption of the possibility of differentiation of echo signals. This assumption is not fulfilled in a real inhomogeneous atmosphere.

Closest to the proposed invention is a known method for optical sensing of an inhomogeneous atmosphere [2], in which light pulses of short duration are sent to an inhomogeneous atmosphere and echo signals are received; provide correction of echo signals to the geometric factor of the lidar; accumulate corrected signals over a given period of time depending on the total length of the investigated area.

In this known solution, the accuracy of determining the characteristics of pollution of a heterogeneous atmosphere is increased due to the fact that the echo signals accumulate over a given period of time depending on the total length of the investigated area. However, the solution [2] is based on the assumption that the ratio of the backscattering coefficient to the attenuation coefficient on the probing path under study is constant. This assumption is not fulfilled in a real inhomogeneous atmosphere.

The technical result of the invention is to improve the accuracy of determining the characteristics of the atmosphere by correctly taking into account the relationship between the coefficient of backscattering and the attenuation coefficient.

In the proposed method, some essential features of the prototype are used, namely: it sends light pulses of short duration into the heterogeneous atmosphere and receives echo signals; provide correction of echo signals to the geometric factor of the lidar; accumulate corrected signals over a given period of time depending on the total length of the investigated area.

Significant distinguishing features of the proposed method is that light pulses are deflected at least at two points of the sensing path in directions toward the total scattering volume, and to determine the transparency of the atmosphere, the optical thickness of the section between the points at which the pulses are deflected is taken into account.

Optical characteristics of pollution of an inhomogeneous atmosphere, in particular optical thicknesses

$${\tau }_{\mathrm{one}}={\displaystyle \underset{R_{\mathrm{one}}}{\overset{R_{\mathrm{one}}+{\Delta }_{\mathrm{one}}}{\int }}\sigma dR,\left(\mathrm{one}\right)}$$

$${\tau }_2={\displaystyle \underset{R_{\mathrm{one}}}{\overset{R_2+{\Delta }_2}{\int }}\sigma dR\left(2\right)}$$

where σ is the attenuation coefficient,

R _i is the distance from the lidar to the point of deviation of the pulse,

Δ _i is the distance from the point of deviation of the pulse to the scattering volume,

found from the system of equations:

$$\frac{\sqrt[g]{S_{\mathrm{one}}\left(R_{\mathrm{one}}\right)}}{{\sigma }_{\mathrm{one}}}-\frac{\sqrt[g]{S_{\mathrm{one}}\left(R_{\mathrm{one}}+{\Delta }_{\mathrm{one}}\right)}}{\sigma }=\frac{2}{g}{\displaystyle \underset{R_{\mathrm{one}}}{\overset{R_{\mathrm{one}}+{\Delta }_{\mathrm{one}}}{\int }}\sqrt[g]{S_{\mathrm{one}}}dR\left(3\right)}$$

$$\frac{\sqrt[g]{S_2\left(R_{\mathrm{one}}\right)}}{{\sigma }_{\mathrm{one}}}-\frac{\sqrt[g]{S_2\left(R_2+{\Delta }_2\right)}}{\sigma }=\frac{2}{g}{\displaystyle \underset{R_{\mathrm{one}}}{\overset{R_2+{\Delta }_2}{\int }}\sqrt[g]{S_2}dR\left(\mathrm{four}\right)}$$

$$\frac{\sqrt[g]{S_2\left(R_2\right)}}{{\sigma }_2}-\frac{\sqrt[g]{S_2\left(R_2+{\Delta }_2\right)}}{\sigma }=\frac{2}{g}{\displaystyle \underset{R_2}{\overset{R_2+{\Delta }_2}{\int }}\sqrt[g]{S_2}dR\left(5\right)}$$

$$\sqrt[g]{\frac{S_2\left(R_{\mathrm{one}}\right)}{S_2\left(R_2\right)}}=\frac{{\sigma }_{\mathrm{one}}}{{\sigma }_2}\exp \left(\frac{2}{g}{\displaystyle \underset{R_{\mathrm{one}}}{\overset{R_2}{\int }}\sigma dR}\right)\left(6\right)$$

$$\sqrt[g]{\frac{S_{\mathrm{one}}\left(R_{\mathrm{one}}\right)}{S_{\mathrm{one}}\left(R_{\mathrm{one}}+{\Delta }_{\mathrm{one}}\right)}}=\frac{{\sigma }_{\mathrm{one}}}{{\sigma }_{}}\exp \left(\frac{2}{g}{\tau }_{\mathrm{one}}\right)\left(7\right)$$

$$\sqrt[g]{\frac{S_2\left(R_2\right)}{S_2\left(R_2+{\Delta }_2\right)}}=\frac{{\sigma }_{\mathrm{one}}}{{\sigma }_{}}\exp \left(\frac{2}{g}{\tau }_2\right)\left(8\right)$$

where S is the power of the backscatter signal, corrected for the geometric factor from the lidar.

In this case, the constant g is also determined in the power-law relationship of the backscattering coefficient with the attenuation coefficient

$$\beta =D{\sigma }^g.\left(9\right)$$

These significant differences can improve accuracy by correctly taking into account the relationship between the backscattering coefficient and the attenuation coefficient.

The physical principles on which measurements are based on the proposed method are that the measured echo signal powers are related to the optical characteristics of an inhomogeneous atmosphere by the known lidar equation. Based on this equation, new, previously unused computational algorithms for determining optical characteristics are developed. In these algorithms, influencing factors are correctly taken into account.

An example implementation of the method (see drawing).

In paragraph 0 place the lidar based on LIVO. The radiation of the probe pulses is carried out in the horizontal direction at a working wavelength of 0.69 μm in the window of transparency of water vapor. Pulse energy 0.07 - 0.1 J. Pulse duration 30 ns. The distance R ₁ from the lidar to the point of deviation of the pulse does not exceed 0.3 km. The distance between the deviation points R ₁ and R ₂ is 0.1 km. Sounding of a heterogeneous atmosphere is carried out in a vertical plane. Light pulses are sent, which are deflected at a point R ₁ in the direction of the scattering volume 1, echo signals are received, which are corrected for the geometric factor from the lidar and accumulate. Light pulses are sent, which are deflected at the point R ₂ in the direction of the scattering volume 2, echo signals are received, which are corrected for the geometric factor from the lidar and accumulate.

The received, corrected, and accumulated echo signals determine the characteristics of the inhomogeneous atmosphere τ ₁ , τ ₂ from the system of equations (3) - (8).

The measurements have the required accuracy in cases where the results of determining the constant g obtained by the calculation formulas (3) - (8) do not depend significantly on the position of the scattering volume 1.

Justification of the materiality of the signs. As follows from the description, each of these signs is necessary, and their entire inextricable combination is sufficient to achieve a technical result - to increase the accuracy of measurements due to a more correct consideration of the influencing factors.

Justification of inventive step. The inventive method was analyzed for compliance with the criterion of "inventive step". To this end, close features of known solutions have been investigated both in this and related fields of technology. So, according to the source [3], a sign of receiving echo signals from the total scattering volume of the inhomogeneous atmosphere was revealed. However, in this well-known solution [3], the total scattering volume of the atmosphere belongs to sensing paths passing in at least three noncollinear directions. Thanks to such an implementation of sending to the atmosphere of light pulses from points spaced in space, the technical result of the method is achieved [3]. In the claimed method, the total scattering volume of the atmosphere belongs to two sensing paths, and to determine the transparency of the atmosphere, the optical thickness of the section enclosed between the points at which the pulses are deflected is taken into account.

Thus, in the opinion of the applicant and the authors, the proposed technical solution ″ Method of multi-position determination of atmospheric optical characteristics ″ in its inextricable combination of features is new, does not explicitly follow from the prior art and allows to obtain an important technical result - improving the accuracy of determinations due to more correct accounting of factors.

Information sources

1. A.S. No. 966639. The method for determining the optical characteristics of scattering media / Sergeev N.M., Kugeiko M.M., Ashkinadze D.A. Bulletin of inventions No. 38, 1982.

2. A.S. No. 390401. The method for determining the transparency of the atmosphere / Kovalev V.A. - Bulletin of inventions No. 30, 1973 (prototype).

3. Patent No. 2439626. The method for determining the transparency of the atmosphere / Egorov A.D., Potapova I.A. Bulletin of inventions No. 1, 2012.

Claims (1)

A multi-position method for determining the optical characteristics of the atmosphere, in which light pulses of short duration are sent to an inhomogeneous atmosphere and echo signals are received; provide correction of echo signals to the geometric factor of the lidar; corrected signals are accumulated over a given period of time depending on the total length of the investigated section, characterized in that the light pulses are deflected at least at two points of the sensing path in directions to the total scattering volume, and to determine the transparency of the atmosphere, the optical thickness of the section between the points at which the pulses are deflected determine the atmospheric pollution characteristics from the received and accumulated echo signals.