RU2477490C1 - Method for determining vertical wind profile in atmosphere - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: method for determining vertical wind profile in atmosphere is based on emission of continuous coherent non-modulated waves in different sounding directions. Emission is performed on one or more wave lengths having attenuation with atmosphere gases. Information on the wind profile at low altitudes is received from Doppler signals at higher attenuation values, and information on the profile at high altitudes is received from Doppler signals received at lower attenuation values considering the known wind profile at lower altitudes.

EFFECT: improving the accuracy of wind profile recovery; providing the possibility of recovering more complicated profiles.

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Description

The invention relates to remote sensing of the atmosphere, to meteorology.

A known method for determining the profile of the projections of velocities on the direction of measurement, based on the radiation of continuous unmodulated radiation at two wavelengths, with different attenuation in the propagation medium and obtain information about the range in relation to the spectral densities of Doppler signals at these wavelengths [1]. This method is limited by the monotonic dependences of the velocity projection on the range.

The closest analogue is the tomographic method for determining the wind profile (from integral Doppler projections obtained along a straight line) described in [2], in which continuous unmodulated radiation is emitted, Doppler spectra of the signal scattered in the opposite direction are recorded, and information about the height H and corresponding velocity V is obtained from the full form of the Doppler spectra, including from a comparison of the radiation power coming from the lower layer of the scatterers, according to the formula:

where H is the current height,

V is the current speed corresponding to the current height,

F (h) is the dependence of the received signal power on the height h (which is a known range function), known for a specific radar,

A is the coefficient of proportionality, depending on the parameters of the measuring system,

S (ν) is the spectral power density of the recorded Doppler signal,

V ₀ - wind speed at the height of the measuring system (at zero height).

In this ratio, coefficient A is determined from the normalization condition for the signal power along the entire sounding beam.

However, this Doppler tomography method is applicable only if the projection of the measured velocity depends on the height V (H) monotonously and leads to large errors when this condition is violated.

The technical result of the proposed method is to increase the accuracy of measurements through the use of wavelengths with different attenuation and phased tomographic determination of wind first in the lower layers, and then in the higher layers of the atmosphere.

To achieve a technical result, wavelengths with attenuation by atmospheric gases are used. With a large value of the attenuation coefficient, the contribution of the upper layers of the atmosphere to the core F (h) of the integral equation (1) is significantly weakened and the relative contribution of the upper layers to the total value of the integral becomes negligible. This allows tomographic determination of wind in the lower layer. Then, signals are used with less attenuation with height and the following sections of the altitude profile V (H) are restored, taking into account information about the wind profile in the lower layer.

For example, if wavelengths are used in the atmospheric oxygen absorption band in the vicinity of 5 mm, then attenuation from 14 dB / km to 0.2 dB / km can be obtained by choosing a wavelength. In this case, the effective height of the measurement layer varies from 0.1 km to 4 km, respectively.

The accuracy of tomographic measurements in the proposed method is further enhanced due to the fact that the probability of a nonmonotonic section V (H) in a thin layer of the atmosphere is significantly lower than in the entire atmosphere.

Figure 1 presents an example of a nonmonotonic profile projection of the wind speed V (H) on a certain sounding direction and the profile recovery sequence of the proposed method.

An example implementation of the method is presented in figure 1. The initial nonmonotonic wind projection profile V (H) is shown by a solid line. The use of radiation with a large attenuation coefficient, for example, γ ₁ = 0.006 m ^-1 , allows, on the basis of equation (1), to restore the lower part of the profile in section 1-2, which is shown by a dotted line in Fig. 1.

In the next step, attenuation is used, for example, γ ₂ = 0.002 m ^-1 and the corresponding Doppler spectrum. Given the known profile in section 1-2, the restoration of section 2-3 is carried out to heights that correspond to a given level of attenuation γ ₂ . As a result of this procedure, the complete wind profile is restored.

In another example, which explains the alternative solution described in the formula, not different wavelengths with different attenuation coefficients are used in the given sounding direction, but the same wavelength with fixed attenuation, for example, γ = 0.006 m ^-1 .

In this case, the change in the contribution of scatterers at a height of H to the spectrum can be controlled by changing the local sounding angle β, since the range of the given layer changes as H / sin (β).

The core of the integral equation for the radar wave zone can be represented as

where H is the height of the layer,

R is the range to the layer at a height of H,

γ is the linear attenuation coefficient,

β is the sounding angle.

It follows from (2) that the smaller the angle β, the stronger the weakening of the contribution of the upper layers to the spectrum. Thus, the use of different elevation angles allows you to get the result described above, without using different wavelengths.

The inventive step of the proposed technical solution is confirmed by the distinctive part of the claims.

Literature

1. Sterdyadkin V.V. USSR copyright certificate No. 1795372, cl. G01P 5/00, 1990.

2. Gorelik A.G., Sterlyadkin V.V. Doppler tomography in radar meteorology, Izv. USSR Academy of Sciences. Physics of the atmosphere and the ocean. 1990.V.26. No. 1. S.47-54.

Claims (1)

A method for determining the vertical profile of the wind in the atmosphere, based on the emission of continuous coherent unmodulated waves in different sensing directions, recording radiation reflected by inhomogeneities carried by the wind, and obtaining from it Doppler signals, characterized in that they emit at several wavelengths, which are attenuated differently atmospheric gases, or at a single wavelength experiencing attenuation by atmospheric gases, information on the wind profile at lower altitudes is obtained from Doppler signals for large values of attenuation, or at low elevation angles, and profile information at high altitudes is obtained from the Doppler signals obtained at lower attenuation or at high elevation angles taking into account the well-known wind profile at the lower altitudes.