METHOD FOR DISTANTLY MEASURING RELATIVE VARIATIONS OF AIR TEMPERATURE BY ACOUSTIC ATMOSPHERIC SOUNDING

摘要

The proposed method for distantly measuring relative variations of air temperature by acoustic atmospheric sounding consists in accomplishing the static air sounding in the vertical direction and in various direction at an angle to the horizon by emitting harmonic acoustic signals, receiving acoustic signals that are reflected from the different atmosphere layers, converting the received acoustic signals into electric signals, and determining the parameters of reflected acoustic signals that are used to calculate the relative variations of temperature. The acoustic signals that are scattered due to the inhomogeneity of the atmosphere layers are received over each sounding direction within identical time intervals after the start of emitting the sounding acoustic signals. The amplitudes of the received acoustic signals are multiplied by a correction coefficient, which is determined to provide required accuracy in measuring the signal parameters while retaining the relationships between the signal phases. The proposed method implies measuring the initial phases of the received acoustic signals, determining the differences of the initial signal phases for the corresponding sounding directions, calculating the differences of the velocities of the acoustic signals by employing corresponding equations, and determining the relative variations of temperature from the said velocity differences. Concurrently with measuring the acoustic signal phases, the signal Doppler frequencies are measured for each of the specified sounding directions. The said Doppler frequencies are used to calculate an error (?D) in determining the differences (???) of the initial signal phases. When sounding the atmosphere in the vertical direction and slant directions, it is necessary to provide the equity of average ranges of the propagation of the received acoustic signals. For this purpose, the initial phases of the received acoustic signals are determined at positions h1, h2, when sounding in the vertical direction, and positions R1, R2, when sounding in the slant direction, so that the ranges between the positions h1, h2 and R1, R2 are equal. To determine the differences of the initial phases of the acoustic signals that correspond to two specified sounding directions, the following equations are employed: ???h2-h1 - ???R2-R1 = (360/T) ? (?h2-1/Ch2-1) - (360/T) ? (?R2-1/CR2-1), where ???h2-1 = ?*Hh2 - ?*Hh1, ???R2-1 = ?*HR2 - ?*HR1, ?*Hh1 = ?Hh1 ? ??D, ?*Hh2 = ?Hh2 ? ??D, ?*HR1 = ?HR1 ? ??D, ?*HR2 = ?HR2 ? ??D, where: ?*Hh1, ?*Hh2, ?*HR1, ?*HR2 are the signal phases that correspond to the positions h1, h2, R1; R2, ??D is an error inmeasuring the signal phase caused by the Doppler effect. To determine the error ??D, the following equation is used: ??D = (360???T?N)/TRC where TTR is the oscillation period of the emitted sounding acoustic signal, N is the number of the oscillations within the specified signal emission period ?t, ?T = TTR - TRC, TRC is the oscilaltion period of the received acoustic signal, Ch2-1 is the sound velocity at the interval h2 - h1, CR2-1 is the sound velocity at the interval R2 - R1.