Laser-Acoustic Hygrometer: Procedure and Results of Field Measurements

Boris S. Agrovskii Institute of Atmospheric Physics, RAS, Moscow, Russia

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Alexandre S. Gurvich Institute of Atmospheric Physics, RAS, Moscow, Russia

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Vitaly P. Kukharets Institute of Atmospheric Physics, RAS, Moscow, Russia

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Valery V. Vorob’ev Institute of Atmospheric Physics, RAS, Moscow, Russia

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Abstract

Trial field measurements of humidity fluctuations are taken by a laser-acoustic hygrometer consisting of a CO laser, a mechanical modulator, a detector, an audio-frequency amplifier, and a device for processing signals. The proposed method is based on measuring the intensity of sound that is generated when pulse-modulated laser radiation is absorbed in the air. The CO laser spectrum (5.0–5.7 μm) is within the fundamental vapor absorption band (5.2–7 μm). This allows a medium-powered CO laser to be employed for measurements of humidity fluctuations. Radiation with a pulse frequency of 16 kHz, which is required for generation of sound waves, is generated by chopper of the CW continuous radiation CO laser. At the point of sound measurement the laser- beam power is about 5 W. An acoustic signal carrying the humidity information is received by a 1.27-cm microphone installed perpendicular to the beam (d = 0.5 cm) at a distance of 3 cm from its axis. The spectra of absolute humidity fluctuations over the frequency range (2 × 10−3–10 Hz) have been calculated from the measurements when relative humidity ranges between 27% and 47%. Noise characteristics of the laser-acoustic hygrometer have been studied.

Corresponding author address: Dr. Vitaly P. Kukharets, Institute of Atmospheric Physics, RAS, Pyzhevsky 3, Moscow 109017, Russia.

Email: kuh@omega.ifaran.ru

Abstract

Trial field measurements of humidity fluctuations are taken by a laser-acoustic hygrometer consisting of a CO laser, a mechanical modulator, a detector, an audio-frequency amplifier, and a device for processing signals. The proposed method is based on measuring the intensity of sound that is generated when pulse-modulated laser radiation is absorbed in the air. The CO laser spectrum (5.0–5.7 μm) is within the fundamental vapor absorption band (5.2–7 μm). This allows a medium-powered CO laser to be employed for measurements of humidity fluctuations. Radiation with a pulse frequency of 16 kHz, which is required for generation of sound waves, is generated by chopper of the CW continuous radiation CO laser. At the point of sound measurement the laser- beam power is about 5 W. An acoustic signal carrying the humidity information is received by a 1.27-cm microphone installed perpendicular to the beam (d = 0.5 cm) at a distance of 3 cm from its axis. The spectra of absolute humidity fluctuations over the frequency range (2 × 10−3–10 Hz) have been calculated from the measurements when relative humidity ranges between 27% and 47%. Noise characteristics of the laser-acoustic hygrometer have been studied.

Corresponding author address: Dr. Vitaly P. Kukharets, Institute of Atmospheric Physics, RAS, Pyzhevsky 3, Moscow 109017, Russia.

Email: kuh@omega.ifaran.ru

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  • Gorshkov, V. I., and L. G. Elagina, 1974: The new model of infrared hygrometer for measurements of turbulent humidity fluctuations over the sea surface (in Russian). TROPEX-72, Leningrad, 663–666.

  • Kolosov, V. V., and A. V. Kuzikovskii, 1988: Investigation of sound thermooptical generation in the atmosphere. Izv. Acad. Sci. USSR Atmos. Oceanic Phys.,1(3), 57–60.

  • Rothman, L. S., and Coauthors, 1992: The HITRAN molecular data base—Editions of 1991 and 1992. J. Quant. Spectrosc. Radiat. Transfer,48, 469–507.

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  • Vorob’ev, V. V., 1979: Estimation of the intensity of sound which arises upon laser light propagation in the atmosphere and its effect on thermal blooming (in Russian). J. Quant. Electron.,6, 327–330.

  • ——, V. A. Myakinin, E. N. Lotkova, and P. E. Dubovskii, 1990: Sound excitation by CO-laser in air. Opt. Atmos.,3(5), 513–517.

  • ——, A. S. Gurvich, V. A. Myakinin, and Yu. V. Golembeovskii, 1996: Humidity fluctuation spectrum measurements using a laser–acoustic hygrometer. Izv. Acad. Sci. USSR Atmos. Oceanic Phys.,32(1), 63–67.

  • Zuber, A., and G. Witt, 1987: Optical hygrometer using differential absorption hydrogen Lyman-alpha radiation. Appl. Opt.,26, 3086–3089.

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