New Lidar method utilizing elastic and Raman scattering for the measurement of backscattering and extinction profiles

Thomas D. Wilkerson; Hans Moosmueller

doi:10.1117/12.177297

3 June 1994 New Lidar method utilizing elastic and Raman scattering for the measurement of backscattering and extinction profiles

Thomas D. Wilkerson, Hans Moosmueller

Author Affiliations +

Proceedings Volume 2112, Tunable Diode Laser Spectroscopy, Lidar, and DIAL Techniques for Environmental and Industrial Measurements; (1994) https://doi.org/10.1117/12.177297
Event: SPIE's International Symposium on Optical Sensing for Environmental Monitoring, 1993, Atlanta, GA, United States

Abstract

We describe a new lidar method capable of distinguishing between molecular and particulate backscattering. This method avoids the use of sophisticated high spectral resolution techniques by employing one laser, two transmitted wavelengths, and the observation of three different lidar return signals. For a system based on a frequency-doubled Nd:YAG laser emitting at 532 nm, Raman shifting in a N₂ gas cell generates a second wavelength at 607 nm. The transmission of laser pulses is alternated between these two wavelengths. When a 532 nm pulse is transmitted, both the backscattering near 532 nm and the Raman-shifted backscattering by atmospheric N₂ near 607 nm are observed. For the lidar transmissions at 607 nm, only the combined particulate and molecular signal is observed. If a region of aerosol-free air occurs at some distance within the lidar range, the product (or geometric mean) of the backscatter ratios can be determined as a function of range, directly from the three relevant lidar equations. Under minimal assumptions as to the change of the aerosol backscatter coefficient between the two transmitted wavelengths, the extraction of absolute extinction and backscatter coefficient range-profiles for both wavelengths is demonstrated. Initial error analysis suggests that the method has considerable promise for quantitative lidar applications. The technique will be useful in tropospheric studies, such as visibility measurements, and at higher altitudes where extinction by volcanic aerosols has to be taken into account in obtaining reliable temperature profiles throughout the stratosphere.

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Thomas D. Wilkerson and Hans Moosmueller "New Lidar method utilizing elastic and Raman scattering for the measurement of backscattering and extinction profiles", Proc. SPIE 2112, Tunable Diode Laser Spectroscopy, Lidar, and DIAL Techniques for Environmental and Industrial Measurements, (3 June 1994); https://doi.org/10.1117/12.177297

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