Application of Raman lidar to air quality measurements
Document ID: 144
Philbrick, C. Russell
Mulik, Karoline R.
The Pennsylvania State University, Department of Electrical Engineering, University Park, PA, U.S.A.
invited paper
Abstract
Raman lidar techniques have been demonstrated which provide most valuable descriptions of the evolution of air pollution events. The vibrational and rotational Raman lidar signals provide simultaneous profiles of meteorological data, ozone and measurements of airborne particulate matter. An operational prototype Raman lidar instrument was prepared and demonstrated for the US Navy and is now used for scientific investigations. It makes use of 2nd and 4th harmonic generated laser beams of a Nd:YAG laser to provide both daytime and nighttime measurements. The Raman scatter signals from vibrational states of water vapor and nitrogen provide robust profiles of the specific humidity in the lower atmosphere. The temperature profiles are measured using the ratio of rotational Raman signals at 530 and 528 nm from the 532nm (2nd harmonic) beam of the Nd:YAG laser. In addition, the optical extinction profiles are determined from the measured gradients in each of several molecular profiles compared to the molecular scale height. We currently use the wavelengths at 284 nm (nitrogen vibrational Raman), 530 nm (rotational Raman) and 607 nm (nitrogen vibrational Raman) to determine profiles of optical extinction. The ozone profiles in the lower troposphere are measured using a DIAL analysis of the ratio of the vibrational Raman signals for nitrogen (284 nm) and oxygen (278 nm), which are on the steep side of the Hartley band of ozone. Several data sets have been obtained during air pollution events and the results from these events have been the subject of recent studies. The examples presented in this paper have been selected to show the new level of understanding of air pollution events that is being gained from applications of lidar techniques.
Keywords: Raman scatter, air pollution, optical extinction, lidar remote sensing, tropospheric ozone
| Citation: | "Application of Raman lidar to air quality measurements", Philbrick, C. R., K. R. Mulik, Laser Radar Technology and Applications V, Vol. Vol. 4035, SPIE, 2000, pp. 22 - 33, CCC: 0277-786X1001 |