Wednesday, 16 January 2002: 3:30 PM
Raman Lidar Techniques Applied to Meteorological Sensing
Raman lidar techniques have been developed and demonstrated which provide measurements of meteorological properties with high spatial and temporal resolution. The vibrational and rotational Raman lidar signals provide simultaneous profiles of water vapor, temperature, ozone and optical extinction due to 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 532 nm (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 measurement programs and the results from these events have been the subject of recent investigations. Examples have been selected to show the new level of understanding of meteorological processes that is gained from applications of lidar techniques. These techniques are expected to provide the primary means for profiling meteorological parameters in the future.