High-spectral-resolution lidar with iodine-vapor filters: measurement of atmospheric-state and aerosol profiles

A high-spectral-resolution lidar can measure vertical profiles of atmospher ic temperature, pressure, the aerosol backscatter ratio, and the aerosol ex tinction coefficient simultaneously. We describe a system with these charac teristics. The transmitter is a narrow-band (FWHM of the order of 74 MHz), injection-seeded, pulsed, double YAG laser at 532 nm. Iodine-vapor filters in the detection system spectrally separate the molecular and aerosol scatt ering and greatly reduce the latter (-41 dB). Operating at a selected frequ ency to take advantage of two neighboring lines in vapor filters, one can o btain a sensitivity of the measured signal-to-air temperature ratio equal t o 0.42%/K. Using a relatively modest size transmitter and receiver system ( laser power times telescope aperture equals 0.19 Wm(2)), our measured tempe rature profiles (0.5-15 km) over 11 nights are in agreement with balloon so undings to within 2.0 K over an altitude range of 2-5 km. There is good agr eement in the lapse rates, tropopause altitudes, and inversions. In princip le, to invert the signal requires a known density at one altitude, but in p ractice it is convenient to also use a known temperature at that altitude. This is a scalable system for high spatial resolution of vertical temperatu re profiles in the troposphere and lower stratosphere, even in the presence of aerosols. (C) 2001 Optical Society of America.