Tropospheric Lidar: Development of Techniques and Practical Measurements

We report the successful development of a hydrogen Raman shifted tunable narrow line alexandrite laser transmitter for near-IR H(2)O spectroscopy. Fourier analysis of the alexandrite laser radiation showed a 10 MHz fundamental linewidth and 20 MHz raman linewidth. As a first test of the transmitter we measured the line strengths and air-broadened widths for 15 lines in the 1140 nm water vapor band. These lines were measured by transmittance of the laser beam through a 55 meter long White cell. The results are compared to the HITRAN-2000 database. Relative to this database, our observed line strengths are larger by a factor of 1.28 (plus or minus 13%) on average, and the line widths by 1.13(plus or minus 21%). Precisions vary from line to line, so these are only representative comparisons to HITRAN-2000. Detailed results for all 15 lines studied are presented. We also present all preliminary work that was done for the development of the system. This research is supported by the US Army Research Office. Purchase of the alexandrite laser was made possible by a grant from the National Science Foundation.