Eye-safe tracking of oil fog plumes by UV lidar

NOAA's Wave Propagation Laboratory operated a plume-tracking lidar during two field experiments investigating atmospheric dispersion in complex terrain. The lidar successfully acquired data on oil fog plume behavior by detecting the elastic backscatter of the pulsed output of a frequency-doubled ruby laser. This UV wavelength (0.3472 microm) met stringent eye safety restrictions. An analysis of signal and noise levels demonstrates that plume definition at a wavelength of 0.3472 microm is superior in many cases to that at 0.6943 microm when pulse energies are low enough to be eye-safe at the range to the plume. This is often true in spite of the high threshold set by the large molecular scatter from the ambient air at the UV wavelength. Backscatter coefficients of oil fog at the shorter wavelength were 1-4x larger than at the longer wavelength.