Lidar observations of the lower tropospheric aerosol structure during BOMEX. Final report

A lidar (laser radar) was flown on a US Air Force WC-130B aircraft over the BOMEX (Barbados Oceanographic and Meteorological Experiment) area during the third experimental period (20 June to 3 July 1969). The instrument used a neodymium laser (1.06 ..mu..m wavelength) and had a firing rate of approximately one pulse per 3.5 seconds. A total of 5192 lidar signatures were collected during the eight flight missions. A computer technique is described that adjusts and corrects the data for the range effect, instrumentation nonlinearities, and pulse-to-pulse variations in transmitted energy, and then objectively performs a contour analysis of the resulting data matrix. Vertical cross sections of normalized lidar signal return obtained in this way are presented along with the associated average vertical profiles. These lidar results are interpreted qualitatively in terms of changes in aerosol density and/or particle size in the lowest 3000 m of the atmosphere. They are compared with vertical profiles of temperature, dew point, and the radionuclides /sup 7/Be and /sup 95/Zr, which were obtained from supplementary data sources. The data analyzed clearly reveal the existence of well-defined scattering layers associated with the sub-cloud layer, the trade-wind inversion, and the Sahara dust stream. The height, thickness, densitymore » and structure of the Sahara dust layer showed large vertical and horizontal variability. The average aerosol scale height determined from this study was 1.48 km (standard deviation of 0.7 km). Lidar returns favorably compare with signatures synthesized by using measured particle size distributions and the Mie theory.« less