PROBABILITY-DISTRIBUTION OF AEROSOL BACKSCATTER IN THE LOWER MARINE ATMOSPHERE AT CO2 WAVELENGTHS

A model of the size distribution of marine aerosols, based on a large compilation of size distribution and meteorological measurements, is combined with the statistics of meteorological parameters over the North Atlantic Ocean to calculate probability distributions of the aerosol backscatter coefficient-beta in the lower boundary layer. Values of beta-range over 5 orders of magnitude, are lognormally distributed for any given location, and show geographical patterns which depend on wind speed and relative humidity. The results indicate that sufficient particles are found in the boundary layer over all areas of the North Atlantic to permit retrieval of the wind profile in this layer with a satellite wind sounder such as that proposed by the Laser Atmosphere Wind Sounder (LAWS). The retrieval rate depends in part on the molecular absorption in the atmosphere of the sounder's laser beam. For a CO2 laser wavelength of 9.11-mu-m the threshold value of beta required by the sounder is exceeded more than 95% of the time; for 10.59-mu-m it is exceeded a minimum of 70% of the time in the tropics.