Sea Salt Aerosol, Atmospheric Radon and Meteorological Observations in the Western South Atlantic Ocean (February 1981).

Abstract : The concentration of sea salt aerosol was measured aboard the USNS HAYES at 16m height in the western South Atlantic Ocean from February 3-19, 1981. Aerosol samples were collected using a NRL-designed, automated sampler coupled to a programmable environmental monitoring system. Simultaneous measurements of wind speed and direction, air and water temperature, relative humidity, barometric pressure and atmospheric radon concentration were also made nearly continuously along the cruise track. Emphasis on functional relationships between synoptic measurements of sea salt aerosol and local wind speed showed the overall correlation between these two parameters to be poor (r approx 0.3 for 249 data point sets), However, when the data is separated into discrete meteorological and/or oceanographic events, most short term correlations are significantly improved. In this region of the South Atlantic Ocean, we attribute the low overall correlation between synoptic measurements of salt aerosol and wind speed to the effects of hysteresis, condensation processes and varying structure of the turbulent boundary layer. The sea surface temperature varied widely during this cruise and seemed to directly influence the atmospheric salt load, regardless of wind speed in many cases. Deterministic predictions of instantaneous sea salt aerosol values will require improved real-time methods for characterizing the marine boundary layer. Alternatively, modelling sea salt aerosol concentrations might be most practically effected using a statistical approach.