During research flight 13, at 30 m above the ocean surface, the CCN concentrations (at 1% supersaturation) were less than 200 cm-3, CN concentrations were less than 600 cm-3, and the scattering and absorption coefficients were 3x10-6 m-1 and 2x10-8 m-1, respectively. These measurements are typical of clean, maritime air. The average, maximum droplet concentration of clouds in this area, at an altitude of 2500 m, was "100 cm-3 but concentrations of drizzle exceeded 200 l-1 at the same level.
Measurements during research flight 17, also at 30 m altitude, showed CCN concentrations greater than 500 cm-3, CN concentrations > 1500 cm-3, and scattering and absorption coefficients of 3x10-7 m-1 and 6x10-7 m-1, respectively. These aerosol properties are a clear signal of anthropogenic origin whose most likely source is Central America, 600-800 Km to the east of the research area. On this day the average maximum droplet concentration of clouds was >400 cm-3 but with very little drizzle or precipitation measured.