Marine air samples were collected off the windward coast of Oahu during Project RED (Rough Evaporation Duct) using filters mounted on both the Twin Otter aircraft and the FLIP research vessel. The filters collected underwent analysis utilizing inductively coupled plasma atomic emission spectrography, ion chromatography and electrospray ionization–ion trap mass spectrometry. These techniques identified a total of 11 inorganic ions, 4 carboxylic acids and 2 carbohydrates accounting for 73% ± 19% of the mass gain observed on the shipboard filters. The results were compared with cloud water samples collected during the aircraft surveys and analyzed under similar conditions. Closure studies on hygroscopic growth factors compared calculations based upon in situ measurements of light scattering by the UW three nephelometer passive humidigraph mounted aboard the Twin Otter and the Ming-Russell model, which predicts hygroscopic growth based upon a dry mass of specified organic and inorganic composition.