Shipborne measurements of aerosol number size distribution and hygroscopicity over the North Pacific Ocean

We report aerosol number size distribution and hygroscopicity data collected over the Pacific Ocean near the Hawaii Ocean Timeseries (HOT) Station ALOHA (centered near 22°N, 158°W). From June 25 to July 3, 2016 our hygroscopicity tandem differential mobility analyzer (HTDMA)/scanning mobility particle sizer (SMPS) system was deployed onboard of NOAA Ship Hi'ialakai that participated in mooring operations associated with the Woods Hole Oceanographic Institution WHOTS project. The ambient aerosol data was collected during the ship's planned operations. The inlet was located at the bow of the ship and the air samples were drawn (using 3/8 inch stainless steel tubing) inside a dry, air-conditioned lab. The region north of Oahu was very clean, with total particle number approximately 200 cm-3, occasionally dropping below 100 cm-3. We compare our particle number size distribution and hygroscopicity data with previously reported estimates. Our measurements contribute to process-level understanding of the role of sea spray aerosol in marine boundary layer cloud condensation nuclei (CCN) budget and provide crucial information to the community interested in studying and projecting climate change using Earth System Models.