The Shoreline Environment Aerosol Study (SEAS): A Context for Marine Aerosol Measurements Influenced by a Coastal Environment and Long-Range Transport*

Abstract

The Shoreline Environment Aerosol Study (SEAS) was carried out in Hawaii on the southeast coast of Oahu in an area exposed to relatively steady onshore flow. This location provided favorable opportunities to test and evaluate new instrumentation designed to improve measurements of marine aerosol and its physical, chemical, and optical properties, including the remote sensing (lidar) of coastal aerosol fields. Data acquired from the diverse instruments deployed before and during SEAS demonstrate that environmental and meteorological features actively influence aerosol measurements at this location. Both a ceilometer and a visibility sensor were operated continuously and found to be effective autonomous tools for characterizing mixed-layer aerosol conditions. These instruments also helped demonstrate that changes in physical and optical properties measured during SEAS were also linked to volcanic aerosol transported across the Pacific in the free troposphere from Japan and later entrained into the marine boundary layer. This and various local effects of wind direction, wind speed, tides, and sampling altitude were superimposed on the variations in offshore marine aerosol. Characterization of these site-specific effects provides a context and guidance for the interpretation of coastal aerosol data and evaluation of SEAS data.