Climatology of aerosol properties at an atmospheric monitoring site on the Northern California coast

Abstract. Between April 2002 and June 2017, the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) made continuous measurements of a suite of in-situ aerosol optical properties at a long-term monitoring site near Trinidad Head (THD), California. In addition to aerosol optical properties, between 2002–2006 a scanning humidograph system was operated and inorganic ion and total aerosol mass concentrations were obtained from filter measurements. Combined analysis of these datasets demonstrates consistent patterns in aerosol climatology and highlights changes in sources throughout the year. THD is predictably dominated by sea salt aerosols, however, marine biogenic aerosols are the largest contributor to PM₁ in the warmer months. Additionally, a persistent combustion source appears in the winter, likely a result of wintertime home heating. While the influences of local anthropogenic sources from vehicular and marine traffic are visible in the optical aerosol data, their influence is largely dictated by wind direction at the site. Comparison of the THD aerosol climatology to that reported for other marine sites shows that the location is representative of clean marine measurements, even with the periodic influence of anthropogenic sources.