Wind speed dependent size-resolved parameterization for the organic mass fraction of sea spray aerosol

For oceans to be a significant source of primary
organic aerosol (POA), sea spray aerosol (SSA) must be
highly enriched with organics relative to the bulk seawater.
We propose that organic enrichment at the air-sea interface,
chemical composition of seawater, and the aerosol
size are three main parameters controlling the organic mass
fraction of sea spray aerosol (OMSSA). To test this hypothesis,
we developed a new marine POA emission function
based on a conceptual relationship between the organic enrichment
at the air-sea interface and surface wind speed. The
resulting parameterization is explored using aerosol chemical
composition and surface wind speed from Atlantic and
Pacific coastal stations, and satellite-derived ocean concentrations
of chlorophyll-a, dissolved organic carbon, and particulate
organic carbon. Of all the parameters examined, a
multi-variable logistic regression revealed that the combination
of 10mwind speed and surface chlorophyll-a concentration
([Chl-a]) are the most consistent predictors of OMSSA.
This relationship, combined with the published aerosol size
dependence of OMSSA, resulted in a new parameterization
for the organic mass fraction of SSA. Global emissions of
marine POA are investigated here by applying this newlydeveloped
relationship to existing sea spray emission functions,
satellite-derived [Chl-a], and modeled 10m winds.
Analysis of model simulations shows that global annual submicron
marine organic emission associated with sea spray
is estimated to be from 2.8 to 5.6 TgC yr-1. This study
provides additional evidence that marine primary organic
aerosols are a globally significant source of organics in the
atmosphere.