Lynn Russell
Professor - Climate, Atmospheric Science and Physical Oceanography,
Scripps Institution of Oceanography, UC San Diego
SIMULATIONS OF SEA SPRAY PARTICLE INTERACTIONS WITH CLIMATE
VARIABILITY AND OBSERVATIONAL APPROACHES TO IMPROVING CONSTRAINTS ON
THOSE SIMULATIONS
Since oceans cover 71% of the Earth surface, sea spray particles
constitute the largest fraction of Earth's natural aerosols (by mass)
and may provide an important source of CCN in remote marine areas as
well as in the pre-industrial atmosphere. In addition, sensitivity
analysis has estimated that 45% of uncertainty in aerosol indirect
forcing since 1750 arises from uncertainties in emissions of natural
aerosols, including sea salt, while only 34% arises from uncertainty in
anthropogenic emissions. This talk will show some recent Earth system
model (CESM) results that illustrate the complicated role of sea spray
in climate, showing both how interannual (meteorological) variability
affects sea spray and how sea spray may cause feedback effects that
enhance the El Nino behavior of the model. These results rely on current
parameterizations of sea spray, which have been shown to generally agree
with satellite-retrieved sea spray particle burdens. However,
quantifying sea spray emissions, even in present day conditions, is
challenging and currently limited. One new approach may allow evaluation
of model sea spray parameterizations more directly than is possible with
satellite retrievals. This approach takes advantage of detailed
particle size distribution measurements on ships and in coastal areas to
evaluate the sea spray number concentration. An even more powerful
metric in identifying marine sea spray particles may be taking advantage
of their complex chemical composition. Characterizing the organic
components of sea spray particles can be used to separate anthropogenic
contributions to the present day marine atmosphere, making it possible
to distinguish ocean biogenic chemical components from those associated
with shipping and coastal sources. An improved understanding of and
predictive capability for these biogenic ocean sources may then lead to
improved observational constraints on model representation of the role
of sea spray in aerosol-cloud-climate interactions.