Abstract
Modeling the shortwave radiation balance over the Southern Ocean region
remains a challenge for Earth system models. To investigate whether this
is related to the representation of aerosol-cloud interactions, we
compared measurements of the total number concentration of sea spray
generated particles within the Southern Ocean region to model
predictions thereof. Measurements were conducted from a container
laboratory aboard the R/V Tangaroa throughout an austral summer voyage
to the Ross Sea. We used source-receptor modeling to calculate the
sensitivity of our measurements to upwind surface fluxes. From this
approach, we could constrain empirical parameterizations of sea spray
surface flux based on surface wind speed and sea surface temperature. A
newly tuned parameterization for the flux of sea spray particles based
on the near-surface wind speed is presented. Comparisons to existing
model parameterizations revealed that present model parameterizations
led to over-estimations of sea spray concentrations. In contrast to
previous studies, we found that including sea surface temperature as an
explanatory variable did not substantially improve model-measurement
agreement. To test whether or not the parameterization may be applicable
globally, we conducted a similar regression analysis using a database of
in situ whitecap measurements. We found that the key fitting parameter
within this regression agreed well the parameterization of sea spray
flux. Finally, we compared calculations from the best model of surface
flux to boundary layer measurements collected onboard an aircraft
throughout the Southern Ocean Clouds, Radiation, Aerosol Transport
Experimental Study (SOCRATES), finding good agreement overall.