Sea salt aerosol production via sublimating wind-blown saline snow particles over sea-ice: parameterizations and relevant micro-physical mechanisms

Xin Yang, Markus Frey, Rachael Rhodes, Sarah Norris, Ian Brooks, Philip Anderson, Kouichi Nishimura, Anna Jones, Eric Wolff

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Abstract

Blowing snow over sea ice has been proposed
as a significant source of sea salt aerosol (SSA) (Yang et
al., 2008). In this study, using snow salinity data and blow-
ing snow and aerosol particle measurements collected in
the Weddell Sea sea ice zone (SIZ) during a winter cruise,
we perform a comprehensive model–data comparison with
the aim of validating proposed parameterizations. Addition-
ally, we investigate possible physical mechanisms involved
in SSA production from blowing snow. A global chemical
transport model, p-TOMCAT, is used to examine the model
sensitivity to key parameters involved, namely blowing-snow
size distribution, snow salinity, sublimation function, surface
wind speed, relative humidity, air temperature and ratio of
SSA formed per snow particle. As proposed in the parame-
terizations of Yang et al. (2008), the SSA mass flux is pro-
portional to the bulk sublimation flux of blowing snow and
snow salinity. To convert the bulk sublimation flux to SSA
size distribution requires (1) sublimation function for snow
particles, (2) blowing-snow size distribution, (3) snow salin-
ity and (4) ratio of SSA formed per snow particle.
The optimum model–cruise aerosol data agreement (in di-
ameter range of 0.4–12µm) indicates two possible micro-
physical processes that could be associated with SSA pro-
duction from blowing snow. The first one assumes that one
SSA is formed per snow particle after sublimation, and snow
particle sublimation is controlled by the curvature effect or
the so-called “air ventilation” effect. The second mechanism
allows multiple SSAs to form per snow particle and assumes
snow particle sublimation is controlled by the moisture gra-
dient between the surface of the particle and the ambient air
(moisture diffusion effect). With this latter mechanism the
model reproduces the observations assuming that one snow
particle produces ∼ 10 SSA during the sublimation process.
Although both mechanisms generate very consistent results
with respect to observed aerosol number densities, they cor-
respond to completely different microphysical processes and
show quite different SSA size spectra, mainly in ultra-fine
and coarse size modes. However, due to the lack of relevant
data, we could not, so far, conclude confidently which one is
more realistic, highlighting the necessity of further investiga-
tion.
Original languageEnglish
Article number1
Pages (from-to)8407-8424
Number of pages18
JournalAtmospheric Chemistry and Physics
Volume19
DOIs
Publication statusPublished - 2 Jul 2019

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