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Climatological‐Scale Analysis of Intensive and
Semi‐intensive Aerosol Parameters Derived
From AERONET Retrievals
Over the Arctic
, N. T. O'Neill
, K. Ranjbar
, S. Hesaraki
, I. Abboud
, and P. S. Sobolewski
CARTEL, Université de Sherbrooke, Sherbrooke, Quebec, Canada,
Air Quality Research Division, Environment and
Climate Change Canada (ECCC), Toronto, Ontario, Canada,
Institute of Geophysics Polish Academy of Sciences,
Abstract We investigated the climatological‐scale, monthly binned, seasonal variation of
AERONET/Dubovik retrievals across six stations in the North American and European Arctic (multiyear
sampling periods ranging from 8 to 17 years). A robust, spring‐to‐summer (StoS) increase in the radius of the
peak of the ﬁne mode (FM) component of the particle size distribution (PSD) was observed for ﬁve of the
six stations. The FM aerosol optical depth (AOD) and the FM effective radius at the individual stations
showed, respectively, a negligible to moderate StoS decrease and a signiﬁcant increase. This was interpreted
as a trade‐off between the waning inﬂuence of smaller FM Arctic haze aerosols and the increasing
inﬂuence of large FM smoke particles. A springtime, pan‐Arctic PSD peak in the 1.3 μm coarse mode (CM)
bin was attributed to Asian dust. It was suggested that the increase in amplitude of a second (4–7μm)
CM peak from July to August at the low‐elevation coastal sites was inﬂuenced by wind‐induced sea salt. The
CM AOD went through a StoS decrease attributed to the decreasing amplitude of the 1.3 μm peak. A
signiﬁcant StoS CM effective radius increase was ascribed to the decreasing inﬂuence of the 1.3 μm peak.
StoS FM fraction increases were largely due to the decrease of the CM AOD (decreasing inﬂuence of
springtime Asian dust). This extensive and intensive climatology of remotely sensed, bimodal properties
will, we believe, provide an important reference for future measurements and modeling of Arctic aerosols.
The dynamics of the Arctic environment has a direct impact on global climate and weather, sea level rise,
and in turn commerce (AMAP, 2017). Its impact, therefore, extends much beyond the Arctic Circle.
According to AMAP (2017), the Arctic's average temperature has risen twice that of the global average in
the past ﬁve decades. This phenomenon is known as Arctic ampliﬁcation. This rise in temperature is mainly
attributed to the heating inﬂuence induced by absorption of thermal radiation by greenhouse gases (GHGs)
(AMAP, 2017). At the same time, it is well established that the greatest uncertainty in the radiative forcing
budget is attributed to aerosols via the direct and indirect effect (Boucher et al., 2013). A study by Najaﬁ
et al. (2015) sheds light on the additional impact made by aerosols. In the models used to study the inﬂuences
of GHGs and aerosols on Arctic temperature, they state that 60% of the GHG‐induced warming has been off-
set by the combined response to other anthropogenic forcings and that these forcings were mostly domi-
nated by aerosols (Najaﬁet al., 2015). It is generally accepted that aerosols mask a fraction of the
warming effect caused by increasing GHGs (Boucher, 2015). The uneven distribution of aerosols in the
atmosphere results in both warming and cooling of the climate system in a way that impacts the weather
(Boucher et al., 2013).
A variety of aerosols, from both anthropogenic and natural sources, can be found in the Arctic atmosphere.
In general, they are transported from lower latitudes along isentropic pathways to the middle or upper Arctic
troposphere. They can also originate locally from erosive and water‐surface interactions over the land and
ocean (see Tomasi et al., 2015 for a detailed overview of the sources of Arctic aerosols). There are two main
formation mechanisms for aerosols: primary aerosols that are injected directly into the atmosphere and sec-
ondary aerosols formed from gas‐to‐particle conversion processes (Seinfeld & Pandis, 2006). The formation
mechanisms result in different types of aerosols having different microphysical properties. In general, the
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All Rights Reserved.
•Spring to summer increase in ﬁne
mode (FM) particle size; likely
associated with waning Arctic haze
and waxing smoke presence
•Springtime, coarse mode (CM)
feature, of small CM particle radius
in the particle size distribution;
likely associated with Asian dust
•Behavior of FM and CM (intensive,
semi‐intensive and extensive)
properties were largely a function of
the ﬁrst two observations
•Supporting Information S1
AboEl‐Fetouh, Y., O'Neill, N. T.,
Ranjbar, K., Hesaraki, S., Abboud, I., &
Sobolewski, P. S. (2020).
Climatological‐scale analysis of
intensive and semi‐intensive aerosol
parameters derived from AERONET
retrievals over the Arctic. Journal of
Geophysical Research: Atmospheres,
125, e2019JD031569. https://doi.org/
Received 28 AUG 2019
Accepted 8 APR 2020
Accepted article online 26 APR 2020
Conceptualization: Y. AboEl‐Fetouh
Data curation: Y. AboEl‐Fetouh
Formal analysis: Y. AboEl‐Fetouh, N.
Funding acquisition: N. T. O'Neill
Investigation: Y. AboEl‐Fetouh, N. T.
Methodology: Y. AboEl‐Fetouh, N. T.
Resources: S. Hesaraki, I. Abboud, P.
Software: Y. AboEl‐Fetouh
Supervision: N. T. O'Neill
Validation: N. T. O'Neill, K. Ranjbar
Visualization: Y. AboEl‐Fetouh, N. T.
Writing ‐original draft: Y.
AboEl‐Fetouh, N. T. O'Neill
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