# In-situ characterization of layered pollution in the wintertime Arctic atmosphere by small sensors

Tjarda J Roberts, Meeta Cesler-Maloney, William Simpson, Jingqui Mao, Brice Barret, Slimane Bekki, Brice Temine-Roussel, Barbara d'Anna, Julia Maillard, François Ravetta, et al.

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## To cite this version:

Tjarda J Roberts, Meeta Cesler-Maloney, William Simpson, Jingqui Mao, Brice Barret, et al. In-situ characterization of layered pollution in the wintertime Arctic atmosphere by small sensors. EGU General Assembly 2021, Apr 2021, Online Meeting, Germany. pp.EGU21-15351, 10.5194/egusphere-egu21-15351. insu-03194356

HAL Id: insu-03194356

https://insu.hal.science/insu-03194356

Submitted on 6 Feb 2022

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In-situ characterization of layered pollution in the wintertime Arctic
atmosphere by small sensors

Tjarda Roberts<fnref n="1" />, Meeta Cesler-Maloney<fnref n="2" />, William Simpson<fnref n="2" />, Jingqui Mao<fnref n="2" />, Brice Barret<fnref n="3" />, Slimane Bekki<fnref n="4" />, Brice Temine-Roussel<fnref n="5" />, Barbara d'Anna<fnref n="5" />, Julia Maillard<fnref n="4" />, Francois Ravetta<fnref n="4" />, Jean-Christophe Raut<fnref n="4" />, Andy Woods<fnref n="6" />, Eleftherios Ioannidis<fnref n="4" />, and Kathy Law<fnref n="4" />

During the Arctic winter, local emissions (e.g. from home-heating, traffic, power station or industry
plumes) coupled to poor dispersion caused by strong temperature inversions can lead to severe
air pollution events. For example, each winter, Fairbanks (Alaska) experiences high abundances of
gaseous pollutants and particulate matter (PM), leading to air-quality exceedances. However, there
is still limited knowledge on the coupled physico-chemical and dynamical processes that cause
wintertime Arctic pollution and aerosol formation under the very cold and low light conditions,
and where levels of oxidants such as ozone at the surface can become depleted under limited
vertical mixing. Here, we demonstrate novel deployment of low cost small sensors measuring
PM2.5, gases (CO, NO, NO2, O3) and meteorological parameters (P, T, RH) to characterize Arctic
atmospheric composition and properties, including mapping vertical distributions.

Our three-week pre-ALPACA (Alaskan Layered Pollution and Chemical Analysis) intensive field-
campaign took place in downtown Fairbanks in Nov-Dec 2019. Small sensor temperature-
dependencies were characterized by instrument cross-comparisons and correction-algorithms
developed. Sensors were then deployed near-ground, on the roof of a 19 m building, and on a
vertical pulley system set-up along the side of the building for vertical profiling. The small sensors
show a strong capability to capture temporal variations in PM2.5, CO, NO and NO2 and O3, across
a wide temperature range: surface gas and particle abundances became elevated during a cold-
polluted period (temperatures as low as -30 C) and again became elevated during a subsequent
warm-polluted period (temperatures around -3 C). Vertical profiling during the warm-polluted
period identified strong temperature inversions associated with near-surface layers of high PM2.5
and CO that are distinct from an overlying clean, warm, humid air-mass. During the cold-polluted
period, temperature inversions were present but less strong, there was little vertical structure in
composition, and PM2.5 was often greater at 20m than at the surface. This finding contrasts with a

<footnote n="1">¹LPC2E-CNRS, Laboratory of Physics and Chemistry of Space and the Environment, Orléans, France (Tjarda.Roberts@cnrs-orleans.fr)</footnote>

<footnote n="2">²Department of Chemistry, University of Alaska, Fairbanks, USA</footnote>

<footnote n="3">³LA-CNRS, Laboratoire d'Aerologie, Toulouse, France</footnote>

<footnote n="4">⁴LATMOS-CNRS, Laboratoire Atmosphères, Observations Spatiales, Paris, France</footnote>

<footnote n="5">⁵LCE-CNRS, Laboratoire Chimie Environnement, Aix-Marseille University, France</footnote>

<footnote n="6">⁶BPI & Department of Earth Sciences, University of Cambridge, UK</footnote>
full winter-season analysis that shows cold surface temperatures typically associated with strong inversions and PM highest at the surface. We invoke plume-rise modelling to show how buoyant plumes from local emissions (e.g. home-heating) can reach heights of about 10-20 m, allowing polluted emissions to rise and accumulate at altitude unless inversions are sufficiently strong to constrain the plume-rise. Causes of the temperature inversions include radiative cooling and advection of overlying warm-air. Our study highlights how small sensor measurements and vertical profiling can help elucidate the coupled processes of atmospheric chemistry, physics, dynamics and emissions that lead to surface air pollution episodes at high latitudes.

This study forms part of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) project https://alpaca.community.uaf.edu/. We are grateful for technical support from Alaska-DEC, LPC2E, UAF, SEOSS, Alphasense and SouthCoastScience.