Arctic black carbon during PAMARCMiP 2018 and previous aircraft experiments in spring
Authors: Ohata Sho , Koike Makoto , Yoshida Atsushi , Moteki Nobuhiro , Adachi Kouji , Oshima Naga , Matsui Hitoshi , Eppers Oliver , Bozem Heiko , Zanatta Marco , Herber Andreas B. 
Published: November 2021

Abstract. Vertical profiles of the mass concentration of black carbon (BC) were
measured at altitudes up to 5 km during the PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model simulation Project) aircraft-based field
experiment conducted around the northern Greenland Sea (Fram Strait) during
March and April 2018 from operation base Station Nord (81.6∘ N,
16.7∘ W). Median BC mass concentrations in individual altitude
ranges were 7–18 ng m−3 at standard temperature and pressure at
altitudes below 4.5 km. These concentrations were systematically lower than
previous observations in the Arctic in spring, conducted by ARCTAS-A in 2008
and NETCARE in 2015, and similar to those observed during HIPPO3 in 2010.
Column amounts of BC for altitudes below 5 km in the Arctic (>66.5∘ N; COLBC), observed during the ARCTAS-A and NETCARE
experiments, were higher by factors of 4.2 and 2.7, respectively, than those
of the PAMARCMiP experiment. These differences could not be explained solely
by the different locations of the experiments. The year-to-year variation of
COLBC values generally corresponded to that of biomass burning activities
in northern midlatitudes over western and eastern Eurasia. Furthermore,
numerical model simulations estimated the year-to-year variation of
contributions from anthropogenic sources to be smaller than 30 %–40 %.
These results suggest that the year-to-year variation of biomass burning
activities likely affected BC amounts in the Arctic troposphere in spring,
at least in the years examined in this study. The year-to-year variations in
BC mass concentrations were also observed at the surface at high Arctic
sites Ny-Ålesund and Utqiaġvik (formerly known as Barrow, the location of
Barrow Atmospheric Baseline Observatory), although their magnitudes were slightly
lower than those in COLBC. Numerical model simulations in general successfully reproduced the observed
COLBC values for PAMARCMiP and HIPPO3 (within a factor of 2), whereas they
markedly underestimated the values for ARCTAS-A and NETCARE by factors of
3.7–5.8 and 3.3–5.0, respectively. Because anthropogenic contributions
account for nearly all of the COLBC (82 %–98 %) in PAMARCMiP and HIPPO3,
the good agreement between the observations and calculations for these two
experiments suggests that anthropogenic contributions were generally well
reproduced. However, the significant underestimations of COLBC for
ARCTAS-A and NETCARE suggest that biomass burning contributions were
underestimated. In this study, we also investigated plumes with enhanced BC
mass concentrations, which were affected by biomass burning emissions,
observed at 5 km altitude. Interestingly, the mass-averaged diameter of BC
(core) and the shell-to-core diameter ratio of BC-containing particles in
the plumes were generally not very different from those in other air
samples, which were considered to be mostly aged anthropogenic BC. These
observations provide a useful basis to evaluate numerical model simulations of
the BC radiative effect in the Arctic region in spring.