[A-CG31] Aircraft and UAV Observations for Earth-planetary sciences

[ACG31-04] Arctic black carbon during PAMARCMiP 2018 and previous aircraft experiments in spring

*Sho Ohata^1,2, Makoto Koike³, Atsushi Yoshida³, Nobuhiro Moteki³, Kouji Adachi⁴, Naga Oshima⁴, Hitoshi Matsui⁵, Oliver Eppers^6,7, Heiko Bozem⁶, Marco Zanatta^8,9, Andreas B. Herber⁸ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Institute for Advanced Research, Nagoya University, 3.Graduate School of Science, The University of Tokyo, 4.Meteorological Research Institute, 5.Graduate School of Environmental Studies, Nagoya University, 6.Johannes Gutenberg University of Mainz, 7.Max Planck Institute for Chemistry, 8.Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 9.Université Paris-Est-Créteil)

Keywords:Aircraft observation, black carbon, Arctic

Vertical profiles of the mass concentration of black carbon (BC) were measured at altitudes up to 5 km during the PAMARCMiP 2018 aircraft experiment (PAM2018) conducted around the Northern Greenland Sea (Fram Strait) during March–April 2018. 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, whereas they were similar to those observed during HIPPO3 in 2010. Vertically integrated BC mass concentrations for altitudes below 5 km in the Arctic (>60°N, C_BC), observed during the ARCTAS-A and NETCARE experiments were higher by factors of 5.3 and 2.5, respectively, than those of the PAM2018 experiment. These differences could not be explained solely by the different locations of the experiments. The year-to-year variation of C_BC values generally corresponded to that of biomass burning activities in northern high latitudes over western and eastern Eurasia. Furthermore, numerical model calculations estimated the year-to-year variation of contributions from anthropogenic sources to be smaller than 20–30%. 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. These year-to-year variations in BC were also observed at the ground surface in Ny-Ålesund and Barrow, although their magnitudes were slightly lower than those in C_BC.

Numerical model calculations generally reproduced the observed C_BC values for PAM2018 and HIPPO3 successfully, whereas they markedly underestimated the values for ARCTAS-A and NETCARE by factors of 3.9–4.3 and 2.9-3.6, respectively. Because anthropogenic contributions account for nearly all of the C_BC (82 – 98%) in PAM2018 and HIPPO3, the good agreements between the observations and calculations for these two experiments suggest that anthropogenic contributions were generally well reproduced. However, the significant underestimations of C_BC 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 quite likely 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 sampled, which were considered to be mostly aged anthropogenic BC. These observations provide useful bases to evaluate numerical model calculations of the BC radiative effect in the Arctic region in spring.