Abstract

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.

Highlights

  • Over the past few decades, the annual average temperature in the Arctic has increased almost twice as fast as it has elsewhere in the world (IPCC, 2021)

  • The modelcalculated COLBC values were derived in three different ways by calculating median or average values for individual altitude ranges: (A) median values along the flight tracks, (B) area-weighted averages within the latitudes and longitudes and the time periods of the aircraft experiments shown in Table 3, and (C) area-weighted averages within the entire region at latitudes north of 66.5◦ N for the time period of an aircraft experiment (Table 5)

  • Median MBC values in individual altitude ranges were 7– 18 ng m−3 at altitudes below 4.5 km. These concentrations were systematically lower than those observed during ARCTAS in 2008 and NETCARE in 2015, whereas they were similar to those observed during HIPPO in 2010

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Summary

Introduction

Over the past few decades, the annual average temperature in the Arctic has increased almost twice as fast as it has elsewhere in the world (IPCC, 2021). Aircraft measurements of Arctic BC were made by the following previous experiments in the spring season when direct radiative forcing of BC in the Arctic is considered to be largest: ARCPAC, ARCTAS-A, and POLARCAT in 2008 (Spackman et al, 2010; Matsui et al, 2011; Wang et al, 2011), PAMARCMiP in 2009 and in 2011 (Stone et al, 2010; Herber et al, 2012), HIPPO3 in 2010 (Schwarz et al, 2013), and NETCARE in 2015 (Schulz et al, 2019; Kodros et al, 2018) From these measurements, vertical profiles of BC mass concentrations, size distributions, and mixing states, as well as source contributions, transport pathways, and loss mechanisms were studied.

Instruments and aircraft experiment
Vertical profile and column amounts of BC mass concentration
Biomass burning fire counts
NOAA 1
Evaluation of BB BC using numerical model simulations
Correspondence to surface BC measurements
Origin of air parcels with enhanced MBC
Microphysical features of BB BC
Summary
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