16:15 〜 16:30
[ACG31-04] Arctic black carbon during PAMARCMiP 2018 and previous aircraft experiments in spring
キーワード：航空機観測、ブラックカーボン、北極
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, CBC), 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 CBC 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 CBC.
Numerical model calculations generally reproduced the observed CBC 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 CBC (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 CBC 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.
Numerical model calculations generally reproduced the observed CBC 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 CBC (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 CBC 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.