Abstract
This study presents an assessment of the impact of black carbon (BC) regional emissions of four Nordic countries (Denmark, Finland, Norway and Sweden – denoted henceforth as DFNS). The surface concentrations, radiative forcing and BC-in-snow forcing were calculated using ECHAM-HAMMOZ global aerosol-climate model and, where possible, evaluated with field observations. We found that the model is reproducing the BC surface concentrations for most of the measurement sites considered within 1–2 standard deviations, with only few exceptions. The radiative forcing (top of the atmosphere, short-wave, clear and total sky) of BC emitted in DFNS on regional (Nordic and Arctic area separately) and global levels was calculated by removing the anthropogenic emissions from DFNS. The total values for clear sky for the three regions are 16.2±1.4, 2.9±0.28 and 0.04±0.022 mW/m2, respectively. The presence of clouds enhanced the BC radiative forcing. The forcing caused by BC deposited on snow is roughly equal to the direct radiative forcing of airborne BC (17.3±3.34 mW/m2 over DFNS, 4.2±0.77 mW/m2 over the Arctic and 0.042±0.012 mW/m2 globally).
6. Acknowledgements
We thank the anonymous reviewers for their careful reviews and suggestions that helped to greatly improve the analyses and discussion presented in this paper. The ECHAM-HAMMOZ model is developed by a consortium composed of ETH Zurich, Max Planck Institut fr Meteorologie, Forschungszentrum Jlich, University of Oxford, and the Finnish Meteorological Institute and managed by the Center for Climate Systems Modeling (C2SM) at ETH Zurich. All the contributors to the black carbon measurements are warmly acknowledged. We would like to thank Academy of Finland (COOL, project 140867, and projects 250348 and 256208) and to PEGASOS project funded by the European Commission und the Framework Program 7 (FP7-ENV-2010-265148) for the financial support.