A. Morrow, R. V. Martin, S. Sharma, L. Huang, A. Herber, R. Leaitch, J. Burkehart, S. M. Li, and P. Liu NETCARE Workshop November 4 th 2014 Understanding the seasonal cycle of Arctic black carbon Motivation Long range transport Reduces snow/ice albedo Increase in gas flaring at higher latitudes Recent availability of seasonally varying emissions Need to understand processes to manage implications Model GEOS-Chem version by 2.5 degree horizontal resolution 47 vertical levels (variable resolution) Driven by GEOS-5 meteorology Seasonal changes derived from ECLIPSE inventory and applied to model emissions Flaring emissions added to modified emissions In situ measurements Ground stations (Aethalometer, filter) PAMARCMiP flight campaign (SP2) Flaring and domestic heating important to represent seasonal cycle Flaring and seasonal heating cycle important for representation of daily events at Alert as well GEOS-Chem emissions are constant by month Discrepancies in interannual variation between PAMARCMiP and ground station measurements at Alert and Ny Alesund PAMARCMiP daily points calculated from aircraft data within 2 lat and 12 lon up to an altitude of 1000 m. Discrepancies in interannual variation between PAMARCMiP and ground station measurements at Alert and Ny Alesund PAMARCMiP daily points calculated from aircraft data within 2 lat and 12 lon up to an altitude of 1000 m. Large interannual variation in PAMARCMiP profiles not resolved with GEOS-Chem PAMARCMiP and GEOS-Chem black carbon Simulated influence of source regions on Arctic BC Conclusions Inclusion of flaring emissions and a seasonal heating cycle better represents ground level measurements More effort needed to understand interannual variation in free tropospheric black carbon Major Arctic source regions are Europe and Asia, with biomass burning playing a moderate role in summer Thanks to all NETCARE members and others who have made data available for comparison and provided advice.