Quasi-hemispheric simulations of black carbon transport to the Arctic using the CAM5 physics in WRF
Résumé
There are large uncertainties in global climate models predictions of black carbon (BC) in the Arctic that could be due to uncertainties in anthropogenic and biomass burning emissions, errors arising from physics parameterizations, and inadequate spatial resolution. In addition to contributing to uncertainties in simulated aerosol radiative forcing, black carbon deposited on snow alters its albedo and consequently the rate of melting. In this study, WRF-Chem is used to simulate the emission, transport, and fate of black carbon during March and April of 2008 using a domain that encompasses most of the northern hemisphere. This period is chosen because a number of field campaigns (e.g. ARCTAS, ISDAC, POLARCAT) took place as part of the International Polar Year that collected measurements of BC and other aerosols that can be used to evaluate model performance in this region. The simulations employ physics parameterizations from the Community Atmosphere Model v5.1 that have recently been ported to the WRF model and made available in the v3.5 release. This includes the Modal Aerosol Model (MAM) that is computationally more efficient than the MADE/SORGAM and MOSAIC aerosol models available in WRF-Chem and is therefore more feasible for long-term simulation periods. Sensitivity simulations are performed that examine the impact of emission estimates and wet removal on BC concentrations over the Arctic in relation to the observations. This includes quantifying the impact of the newly developed emissions inventory (developed within the EU project ECLIPSE) that contains a first estimate for a source of BC emissions (gas flaring) adjacent to the Arctic Ocean that has been previously omitted from most studies.