Black carbon observations during the HIPPO campaign

Black carbon (BC) is the primary aerosol absorber of shortwave radiation and, hence, a significant climate forcing agent. It further influences climate through a variety of poorly understood mechanisms including snow/ice albedo and cloud effects. Unlike most of the greenhouse gas species measured during HIPPO, black carbon (BC) aerosol has a very short lifetime in the atmosphere and substantial morphological complexity. The substantial uncertainty associated with BC's role in climate remains an important challenge to the atmospheric science community. The ensemble of all 5 HIPPO phases represents an unprecedented dataset of BC mass loadings, size distributions and mixing state in the remote Pacific and Polar Regions that can be applied to reducing this uncertainty. The HIPPO mission sampled many different air mass types including the clean remote atmosphere characterized by low BC loadings and aged particles, relatively polluted Asian outflow, southern hemisphere biomass burning emissions, and Arctic haze. Here we present an overview of the HIPPO BC observations and their impacts on current understanding of atmospheric BC. For example, different parameterizations of the BC wet removal process by ice formation through freezing, riming and the Bergeron process have been used in the GFDL AM3 global model to improve model agreement with the observations; the spatial scale of BC plumes have been assessed to address fundamental model uncertainties arising from limited model resolution; and model bias in BC amounts examined in the GEOS-Chem model.