Indirect Cloud Effects from Biomass Burning Smoke in the Arctic and Subarctic: Insights from Multiple In-Situ Datasets

The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North America, for example, the burned area is expected to increase by 200- 300% over the next 50-100 years. In some cases, local and long-range smoke transported to the Arctic has already increased aerosol concentrations twofold, which previous studies suggest could have a large effect on cloud microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly understood, in part due to the confounding influence of varying meteorological and surface conditions. Here, we use data from several aircraft campaigns in the Arctic and subarctic (the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites-B campaign (ARCTAS-B), the Indirect and Semi-Direct Aerosol Campaign (ISDAC), and the First ISCCP Regional Experiment Arctic Clouds Experiment (FIRE.ACE)) to compare cloud microphysics in liquid, ice, and mixed-phase clouds sampled at similar temperature and pressure in the presence and absence of biomass burning smoke. Care is taken to place findings in context of meteorological conditions. Preliminary data from the ARCTAS-B campaign suggest a noticeable impact of smoke on cloud properties in the liquid phase, consistent with the Twomey effect (smaller cloud droplet radius), and greater liquid water path and estimated cloud optical depth. Continuing work involves using the combination of field cases and satellite data from MISR, MODIS, CALIPSO, and other sources to more fully characterize the impact of smoke on Arctic clouds.