Assessing the direct aerosol radiative forcing in the Arctic region produced by the recent eruption of Redoubt Volcano

Northern high latitude volcanoes can have a profound impact on regional climate, and depending on the transport and concentrations of plume constituents, may have a global effect. There has been a growing interest in understanding the impact of volcanic (natural) aerosols on the Arctic region and its importance compared to other aerosol types. In this study, we examine the extent to which the eruption of Mount Redoubt volcano (Alaska, USA (60.49◦N, 152.74◦W) affected the radiative energy balance at the local and region scales. We analyze both the direct radiative forcing at the top-of-the-atmosphere and at the surface examining the shortwave (SW) and longwave (LW) components of the forcing. Our approach includes analysis of A-Train satellite constellation data in conjunction with radiative transfer modeling. From 22 March to 4 April, 2009, there were multiple volcanic eruptions, injecting gaseous and particulate species into the stratosphere. For this time period, we performed a detailed satellite data analysis on a day-by-day basis to characterize the dynamics of the spatiotemporal distribution and properties of sulfate and ash particulates, and some gases. The results were incorporated into the radiative transfer modeling. Simulations were performed to examine the sensitivity of the radiative forcing to composition and size distribution of aerosols, vertical profile of aerosol loadings, surface albedo, and solar zenith angle. Considering realistic aerosol-laden and environmental conditions, we assess changes in SW and LW components of the radiative balance caused by the volcanic eruption. Our results show that the radiative forcing due to volcanic aerosols in the Arctic can dwarf forcings due to other types of aerosols, such as those produced by biomass burning.