Model- and Observation-Based Climatology of Arctic Aerosols and Their Climate Impacts

Recent studies suggested that the Arctic region is frequently polluted by atmospheric aerosols, including biomass-burning smoke, dust, sulfate and sea salt, that are mostly transported from lower latitudes. These transported aerosol particles could alter the regional radiation budget and affect Arctic climate. Additionally, when light-absorbing aerosols, like biomass-burning smoke, deposit onto snow- and ice-covered surfaces, they may darken the surface and accelerate the ice-albedo feedback process and ice melt. With the increased wildfire activities in the boreal region in recent years, the transport of smoke particles to the Arctic, and its impact on the Arctic climate, is becoming an increasing concern. Thus, a better understanding of aerosol climatology and trends from both modeling and observational-based methods is needed. In this study, we use a suite of aerosol reanalyses, consisting of the U.S. Navy Aerosol Analysis and Prediction System ReAnalysis version 1 (NAAPS-RA v1), the NASA MERRA-2, the ECMWF CAMSRA, and a novel analysis system developed for the Arctic region, to study the climatology, trend, and extreme event statistics of aerosol optical depth (AOD) and deposited aerosols over the Arctic region. Our novel Arctic aerosol reanalysis system benefits from the incorporation of OMI aerosol index (AI) data, which are able to detect absorbing aerosols over the bright surfaces in the Arctic (including snow, ice, and cloud) where traditional, passive-based sensors struggle to retrieve aerosol properties. These aerosol optical depth (AOD) analyses are verified against both ground- (AERONET) and satellite-based (MODIS, MISR, and CALIOP) remotely-sensed data, while the aerosol deposition estimates are verified against in-situ snow impurity measurements. We also conduct a first-of-its-kind study to derive an observation-based estimate of airborne aerosol radiative forcing over the Arctic using co-located MODIS, CERES and OMI satellite measurements.