Optical properties of boreal region biomass burning aerosols in central Alaska and seasonal variation of aerosol optical depth at an Arctic coastal site

Abstract

Long-term monitoring of aerosol optical properties at a boreal forest AERONET site in interior Alaska was performed from 1994 through 2008 (excluding winter), Large interannual variability was observed, with some years showing near background aerosol optical depth (AOD) levels while 2004 and 2005 had August monthly means similar in magnitude to peak months at major tropical biomass burning regions. Single scattering albedo at the boreal forest site ranged from ~0.91 to 0.99 with an average of ~0.96 for observations in 2004 and 2005. This suggests a significant amount of smoldering combustion of woody fuels and peat/soil layers that would result in relatively low black carbon mass fractions for smoke particles. The fine mode particle volume median radius during the heavy burning years was quite large, resulting in a greater relative scattering component of extinction. Additionally, monitoring at an Arctic Ocean coastal site (Barrow, Alaska) suggested transport of smoke to the Arctic in summer resulting in individual events with much higher AOD than that occurring during typical spring Arctic haze. However, the springtime mean AOD(500 nm) is higher during late March through late May (~0.150) than during summer months (~0.085) at Barrow partly due to very few days with low background AOD levels in spring compared with many days with clean background conditions in summer.

Citation

Eck, T.F.; Holben, B.N.; Reid, J.S.; Sinyuk, A.; Hyer, E.J.; O'Neill, N.T.; Shaw,G.E.; Vande Castle, J.R.; Chapin, F.S.; Dubovik, O.; Smirnov, A.; Vermote, E.; Schafer, J.S.; Giles, D.; Slutsker, I.; Sorokine, M.; Newcomb, W.W. 2009. Optical properties of boreal region biomass burning aerosols in central Alaska and seasonal variation of aerosol optical depth at an Arctic coastal site. Journal of Geophysical Research. Vol.114: D11201.