Evolution of Biomass Burning Aerosols: Implications on Regional Aerosol Distributions

 

Authors

Yan Feng — Argonne National Laboratory
Harshvardhan Harshvardhan — Purdue University
Paytsar Muradyan — Argonne National Laboratory
V. Rao Kotamarthi — Argonne National Laboratory
Arthur J Sedlacek — Brookhaven National Laboratory

Category

Absorbing aerosol

Description

Elevated biomass burning aerosols interact with clouds thermodynamically by perturbing the lower atmosphere thermal structure as well as microphysically. These effects strongly depend on the vertical distribution and optical properties of aerosols in the long-distance transport (Feng et al., 2016). On the other hand, the evolution of biomass burning aerosols is modulated by clouds. A recent study has shown that global climate models have a poor representation of the vertical extent of the aerosol layers when transported far from the biomass burning sources in South Africa (Das et al. 2017). In the present study, we examine the evolution of biomass burning aerosols using the 2016 data gathered during the DOE LASIC campaign by instruments of the ARM Mobile Facility 1 (AMF-1) on Ascension Island (AI), combined with supplementary remote sensing and satellite observations of the aerosol plumes along the transport tracks. Three peak events of observed black carbon (BC) and aerosol extinction on AI were identified on June 24, August 13 and Aug 30, 2016. During all of the three episodes, fine-mode aerosol absorption and scattering dominate, suggesting non-marine sources. Compared to the two episodes in August, the column aerosol optical depth is low on June 24, contributed mainly by the boundary layer aerosols. Additionally, the ratio of organic matter relative to the BC mass concentration on June 24 is also higher (~4) than the August episodes (~2.5) as well as with a higher CCN concentration. Back trajectories indicate that this may be related to the longer aging time from the continental sources for the June 24 aerosols. Both surface measurements and vertical profiles from the MPL and CALIPSO data show the frequent occurrences of high aerosol concentrations in the boundary layer, which have chemical and optical properties similar to the elevated biomass burning aerosol layers than marine aerosols. This has important implications on the regional aerosol distributions and interactions with clouds. We will examine and present the comparison with the evolution of biomass burning aerosols simulated by the global climate model (CAM5).