Uncertainty in the representation of biomass burning (BB) aerosol optical properties in climate
models is reflected in how models predict aerosol effects on incoming solar radiation. Depending
on the model, the aerosol effect can range from cooling to warming. By relating the single
scattering albedo (SSA) and black carbon-to-total carbon ratio (BC:TC) from a diverse set of
global BB observations to several Earth System Models/Chemical Transport Models we identify
varying degrees of underestimation in BB aerosol SSA by these models. Through modifications
of the three main factors that affect SSA calculation – BB aerosol refractive index, size, and
mixing state – we are able to improve the Community Atmosphere Model version 5 (CAM5)
agreement with observations, leading to a change in BB global direct radiative effect from 0.06
W m-2 to -0.01 W m-2. Similar improvements in other models have the potential to reduce
uncertainty in modeled BB optical properties and may lead to a larger cooling effect due to BB
aerosols than previously shown.
Revised: March 1, 2021 |
Published: January 12, 2021
Citation
Brown H., X. Liu, R. Pokhrel, S. Murphy, Z. Lu, R. Saleh, and T. Mielonen, et al. 2021.Biomass burning aerosols in most climate models are too absorbing.Nature Communications 12, no. 1:277.PNNL-SA-153916.doi:10.1038/s41467-020-20482-9