Strong particle production and condensational growth in the upper troposphere sustained by biogenic VOCs from the canopy of the Amazon Basin

[摘要] Nucleation and condensation associated with biogenicvolatile organic compounds (BVOCs) are important aerosol formation pathways,yet their contribution to the upper-tropospheric aerosols remainsinconclusive, hindering the understanding of aerosol climate effects. Here,we develop new schemes describing these organic aerosol formation processesin the WRF-Chem model and investigate their impact on the abundance of cloudcondensation nuclei (CCN) in the upper troposphere (UT) over the AmazonBasin. We find that the new schemes significantly increase the simulated CCNnumber concentrations in the UT (e.g., up to ∼  400 cm −3 at 0.52 % supersaturation) and greatly improve the agreement with theaircraft observations. Organic condensation enhances the simulated CCNconcentration by 90 % through promoting particle growth, while organicnucleation, by replenishing new particles, contributes an additional 14 %.Deep convection determines the rate of these organic aerosol formationprocesses in the UT through controlling the upward transport of biogenicprecursors (i.e., BVOCs). This finding emphasizes the importance of thebiosphere–atmosphere coupling in regulating upper-tropospheric aerosolconcentrations over the tropical forest and calls for attention to itspotential role in anthropogenic climate change.

[学科分类] 医学（综合）