Global Modeling and Source Attribution of Atmospheric Brown Carbon and Its Associated AAOD Using an Innovative...

Area of Science:

• Atmospheric Chemistry
• Climate Science
• Aerosol Science

Background:

• Brown carbon (BrC) aerosols absorb solar radiation, contributing to global warming and cryosphere snowmelt.
• Accurate quantification of BrC's global impact is hindered by its complex composition and atmospheric transformations.

Purpose of the Study:

• To develop and implement an advanced module (ABS-BrC) for simulating BrC absorptivity, accounting for chemical aging.
• To differentiate source contributions to BrC concentrations versus their radiative impact (AAOD).

Main Methods:

• Developed an absorptivity basis set module for BrC (ABS-BrC).
• Categorized BrC into four classes based on light absorption.
• Incorporated chemical aging processes into simulations.
• Conducted global simulations to analyze BrC source contributions to concentration and AAOD.

Main Results:

• Secondary BrC formation dominates concentration (45.8%) but has a smaller AAOD contribution (16.6%).
• Wildfire-sourced BrC, though lower in concentration, accounts for the majority (54.2%) of global BrC AAOD.
• Dark BrC (d-BrC) contributes significantly (30-64%) to global BrC AAOD, with critical Arctic warming impacts.

Conclusions:

• BrC source-specific radiative impacts differ significantly from concentration contributions.
• Wildfire and dark BrC are key drivers of BrC's radiative forcing.
• The ABS-BrC module is crucial for improving Earth system model accuracy in assessing BrC's climate impact.