Nitrogen dominates global atmospheric organic aerosol absorption

Area of Science:

• Atmospheric chemistry
• Climate science
• Aerosol science

Background:

• Atmospheric organic aerosols (OAs) play a crucial role in Earth's climate by absorbing sunlight.
• The relationship between OA composition changes and their light absorption properties remains poorly understood.

Purpose of the Study:

• To investigate the role of brown nitrogen (BrN) in OA light absorption.
• To quantify BrN's contribution to OA radiative effects and understand its evolution with aging.

Main Methods:

• Utilized a global model to quantify BrN abundance and its optical properties.
• Tracked the chemical aging of BrN and assessed its radiative absorption.
• Analyzed BrN's contribution to OA surface and global absorption.

Main Results:

• Brown nitrogen (BrN) is the dominant component responsible for OA light absorption, contributing 76% over the US and 61% to global absorptive optical depth.
• The variability in OA absorptive capacity is mainly influenced by BrN sources and aging processes.
• BrN accounts for 18% of the global absorptive direct radiative effect of carbonaceous aerosols, with biomass burning as a major source.

Conclusions:

• A nitrogen-centric framework is established for attributing the climate impacts of OAs.
• BrN's significant role highlights the need to consider nitrogenous compounds in climate models.
• Understanding BrN sources and aging is critical for accurate climate change projections.