Black carbon scavenging by low-level Arctic clouds.

Area of Science:

• Atmospheric Science
• Climate Science
• Arctic Research

Background:

• Black carbon (BC) from human and natural sources significantly affects polar climates.
• Understanding BC's interaction with Arctic clouds is crucial for atmospheric deposition.
• Long-term observational data on equivalent black carbon (eBC) in Arctic clouds is limited.

Purpose of the Study:

• To investigate the behavior and seasonal cycle of equivalent black carbon (eBC) within Arctic clouds.
• To analyze factors influencing BC scavenging by clouds, such as cloud water content and temperature.
• To identify potential sources of BC affecting Arctic cloud composition.

Main Methods:

• Utilized the first long-term observational dataset of eBC inside and outside clouds.
• Collected data at Zeppelin Observatory, Svalbard, a key Arctic monitoring site.
• Employed trajectory analysis to determine air mass origins and potential BC sources.

Main Results:

• Observed a distinct seasonal cycle of cloud residual eBC, peaking in early spring (Arctic haze) and decreasing in summer.
• Found a positive correlation between the scavenged fraction of eBC and cloud water content.
• Noted lower eBC scavenging at low temperatures, suggesting mixed-phase cloud processes influence retention.

Conclusions:

• Arctic haze significantly contributes to elevated eBC concentrations in clouds during spring.
• Cloud properties, specifically water content and temperature, play a key role in BC scavenging efficiency.
• Air mass origin differences highlight the importance of collocated aerosol-cloud measurements for accurate source attribution.