High frequency new particle formation in the Himalayas

Area of Science:

• Atmospheric Science
• Environmental Science
• Climatology

Background:

• South Asian air pollution poses global environmental risks, potentially affecting the monsoon and glacier retreat.
• Accurate particulate source data is crucial for simulating future climate changes in the region.

Purpose of the Study:

• To present the first evidence of frequent new particle formation events at high altitudes in the Himalayas.
• To investigate the characteristics and origins of these high-altitude particle formation events.

Main Methods:

• Analysis of a 16-month aerosol size distribution record from the Nepal Climate Observatory at Pyramid (5,079 m).
• Monitoring of ion cluster concentrations and particle growth during new particle formation events.
• Correlation of event initiation with wind patterns (downslope vs. upslope thermal winds).

Main Results:

• New particle formation events occur on over 35% of days at high altitudes, driven by ultrafine particles.
• Ion clusters form and grow to 10 nm within hours, confirming in situ nucleation at high altitudes.
• Events initiate with the morning shift from downslope to upslope winds, suggesting pollution transport from valleys.

Conclusions:

• High-altitude new particle formation is a significant source of atmospheric particles in the Himalayas.
• These particles can be injected into the free troposphere, influencing regional climate and atmospheric chemistry.
• Understanding these events is vital for predicting climate change impacts in South Asia.