Journal Article

Biogenic particles formed in the Himalaya as an important source of free tropospheric aerosols

Kontkanen, J., Hutterli, M., Petäjä, T., Baltensperger, U., Sellegri, K., Junninen, H., Bianchi, F., Laj, P., Zha, Q., Bigi, A., Yao, L., Dommen, J., Kerminen, V.-M., Riva, M., Kulmala, M., Mirme, S., Marinoni, A., Dada, L., Hoyle, C. R., Molteni, U., Ahonen, L. R., Worsnop, D. R., Buenrostro Mazon, S., Kangasluoma, J., Lehtipalo, K., Yan, C., Bonasoni, P., Sinclair, V. A., Rose, C.

2021

Overview

Aerosols of biogenic and anthropogenic origin affect the total radiative forcing of global climate. Poor knowledge of the pre-industrial aerosol concentration and composition, in particular of particles formed directly in the atmosphere from gaseous precursors, constitutes a large uncertainty in the anthropogenic radiative forcing. Investigations of new particle formation at pre-industrial-like conditions can contribute to the reduction of this uncertainty. Here we present observations taken at the remote Nepal Climate Observatory Pyramid station at 5,079 m above sea level, a few kilometres from the summit of Everest. We show that up-valley winds funnel gaseous aerosol precursors to higher altitudes. During this transport, these are oxidized into compounds of very low volatility, which rapidly form a large number of aerosol particles. These are then transported into the free troposphere, which suggests that the whole Himalayan region may act as an ‘aerosol factory’ and contribute substantially to the free tropospheric aerosol population. Aerosol production in this region occurs mainly via organic precursors of biogenic origin with little evidence of the involvement of anthropogenic pollutants. This process is therefore likely to be essentially unchanged since the pre-industrial period, and may have been one of the major sources that contributes to the upper tropospheric aerosol population during that time. Newly formed biogenic particles in the Himalaya increase free-tropospheric background aerosol concentration by a factor of up to two.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 704/106/35 / 704/106/35/824 / 704/172/169/824 / Aerosol concentrations / Aerosol particles / Aerosol production / Aerosols / Anthropogenic factors / Atmospheric and Oceanic Physics / Climate / Earth and Environmental Science / Earth Sciences / Earth System Sciences / Geochemistry / Geology / Geophysics/Geodesy / Global climate / Meteorology / Ocean, Atmosphere / Particle formation / Physics / Pollutants / Precursors / Radiative forcing / Sciences of the Universe / Sea level / Troposphere / Uncertainty / Valley winds / Volatility / Winds