The seasonal cycle of ice-nucleating particles linked to the abundance of biogenic aerosol in boreal forests

Atmospheric Chemistry and Physics Discussions

article

Schneider, Julia¹  Brasseur, Zoé²  Wu, Yusheng²  Hakala, Simo²  Duplissy, Jonathan²  Moisseev, Dmitri²  Kulmala, Markku²  Adams, Michael P.⁴  Murray, Benjamin J.⁴  Korhonen, Kimmo⁵  Hao, Liqing⁵  Höhler, Kristina¹  Thomson, Erik S.⁶  Castarède, Dimitri⁶  Leisner, Thomas¹  Petäjä, Tuukka²  Möhler, Ottmar¹  Heikkilä, Paavo⁷  Keskinen, Jorma⁷  Bertozzi, Barbara¹  Bogert, Pia¹  Schorr, Tobias¹  Umo, Nsikanabasi Silas¹  Vogel, Franziska¹ 

[1] Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology;Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki;Helsinki Institute of Physics, University of Helsinki;Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds;Department of Applied Physics, University of Eastern Finland;Atmospheric Science, Department of Chemistry and Molecular Biology, University of Gothenburg;Aerosol Physics Laboratory, Physics Unit, Faculty of Engineering and Natural Sciences, Tampere University

DOI  :  10.5194/acp-21-3899-2021

学科分类：大气科学

来源: Copernicus Publications

【 摘 要 】

Ice-nucleating particles (INPs) trigger the formation of cloud ice crystals in the atmosphere. Therefore, they strongly influence cloud microphysical and optical properties and precipitation and the life cycle of clouds. Improving weather forecasting and climate projection requires an appropriate formulation of atmospheric INP concentrations. This remains challenging as the global INP distribution and variability depend on a variety of aerosol types and sources, and neither their short-term variability nor their long-term seasonal cycles are well covered by continuous measurements. Here, we provide the first year-long set of observations with a pronounced INP seasonal cycle in a boreal forest environment. Besides the observed seasonal cycle in INP concentrations with a minimum in wintertime and maxima in early and late summer, we also provide indications for a seasonal variation in the prevalent INP type. We show that the seasonal dependency of INP concentrations and prevalent INP types is most likely driven by the abundance of biogenic aerosol. As current parameterizations do not reproduce this variability, we suggest a new mechanistic description for boreal forest environments which considers the seasonal variation in INP concentrations. For this, we use the ambient air temperature measured close to the ground at 4.2 m height as a proxy for the season, which appears to affect the source strength of biogenic emissions and, thus, the INP abundance over the boreal forest. Furthermore, we provide new INP parameterizations based on the Ice Nucleation Active Surface Site (INAS) approach, which specifically describes the ice nucleation activity of boreal aerosols particles prevalent in different seasons. Our results characterize the boreal forest as an important but variable INP source and provide new perspectives to describe these new findings in atmospheric models.

【 授权许可】

CC BY