Heterogeneous formation of polar stratospheric clouds – Part 1: Nucleation of nitric acid trihydrate (NAT) ...

• Main Authors: Hoyle, Christopher R., Engel, Ines, Luo, Beiping P., Pitts, Michael C., Poole, Lamont R., Grooß, Jens-Uwe, Peter, Thomas
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2013
• Subjects: Arctic
• Online Access: https://dx.doi.org/10.3929/ethz-b-000072349; http://hdl.handle.net/20.500.11850/72349

Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The ... : Atmospheric Chemistry and Physics, 13 (18) ...