Description: Vortex-wide chlorine activation by a mesoscale PSC in the Arctic winter of 2009/10

This title appears in the Scientific Report : 2016

Vortex-wide chlorine activation by a mesoscale PSC in the Arctic winter of 2009/10

In the Arctic polar vortex of the 2009/10 winter temperatures were low enough to allow widespread formation of polar stratospheric clouds (PSCs). These clouds occurred during the initial chlorine activation phase which provided the opportunity to investigate the impact of PSCs on chlorine activation...

Personal Name(s):	Wegner, Tobias
	Pitts, Michael C. (Corresponding author) / Poole, L. R. / Tritscher, Ines / Grooss, Jens-Uwe / Nakajima, H.
Contributing Institute:	Stratosphäre; IEK-7
Published in:	Atmospheric chemistry and physics, 16 (2016) S. 4569-4577
Imprint:	Katlenburg-Lindau EGU 2016
DOI:	10.5194/acp-16-4569-2016
Document Type:	Journal Article
Research Program:	Composition and dynamics of the upper troposphere and middle atmosphere
Link:	OpenAccess
	Publikationsportal JuSER

Please use the identifier: http://dx.doi.org/10.5194/acp-16-4569-2016 in citations.
Please use the identifier: http://hdl.handle.net/2128/13082 in citations.

In the Arctic polar vortex of the 2009/10 winter temperatures were low enough to allow widespread formation of polar stratospheric clouds (PSCs). These clouds occurred during the initial chlorine activation phase which provided the opportunity to investigate the impact of PSCs on chlorine activation. Satellite observations of gas-phase species and PSCs are used in combination with trajectory modeling to assess this initial activation. The initial activation occurred in association with the formation of PSCs over the east coast of Greenland at the beginning of January 2010. Although this area of PSCs covered only a small portion of the vortex, it was responsible for almost the entire initial activation of chlorine vortex wide. Observations show HCl (hydrochloric acid) mixing ratios decreased rapidly in and downstream of this region. Trajectory calculations and simplified heterogeneous chemistry modeling confirmed that the initial chlorine activation continued until ClONO2 (chlorine nitrate) was completely depleted and the activated air masses were advected throughout the polar vortex. For the calculation of heterogeneous reaction rates, surface area density is estimated from backscatter observations. Modeled heterogeneous reaction rates along trajectories intersecting with the PSCs indicate that the initial phase of chlorine activation occurred in just a few hours. These calculations also indicate that chlorine activation on the binary background aerosol is significantly slower than on the PSC particles and the observed chlorine activation can only be explained by an increase in surface area density due to PSC formation. Furthermore, there is a strong correlation between the magnitude of the observed HCl depletion and PSC surface area density.