English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In the 2002 Antarctic polar vortex enhanced HOCl mixing ratios weredetected by the Michelson Interferometer for Passive AtmosphericSounding both at altitudes of around 35 km (1000 K potential temperature),where HOCl abundances are ruled by gas phase chemistry and at around 18–24 km(475–625 K), which belongs to the altitudedomain where heterogeneous chlorine chemistry is relevant.At altitudes of 33 to 40 km polar vortex HOCl mixing ratios were found to bearound 0.14 ppbv as long as the polar vortex was intact, centered at the pole,and thus received relatively little sunlight. This is the altitude regionwhere in midlatitudinal and tropic atmospheres peak HOCl mixing ratiossignificantly above 0.2 ppbv (in terms of daily mean values) are observed.After deformation and displacement of the polar vortex in the courseof a major warming, ClO-rich vortex air was more exposed to sunlight,where enhanced HOx abundances led to largely increased HOClmixing ratios (up to 0.3 ppbv), exceeding typical midlatitudinaland tropical amounts significantly. The HOCl increase was preceded by anincrease of ClO. Model runs could reproduce these measurements only when theStimpfle et al. (1979) rate constant for the reaction ClO+HO2→HOCl+O2 was used but not with the current JPL recommendation.At an altitude of 24 km, HOCl mixing ratios of up to 0.15 ppbv were detected.This HOCl enhancement, which is already visible in 18 September data, isattributed to heterogeneous chemistry, which is in agreement with observationsof polar stratospheric clouds. The measurements were compared to a model runwhere no polar stratospheric clouds appeared during the observation period.The fact that HOCl still was produced in the model runsuggests that a significant part of HOCl was generated from ClO rather thandirectly via heterogeneous reaction. Excess ClO, lower ClONO2 andearlier loss of HOCl in the measurements are attributed to ongoingheterogeneous chemistry which is not reproduced by the model.On 11 October, polar vortex mean daytime mixing ratios were only 0.03 ppbv

HOCl chemistry in the Antarctic Stratospheric Vortex 2002, as observed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)