Abstract
Abstract. Improvements are made to two areas of the United Kingdom Chemistry and Aerosol (UKCA) module, which forms part of the Met Office Unified Model (UM) used for weather and climate applications. Firstly, a solar cycle is added to the photolysis scheme. The effect on total column ozone of this addition was found to be around 1 %–2 % in midlatitude and equatorial regions, in phase with the solar cycle. Secondly, reactions occurring on the surfaces of polar stratospheric clouds and sulfate aerosol are updated and extended by modification of the uptake coefficients of five existing reactions and the addition of a further eight reactions involving bromine species. These modifications are shown to reduce the overabundance of modelled total column ozone in the Arctic during October to February, southern midlatitudes during August and the Antarctic during September. Antarctic springtime ozone depletion is shown to be enhanced by 25 DU on average, which now causes the ozone hole to be somewhat too deep compared to observations. We show that this is in part due to a cold bias of the Antarctic polar vortex in the model.
Highlights
Stratospheric chemistry is a crucial aspect of chemistry– climate models primarily due to the coupling of ozone with atmospheric dynamics
The percentage difference in the global mean total column ozone (TCO) in the solar cycle run relative to the control run is indicated by the red curve
The additional bromine reactions are at maximum effect in early spring, when they amount to 20 Dobson units (DU) of additional ozone depletion
Summary
Stratospheric chemistry is a crucial aspect of chemistry– climate models primarily due to the coupling of ozone with atmospheric dynamics. The SAM affects numerous other climate features, e.g. Antarctic surface temperatures (Thompson and Solomon, 2002; Marshall, 2007; Gillett et al, 2006), the Southern Ocean storm track (Yin, 2005), the atmospheric blocking frequency (Dennison et al, 2016) and sea ice (Hall and Visbeck, 2002; Sen Gupta and England, 2006). Ozone-depleting reactions involving only oxygen compounds are known as the Chapman cycle (Chapman, 1930). One of the main modes of variation in solar radiation is the 11-year cycle (Solanki et al, 2013, and references therein). This cycle is known to have a signif-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
