2026-09-23T21:25:21Zhttps://api.repository.cam.ac.uk/server/oai/request

oai:www.repository.cam.ac.uk:1810/2743592021-04-21T17:40:36Zcom_1810_721com_1810_256064col_1810_218856

Chemistry-climate modelling studies of decadal and interdecadal variability in stratospheric ozone and climate: The 11-year solar cycle and future ozone recovery 10.17863/CAM.21481 Bednarz, Ewa Monika Pyle, John A. The Earth’s atmosphere constitutes a complex system subject to a large number of forcings of both natural and anthropogenic origin; these influence its evolution on a range of timescales. This thesis makes use of the UMUKCA global chemistry-climate model to explore several aspects relating to the atmospheric response to the 11-year solar cycle forcing and future stratospheric ozone recovery. Firstly, following recent improvements in the model, the atmospheric response to the solar cycle forcing simulated in UMUKCA is discussed. It is shown that while some features show a broad resemblance to observations/reanalysis, there are clear differences with regard to other features; the latter could result from model deficiencies and/or uncertainties in the observed response. The role of analysis method and of interannual variability is also addressed. Secondly, the solar cycle response is separated into the individual contributions from direct radiative heating and from ozone production using a set of sensitivity experiments. It is shown that while the tropical yearly mean responses to the two components are generally linearly additive, this is not necessarily the case in the high latitudes. It is suggested that solar-induced ozone changes could be important for modulating the Southern Hemisphere dynamical response. Thirdly, the role of the representation of the solar ozone response is studied. It is shown that the choice of the solar ozone response prescribed in the radiation scheme in non-interactive ozone experiments has a substantial impact on the simulated temperature response to the solar cycle forcing. The Northern Hemisphere dynamical responses are found to be generally similar within the uncertainty. A comparison with an interactive ozone case is also discussed. Lastly, future ozone recovery is investigated using a seven-member ensemble of 1960- 2099/1980-2080 integrations. The long-term evolution of ozone in different regions is found to be generally consistent with previous modelling studies. The long-term trends and variability in springtime Arctic ozone and its chemical, radiative and dynamical drivers are assessed. It is shown that Arctic ozone increases in the future, consistent with future reduction in stratospheric chlorine, stratospheric cooling and strengthening large-scale circulation. Yet, the large interannual variability is found to continue and to facilitate episodic ozone reductions, with halogen chemistry becoming a smaller but non-negligible driver of future springtime Arctic ozone variability for many decades. University of Cambridge 2018-04-28 Thesis Doctoral Doctor of Philosophy (PhD) en ERC (the ACCI project, grant number 267760) https://www.repository.cam.ac.uk/handle/1810/274359 controlled.access https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/78d86274-a1d5-49c6-9d0f-a5218d09c532/download 87eda9de84448d1f82354d60eee3eb5f https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/40ec4515-5ac2-4757-bf8b-b67b312547e5/download 0b00774033b6b15bb7bc77cc674f02b9 https://www.rioxx.net/licenses/all-rights-reserved/ ozone chemistry-climate interactions atmospheric modelling CCM 11-year solar cycle stratosphere atmospheric dynamics UM-UKCA atmospheric chemistry