Numerical modelling of oxidising processes in the troposphere

The Cambridge 3D chemical and transport model (TOMCAT) has been developed and used to separate the two sources of O3, in situ O3 production and downward transport of O3 from the stratosphere/upper troposphere. The main source of tropospheric O3 in the model is from downward transport from the stratosphere/upper troposphere. Photochemical production of O3 depends on downward transport from the stratosphere/troposphere, where this transport is determined by the tropopause definition used. These results have been compared with other CTMs and reasonable agreement is found. Analyses of the TOMCAT model integrations are done for key tropospheric species (e.g. O3, CO, NMHCs and NOy) by comparison with measurements obtained over the North Atlantic region between August and October 1997. The period contains several international aircraft measurement campaign: ACSOE, NARE, TACIA and SONEX. The model was used to predict the O3 budget over the North Atlantic region for this flight campaign period. The O3 budget was found to be determined by an influx of O3 rich air from North America and photochemical O3 destruction occurring over the North Atlantic, resulting in a negative O3 budget overall. The model was used to examine the effect of continental emissions on O3 production. The long-range transport of continental emissions emitted from North America, Europe and Asia were investigated to determine how long-range the effects of these emissions can be. Results shown is this thesis suggest that Asian emissions have a global impact on O3 production, and that North American emissions have a significant impact on O3 production in the Northern Hemisphere.EThOS - Electronic Theses Online ServiceGBUnited Kingdo