In this thesis, the TOMCAT and HadGEM2-ES models are used to improve the understanding of the complex interactions between tropospheric ozone and the global biosphere. The focus is on the impacts of surface ozone on crops, impacts of land surface vegetation changes on tropospheric ozone and the effects of vegetation ozone damage on tropospheric chemistry through changes in dry deposition and BVOC emissions. This thesis presents the first estimates of the impact of ozone precursor emissions from each of the northern hemisphere’s major industrialised regions (N America, SE Asia and Europe) on crop yields globally and in continents downwind of each region. Using a range of ozone crop damage metrics, 100% reductions in SE Asian anthropogenic NOx emissions tend to produce the greatest global reduction in crop production losses (42.3-95.2 %). A 100% reduction in N American anthropogenic NOx emissions produces the largest transboundary impact, resulting in European production loss reductions of between 14.2% and 63.2 %. Preindustrial model tropospheric ozone distributions are shown to be sensitive to the model vegetation coverage and representation of biosphere atmosphere processes. Simulations with HadGEM2-ES indicate a pre-industrial ozone burden which ranges from 200.4 Tg to 220.9 Tg with the variation resulting from differences in the model land vegetation distribution, the CO2 mixing ratio the vegetation was exposed to and the model climate setup. The change in pre-industrial to present day ozone burden ranged from 71.9 Tg to 92.5 Tg translating into an estimated radiative forcing of 0.227Wm−2 to 0.244Wm−2. The response of ozone concentrations to land cover changes is greater than the response to changes in the CO2 mixing ratio the vegetation is exposed to. The ozone distribution is shown to be more sensitive to changes in the rates of isoprene emissions than to changes in dry deposition processes. The effects of ozone damage have a self limiting effect on ozone and NOy dry deposition leading to a rise in surface ozone concentrations. Depending on plant sensitivity to ozone damage, mean total stomatal uptake was shown to decline by 0.22 to 0.42 mmolO3m−2 resulting in average surface ozone concentrations rising by 0.02 to 0.03 ppbv, with local increases of up to 14 ppbv. The effects of ozone damage on photosynthesis is to reduce isoprene emissions, producing slight drops in ozone over the more polluted regions offsetting the rise in concentrations due to the dry deposition effect. The inclusion of both effects resulted in a net rise in surface ozone concentrations indicating the dry deposition response to ozone damage dominates over the effects on isoprene emissions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:605189 |
| Date | January 2012 |
| Creators | Hollaway, Michael John |
| Contributors | Arnold, Steve ; Chipperfield, Martyn ; Collins, Bill |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.whiterose.ac.uk/6374/ |
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