It is important to understand how O<sub>3</sub> is generated and processed in the atmosphere. New critical levels that use accumulated stomatal uptake rather than atmospheric concentration have recently been set by the UNECE to quantify the effect of O<sub>3</sub> on vegetation. There are models available that can estimate the stomatal flux but the non-stomatal component is not well described. The total flux of O<sub>3</sub> was measured over grassland in central Scotland during 2001 to 2004 using micrometeorological methods and the uptake by stomata estimated by similarity with the water-vapour flux. The non-stomatal component is estimated using R<sub>ns </sub>=(R<sub>c</sub><sup>-1</sup> - R<sub>s</sub><sup>-1</sup>)<sup>-1 </sup>where R<sub>ns </sub>= non-stomatal surface resistance to ozone deposition, R<sub>c</sub> = total canopy resistance, R<sub>S</sub> = stomatal resistance. The dataset is used to examine the processes controlling deposition at this site with a view to providing a suitable parameterisation for the stomatal and non-stomatal components. There are two forms of model commonly used to estimate stomatal resistance: Jarvis type multiplicative models, and Ball-Berry photosynthesis based approaches. Measurements of plant physiology where made during 2001 and 2002 to parameterise a Ball-Berry type model; a standard parameterisation from EMEP is used for the Jarvis type then tuned to fit the measured data. The non-stomatal component is also important if O<sub>3</sub> concentrations are to be accurately modelled. Parameterisations based on the variation of R<sub>ns </sub>with surface temperature and wetness are developed. These “new” stomatal and non-stomatal formulae are implemented in a total-deposition model and the results compared to the measured data. Finally estimates of current and future critical levels for vegetation are calculated and their implications for effects examined.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:645077 |
| Date | January 2005 |
| Creators | Coyle, Mhairi |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14729 |
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