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Title: The gaseous exchange of ozone at terrestrial surfaces : non-stomatal deposition to grassland
Author: Coyle, Mhairi
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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It is important to understand how O3 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 O3 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 O3 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 Rns =(Rc-1 - Rs-1)-1 where Rns = non-stomatal surface resistance to ozone deposition, Rc = total canopy resistance, RS = 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 O3 concentrations are to be accurately modelled. Parameterisations based on the variation of Rns 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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available