Surface deposition is an important sink for tropospheric ozone. The rate of ozone
deposition may be measured by measuring the downward flux of ozone in the atmospheric
surface-layer.
This thesis presents eddy correlation measurements of ozone fluxes, taken on eight days in
August, 1994, at a grassland site located in the Lower Fraser Valley of British Columbia. Surface
resistances to ozone deposition were calculated from the flux measurements. Much of the
variability in measured surface resistances was found to be attributable to variations in ambient
light levels and in the degree of moisture stress at the site. Measurements of surface resistance
from this site agreed quite well with other measurements of ozone deposition to grassland
surfaces.
Measured surface resistances were compared to surface resistances calculated using the
Wesely (1989) parameterization (W89) for surface resistance. W89 underestimated surface
resistance, particularly in the mid afternoon and early evening. This was attributed to the model's
neglect of the effects of water stress on stomatal resistance, as well as to a low value for
resistance to ground surface deposition in the model.
The eddy correlation fluxes were compared to ozone fluxes derived using an assumption
of cospectral similarity between ozone and heat flux and to ozone fluxes measured using the
variance method and the gradient method. The cospectral similarity method worked well and
allowed a considerable relaxation of the sampling speed requirements of the eddy correlation
method. The variance method produced biased flux measurements due to high frequency noise
from the ozone sensor. Flux measurements using the gradient method had a great deal of scatter,
due to inaccuracies in the measurement of gradients.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/4343 |
| Date | 05 1900 |
| Creators | Kellerhals, Markus |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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