UBC Theses and Dissertations
Occurrence and utilization of fog Hayes, Derek
The thesis is proposed that, under certain favourable conditions, water may be deposited from fogs on to plants, and utilized by them. Where other sources of water are scarce, this addition may be critical for their survival. The physical characteristics, and the spatial and temporal occurrence of fogs are discussed. An attempt is made to define some of the associated meteorological conditions, and some of the causal mechanisms, of certain common fog types, by a detailed analysis of the temporal coincidence of fog and certain meteorological parameters at Vancouver International Airport. This information is then used to construct a conditional probability model for the prediction of fog occurrence. The techniques of mechanically measuring interception of water from fogs are next considered. Experiments with screened raingauges, in England, and a gauze - cylinder type recording fog gauge, at Vancouver International Airport, are described, and the significance of the results assessed. It is hypothesized that there are two main pathways of fog water utilization by vegetation; the evidence for each is assessed. These are direct absorption of deposited water, which usually occurs under moisture stressed conditions, and drip to the ground, with replenishment of soil water, and subsequent normal root absorption. It is considered that certain plant morphologies, at various scales, influence the amount of water that may be intercepted from fog. These are discussed, and attempts are made at experimentation, using laboratory fog simulation. The difficulties of accurately measuring fog drip amounts from complex vegetation types are evaluated, and some simple models of fog drip assessed.
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