Despite its relevance to many aspects of urban climate and to several practical
questions, urban dew has largely been ignored. Here, simple observations, an outof-
doors scale model, and numerical simulation are used to investigate patterns of
dewfall and surface moisture (dew + guttation) in urban environments. Observations
and modelling were undertaken in Vancouver, B.C., primarily during the summers of
1993 and 1996.
Surveys at several scales (0.02-25 km) show that the main controls on dew
are weather, location and site configuration (geometry and surface materials).
Weather effects are discussed using an empirical factor, Φw. Maximum dew
accumulation (up to ~0.2 mm per night) is seen on nights with moist air and high Φw,
i.e., cloudless conditions with light winds. Favoured sites are those with high Ψsky
and surfaces which cool rapidly after sunset, e.g., grass and well insulated roofs.
A 1/8-scale model is designed, constructed, and run at an out-of-doors site to
study dew patterns in an urban residential landscape which consists of house lots, a
street and an open grassed park. The Internal Thermal Mass (ITM) approach is used
to scale the thermal inertia of buildings. The model is validated using data from fullscale
sites in Vancouver. Patterns in the model agree with those seen at the fullscale,
i.e., dew distribution is governed by weather, site geometry and substrate
conditions. Correlation is shown between Ψsky and surface moisture accumulation.
The feasibility of using a numerical model to simulate urban dew is
investigated using a modified version of a rural dew model. Results for simple
isolated surfaces—a deciduous tree leaf and an asphalt shingle roof—show promise,
especially for built surfaces. [Scientific formulae used in this abstract could not be reproduced.] / Arts, Faculty of / Geography, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/9932 |
| Date | 05 1900 |
| Creators | Richards, Katrina |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 15054391 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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