OBJECTIVES:
To characterise how temperature,
precipitation, and in particular, extreme winds are affected by the presence
of complex topography within the McGregor Model Forest landscape.
DESCRIPTION:
The
microclimate of the forest is a key physical determinant of ecological
pattern and process. Temperature and precipitation act as limitations
on ecosystem productivity, whereas extreme wind events may be an important
factor in the disturbance ecology of the forest landscape. In complex
terrain like the McGregor Model Forest, these climatic factors interact
in diverse ways to affect vegetation patterns and dynamics of the landscape.
However, meteorological data is not typically available for areas which
are sparsely populated or which have mountainous terrain. Interpolative
models must often be used to extrapolate meteorological parameters to these
areas. Complementary to the efforts of Ross Benton (Forest Practices)
to test and develop a model for extrapolating temperature and precipitation
(McGregor Model Forest Climate Model, or MMFCliM), the investigators of
this project developed a technique for extrapolating severe winds, in order
to identify areas within the McGregor Model Forest which are adversely
prone to high winds.
Three climate monitoring stations, in addition to one installed by Ross Benton, were deployed to collect validation data for the joint modelling efforts. As a prelude to this joint work, the investigators located all relevant climate records for the surrounding area and compiled this information into a climate report for the Model Forest (Murphy, 1996). In addition, an analysis of the climatic temperature correlations was provided to Ross Benton for his consideration in the development of MMFCliM. The investigators then turned their attention to the study of extreme winds.
Prior to developing a technique
for extrapolating severe winds, it was first necessary to determine whether
severe-wind events in the Model Forest are primarily due to convective
wind bursts (summertime events mainly), or due to synoptic scale wind storms
(wintertime events mainly). For this purpose, a statistical analysis
of historical wind extremes recorded in the central-interior of British
Columbia was undertaken. The results of this extreme value analysis
were submitted as an interim report to the Model Forest (Murphy and Jackson,
1997) and suggested that southerly gusts associated with winter cyclones
moving along the Pacific Coast are the most significant contributor to
extreme-wind events in the Central-Interior. Using the principles
of synoptic climatology, three daily mean sea-level pressure maps were
identified as model scenarios for moderate, strong and severe winds under
a southerly flow condition (Murphy and Jackson, 1998). These storm
scenarios are now being used to initialize a series of numerical weather
simulations in order to characterize areas of the McGregor Model Forest
which are prone to severe winds under a synoptic southerly flow.
REPORTS AND PRODUCTS:
CONTACTS:
Peter Jackson and Brendan Murphy, University of Northern British Columbia, Prince George, BC.
Ross Benton, Canadian Forest Service
(PFC) 506 West Burnside Rd., Victoria, BC V8Z 1M5
PARTNERS:
Canadian Forest Service, University
of Northern British Columbia
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