This book explores Canada's surface physical climates. It concentrates on Canada's surface because the strongest exchanges take place there and because the ecological and economic impact of climate arise directly from surface processes. However, the total climate also contains a large dynamic component that is brought to Canada by winds and ocean currents. In this first chapter we explore the concept of the total climate - dynamic and physical -and relate it to other things. The rest of the book examines such relationships in the context of specific surface types: forests, lakes, soils, agricultural fields, glaciers, and others. It also...

This chapter sets out the way an individual surface is affected by the large-scale external controls outlined in chapter 1 and the nature of its response. The surface is bathed by heat from the sun, buffeted by winds driven by the large-scale circulation and synoptic systems that migrate over it, and occasionally inundated with rain and snow. Some of these inputs are cyclical (for example, the daily and annual variation of solar heating), and some are quasi-random (for example, storm winds and precipitation). The response of the surface is determined by those of its properties that govern absorption, reflection, and...

Most of chapter 2 addresses an important, but special case: the atmosphere in equilibrium with its underlying surface. In such situations the near-surface turbulent fluxes of heat, moisture, and momentum (and any other properties of interest) do not vary in the horizontal. For this condition to be met, surface properties such as temperature, moisture, and roughness, which act as sources or sinks for the fluxes, must be horizontally uniform, at least in the upwind direction. Much of the material presented in the chapters that follow also explicitly or implicitly assume that the surface is horizontally homogeneous. This is clearly not...

The presence of a such an unequivocal season as the Canadian winter distinguishes our climate from that of neighbours in the Americas, is deeply embedded in the national psyche, and remains a key to the worldwide perception of Canada. Comparative climatological analyses define December, January, and February as the winter period. Table 4.1 summarizes the average annual cold, snowy weather conditions in that period for the climatic regions of Canada. As expected, a strong north-south temperature gradient prevails in the interior (Resolute, NWT; Churchill, Man.; Thompson, Man.; Saskatoon, Sask.; and Toronto, Ont.), while the Atlantic and Pacific coasts have the...

What are the coastal zones of Canada? In British Columbia we might include the region west of and including the slopes of the Coast Range, plus all of Vancouver Island and the Queen Charlotte Islands but not the precipitation shadow behind the Coast Range. In northern and Atlantic Canada zone boundaries are harder to draw. Areas within about 200 km of the coast are affected by the adjacent ocean and should be included. However, placing a boundary on the coastal zones in these regions is very difficult. For our purposes, we bring in all of Nova Scotia, New Brunswick, Prince...

While oceans are vital climate on a global scale, lakes can significantly affect local and regional climate. Lakes transport and store heat, respond to atmospheric forcing and feed-back to affect the overlying air. Air and water exchanges of heat and moisture have climatological implications not only for the water body but also on the climate of the overlying air and areas adjacent to the water mass. To understand the interactions and effects of lakes on climate we must examine the physical characteristics of water bodies and the temporal and spatial variation of the exchanges of momentum, heat, and water.

Much...

Wetland ecosystems can be found over the entire land surface of the earth in a wide range of climatic settings from the tropics to the polar regions. Wetlands are estimated to cover 5.3 million km² (Matthews and Fung, 1987), or a little less than 4 per cent of the earth's total land area. Over 50 per cent of all wetlands occur in the northern hemisphere, between 45°N and 70°N, in the latitudes that correspond to the cool temperate, boreal, and subarctic ecotones. At these latitudes, wetlands can cover 25 per cent of the landscape, and in Canada and Russia continuous...

The Canadian Arctic Archipelago extends from Resolution Island (61°N) to the northern tip of Ellesmere Island (83°N), about 800 km from the North Pole. Other than the southern part of Baffin Island and several small islands, the archipelago lies within the Arctic Circle (Figure 8.1). Many deep sounds and channels separate the islands, but the sea's surface is covered by ice for most of the year, with multi-year ice cover present over the Arctic Ocean. The general topography of the western islands tends to range from undulating to flat-lying, with elevation averaging below 300m, so the area is classified as...

Extending from the southern Arctic Islands to the close-crowned boreal forest, the low arctic and subarctic region is underlain largely by continuous and discontinuous permafrost and is traversed by the arctic treeline (Figure 9.1). It is bounded on the west by the Western Cordillera and has its eastern limit in western Labrador. The region is non-mountainous and consists of the broad landscape categories of tundra, open subarctic forest, and northern lakes (Figure 9.2 and 9.3). Each category contains several types of terrain, distinguished by vegetation, soil type, and wetness factors.

The vegetation and terrain of tundra are quite varied, ranging...

The Cordillera of Canada exhibits a physiographic complexity unmatched by most other natural environments considered in this book. The landscape displays a multiplicity of slope angles and azimuths and is made even more complex by the diversity of surface types. Not only is the variability readily apparent at the micro-scale, but there are latitudinal changes too, for the alpine zone decreases in altitude as one moves further north. In addition, the effects of continentality produce longitudinal gradations. One of the outstanding characteristics of the Cordillera therefore is the tremendous spatial variability of the surface, which consequently produces a wide range...

The forests of Canada can be divided into eight distinct regions that reflect the country's different climatic regimes (Figure 11.1). The uniqueness of the climate of forests compared to most other vegetated surfaces is largely a result of their lower albedo, lower stomatal conductance, and higher aerodynamic roughness. The last-named induces efficient mixing in the boundary layer above forests, which has characteristically small temperature gradients (< 0.10 °C m^-¹) and humidity gradients (< 10 Pa m^-¹).

The forest regions and their boundaries are related to macroclimatic controls -usually measures of available radiant energy and aridity. However, exact cause and effect...

Successful farming requires harmony with the climate. Sometimes this harmony has been achieved only after many seasons of trial and error in growers’ fields. But on occasion the winding pathway to farming success can be shortened by scientific discovery of the biophysical principles that underlie interactions between crops and climate. This is the rationale behind the science of “agrometeorology,” which seeks to understand crop performance in terms of exchanges of radiant energy, heat, water, and atmospheric gases between plants and the atmosphere.

This chapter first explores the physical principles that link energy and climate at the level of a leaf...

The study of the physical climates of cities is young. A summary of Canadian work in 1965 started with the statement: “Until fairly recently, meteorologists have turned their backs on cities” (Thomas, 1971). Even today coverage is patchy in terms of both subject and geographical location. Therefore, in order to give a balanced treatment, this chapter draws on non-Canadian examples and general principles. It also relies heavily on work from Vancouver, BC.

Almost 80 per cent of Canadians live in urban areas, and part of the surface climate they experience is something they have inadvertently created for themselves. Every lot...

During the last two hundred years human activity has raised atmospheric concentration of carbon dioxide (CC₂) by over 25 per cent, from perhaps 280 ppmv at the beginning of the industrial revolution to 360 ppmv in 1996. Further, methane concentration has more than doubled, from 0.7 ppmv to over 1.7 ppmv. Current concentrations of these gases already greatly exceed any level that has existed during the last 160,000 years. Recent rates of change appear greater than those that have occurred naturally, as demonstrated by the record of air bubbles trapped in antarctic ice (Chappellaz et al., 1990). Carbon dioxide and...

As previous chapters have so amply demonstrated, there is a wide spectrum of “surface climates” across Canada. These are evident not only at the relatively large scales revealed by the national network of climate-observing stations (coastal, forest, Prairie, city, and so on) but at ever-smaller scales, each embedded in a larger one (a bay, a forest clearing, a ploughed field, an urban canyon). This epilogue seeks to place the study of these climates in their historical perspective and looks ahead to the exciting challenges facing Canadian surface climatologists in the next century.

I begin with a brief historical overview of...