28
G.A. McBean
the mean climate and its variations. Through better understanding of the
factors controlling the climiate , we can gain the possibility of predicting
climate variability and change . In this chapter, we cannot comprehensively cover all aspects of the climate of this region , as has been done in
works such as Hare and Thomas (1974) and Bryson and Hare (1974).
Instead, emphasis will be given here to only two features: 1) the precipitation variability of the British Columbia region (which is representative
of the mid-latitude westerlies climate zone); and 2) ocean upwelling ,
which influences regional climate. Spatial and temporal variations in
precipitation are probably the single most important factor in determining
vegetation types and ecosystem distributions along the western part of
North America. Upwelling is included to highlight the interactions of the
oceans and atmosphere in the coastal regions.
The climatic factors discussed here are central to several programs with
international global change activities. Variability of precipitation is a
key component of the Global Energy and Water Cycle Experiment
(GEWEX) of the World Climate Research Programme. Oceanic upwelling
will be an important physical process for the Land-Ocean Interactions in
the Coastal Zone (LOICZ) Project of the International GeosphereBiosphere Programme (IGBP). These physical factors will strongly
influence regional ecosystems , which are the focus of the Global Change
and Terrestrial Ecosystems (GCTE) and Joint Global Ocean Flux Study
(JGOFS), both of the IGBP.
Scales of Variation and Predictability
When we deal with natural ecosystems , it is important to remember the
interactions of differing spatial scales and response times. There is a full
range of natural variability , from millisecond and millimeter scales of
turbulence through global and decadal scales of climate variations. For
most natural systems, time and space scales are linked. Small features
tend to change more rapidly than larger features, but their other characteristics are also important. Generally, we can say that dynamically, the
atmosphere adjusts in a few days; it will reestablish its radiative equilibrium
in about a month; and water cycles through .the atmosphere in about 10
days. Our best estimates of other adjustment times include a few months
for soil moisture and about a year for snow and sea ice. The upper layers
of the ocean adjust in months through to the seasonal cycle, while the
deep ocean may take centuries to respond to a change in external forcing.
Connected to this concept of time and space scales is the concept of
predictability. It is not possible to predict the evolution of a phenomenon
beyond a few of its time scales.
Climate prediction from an initial state of a sequence of future climate
states (Lorenz referred to this as prediction of the first kind) (Palmer,
G.A. McBean
the mean climate and its variations. Through better understanding of the
factors controlling the climiate , we can gain the possibility of predicting
climate variability and change . In this chapter, we cannot comprehensively cover all aspects of the climate of this region , as has been done in
works such as Hare and Thomas (1974) and Bryson and Hare (1974).
Instead, emphasis will be given here to only two features: 1) the precipitation variability of the British Columbia region (which is representative
of the mid-latitude westerlies climate zone); and 2) ocean upwelling ,
which influences regional climate. Spatial and temporal variations in
precipitation are probably the single most important factor in determining
vegetation types and ecosystem distributions along the western part of
North America. Upwelling is included to highlight the interactions of the
oceans and atmosphere in the coastal regions.
The climatic factors discussed here are central to several programs with
international global change activities. Variability of precipitation is a
key component of the Global Energy and Water Cycle Experiment
(GEWEX) of the World Climate Research Programme. Oceanic upwelling
will be an important physical process for the Land-Ocean Interactions in
the Coastal Zone (LOICZ) Project of the International GeosphereBiosphere Programme (IGBP). These physical factors will strongly
influence regional ecosystems , which are the focus of the Global Change
and Terrestrial Ecosystems (GCTE) and Joint Global Ocean Flux Study
(JGOFS), both of the IGBP.
Scales of Variation and Predictability
When we deal with natural ecosystems , it is important to remember the
interactions of differing spatial scales and response times. There is a full
range of natural variability , from millisecond and millimeter scales of
turbulence through global and decadal scales of climate variations. For
most natural systems, time and space scales are linked. Small features
tend to change more rapidly than larger features, but their other characteristics are also important. Generally, we can say that dynamically, the
atmosphere adjusts in a few days; it will reestablish its radiative equilibrium
in about a month; and water cycles through .the atmosphere in about 10
days. Our best estimates of other adjustment times include a few months
for soil moisture and about a year for snow and sea ice. The upper layers
of the ocean adjust in months through to the seasonal cycle, while the
deep ocean may take centuries to respond to a change in external forcing.
Connected to this concept of time and space scales is the concept of
predictability. It is not possible to predict the evolution of a phenomenon
beyond a few of its time scales.
Climate prediction from an initial state of a sequence of future climate
states (Lorenz referred to this as prediction of the first kind) (Palmer,