2. Factors Controlling the Climate of the
West Coast of North America
G.A. McBean
The west coast of North America extends from the tundra near the Arctic
Ocean to the tropical jungles of Panama , with a wide variety of climates
in between. Lawford (this volume) discusses the north-south variations
throughout the range of the Americas. A special American Geoph ysical
Union monograph , edited by Peterson (1989), is devoted to "Aspects of
climate variability in the Pacific and the western Americas" and provides
a valuable source of information on this topic. In that same volume,
Roden (1989) and Tabata (1989) examine the long-term variability of
the west coast and northeast Pacific Ocean climate. Walters and Meier
(1989) show that variations in glacial mass balances in western North
America are related to the steering effect of the Aleut ian/Gulf of Alr.ska
low.
Here the focus will be on the coastal zones between latitudes 60°Nand
30
0N
, which can be divided into two general climate regimes: namely, the
mid-latitude climate under the control of the westerly wind circulation;
and the areas of the subtropical high pressure zones, where oceanic
upwelling is an important factor. The equatorial climate regimes, with the
dominance of the intertropical convergence zone , will not be discussed.
Important features of the zones under consideration are the seasonal
variations as the westerlies and the high-pressure cells move north and
south , and the superimposed , longer-term variations due to natural factors
in the climate system. Oceans play an important role in determining both
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