The Geography and Climate of North America

1
The Geography and Climate of North America
2
Orography

• The Cordillera, extensive system of mountain
  ranges stretching from Alaska , through British
  Columbia, Sierra Nevada, the Coast and Cascade
  ranges, and the Rocky Mountains and the Sierra
  Madre in Mexico.

3
The Climates of North America ( Based on Bryson
and Hare, 1974)

• The dominant geographic features of N. America
  are the high Cordillera and the eastern Lowlands
• The Cordillera is a most significant obstacle to
  the zonal westerly and to the easterly trade
  winds
• The plains allow unobstructed path to great
  meridional excursions of both Arctic and Tropical
  air masses

• The Cordillera consists largely of a 1.5-2 km
  plateau with superimposed mountain ranges

4
Transport Pathways

• wegwegweg

• Low level westerly winds impinging on the
  Cordillera barrier are mostly deflected, some
  pass through to the Plains
• At about 500 N the low-level westerly zonal flow
  divides into northerly and southerly branches
  along the western slopes.
• There are three main routes for the low-level
  westerlies to cross the Cordillera the most
  notable is the Columbia-Snake-Wyoming Channel.
• In Mexico, the southward deflected westerlies
  usually do not cross the Sierras.
• Over the Gulf of Mexico, the low level easterly
  the trade winds are usually deflected northward.
• South of the Yucatan, the trade winds cross the
  continent and turn southward.

5
Features of Air Flow over North America

• North America is under the influence of Pacific,
  Arctic and Tropical air masses.
• Between 300-500 the the strong westerlies and a
  more broken mountain barrier allows maximum
  eastward transit of Pacific air.
• This jet of westerly flow penetrating NAM at
  mid-latitudes entrains and mixes with air from
  the Arctic and the tropics.
• This unique distribution of land, sea and
  mountains produces a highly variable weather
  From one day to another, mild, sunny air from the
  Rocky Mountains may replace moist, warm, cloudy
  tropical air and then give way to cold Arctic
  air.

6
Seasonal Air Flowover North America
January
April

• NAVAIR, 1966

October
July