Section 2: Atmospheric Phenomena UNIT 1 - EARTH AS A SYSTEM Section 2: Atmospheric Phenomena

CORIOLIS EFFECT Due to earth’s rotation, winds heading due North or South are deflected from their straight path. Northern Hemisphere: deflect to the right Southern Hemisphere: deflect to the left

PRESSURE GRADIENTS Differences in pressure among areas of the atmosphere lead to differences in weather.

EARTH’S ATMOSPHERE IS DIVIDED INTO “CELLS” Hadley Cell Animation

Cold, dry air falls Polar Cell Moist air rises — rain Polar cap Ferrel Cell Arctic tundra Evergreen coniferous forest 60° Cool, dry air falls Temperate deciduous forest and grassland 30° Desert Hadley Cell Tropical deciduous forest Moist air rises, cools, and releases Moisture as rain 0° Equator Tropical rain forest Tropical deciduous forest 30° Desert Hadley Cell Temperate deciduous forest and grassland Cool, dry air falls 60° Ferrel Cell Polar cap Cold, dry air falls Moist air rises — rain Polar Cell

EL NIÑO – SOUTHERN OSCILLATION Periodic shift in climate on a large scale Unknown cause, but driven by changes in pressure; occurs every several years (varies) Trade winds slow, causing warm water that is normally focused in the western Pacific to flow back to the east. This slows upwelling off the coast of N. and S. America, devastating fisheries and increasing precipitation Often followed by the reversing of this trend (La Nina – STRONGER than usual trade winds) Most devastating in recent history: 1997/1998

THE START OF AN EL NIÑO

MOST RECENT EL NIÑO CONDITIONS