Discussion Review 4/3 AOSC 200 Sarah Benish

Outline I. Local Wind Systems II. Global Winds III. Atmosphere-Ocean Interactions

I. Local Winds: Sea Breeze As the surface warms, convection begins. The rising air “pushes” up the isobars, creating a pressure gradient. As air over land expands, a low pressure system forms at the surface and winds blow from ocean to land.

Land Breeze

Valley Breeze Sun heats the valley walls, which heats the surface air. The heated air (being less dense), rises as a gentle upslope wind. At night, the flow reverses

Mountain Breeze Reverse of valley breeze; happens at night. Cooler, more dense air glides downslope into valley.

Katabatic Winds Any downslope wind, but usually reserved for downslope winds that are stronger than mountain breezes.

Chinook Winds Warm, dry, downslope wind that descends on the eastern slope of the Rocky Mountains Strong westerlies aloft flow over a north-south trending mountain range As the air descends, it is compressed and warmed. Main source of warmth? Compressional heating.

Santa Ana Winds A warm, dry wind that blows downhill from east or northeast into southern California Source of heating? Compressional heating Cold, dense air from high deserts moves through mountain passes. Warms as it descends into coastal regions.

II. Global Winds Single Cell Model Assumptions: 1. Surface is uniformly covered with water 2. Sun is always directly over the equator 3. Earth does not rotate But this does not explain the mid-latitude westerlies! Three-Cell Model Allows the earth to spin

ITCZ Intertropical Convergence Zone Where the northeast trade winds meet with the southeast trade winds Usually very wet since rising air develops into huge thunderstorms that drop huge amounts of rain

III. Atmosphere-Ocean Interactions

Ekman Transport Ocean water is moved by wind Also affected by Coriolis forces

Ekman Spiral Wind blows parallel to the coastline. As the wind blows over the ocean, the surface water is moved. As surface water moves, it bends slightly to the right due to the Coriolis effect. The water beneath the surface also moves, and it too moves slightly to its right. As the surface water drifts away from the coast, cold, nutrient-rich water from below rises (upwelling) to replace it. Upwelling is the strongest and surface water is the coolest where wind parallels the coast.

El Niño Easterly trade winds weaken and warm water is transported from the western Pacific to the Eastern Pacific. Southern Oscillation: seesaw pattern of reversing air pressure at opposite ends of the Pacific Ocean. ENSO: basically simultaneous pressure reversals and ocean warming. Global Weather? W. Pacific: Less rainfall as warm Pacific water moves east Shift in rain patterns moves subtropical jet stream from normal path Change in path of sub-tropical jet allows El Niño to affect weather in mid-latitudes

Key Terms Sea breeze Land breeze Valley breeze Mountain Breeze Katabatic wind Chinook Wind Santa Ana Winds Polar cell Ferrel cell Hadley cell Trade winds ITCZ Ekman Transport Upwelling ENSO El Niño

Game First word: without saying key words, walk around the room describing your concept until you find your partner. Second word: With your partner, play Pictionary with your second words. Be sure to label where high and low pressure systems are, if applicable. WORDS YOU CANNOT SAY: Land Breeze Sea Wind Trade Cell Mountain Etc.