ATMOSPHERIC CIRCULATION NOTES- AIR/SEA INTERFACE, CORIOLIS, & WIND

OVERVIEW Atmosphere and ocean one interdependent system Solar energy creates winds Winds drive surface ocean currents and waves Examples of interactions: El Niño Currents

AIR/SEA Ultimately all winds are generated by unequal heating of the Earth by the sun. Parallel rays from the sun hit a round earth, so only at the equator does energy from the sun fall on a flat surface at a right angle to the sun At the equator, radiation from the sun is particularly intense, and the air above the tropical oceans warms rapidly each day. When heated, it expands and becomes less dense Results: moist, hot air rises far above the equator (low pressure)

AIR/SEA But expanding air cools and cannot retain moisture… Instead, water vapor condenses to liquid water, clouds form, and rains fall in the tropics. The now dry air move north or south as strong upper atmospheric winds blow, convecting heat toward the poles

MOVEMENTS IN ATMOSPHERE Air (wind) always moves from regions of high pressure to low Cool dense air, higher surface pressure Warm less dense air, lower surface pressure

PHYSICAL PROPERTIES OF ATMOSPHERE Warm air, less dense (rises) Cool air, more dense (sinks) Moist air, less dense (rises) Dry air, more dense (sinks) Rises = Low pressure Sinks = High Pressure

AIR MOVEMENT Warm air rises Heat makes molecules move more Further-apart molecules = lower density Less dense air rises above more dense air Cold air sinks Colder molecules move less Become packed more closely together Denser cool air sinks below less dense air

MOVEMENTS IN AIR ON A ROTATING EARTH Coriolis effect Coriolis effect causes deflection in moving body Due to Earth’s rotation to east Most pronounced on objects that move long distances across latitudes Deflection to right in Northern Hemisphere Deflection to left in Southern Hemisphere Maximum Coriolis effect at the equator No Coriolis effect at the poles

THE CORIOLIS EFFECT In the Northern Hemisphere: Objects are deflected to the right Faster-moving objects are deflected more Deflection is stronger closer to the poles In the Southern Hemisphere: Objects are deflected to the left Faster-moving objects are deflected more Deflection is stronger closer to the poles

NORTHERN HEMISPHERE DEFLECTION N E S W Equator Coriolis Effect

NORTHERN HEMISPHERE DEFLECTION N E S W Equator Coriolis Effect

SOUTHERN HEMISPHERE DEFLECTION N E S W Equator Coriolis Effect

SOUTHERN HEMISPHERE DEFLECTION N E S W Equator Coriolis Effect

EXAMPLES: A plane leaves Myrtle Beach (South Carolina) for Montreal, but does not correct for the Coriolis Effect. Where does it wind up in relation to its intended destination? A plane leaves Myrtle Beach (South Carolina) for San Diego, but does not correct for the Coriolis Effect. Where does it wind up in relation to its intended destination? Coriolis Effect

San Diego Aerial Image: NASA Montreal Coriolis Effect

San Diego Aerial Image: NASA Montreal Coriolis Effect Not To Scale Coriolis Effect

Due to coriolis, unequal solar heating, and convection, air patterns actually look like this …sort of

COASTAL WINDS Solar heating Different heat capacities of land and water Sea breeze Sea breeze From ocean to land Land breeze Land breeze From land to ocean Fig. 6.13

GLOBAL WIND PATTERNS

ATMOSPHERIC CIRCULATION MAP *Winds - High to Low Pressure *Northern Hemisphere: CounterClockwise; Deflect Right *Southern Hemisphere: Clockwise; Deflect Left

YOUR DIAGRAM