Air Masses and Winds

Air Masses Air Mass = large body of air that takes on characteristics of the area over which it formed Conditions: Over land = dry Over water = wet Polar regions = cold Tropical regions = warm

Air Masses Types of Air Masses: Continental polar (cP) – cold, dry Continental topical (cT) – warm, dry Maritime polar (mP) – cold, wet Maritime tropical (mT) – warm, wet

mP cP cT mT Continental Polar Maritime Tropical Continental Tropical Maritime Polar Maritime Tropical mT

Winds When air is heated: Its density decreases Warm air rises, produces an area of low pressure Cooler, denser air produces an area of high pressure, and moves in under rising air

Winds Wind: caused by uneven heating and cooling at the Earth’s surface Temperature differences create density differences, which create pressure differences Air moves from high pressure to low pressure, causing circulation of air

Local winds Blow from any direction Cover short distances Caused by differences in heating and cooling rates of land and water Land & Sea Breeze Animation

Local winds Sea breeze –during the day solar radiation warms the land more than water air moves inland from the ocean due to air over land heating up quicker (and is less dense than the ocean air) Land breeze –at night when cool air from land flows seaward air moves toward the ocean as the land air cools quicker

Land and Sea Breezes

Local winds Monsoon – seasonal wind, major land and sea breeze Land is cooler than ocean in winter, thus air flows away from land (dry weather) In summer, monsoon winds bring rain to the land

Describe what happens in a monsoon.

Global Winds Do all places on Earth receive the same amount of solar radiation? NO!! So on a small scale, uneven heating results in local winds such as land and sea breezes. What do you think this uneven heating will cause on a large scale?

Global Winds Global Winds! But factors other than simple temperature differences affect global winds…

Earth Science Reference Tables Earth Science Reference Tables Page 14 Page 14 Global Winds Global Winds

Coriolis Effect Objects do not move in a straight line The Earth’s rotation causes moving particles such as air to be deflected to the right in the northern hemisphere

Coriolis Effect The Coriolis Effect combines with the heat imbalance found on Earth to create distinct global wind systems.

Global winds

Doldrums Windless zone at equator Air rises straight up Doldrums

Global winds Trade winds Blow toward equator from 30  N or S Descending air Blow to SW in N. Hemp. Blow to NW in S. Hemp. Trade Winds

Global winds Prevailing westerlies Between 30  and 60  N or S Blow opposite the trade winds Blow from SW to NE in N. Hemp. Prevailing Westerlies

Global winds Polar easterlies cold dry, dense, horizontal air currents Blow from NE to SW at N Pole Blow from SE to NW at S Pole Polar Easterlies

Jet Stream Jet stream: high altitude winds at top of troposphere Blow west to east Latitude varies with season