Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Wind Air stops rising when it meets air of equal density, then diverges at high level to produce more wind which eventually sinks elsewhere to complete the circulation cell Pressure, Wind and Weather Systems WINDS are horizontal flows of air; winds blow from areas of high pressure to areas of low pressure (nature tries to equalise pressure) � Insolation Air heated by contact with ground expands; becomes less dense and rises Denser air drawn in at low level to replace rising, less dense air LOW PRESSURE Sun heats up ground Denser air drawn in at low level to replace rising, less dense air Land and Sea Breezes Land & Sea Breezes Land Breeze Sea Breeze (cool land/warm sea) (warm land/cool sea) Cool air over land moves out toward the water and takes the place of rising air. Warm air over the water rises. Warm air over the land rises. Cool air over the water moves toward land and takes the place of the warmer air that has risen. A. As the land heats faster than the water throughout the day, air starts to rise and air from over the sea will come in to replace it. This is a sea breeze circulation (takes place during the day). B. As the land cools faster than the water throughout the day, the air begins to sink over land and rise over water. This is a land breeze circulation (takes place during the night) Land/Sea breeze The temperature differences between land and water occur because water has a much higher heat capacity than land. This means more heat is required to raise the temperature (or drop the temperature) of water than that of land. These temperature differences cause pressure gradient forces that force the breezes satellite Animation Cyclones and Anticyclones Northern Hemisphere: Cyclone Anticyclone Cyclone: Low pressure, Counterclockwise winds, cloudy and rainy weather Anticyclone: High Pressure, Clockwise winds, sunny weather Southern Hemisphere: Cyclone Anticyclone Cyclone: Low Pressure, clockwise, cloudy or rainy weather Anticyclone: High Pressure, counterclockwise, sunny weather How High and Low Pressure Works http://www.usatoday.com/weather/tg/whighl ow/whighlow.htm How Low Pressure Areas Work http://www.usatoday.com/weather/tg/wlowpr es/wlowpres.htm How High Pressure Areas Work http://www.usatoday.com/weather/tg/whighp /whighp.htm Highs have sinking air above them, lows have rising air. Sinking air over highs causes dry weather, Rising air above lows can condense and form clouds or rain or both. WIND DIRECTION & STRENGTH Wind strength depends on the difference in pressure between the high and low Farmers plant trees to protect orchards, pressure systems, and the houses, stock or prevent soil erosion distance between them. � This is called the PRESSURE GRADIENT; it is a similar concept to the physical slope between two places, shown on Locally, wind is channelled a contour map. Pressure is down streets (wind canyons). shown by ISOBARS on a weather map. Strong winds also occur � Pressure difference in low latitudes due to essentially depends on the stronger heating and temperature difference steeper presure gradients. between the two places. Hurricanes and A steep pressure gradient results tornadoes are both from a large pressure difference Strong polar winds due to low tropical phenomena. or short distance between places friction and causes strong wind. � Hurricane in Florida Tornado in USA Beach windbreaks reduce windsped by increasing friction Wind Speeds down a Pressure Gradient Weather map Coriolis Types of Surface winds: 1. Trade winds- occurs between 30o N and 30o S latitude. 2. Prevailing Westerly- occur between 30o to 60o in both hemispheres. They blow west to east. 3. Polar Easterlies- occurs between 60o and the poles in both hemispheres. They blow east to west. Ocean Currents Ocean Currents: movement of ocean water The main cause is the Coriolis Effect Coriolis Effect: the rotation of the Earth causes the oceans water to circle away from the equator Currents generally help to control climate and are useful in moving nutrients throughout the oceans Northern Hemisphere currents move clockwise; while currents in the Southern Hemisphere move counterclockwise. Earth Science Reference Table