Winds
What is Wind? The horizontal movement of air from High pressure to Low pressure. HL Air moving up or down (vertical) is called a current
What causes wind? diferences in pressure H= High L= Low
Pressure is caused by the characteristics of the air X X X X X X X X X X X X Molecules move faster and are farther apart. Warmer Air Less Dense Molecules are close together and move slowly. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Cooler Air More Dense
Warm Air Rises Cool Air Sinks Cool Air Sinking Warm Air Rising Warm Air Rising
Convection Currents Cool Air Sinking Cool Air Sinking Warm Air Rising
High Pressure H AHHHH! High Pressure Ok, High Pressure is Dense (heavy) Cool Creates Clear Skies
Low Pressure Whew! Low Pressure L Ok, Low Pressure is Less Dense (heavy) Warmer Brings Lousy Weather Whew! Low Pressure L
High Pressure = Happy Weather H Low Pressure = Lousy Weather L
Wind blows from areas of to areas of high pressure low pressure
Winds Blow from HIGH to LOW
counterclockwise wind direction counterclockwise wind direction low pressure high pressure warm or cold air air rising or sinking clouds or no clouds clockwise or counterclockwise wind direction winds toward or away from the center low pressure high pressure warm or cold air air rising or sinking clouds or no clouds clockwise or counterclockwise wind direction winds toward or away from the center warm cold rising sinking clouds no clouds counter clockwise clockwise toward away
This is because the air is Therefore, clouds CANNOT form. In a high pressure area, air will (rise, sink) because the air is (less, more) dense. This is because the air is (cold, warm) and (rises, sinks). Therefore, clouds CANNOT form.
This is because the air is In a low pressure area, air will (rise, sink) because the air is (less, more) dense. This is because the air is (cold, warm) and (rises, sinks). Therefore, clouds are LIKELY to form.
There Are Two Kinds of Winds: Global and Local Global Winds are Winds that blow over long distances around the Earth. Local Winds are winds that blow a short distance.
Global Winds
Why Do Different Parts of the Earth Have Different Temperatures? North Pole Equator South Pole Thus, radiation is more intense near the equator compared to the poles. For this reason, it’s warmer near the equator than at the poles.
Global Thermal Temperatures
Air Rises at the Equator Air at the Equator is warm. Warm air rises. The Equator is a Low Pressure area. Warm Air Rises
What Happens to Rising Air at the Equator? At the Equator, air rises; As the air moves upward, it cools, The air begins to turn to move downward. Cold air sinks at the 30o zone. Cool Air Sinks
High Pressure to Low Pressure Winds blow from High Pressure to Low Pressure Low Pressure HIGH PRESSURE Low Pressure HIGH PRESSURE Low Pressure HIGH PRESSURE
Let’s Label High Pressure 90°N Low Pressure 60 °N High Pressure 30°N High Pressure 30°S Low Pressure 60°S High Pressure 90°S
How are winds named? The direction from which they come
Names of Winds IMPORTANT: Winds are named from the direction they come. North winds comes from the north; south winds come from the south. Southeast winds come from the southeast and blow northwest; Northeast winds come from the northeast and blow to the southwest.
Let’s Label Easterlies Polar Easterlies Trade Winds Trade Winds Polar Easterlies
Trade Winds The TRADE WINDS are the winds blowing towards the equator. These winds are Easterlies, blowing from the east. South of the equator, the winds blow from the southeast North of the equator, the winds blow from the northeast. They were named because traders from Europe sailed in these zones on their way to the new world.
Let’s Label Westerlies Prevailing Westerlies Prevailing Westerlies
North is Located in the Westerly Wind Belt
Why Don’t The Winds Blow in Straight Lines? Cold air from both the South Pole and North Pole blows towards the 60o zone But the air doesn’t flow in a straight line
Coriolis Effect Since the earth rotates, winds do not blow directly from north to south or south to north. Winds curve They curve because the earth rotates or spins on its axis. The Coriolis Effect is the curving of winds due to the earth’s rotation.
The ball is going straight, but it looks like it is curving.
Global Wind Animation http://www.geo.hunter.cuny.edu/~tbw/wc.notes/7.circ.atm/animations/GlobalWind.html
Zones of NO WIND Doldrums At the equator, which is 0o latitude, there is a windless zone called the Doldrums. Horse Latitudes At 30o N and 30o S, there is a windless zone called the Horse Latitudes.
Horse Latitudes And The Doldrums Westerlies Horse Latitudes Polar Easterlies Horse Latitudes And The Doldrums Westerlies Horse Latitudes Trade Winds Doldrums Trade Winds Horse Latitudes Westerlies Polar Easterlies
Doldrums Since the Trade Winds blow from both the North and South, a calm zone occurs. This zone is called the “DOLDRUMS.” In this zone, there are no winds. Ships often got stalled for long periods because they needed wind to blow their sails.
Horse Latitudes The Horse Latitudes are zones of calm winds at the 30o Latitude Lines. The term horse latitudes originates from the days when Spanish sailing vessels transported horses to the West Indies. Since there was no wind, the sail ships that entered this zone, would get stuck for weeks. Since water and food shortages occurred, the crews found it necessary to throw their horses overboard.
30o North and South Latitude Sinking air means no clouds or rain. Along this latitude, (between 15o to 35o) many of the major deserts are found This is an area of high pressure. Air from the Equator and from the 60o Latitudes cool and descend at the 30o Latitude. H H
Local Winds Winds that blow short distances and in any direction (depending on pressure) Remember, winds always blow from areas of high pressure to low pressure.
Sea Breeze Land Breeze any wind that blows from a large body of water toward or onto a landmass Land Breeze is the reverse effect: dry land also cools more quickly than water and, after sunset a sea breeze dissipates and the wind instead flows from the land towards the sea