Winds

Did you know… Alaska is the windiest state. The fastest “regular” wind was 231 mph (372 kph), recorded at Mount Washington (NH), on April 12, 1934. During a May 1999 tornado in Oklahoma, researchers clocked the wind at 318 mph (513 kph).

winds are named for the direction they come FROM. Why air moves… **wind is the horizontal movement of air from HIGH pressure (sinking air) to LOW pressure (rising air) unequal heating by the Sun (called insolation) creates unequal air pressure. the greater the pressure/temperature difference, the faster the wind moves. winds are named for the direction they come FROM.

Question: Would there be winds if the Earth’s surface were the same temperature everywhere? Explain. NO—air moves from high to low pressure

**Measuring Winds anemometer=wind speed windsock=wind direction & speed (not as accurate) wind vane= wind direction

Beaufort Scale (don’t memorize)

Cooling effect of wind Wind Chill Chart

Pressure Belts Convection (Hadley cells) Currents the equator receives more direct sunlight/heat so low pressure is created (warm air rises), & then moves toward the cold poles where it cools & begins to sink. the poles receive a lot less sunlight/heat so high pressure is created (cool air sinks), this cold sinking air moves toward the equator. convection cells occur every 30° latitude.

Convection cells occur every 30° latitude from the equator (0°)

The Doldrums At the equator (0°) winds do not blow, this is due to an area of low pressure (rising warm air) caused by tropical temperatures.

Trade Winds Located between 0°-30° north and south of the equator. These winds blow from 30° almost to 0° (equator). These winds were called trade winds because they were used by early merchants and sailors; although their proper name is tropical easterlies.

Horse Latitudes Occur at 30° north and south of the equator. In this high pressure area winds are very calm. This is where most of the words deserts are located due to sunny skies, calm winds, & dry air.

Prevailing Westerlies Located between 30°-60° north and south of the equator. Wind belts found here flow toward the poles from west to east carrying warm air. These winds influence weather in the United States.

Polar Easterlies Located between 60°-90° north and south of the equator. Polar easterlies form due to cold sinking air that is moving from the poles to 60° latitude creating cold temperatures.

Jet Streams Fast flowing, high-speed (75-125mph), narrow streams or bands of air located 10 kilometers above Earth’s surface. The jet streams separate warm air from cold air

Global Winds

Coriolis Effect ~ water and air appear to flow to the right in the northern hemisphere and the left in the southern hemisphere due to the Earth’s rotation

Local Winds Local wind happen due to local geographic features such as shorelines and mountains etc. ex: sea and land breeze (handout) due to day/night heating ex: mountain and valley breeze due to differences in temperature AND elevations

Sea breeze (top) Land breeze (bottom) H L H

Sea Breeze (day)

Land Breeze (evening)

Land/sea breeze animation Land/sea breeze (animated website)

Water has a very high SPECIFIC HEAT (takes a lot of thermal energy to increase the temperature of water)— (water heats and cools very slowly, while sand (low S.H.) heats and cools quickly)

Questions In which direction does a sea breeze move? toward the land In the atmosphere, what happens in a convection current? warmer air rises and cooler air sinks Land absorbs radiation from the sun slower than water. faster than water. at the same rate as water. almost never.

What pressure combination produces global winds What pressure combination produces global winds? _______-pressure polar air and _____-pressure equatorial air high, low What is mainly responsible for the unequal heating of Earth’s surface? the material on Earth’s surface (like water compared to sand)

What makes global winds curve rather than move in straight lines? Earth’s rotation on its axis (Coriolis) ____________ winds blow almost constantly in predictable directions. global Warm air has _______ pressure and _____ density. low, low

Questions If global winds moved north and south in straight lines, you could conclude that Earth did not rotate on its axis Water absorbs radiation from the sun more slowly than land. faster than land. at the same rate as land. almost never.