Wind

What is Wind? Wind is the movement of air from a region of high pressure to a region of lower pressure. These areas of high and low pressure are created from temperature differences caused by the sun heating the earth, which in turn heats the atmosphere. Air moves from high to low pressure area -so- The lower the pressure area the stronger the wind.

Local winds are... Winds that blow over short distances Caused by unequal heating of the earth’s surface within a small area Form only when no winds are blowing from far away

Sea (large open water) Breeze onto Land: Land heats more quickly during day than the adjacent water. A sea-breeze is formed by increasing temperature differences between the land and water which create a pressure low over the land due to its relative warmth and forces higher pressure, cooler air from the sea to blow onto the land..

Land Breeze from sea or a Lake At night, the land cools off quicker than the open water. If the land cools below that of the adjacent open water, the pressure over the water will be lower than that of the land. This creates a land breeze flowing back out towards the open water.

Valley Breeze: (occurs mainly in afternoons) During the day, sunlight warms valley walls, which warm the air in contact with them. The heated air rises and forms the valley breeze As the warm air rises and cools over the mountains, clouds may form from the warm moist air condensing..

Mountain Breeze: (occurs evenings and night) This wind is formed at night by the cooling along mountainsides. As the slopes become colder than the surrounding atmosphere, the air closest to the mountainside cools and drains down into the valley. The cool air sinks and forms mountain breeze.

Global Winds Global winds blow steadily from a specific direction over long distances The movement air makes between the equator and the poles produces global winds.

Air Movement (AKA wind) on planet Earth:

Here are the global winds in motion… Notice that air rises and sinks as it heats and cools in three separate systems. –The prevailing westerlies rise in a different direction than the trade winds and polar easterlies! The earth also spins, creating the direction the winds move on the surface of the earth. In simple terms, as air begins flowing from high to low pressure, the Earth rotates under it, making the wind follow a curved path. That is why on a 1 dimensional map, the arrows of the global winds are curved. Global wind patterns

What are the trade winds? The trade winds are air movements toward the equator moving from east to west. They are warm, steady breezes that blow almost continuously. For hundreds of years sailors (and pirates…arg!) used them to sail their ships from Europe to South America and the West Indies.

What are the prevailing westerlies? Between thirty and sixty degrees latitude, the winds that move toward the poles appear to curve to the east. Because winds are named from the direction in which they originate, these winds are called prevailing westerlies. Prevailing westerlies in the Northern Hemisphere are responsible for many of the weather movements across the United States and Canada. That is why we look at the weather happening in California to help predict our weather

What are the polar easterlies? Cold air near the poles sinks and flows back toward lower latitudes. The polar easterlies meet the prevailing westerlies at about 60° north at south latitudes, along a region called the polar front. The mixing of warm and cold air along the polar front has a major effect on weather changes in the United States. Again, because these winds begin in the east, they are called easterlies.

What are the doldrums? The doldrums is an area of calm weather. The trade winds coming from the south and the north meet near the equator. These converging trade winds produce general upward winds as they are heated, so there are no steady surface winds.

What are the horse latitudes? The horse latitudes is another belt of calm air. Warm air that rises at the equator and moves toward the poles stops moving and sinks in this area. Hundreds of years ago, sailors stuck in this area where wind doesn’t blow ran out of food and water for their horses and had to throw the horses overboard. That is how the area got the name “horse latitude”.

The Jet Stream Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. The winds blows from west to east in jet streams but the flow often shifts to the north and south. Jet streams follow the boundaries between hot and cold air. Since these hot and cold air boundaries are most pronounced in winter, jet streams are the strongest for both the northern and southern hemisphere winters

Measuring Wind Wind is measured with a tool called the Anemometer. Beaufort Wind Scale- this scale is used as an indication of how strong winds are. Take a look at how winds are rated.Beaufort Wind Scale

Now let’s measure our own wind… Take your homemade ghetto fab anemometer outside and measure the wind in a few places. I want you to investigate how buildings and the surrounding landscape affect how much wind you get.