After completing this lesson, you will be able to explain what a local wind is, give some examples of types of local winds, and know where they might be found. A short quiz will follow.
What Is a Local Wind?
Wind is everywhere. It flows through a quiet valley, across every sea, and along coasts and beaches. Wind causes clouds to move over and rain on the city next door or makes your hat blow off and fly down the street.
This of course isn’t to be confused with the kind of wind that causes people to have to hold their noses in crowded classrooms. No, this kind of wind is a flow of the air across parts of the earth.Winds can be global or local.
Global winds travel large distances and fall into general patterns. Trade winds tend to flow diagonally toward the equator, easterlies go west, and westerlies go east. But in today’s lesson, we’re talking about local winds.
Local winds are on a much smaller, nearby scale. Your particular home city might have winds that tend to come from the east during one season and the west during another. Or, it might be totally different. The pattern of typical winds you get in a local area is what we call a local wind. Usually they’re on the scale of tens of miles to hundreds of miles. These winds can be cold or hot, dry or wet. They can be mild and safe or violent and dangerous.
Local winds have a big affect on the weather conditions. They move clouds and moisture around and can make an area wetter or dryer.
Sea and Land Breezes
Let’s go through a few examples. One kind of local wind is a sea breeze. A sea breeze happens because the land and sea are heated differently. During the day, the land heats faster than the sea because it takes the sun longer to warm the entire ocean than just a few inches of land. The land then heats the air above it, whereas the air above the ocean stays cooler.
Warm air is less dense;the particles are spread apart. Because of this, the cold sea air is attracted towards the warm, land air. The particles of the more tightly packed sea air want to spread out into the available space. This causes the air to rush towards the coast. This difference in warming is part of why coastal areas tend not to vary as much in temperature between winter and summer. You can see this effect in the mild weather of San Francisco.The opposite of a sea breeze is a land breeze.
Sea breezes happen during the day, and land breezes happen during the night. The reason is similar; the sea doesn’t cool down at night as quickly as the land. This causes the land to become cooler than the sea, and the cold land air is attracted to the warmer, sea air.
The air rushes out towards the sea, forming a land breeze. Sea and land breezes happen in a consistent day-night cycle.
Valley and Mountain Breezes
Another pair of local winds are valley and mountain breezes, such as those found in Yosemite Valley (or really any mountainous valley).
These two winds also happen one after another in a daily cycle. During the day, the sun heats up the valley’s air, causing it to rise up the sides of the valley (the valley breeze). At night it cools again and descends back down the slope (the mountain breeze).
Area-Specific Local Winds
It’s important to note that not all local winds fit into these particular types: land, sea, mountain, valley. There are plenty of other local winds that are specific to an area. A famous example is southern California’s Santa Ana winds. These are hot, dry winds which blow from the northeast and east across the area.
They carry hot air and dust from the deserts in Arizona and Nevada and happen mostly in autumn and winter. They’re not particularly nice because they dry the area out and make wildfires more likely.
A local wind is a flow of air that tends to happen in a predictable way in a particular, local area. They can be over distances of tens of miles or as much as hundreds of miles. If the scale gets too large, they’re no longer local winds but are global instead.
Examples of local winds include sea breezes, which blow from the sea to the land and keep coastal temperatures more mild, and land breezes, which blow from the land toward the sea, usually at night. Valley breezes cause warm air to rise out of the valley during the day, and mountain breezes return it during the cool of night. A specific example would be California’s Santa Ana winds, which bring hot dry air from the northeast and east into southern California during the autumn and winter. This tends to dry the area further and make wild fires more likely.