Local and Global Winds

• Wind is air flowing from high to low pressure areas.
• Local wind refers to air flowing over a smaller area due to varying air pressures.
• For wind to be considered local, it blows over an area between tens to hundredths of miles wide.

Global Winds

• Uneven heating from the Earth's tilt causes global wind belts.
• Global wind belts occur every 30 degrees in latitude, covering areas greater than 500 miles.
• Global winds include trade winds and prevailing westerlies.

Cause of Local Winds

• Local winds are affected by Earth's heating and land barriers.
• The Earth's surface has structures that the sun heats at different rates.
• Water has a high specific heat, needing much energy to raise its temperature.
• Land heats faster than water, thus the air above it heats faster too.
• Warm air is less dense and rises; cool air is denser and sinks.
• Air pressure and density have an inverse relationship.

Air Pressure and Wind Speed

• Rising air causes lower air pressure; sinking air causes higher air pressure.
• Wind moves from high to low pressure areas, seeking equilibrium.
• The rate of wind movement depends on the pressure gradient.
• High pressure differences result in faster wind speed and vice versa.

Types of Local Winds

• Types of local winds are sea breezes, land breezes, valley breezes, and mountain breezes.
• Sea and land breezes occur on coasts and mountain and valley breezes occur near mountains and valleys.

Sea Breezes

• Sea breezes occur when cool air from the ocean blows toward the land during the day.
• During summer, land heats faster than nearby water, causing air to rise over the land, creating low pressure.
• Cooler air over the ocean replaces the rising air, creating a convection cycle and a sea breeze.
• Coastal temperatures are milder due to water's high specific heat, warming the area in changing seasons.

Land Breezes

• Land breezes are when the wind blows out to the ocean from the land at night and is the opposite of sea breezes.
• The land cools down faster than the ocean at night.
• The air over the land cools and falls (high pressure), while air over the water rises (low pressure).
• Cooler air from the land moves out to the ocean.

Valley Breezes

• Valley breezes occur during the day.
• Valley air heats up faster than mountain air.
• Air over the valley rises, creating low pressure, causing warm air from the valley climbs the mountain.
• During the day, the wind will not be felt in the valley.

Mountain Breezes

• Mountain breezes are when wind flows from the mountain to the valley during the night.
• They are antagonistic to valley breezes, because they work opposite each other.
• The mountain cools down faster than the valley at night.
• Cold air over the mountain sinks and flows down towards the valley.
• The air over the valley is warmer and rises to create a low-pressure area--the cooler air from the mountain swoops down the mountain to the valley.
• At night, the wind will be felt in the valley.

Area-Specific Local Winds

• Some winds do not fit into the categories, as they are caused by gravity over larger than normal regions due to seasonal or storm reasons.

Santa Ana Winds

• Santa Ana winds occur in California, caused by a high-pressure system east of the Sierra Nevada Mountains.
• Air falls down the mountain toward the warmer west coast, picking up speed through mountain chains.
• These winds carry warm, dry air and can cause wildfires after the summer drought season.

Katabatic Winds

• Katabatic winds are found in places like Antarctica and the Scottish Highlands.
• Cold air sinks down mountains or higher elevations due to gravity.

Monsoons

• Monsoons are seasonal and change direction between winter and summer.
• They are larger sea and land breezes, affecting continents like Southern Asia, but are not global winds.

Understand the differences between global and local winds. Explore the causes of local winds, including the impact of Earth's structures and specific heat. Learn how air pressure and density influence wind patterns.