WLWeather Lab NC

Day 12 of 30

Pressure Gradients and Local Winds

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Learning target

I can explain how pressure differences drive wind and reverse local breezes.

Essential question

Why can a coastal breeze change direction after sunset?

Scaffolded notes

Build the idea

1

Wind responds to pressure differences

Air accelerates from areas of relatively higher pressure toward areas of relatively lower pressure. A larger pressure change across the same distance is a stronger pressure gradient and can produce faster wind. Friction and Earth's rotation modify the path.

2

Land and water heat at different rates

During a sunny day, land usually warms faster than nearby water. Air over land warms and rises, creating relatively lower surface pressure; cooler air moves inland from over the water as a sea breeze. At night, land cools faster, and the near-surface flow can reverse as a land breeze.

3

Mountains create daily wind patterns

Sunny mountain slopes warm air during the day, encouraging upslope flow. At night, slope air cools, becomes denser, and drains downhill. North Carolina terrain can also channel and redirect larger weather-system winds.

Stop and explain

Check your thinking

1. What causes the surface sea breeze during the day?

Possible response: Land warms faster, air rises over land, and cooler higher-pressure air moves inland from over water.

2. What does a strong pressure gradient suggest?

Possible response: Potentially stronger wind.

Interactive challenge

Try the science

At noon the land is much warmer than the ocean. Which near-surface wind is most likely?

Before you leave

Exit ticket

Draw or describe the daytime surface wind direction at a beach.