PITTSBURGH (KDKA) — When you go to the beach, you may notice in the afternoon, how the wind blows off the water toward the land.
If you stay at the beach until nighttime, you may also notice how the opposite is true. This is because of the sea breeze or lake breeze, and the land breeze. So what is going on?
First we need to realize it takes a lot more energy to heat up water than it does to heat up land.
This means you get hot spots and cooler spots developing right next to each other, since they take different amounts of time to warm up and cool off.
As the land heats up more quickly than the water, you create an area of low pressure.
This causes the air above the land to rise, because it is warmer.
Since that warm air is rising, the cooler air is pulled off of the water, where the air pressure is higher, to fill the empty space where the warmer air once was.
This causes “sea breezes” or “lake breezes”, since the wind is coming off the water.
At night, since the land cools off quickly, that means the water is warmer, so the opposite is true.
Low pressure forms over the water, while the land’s air pressure stays higher.
This creates a “land breeze”, since the wind is coming off the land.
This is an easy experiment to do at home.
All you need is sand, water, similar-sized baking dishes, a stick of incense (get one that has a smell you enjoy), a heat source, a freezer and a responsible adult.
First off, bake some sand in the oven until it warms up.
It only needs to get to 90° to 100°F.
You can also heat the sand in a pot, then put it in a dish.
This might make the experiment a bit messier, though.
Place the dish with the hot sand right next to a dish with water and ice.
Now, light the incense, and hold it closely between the two dishes.
When doing this, make sure there is no wind coming from a different source.
You should see the smoke from the incense blow toward the hot sand, since the air is rising on that side, thanks to the heat and low pressure.
You can do this experiment the other way, too.
You can chill some sand in the freezer.
Place the cold sand in a dish.
Now, put hot water in the other dish.
Now which way does the smoke from the incense blow? You should see it favor the water, since the air above that is rising, creating the low pressure there.
When you clean up, make sure you don’t rinse sand down the drain.
It could cause plumbing problems, and I don’t want to do a “Hey Ray, How Come My Drain Is Backing Up” experiment!