The bigger the difference in temperature, the stronger the wind. For example, hot land temperatures next to cold ocean temperatures will create a stronger sea breeze than land temperatures that are only a little bit warmer than the ocean temperatures.
So during the afternoon when the temperatures differences are normally at their highest, the sea breeze will normally be at its strongest, bringing relief from the heat to beachgoers. This process also works in reverse at night. Only this time it is known as the land breeze. The land breeze is a coastal breeze at night blowing from the land to the ocean.
It is caused by the difference in the rates of cooling of the land and of the ocean. Once again, the bigger the difference in temperature between the two, the stronger the wind. I thought it was just coincidence but there is a scientific explanation for it. It has to do with the relationship between sunlight and air pressure. The sun rises each morning and when it does, the earths surface begins to warm. Solid objects such as roads, sand and rocks absorb the radiation faster and get hotter than liquids as such as large bodies of water, lakes, ponds, the ocean etc..
At the beach, the sand and roads heat up a lot faster and get hotter than the ocean water. This uneven heating of the earth in that location sets up areas of different air pressure zones. The hotter areas being low pressure and the cooler areas being more high pressure. When this happens, the lighter air from the warmer low-pressure zones rises and is replaced by denser, colder air from the high-pressure zones.
In the morning, the sea breeze blows from the ocean towards the beach. In the evening, the situation becomes reversed as the land becomes cooler than the ocean and the winds blow in the opposite direction, towards the ocean. Ugh its the worst.. How much wind is too much when you want to have a fun day at the beach? When winds exceed 15 mph, its usually bordering on the unpleasant.
The winds make it difficult to read, your umbrella might fly off, chairs might be carried away and the sand can be kicked up by the wind, becoming a hazard if it gets into your eyes. Winds below 15 mph can still affect various beach activities. Above the cold-water dish the air cools and becomes denser, leading to a local high air pressure zone. To balance out the air pressure differences the air moves from the high air pressure zone the water dish to the low air pressure zone the sand dish , and the smoke is carried along with it.
If you remove the temperature difference, as you did in your second test, no airflow will be created. In the last test you created a land breeze from the sand to the water, which happens at night when the air flows from beach to ocean.
In this case the sand is cooler than the water, which reverses the airflow due to the changes in air pressure above both the beach and ocean. This activity brought to you in partnership with Science Buddies. Already a subscriber? Sign in. Thanks for reading Scientific American.
Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Key concepts Physics Air pressure Density Heat capacity Temperature Introduction A hot summer day is the perfect time to go to the beach and cool down in the brisk ocean water.
Materials Two same-size baking dishes, preferably glass Sand enough to fill one baking dish Workspace that has no wind Pot Stove Incense stick Lighter Adult helper Ice water Hot water Freezer Large cardboard box optional, if needed to shield any breezes Thermometer optional Preparation Put the sand in a pot, and with the help of an adult heat it on the stove until it is very hot to the touch about 70 to 80 degrees Celsius.
Procedure Place the hot sand in one of the baking dishes. Carefully feel the sand with your fingers. How hot is the sand? Fill the other baking dish with ice water. Feel the temperature of the water with your fingers.
How cold is the water? Put the dishes next to each other at a place where there are no external winds. You can use the cardboard box to shield the dishes from any airflow. Make sure there is no air movement above the dishes. Wind is air in motion. And as you probably know, air is all around us down here on mother Earth. What causes winds to blow and form is the compression of air. But as always, to be able to fully understand something we have to understand something else first.
So lets start by looking at air pressure and what it is. Air pressure describes how air is pressed together, also known as compressed. Imagine a sponge. A big, yellow sponge. When it just sits there on the table it stretches out into its full size. What happens if you squeeze it? If you press it with both your hands into a small ball it becomes hard and solid. So how can this help us understand air pressure?
The air can be compared to a sponge because it can be compressed, or squished in the same way. When air presses down on the air below it, the air molecules gets squeezed closer together. Air compressed is also called high pressure. So you can maybe imagine what low pressure is?
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