Dr. Universe: How does land affect the weather? — Isaac, 7, Baltimore, Md.

Dear Isaac,
The surface of the earth is covered in all kinds of landforms. We have tall mountains, deep valleys, wide canyons, and scenic shorelines — I bet you could think of a few others, too. A little less than a third of our planet is land and the rest is mostly ocean. Both affect the weather, said my friend Nic Loyd, a meteorologist at Washington State University.

We get different weather patterns depending on a few conditions, such as how much sun the land gets, if the land is near mountains or ocean, and how air circulates through the atmosphere.

If you are out on the ocean, you might not feel a big temperature difference between night and day. But we do feel a bigger difference in temperature on land. Especially when conditions are clear and calm, the weather can be very warm in the afternoon and chilly by the morning. Loyd explains that land normally warms up and cools down more quickly than water.

You can test this out at home. Fill up one plastic tub with sand or dirt and fill up another plastic tub with water. Put them out in the sunshine. Using a thermometer, take the temperatures of the two tubs every ten minutes for thirty minutes. Record your results to find out which one heated up faster. You may want to try this a few times just to make sure your results are accurate. Water actually absorbs at least as much energy from the sun as the land does —but water just isn’t capable of warming up as fast as land, or in your case, sand or dirt.

The different types of land around the planet also impact the weather. One good example is mountains, Loyd said. The air is usually much colder if you are up high in the mountains. That’s also where we see a lot of glaciers, ice, and snow all year long. In the mountains, the air is thinner and it doesn’t trap in the heat very well.

Exactly what covers that land also influences the weather. Forests, cities, plains, or deserts can absorb a lot of the sunlight that reaches them, warming the air above the land. But when land is covered in snow, much of the sunlight is reflected away instead of being absorbed into the land. This also helps keep snowy areas colder.

So yes, the land, as well as the water, affects the kind of weather we experience on our planet. But the weather can also affect the land. Just think of the rain that helps plants grow on farms. Or the sun that gives plants energy they need to grow. Can you think of other ways the weather might change the land? Can you think of how these changes might shape the land over a long period of time? Send your ideas to Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe