Bill Burton: It's time for us to take a look at the Science Behind the Forecast. I'm joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.
Tawana Andrew: Good morning. Today's topic is something that we kind of overlook when it comes to our daily weather.
BB: We can overlook it because they seem to be there almost all the time, right above our heads. Well above our heads in some cases. We're talking about clouds today. What do we need to know about clouds?
TA: We know that the sunlight is always beaming down towards the earth, right? So if the skies are clear, then more heat is reaching the ground, typically leading to warmer temperatures. But on cloudy days, those clouds reflect the sun's light right back into space, keeping a lot of that solar energy away from the surface and having overall a net cooling effect. So it's been found that clouds reflect 30 to 60% of the sunlight that hits them. Which is why they appear white, because of all of that light that they are reflecting. But at night, clouds have a net warming effect. Think having a blanket over you, how it traps that heat? Same thing with the clouds at night, because it traps the heat and re-emits that heat towards the planet's surface. That is why, with clear skies, you typically have cooler temperatures at night, because that heat is easily radiated back into space.
Now, not all clouds are going to keep you cooler, though, because high altitude clouds, cirrus clouds, the thin, wispy ones that kind of look like strips of cotton candy? Those are typically colder than what's found closer to the Earth's surface, and these upper level clouds actually work very well at trapping heat and radiating less of that heat into space. So overall, they have a net warming effect. And one study found that these clouds can increase temperatures by as much as 13 degrees Fahrenheit.
BB: 13 degrees? That's a pretty significant change.
TA: Exactly. Because it's letting some of that solar radiation in, but it's trapping it from getting back out, and then you're just kind of stuck with all of that heat there. But the lower level warm clouds actually release more energy than the cold, high altitude clouds. And without these low level clouds, the planet would actually lose nearly the same amount of energy as it does to space with these clouds in place. They really don't have that much of a difference when it comes to overall temperatures across the entire planet, but during the day, those low, thick clouds, so think stratus clouds, those gloomy, kind of gray clouds, those can reflect up to 90% of light. While high, thin clouds, like the cirrus clouds that we talked about, may reflect as little as 10% of incoming radiation. So the clouds you have overhead, play a big role. And keep in mind that clouds overall have a net cooling effect of nine degrees Fahrenheit on our climate. So, they're pretty important, and summer would be really tough without them.
BB: Let's hear it for clouds! And now we understand just how critical clouds are to everything about the planet, thanks to this edition of Science Behind the Forecast with WAVE 3 meteorologist Tawana Andrew. Thanks for the knowledge, Tawana.
TA: Of course.
