2.4: Reflection, Albedo, and Land Cover
- Page ID
- 39712
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Radiation that isn’t absorbed by the atmosphere is either absorbed by the surface of the earth, reflected by the surface of the earth, or reflected by clouds. With the exception of some surface covers, which we will cover below, the Earth’s surface absorbs almost 100% of the radiation that reaches it. However, many objects both in the atmosphere and on Earth’s surface are good reflectors of sunlight. Every object has a property called Albedo that represents the percentage of sunlight it reflects. While you can measure albedo by calculating the ratio of sunlight reflecting off an object to sunlight hitting the object, you can actually estimate the albedo simply by looking at how dark/light colored the object is. If you’ve ever worn a dark-colored t-shirt, or driven in a car with dark interiors, you probably know that dark objects don’t reflect much of the sunlight that hits them… and thus have a low albedo. Objects with a low albedo absorb the radiation instead, causing them to heat up. On the other hand, if you’ve ever gone skiing and been snow-blinded, or had a bad sunburn, you probably know that light-colored objects have higher albedos, thus reflecting sunlight and keeping them cool. A simple guide to albedo is found in Figure \(\PageIndex{1}\).
Simply put, the lighter an object's color is, the higher the albedo. Let's put this to the test. Figure \(\PageIndex{2}\) is a typical snow-covered mountainside and Figure \(\PageIndex{3}\) is a typical building in an urban area.
Figure \(\PageIndex{2}\): A snow capped mountain (Public Domain; Wikimedia Commons)
- Ice and Snow, like what is pictured in \(\PageIndex{2}\), would likely have a __________________ albedo.
- High
- Middle
- Low
- On the other hand, urban areas, such as the one pictured in \(\PageIndex{3}\), most likely have a _____________________ albedo.
- High
- Low
We know that objects that reflect sunlight are cooler while objects that absorb sunlight are warmer
- Therefore, urban areas are likely going to be ______________ than ice-covered locations.
- Warmer
- Colder
The phenomenon covered above is called the Urban Heat Island Effect.