Albedo Defined: How temperatures are affected by the reflectivity of objects

Weather Glossary

Albedo can be defined in many ways, but is used often to describe the reflective nature of snow. Generally speaking it’s an overall measure of how much light is reflected without being absorbed when hitting an object, or the fraction of incoming solar radiation that gets reflected back into space.

How does it work?

Photo courtesy of climate.ncsu.edu

If something has a high albedo, it reflects larger amounts of light energy back into the atmosphere. If something has a low albedo, it absorbs most of the light that hits it. As more light is reflected off an object, the less heat energy it holds. When more light is absorbed, the more the object takes in that heat. Albedo is measured as a unit-less quantity describing how well a surface reflects this solar energy with a number between 0 and 1; 1 being the highest and 0 the lowest. For reference, snow has an albedo of about 0.95 which is almost 1, meaning it has a very high albedo or reflectivity.

As shown in the figure above, color plays a big role in albedo where lighter colors like white have a higher albedo, and darker colors like black have a lower albedo. This is why snow has such a high albedo and reflects most of the light that hits it, and therefore isn’t able to absorb heat as well as other objects.

Why do we care about albedo?

Albedo plays a big role in forecasting temperatures during the winter when there’s snow on the ground as it can drastically drop temperatures to much colder than what models are putting out at night. It can also prevent temperatures from getting too warm during the day since snow is more reflective than an absorber of the sun’s energy. Cloud cover plays also plays a partnering role in forecasting high and low temperatures for an area.

Bright, white clouds play a role in both reflecting energy back into space during the day, while clouds at night keep some of that energy at the surface in as it’s reflected off the ground and back to the clouds where it can’t escape. When no clouds are present and a fresh blanket of snow is on the ground, this can really drop temperatures at night with a process known as radiational cooling. All of these factors come together and affect local temperature fluctuations from day to night.

Ice plays a role in albedo too. For more on albedo and ice, click HERE.

Earth’s Albedo

Albedo not only plays a part of weather forecasting, but plays an even bigger role in the energy distribution and balance around earth! In order for temperatures on earth to remain constant throughout the year, you need the same amount of energy coming in as being released or reflected back into space.

The Earth is constantly trying to maintain a steady balance of incoming and outgoing radiation, much like how the atmosphere is always trying to restore its own balance in the form of temperature fronts and pressure changes; weather that we see every day! Keeping track of Earth’s energy budget is important not only from a climate stand point, but from a weather one too as it can affect how much water is being cycled and evaporated, and therefore affecting large scale precipitation patterns.

Humans have a big effect on albedo, and in turn the overall balance of energy on earth as it affects long term temperature changes. As we continue to change the surface landscape, use transportation, and inflict other changes to the land, this causes an imbalance in how much energy is being absorbed and how much is being reflected away.

Copyright 2021 Nexstar Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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