![]() The surface albedo can vary between zero (all incident sunlight is absorbed at the surface and none is reflected) and one (all incident sunlight is reflected from the surface and none is absorbed). A quantitative measure of this reflected sunlight is described by the albedo, which is the fraction of sunlight reflected by a surface area to that incident on the surface area in all directions, typically in a given spectral band. Much of this activity can be detected by the changes over time in the amount of sunlight reflected by the Earth's surface at various wavelengths. ![]() Image Credit: Przemyslaw "Blueshade" Idzkiewicz, NASAĪbout 50 million square kilometers of the Earth's terrestrial surface undergo a transition each year from freeze to thaw, thus setting off a series of processes in the global biosphere. And when the South Pole tilts toward the Sun, it’s winter in the Northern Hemisphere. So, when the North Pole tilts toward the Sun, it’s summer in the Northern Hemisphere. Throughout the year, different parts of Earth get the sun’s direct rays. As Earth orbits the sun, its tilted axis always points in the same direction. In this section, we will learn why seasons in the Arctic are so much different than other locations on Earth.įirst of all, we experience day and night because the Earth is always rotating upon its axis, but Earth’s axis is actually tilted at an angle of 23.5 degrees. The flow of energy in the Arctic is heavily influenced by the seasons. When do albedo values change? Seasonal Changes in Earth's Surface Albedo When a surface reflects incoming sunlight, it sends the energy back to space, where it doesn’t affect temperature or climate. A value of 1 means the surface is a "perfect reflector" that reflects all incoming energy.Īlbedo is important to Earth scientists because it plays a significant role in our planet’s average surface temperature. Absorbed solar energy can be used to heat the surface, evaporate water, or, when sea ice or snow is present, melt the surface. A value of 0 means the surface is a "perfect absorber" that absorbs all incoming energy. Albedo commonly refers to the "whiteness" of a surface, with 0 meaning black and 1 meaning white. Blacktop has a much lower albedo than concrete because the black surface absorbs more energy and reflects very little energy.Īlbedo is a non-dimensional, unitless quantity that indicates how well a surface reflects solar energy. You understand the concept of low albedo intuitively when you avoid walking barefoot on blacktop on a hot summer day. Surfaces with low albedos include forests, the ocean, and some urban surfaces, such as asphalt.Īlbedo generally applies to visible light, although it may involve some of the infrared region of the electromagnetic spectrum. Surfaces with high albedos include sand, snow and ice, and some urban surfaces, such as concrete or light-colored stone. A surface with a high albedo will reflect more sunlight than a surface with low albedo. The relative amount (ratio) of light that a surface reflects compared to the total incoming sunlight is called albedo. They both addressed competition with China, national security concerns, and the importance of private-public partnerships.When sunlight reaches the Earth’s surface, some of it is absorbed and some is reflected. Director Panchnathan addressed STEM (science, technology, engineering and math) education investments, technology innovation, and quantum computing. Administrator Nelson answered a variety of questions, including Russia and the International Space Station, the 2025 Artemis Mission to the Moon, climate change, and infrastructure. T22:14:57-04:00 NASA Administrator Bill Nelson and National Science Foundation Director Sethuraman Panchanathan testified before the Senate Appropriations Subcommittee on Science at a hearing on their agency’s fiscal year 2023 budget request.
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