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The average albedo of Earth is about 0.3. [15] This is far higher than for the ocean primarily because of the contribution of clouds. Earth's surface albedo is regularly estimated via Earth observation satellite sensors such as NASA's MODIS instruments on board the Terra and Aqua satellites, and the CERES instrument on the Suomi NPP and JPSS.
Cloud albedo strongly influences the Earth's energy budget, accounting for approximately half of Earth's albedo. [1] [2] Cloud albedo is influenced by the conditions of cloud formation and variations in cloud albedo depend on the total mass of water, the size and shape of the droplets or particles and their distribution in space. [3]
The Bond albedo is a value strictly between 0 and 1, as it includes all possible scattered light (but not radiation from the body itself). This is in contrast to other definitions of albedo such as the geometric albedo, which can be above 1. In general, though, the Bond albedo may be greater or smaller than the geometric albedo, depending on ...
Earth has an albedo of about 0.306 and a solar irradiance (L / 4 π D 2) of 1361 W m −2 at its mean orbital radius of 1.5×10 8 km. The calculation with ε=1 and remaining physical constants then gives an Earth effective temperature of 254 K (−19 °C). [11] The actual temperature of Earth's surface is an average 288 K (15 °C) as of 2020. [12]
Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution.
The reflected fraction is known as Earth's bond albedo (R), is evaluated at the top of the atmosphere, and has an average annual global value of about 0.30 (30%). The overall fraction of solar power absorbed by Earth is then (1−R) or 0.70 (70%).
is Earth's average albedo, measured to be 0.3. [11] [12] is Earth's average surface temperature, measured as about 288 K as of year 2020 [13] is the effective emissivity of Earth's combined surface and atmosphere (including clouds). It is a quantity between 0 and 1 that is calculated from the equilibrium to be about 0.61.
If we wish to estimate what the temperature of the Earth would be if it had no atmosphere, then we could take the albedo and emissivity of the Moon as a good estimate. The albedo and emissivity of the Moon are about 0.1054 [ 45 ] and 0.95 [ 46 ] respectively, yielding an estimated temperature of about 1.36 °C.