Albedo in an albedo range of 0.1 to 0.4. The average albedo of Earth is about 0.3. 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. As the amount of reflected radiation is only measured for a single direction by satellite, not all directions, a mathematical model is used to translate a sample set of satellite reflectance measurements into estimates of directional-hemispherical
Incompressible surface Incompressible surface In mathematics, an incompressible surface is a surface properly embedded in a 3-manifold, which, in intuitive terms, is a "nontrivial" surface that has been simplified as much as possible by compressing disks. They are useful for decomposition of Haken manifolds and for normal surface theory. Let "S" be a compact surface properly embedded in a smooth or PL 3-manifold "M", and suppose that there is a disk "D" embedded in "M" such that where the curve ∂"D" does not bound a disk inside of "S". Then "D" is called a compressing disk for "S", and we call "S"