| Popis: |
The EPIC instrument onboard the DSCOVR spacecraft, located near the Earth-Sun gravitational plus centrifugal force balance point, Lagrange-1, measures Earth reflected radiances in 10 wavelength channels ranging from 317.5 nm to 779.5 nm. Of these channels, four are in the UV range 317.5, 325, 340, and 388 nm, which are used to retrieve O3, 388 nm scene reflectivity (LER Lambert Equivalent Reflectivity), SO2, and aerosol properties. These quantities are derived synoptically for the entire sunlit globe from sunrise to sunset every 68 minutes or 110 minutes for summer or winter at the receiving antenna in Wallops Island, Virginia, respectively. Depending on solar zenith angle, either 317.5 or 325 nm channels are combined with 340 and 388 nm to derive ozone amounts. As part of the ozone algorithm, the 388 nm channel is used to derive LER. The retrieved ozone amounts and LER are combined to derive the erythemal irradiance for the sunlit Earth's surface at a resolution of 18 × 18 km2 near the center of the Earth's disk using a computationally efficient approximation to a radiative transfer calculation of irradiance. Corrections are made for altitude above sea level and for the reduced transmission by clouds based on retrieved LER. |
