UARS data levels

The definition of the data levels used to describe the different stages in the processing of UARS data.

Level 0

data are the basic telemetry data from the instruments after time-reversal and decommutation into specific sensor files. Level 0 data have a common format.

Level 1

data are the physical parameters actually measured by the sensors (e.g., atmospheric radiances in the case of the limb sounding instruments). Level 1 data have sensor-specific file formats.

Level 2

data are the geophysical parameters calculated from Level 1 data, such as atmospheric temperature profiles, gas concentrations, winds, or solar spectral irradiances. Atmospheric data at Level 2 are related directly to the instrument measurement "footprint", i.e., the character of the altitude scan is determined by a given instrument's scan rate, integration time, and viewing direction, as well as the spacecraft's orbital velocity. Level 2 data also have sensor-specific file formats.

Level 3A

atmospheric data reflect the geophysical information of Level 2 transformed into a common format and equally spaced along the measurement trajectory in time ("Level 3AT", at 65.536 second centers) or latitude ("Level 3AL", every four degrees). Level 3A data have common file formats.

Level 3B

atmospheric data consist of two daily latitude-longitude cross sections at approximately one-half scale height altitude intervals. (The two cross sections reflect segregation by north-going and south-going satellite data, which differ by 12 hours local time at the Equator.) These data are stored as 13 Fourier coefficients for each height around the latitude circles defined by Level 3AL. Level 3B data also have a common file format.