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
- 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.