Global GPS radio occultation observations from CHAMP and SAC-C satellites measure atmospheric Doppler shift and bending angle at 1.2 and 1.6 GHz frequencies. Over 200 daily occultation events per satellite provide data at a one-second or better time resolution. The dataset is produced by SCIOPS from Level 1B processing of signals recorded by JPL Blackjack GPS receivers.
Use Cases
- Derive atmospheric refractivity profiles from measured Doppler shift and bending angle data.
- Compute temperature and pressure profiles between 60 km and the troposphere using inverted phase delay measurements.
- Estimate water vapor density in the lower troposphere by combining refractivity data with independent temperature knowledge.
- Validate weather models like NCEP and ECMWF by comparing retrieved temperature profiles for consistency checks.
- Calculate geopotential heights and derived wind fields using independent height and pressure data from occultation events.
Strengths
- Sub-kilometer vertical resolution for atmospheric profiling.
- Sub-Kelvin temperature accuracy below 45 km altitude.
- Over 200 globally distributed occultation events recorded per satellite per day.
Limitations
- Profile derivation assumes local spherical symmetry about the tangent point, which may not hold in all atmospheric conditions.
- Water vapor retrieval in the troposphere requires independent temperature knowledge, adding a data dependency.
- The active data collection period for the specific LEO satellites (CHAMP, SAC-C) is not stated, potentially limiting temporal coverage.
Provenance
- Source
- NASA Earthdata (SCIOPS organization)
- Collection Method
- Signals from GPS satellites setting behind Earth's limb, recorded by JPL Blackjack GPS receivers on CHAMP and SAC-C low-earth-orbiters.
- Time Range
- null
- Freshness
- null
- Geography
- Global coverage from satellite occultations.