Recorded presentation10B.2
Estimates of the precision of GPS radio occultation bending angles from the COSMIC/ FORMOSAT-3 mission
William Schreiner, UCAR, Boulder, CO; and B. Kuo, C. Rocken, S. Sokolovskiy, and D. Hunt
The Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) / Formosa Satellite 3 (FORMOSAT-3) is a six-satellite radio occultation (RO) mission that was successfully launched in mid-April, 2006. An important feature of the COSMIC constellation is that immediately after launch, the six satellites were clustered together in one orbit. During the first months after the launch the separation between each satellite pair was about 1-2 s in time (about 10 km along the orbit) and gradually increased with time. This small separation allowed for pairs of closely collocated occultations from one GPS satellite with almost parallel occultation planes. Thus, this COSMIC cluster mode gives a unique opportunity to estimate the precision of RO by examining the differences of the retrieved parameters from the collocated occultation pairs. An initial analysis of ~4,700 pairs of collocated COSMIC occultations from Apr – Dec 2006 shows an RMS difference of bending angles of about 0.3% at an impact height of 20 km (for tangent point separations less than 10km). Additional results will be presented that consider variations of RO bending angle precision due to impact height, latitude, local time, tangent point separation distance, GPS satellite oscillator type and near real-time versus post-processed analyses. Although the analysis of collocated occultations only provides estimates of precision and not accuracy, results from this study provide RO bending angle error characteristics that will be useful for the assimilation of these data by numerical weather models and also potentially by climate models in the future.
Session 10B, Atmospheric Observations for Weather and Climate: COSMIC—III
Wednesday, 14 January 2009, 1:30 PM-2:30 PM, Room 131C
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