A global analysis of atmospheric refractivity anomalies

In early 2006, the US-Taiwan joint satellite mission known as the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) will launch six Low Earth Orbit (LEO) satellites. These satellites, each equipped with an advanced Global Positioning System (GPS) receiver, will use radio occultation (RO) limb sounding technology to profile the Earth's atmosphere with unprecedented accuracy and vertical resolution. The GPS RO soundings available from COSMIC will make significant contributions to global weather prediction, ionospheric research, and climate monitoring. To demonstrate the potential value of GPS RO data in climate research, we analyzed atmospheric refractivity obtained from GPS RO data in a recent single-satellite German mission, known as the CHAllenging Mini Payload for Geophysical Research and Application (CHAMP). This study examined the refractivity anomalies by altitude and latitude per season of CHAMP GPS RO data, provided by UCAR's COSMIC Data Analysis and Archive Center (CDAAC), from May 2001 through present. Refractivity anomalies across the globe were illustrated in color plots that identified any persistent anomaly patterns. A structure has been identified over the tropical stratosphere from 20-30km, which may possibly have a relationship with the Quasi-Biennial Oscillation (QBO). Results show that GPS refractivity data can be used to identify specific trends between seasons as well as identify multi-year phenomenon such as QBO. This study highlights the usefulness of refractivity values from GPS RO data in climate research.