Application of GPS radio occultation data to weather
analysis and prediction and climate
Richard Anthes
Director, University Corporation for Atmospheric
Research
The atmospheric limb sounding
technique making use of radio signals transmitted by the Global Position System
(GPS) has emerged as a promising approach for global meteorological
observations. As demonstrated by the proof-of-concept GPS Meteorology (GPS/MET)
experiment and more recently by the CHAMP and SAC-C missions, the GPS radio
occultation sounding data are of high accuracy and high vertical resolution. In
late 2005, the joint U.S.-Taiwan COSMIC mission will be launched and is
expected to collect up to 3,000 radio occultation soundings per day. These data
will be available in near real-time for global weather analysis and prediction.
Radio occultation measures
phase and amplitude of the microwave signals emitted from GPS. These
signals are inverted to obtain profiles of signal bending, atmospheric refractivity,
pressure temperature and water vapor. The main purpose of the upcoming COSMIC
mission is to demonstrate the value of these radio occultation products for
weather forecasting and climate monitoring. This presentation will provide an
overview of the COSMIC program, the status of data inversion, and issues
related to assimilating this new data type into weather
models. It will also show some recent results applicable to
climate studies, including gravity wave and tropopause climatology, identification
of bias errors in global NWP models, generation of stratospheric waves by
tropical convection and identification and structure of Kelvin waves, mixed
Rossby-gravity waves and the QBO.
For more information on
COSMIC please see http://www.cosmic.ucar.edu/
.