1. GPS Radio-Occultation data (COSMIC mission) Lidia Cucurull NOAA Joint Center for Satellite Data Assimilation

2. COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) 6 Satellites launched in April 15 2006 Three instruments: GPS receiver, TIP, Tri-band beacon Demonstrate quasi-operational GPS limb sounding with global coverage in near-real time Climate Monitoring web page: www.cosmic.ucar.edu

3. GPS Occultation Basic measurement principle: Deduce atmospheric properties based on precise measurement of phase delay and amplitude.

4. Characteristics of GPS RO Data n Limb sounding geometry complementary to ground and space nadir viewing instruments –High vertical resolution (0.1 km surface - 1km tropopause) –Lower horizontal resolution (~300 km) n High accuracy (equivalent to < 1 deg K from 5-25 km) n All weather-minimally affected by aerosols, clouds or precipitation n Independent of radiosonde calibration n No instrument drift n No satellite-to-satellite observational bias

5. GPS radio occultation measurements & processing s 1, s 2, a 1, a 2 s 1, s 2  1,  2  N T, e, P Raw measurements of phase and amplitude of L1 and L2 Raw measurements of phase of L1 and L2 Bending angles of L1 and L2 Bending angle Refractivity Single path Spherical symmetry & Satellites orbits. Ionospheric effect cancellation climatology Auxiliary meteorological data Radio holographic method, Multi path

6. Forward Models: Refractivity: Bending angle:

7. n COSMIC became operationally assimilated at NCEP on May 1st 2007, along with the implementation of the new NCEP’s Global Data Assimilation System (GSI/GFS). n Profiles of refractivity were selected for implementation in operations, while the tuning of the assimilation of bending angles is currently being analyzed at NCEP. n Several impact studies for selected periods show a positive impact in model skill when COSMIC profiles are assimilated on top of the conventional/satellite observations. n UCAR Post-processing GPSRO data from CHAMP (one satellite, ~ 2001) and COSMIC (six satellites) missions can be made available for CFSRR. COSMIC - Status