GPS Radio-Occultation data (COSMIC mission)
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GPS Radio-Occultation data (COSMIC mission) Lidia Cucurull NOAA Joint Center for Satellite Data Assimilation
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GPS Radio-Occultation data (COSMIC mission). Lidia Cucurull NOAA Joint Center for Satellite Data Assimilation . COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate). - PowerPoint PPT Presentation
Transcript of GPS Radio-Occultation data (COSMIC mission)
GPS Radio-Occultation data (COSMIC mission)
Lidia Cucurull NOAA
Joint Center for Satellite Data Assimilation
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
GPS Occultation
Basic measurement principle:
Deduce atmospheric properties based on precise measurement of phase delay and amplitude.
Characteristics of GPS RO Data
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)
High accuracy (equivalent to < 1 deg K from 5-25 km) All weather-minimally affected by aerosols, clouds or precipitation Independent of radiosonde calibration No instrument drift No satellite-to-satellite observational bias
GPS radio occultation measurements & processing
s1, s2, a1, a2
s1, s2
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 cancellationclimatology
Auxiliary meteorological data
Radio holographic method, Multi path
Forward Models:
Refractivity:
€
N = 77.6 PT
+ 3.73×10−5 PwT 2
Bending angle:
)()(
ln2)( 2/122
nrx
dxaxdxnd
aaa
=
∫ −−=
∞
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).
Profiles of refractivity were selected for implementation in operations, while the tuning of the assimilation of bending angles is currently being analyzed at NCEP.
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.
UCAR Post-processing GPSRO data from CHAMP (one satellite, ~ 2001) and COSMIC (six satellites) missions can be made available for CFSRR.
COSMIC - Status
