GPS RadioOccultation 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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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

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

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GPS radio occultation measurements processing
Raw measurements of phase and amplitude of L1 and
L2
s1, s2, a1, a2
Radio holographic method, Multi path
Bending angles of L1 and L2
Spherical symmetry Satellites orbits.
a1, a2
Bending angle
Single path
a
s1, s2
Refractivity
Ionospheric effect cancellation
N
climatology
Raw measurements of phase of L1 and L2
T, e, P
Auxiliary meteorological data
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Forward Models

• Refractivity

Bending angle
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COSMIC - Status

• COSMIC became operationally assimilated at NCEP
  on May 1st 2007, along with the implementation of
  the new NCEPs 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.