Use of GPS Radio Occultation Data for Climate Monitoring

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Use of GPS Radio Occultation Data for Climate
Monitoring

• Y.-H. Kuo, C. Rocken, and R. A. Anthes
• University Corporation for Atmospheric Research

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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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Radio occultation for Climate
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Radiosonde Stations and Manufacturers
Vaisala/Australia IM-MK3/India
Shang/China MEISEI/Japan Mars/MRZ VIZ
AIR
Others
From Junhong Wang
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Quantifying Regional Differences

• Calculate the mean absolute difference in
  refractivity between CHAMP and Radiosondes (NCR)
  between 5 25 km.
• Calculate the corresponding mean of the absolute
  value of the difference in refractivity between
  CHAMP and the ECMWF (NCE)
• Perform calculation using radiosonde data from
  different regions of the world from June 2001 to
  March 2004.

From D.Rossiter (UCAR Summer Student)
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Statistics of CHAMP - Radiosonde Comparison
Fractional Refractivity Differences between 5
25 km
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Climate change to doubling CO2

• Perhaps the most accurate and stable global
  thermometer for estimating climate change
• Most accurate where model-predicted temperature
  changes are large in upper troposphere and lower
  stratosphere

Meehl et al. 2000, J. Climate.
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GPS - NCEP/NCAR reanalysis refractivity
difference at 300 mb
Northern Hemisphere
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GPS - ECMWF analysis refractivity difference at
300 mb
Northern Hemisphere
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GPS - radiosonde refractivity difference at 300 mb
Northern Hemisphere
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GPS - NCEP/NCAR reanalysis refractivity
difference at 300 mb
Southern Hemisphere
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GPS - ECMWF analysis refractivity difference at
300 mb
Southern Hemisphere
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GPS - radiosonde refractivity difference at 300 mb
Southern Hemisphere
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Temperature change as detected by GPS RO
300 mb
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Temperature change as detected by GPS RO
50 mb
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Temperature change as detected by GPS RO
10 mb
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COSMIC (Constellation Observing System for
Meteorology, Ionosphere and Climate)

• 6 Satellites launched in late 2005
• Three instruments
• GPS receiver, TIP, Tri-band beacon
• Weather Space Weather data
• Global observations of
• Pressure, Temperature, Humidity
• Refractivity
• Ionospheric Electron Density
• Ionospheric Scintillation
• Demonstrate quasi-operational GPS limb sounding
  with global
• coverage in near-real time
• Climate Monitoring

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COSMIC Status
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GPS radio occultation missions
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Distribution of GPS Occultation events in 24 hrs
with EQUARS (2006, inclination anglelt20o) and
COSMIC (2005, 6 LEO satellites at 72o)
COSMIC

Dense data rate in equatorial region
Global coverage, but less data at low latitudes