Using GPS data to study gravity waves

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Using GPS data to study gravity waves
Bill Randel ACD
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GPS Radio Occultation
Basic measurement principle Deduce atmospheric
properties based on precise measurement of phase
delay and amplitude.
high vertical resolution!
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Sample of GPS tropical temperature profiles
note enhanced variability above 15 km
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Availability of GPS data

• GPS/MET (1995-1997)
• CHAMP and SAC-C (2001-present)
• COSMIC (2006) (6 satellites)

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Gravity waves observed by GPS/MET
maximum in tropics (see Alexander et al., JAS,
2002)
Tsuda et al., JGR, 2000
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Power spectrum of vertical temperature
fluctuations from GPS/MET
Tsuda and Hocke, 2002
GPS can resolve scales to 0.5 km (or better)
1 km
10 km
0.5 km
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Kelvin waves near the tropopause
eastward traveling Kelvin waves
Randel and Wu, 2005
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Residual temperature variance (small scales)
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Residual variance (small scales)
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Residual (small-scale) wave variance
tropopause
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Residual (small-scale) wave variance
zero wind line
tropopause
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Model simulation of gravity waves forced by deep
convection
Alexander and Holton, 2000
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Gravity waves interacting with a critical level
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Gravity waves interacting with a critical level
critical level
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Residual (small-scale) wave variance
zero wind line
tropopause
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Future COSMIC EQUARS Soundings in a Day
COSMIC EQUARS Radiosondes
GPS radio occultation Data will be available in
2006