Observing small-scale waves with satellite nadir and limb techniques

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Observing small-scale waves with satellite nadir
and limb techniques

• Dong Wu

NCAR gravity wave retreat, 26-30 July
2006, Boulder, CO
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Key Questions Associated with Satellite
Observations
Radiance I'

• What atmospheric variables (e.g., T, ?, ?electron
  clouds) cause radiance fluctuations?
• What wave scales are these instruments sensitive
  to (i.e., visibility function, smoothing, cutoff,
  noise)?
• How can these observations be used to improve
  model physics and parameterization (e.g., wave
  source, propagation, breakdown)?

Atmosphere T', ?', u', v'
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Convolution Between Small-Scale Waves with Sensor
Weighting Functions
e.g. AIRS, AMSU
Waves
(A) Nadir or Slant Path

• good horizontal resolution
• limited vertical resolution
• sensitive to waves of large lz/lh ratios in T
• instruments e.g., AMSU-A, AIRS, SSMIS

e.g. MLS
(B) Limb and Opaque Path

• good horizontal resolution
• limited vertical resolution
• sensitive to waves of moderate lz/lh ratios in T
• instruments e.g., MLS

Waves
(C) Limb and Transparent Path
e.g. CLAES, GPS
Waves

• good vertical resolution
• limited horizontal resolution
• sensitive to waves of small lz/lh ratios in ?
• instruments e.g., LIMS, CRISTA, GPS,
• SABER, MLS, CLAES, HIRDLS

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Instruments for T Sounding (Types A and B)
MLS UARS (1991-1997) Aura (2004-)
AMSU-A N-15 (1998-) N-16 (2000-) N-17
(2002-2004) N-18 (2005-) Aqua (2002-)
AIRS (Aqua 2002-)
UARSMLS
Possible cloud contamination
Temp Weighting Func
Temp Weighting Func
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21 Jan. 2003
80 hPa
40 hPa
Jet Streaks over N. Atlantic
20 hPa
10 hPa
Wu and Zhang (JGR 2004)
5 hPa
2 hPa
80 hPa, 14 Jan. 2003
Mountain Waves over Scandinavia
Eckermann et al. (ACPD 2006)
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AMSU-A radiance variance at 5 hPa for June-Aug
2003
Wu et al (ASR 2006)
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Gravity wave dispersion relation
AIRS
TES (nadir)
Aura MLS
UARS MLS
AMSU-A
CRISTA-1
?
?
Mountain Waves
CLAES (1 profile)
Convectively generated waves
GPS (1 profile)
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GPS/CHAMP 50-Hz Data
Raw data
Receiver power
L1 Phase Delay
E-region irregularities
Iono-free phase
L1 phase
SNR
Perturbations
Neutral atmos. irregularities
Iono-free phase
SNR
L1 phase
Wu et al. (JASTP, 2005)
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GPS/CHAMP Variances for July 2002
Receiver power
L1 Phase Delay
L2 Phase Delay
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CHAMP variances in the upper troposphere and
lower stratosphere
Receiver power
L1 Phase Delay
Short-scale components
28km
25km
Long-scale components
22km
18km
2001
2003
2005
2007
2001
2003
2005
2007
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CHAMP variances in the E-region ionosphere
Receiver power
L1 Phase Delay
120km
Variations are stronger in NH than in SH.
Annual variations dominate
100km
QBO variations make the variances stronger in NH
2003 and 2005 in SH 2002 and 2004.
80km
60km
Effects of the 11-year solar activity are evident
mostly at latitudes gt 60.
2001
2003
2005
2007
2001
2003
2005
2007
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The Quasi-Biennial Oscillation
Baldwin et al. (1999)
UARS HRDI winds
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Discussions

• Consistency among observations
• CRISTA, MLS, LIMS
• MLS, AMSU-A, AIRS
• GPS, radiosonde
• MLS, GPS
• Observational constraints on model parameters
• GCM
• Mesoscale models
• Sampling issues and statistics of transient
  processes

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Backup materials
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• Multiple wave sources
• Filtering at different altitudes

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Figure 3a GPS/CHAMP January 2002
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Figure 5 GPS/CHAMP July 2002
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Gravity waves excited by typhoons
Chen et al. (2006)
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AIRS Radiance perturbations
13 Jan 2003
Waves excited by convective storms
14 Jan 2003
15 Jan 2003
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Study of gravity waves with extended ARPS
(Limpasuvan et al. 2006)
T after convolved with AIRS wfunc
AIRS T
Simulated T
24 January 2005
Estimated ltuwgt
Mean wind before
Mean wind after