Developments Of OPTRAN And Preparation For Its Use To High Spectral Resolution Sounder

1
Developments Of OPTRAN AndPreparation For Its
Use ToHigh Spectral Resolution Sounder

• Yoshihiko Tahara (UCAR, JMA, NCEP)
• Paul van Delst (CIMSS, NCEP)
• John C. Derber (NCEP)
• Larry M. McMillin (NESDIS)
• Xiaozhen Xiong (NESDIS)
• Thomas J. Kleespies (NESDIS)

2
OPTRAN Meets Hardship

• Absorption coefficient prediction
• A large number of equations
• 2,140,200 equations for AIRS 2378 channels
• Hard to validate all
• Numerous coefficients
• 98 Mbytes for AIRS 2378 channels
• A lot of computer resources
• Hard to introduce high spectral resolution
  sensors
• Hard to keep updated
• Hard to be more developed
• More absorbers, more predictors, more layers, etc

3
New Prediction Form

• Coefficients traced over 300 layers by
  polynomials
• Equations reduced by a factor of 1/300
• Coefficients reduced more than 95
• 1 additional atmospheric predictor introduced
• No vertical interpolation

4
Weight to Generate Trans Coef

• Impossible to transfer all information from 300
  equations to one
• Weight enables to transfer the essential
  information.

NOAA/HIRS Ch 3
ln Abs CoefError
Trans Error
Weight
Trans
5
Atmospheric Predictors

• 17 atmospheric predictors
• 2 new predictors
• Q/T2 for wet continuum
• P1/4 for ozone

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Choice of Predictors

• 21778 predictor set possibilities for each gas
  and channel
• Transmittance calculation error is monitored to
  select the best.
• Stability index is introduced to monitor
  computation stability

Validated best predictors
Less than 24 hrs to find best sets for 500 chs
using 10 CPUs on IBM SP4
7
LBL Transmittances

• UMBC atmospheric profiles (for generating
  coefficients)
• 48 profiles
• 101 levels (0.005 -- 1100 hPa)
• CIMSS atmospheric profiles (for independent
  verification)
• 32 profiles
• 101 levels (0.005 -- 1100 hPa)
• Transmittances (Infrared)
• LBLRTM Ver 6.12 with HITRAN2000 AER updates
• 6 angles for each atmos profile
• Sep 2002 AIRS SRFs for AIRS
• Central frequencies generated based upon the SRFs

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Dependent ComparisonNOAA16/HIRS3
S.D.
Bias
9
Independent ComparisonNOAA16/HIRS3
S.D.
Bias
10
Dependent ComparisonAqua/AIRS
S.D.
Bias
11
Independent ComparisonAqua/AIRS
S.D.
Bias
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Design of NWP Experiment

• Start up Oct 1st -- Oct 7th, 2002
• Experiment Oct 8th -- Nov 7th, 2002
• 8-day forecast Every 00 UTC initial in the
  experimental period
• Control run OPTRAN used in the NCEP
  operational NWP system
• Test run New OPTRAN with recalculated bias
  correction tables
• Trans coef CIMSS 45-layer profile set is used
  for BOTH OPTRAN to generate transmittance
  coefficients
• NWP system NCEP global system implemented in
  Oct, 2002
• Resolution reduced to T170L42
• Sat. channels The same as the operational
  except too high peak channels NOAA14/HIRS2MSU,
  NOAA15/AMSU, NOAA16/HIRS3AMSU

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SSI with New OPTRAN
00z Oct 1, 2002
00z Oct 8, 2002
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NOAA16/HIRS3 Tb Comparisons

• No Bias Correction
• 21z Oct 7, 2002 to21z Nov 7, 2002
• Global (90S - 90N)
• No use forCh 1,16,17,18 19
• of samples

S.D. Tb error
Mean Tb error
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• NOAA16/HIRS
• Tb Scan Angle Comp
• 21z Oct 8 - 21z Nov 7
• Red - New OPTRAN
• Blue - Orig OPTRAN

Ch8 - SD
Ch8 - Mean
Ch2 - SD
Ch2 - Mean
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NOAA16/HIRS3 Ch.8
CNTL RUN -- OLD OPTRAN
TEST RUN -- NEW OPTRAN
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NOAA16/HIRS3 Tb Comparisons

• After Bias Cor
• 21z Oct 7, 2002 to21z Nov 7, 2002
• Global (90S - 90N)
• No use forCh 1,16,17,18 19
• of samples

S.D. Tb error
Mean Tb error
18
NOAA16/AMSU Tb Comparisons

• No Bias Correction
• 21z Oct 7, 2002 to21z Nov 7, 2002
• Global (90S - 90N)
• No use forCh 12, 13 and 14
• of samples

S.D. Tb error
Mean Tb error
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NOAA16/AMSU Tb Scan Angle Comp 21z Oct 8 - 21z
Nov 7 Red - New OPTRAN Blue - Orig OPTRAN
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NOAA16/AMSU Tb Comparisons

• After Bias Cor
• 21z Oct 7, 2002 to21z Nov 7, 2002
• Global (90S - 90N)
• No use forCh 12, 13 and 14
• of samples

S.D. Tb error
Mean Tb error
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Impacts on AnalysisMean Diff (8 - 15 Oct)
T 500hPa
TPW
T 200hPa
O3MR 10hPa
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Impact on AnalysisZonal Mean Diff (8 - 15 Oct)
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Impacts of New OPTRAN on Global Fcst
NH 1000 Z
SH 1000 Z
SH 500 Z
NH 500 Z
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Impacts of New OPTRAN on Global Fcst
Trop 850 Vct Wind
Trop 200 Vct Wind
25
AIRS Real-time Tb Comparisons(Preliminary, 20 -
24 Feb)
Ch 28 656.1 SD 0.76 MN 0.16
Ch 253 722.1 SD 0.39 MN 0.29 (clr sky)
Ch 1082 1036.5 SD 0.63 MN 0.33 (clr sky)
Ch 1756 1524.4 SD 1.22 MN 0.44 (clr sky)
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AIRS Real-time Tb Comparison(Preliminary, 20 -
24 Feb)
S.D.
Bias
Num
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Conclusion

• Equations and coefficients in OPTRAN are reduced
  significantly --gt New sensors are welcome.
• Offline validation shows new OPTRAN has
• Around 0.1 deg or less SDs for most channels
• 0.2 0.3 deg SDs for ozone channels
• NWP experiment shows new OPTRAN has
• Better Tb calculation for ozone channels
• Small SD increase in no bias correction Tbs for
  some IR chs,and small SD decrease for some MW
  chs
• Angle dependent variation for low peak IR chs
• Same SDs for bias corrected Tbs
• Some consistent changes in analysis fields
• Positive impact on SH forecast, neutral on NH and
  Trop
• Good results from AIRS preliminary study