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© Crown copyright Met Office
CAVIARUpdate to Met Office work on field campaignsStuart Newman
Imperial College, 29 March 2011
© Crown copyright Met Office
Contents
This presentation covers the following areas
• New data
• Recent work on Camborne B400 case study
• Improved ARIES profile retrievals
• CAVIAR 1.0 continuum in LBLRTM
• Agreement/discrepancies in continuum coefficients
© Crown copyright Met Office
Recap on ARIES case study data
Campaign Good ARIES nadir data? Good ARIES zenith data?
Camborne (field of view mis-pointing
corrected end 2008)
Jungfraujoch
• Result: lack of data sensitive to the self-broadened continuum in range 800-1200 cm-1
• Also desirable to have night-time data to probe spectrum > 2000 cm-1 contaminated by solar radiation in daytime
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New flights during FAAM detachment to Exeter airport
• CAVIAR evening flight on 7 March
• VACAR-CAVIAR evening flight on 18 March
• ARIES performed mostly ok…
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Very preliminary analysis
Very dry layer
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Very preliminary analysis
Orbits to increase zenith slant path
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Very preliminary analysis
© Crown copyright Met Office
Very preliminary analysis
© Crown copyright Met Office
Very preliminary analysis
Reduce bias with better T-dependence?
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B400 case (18/9/2008) revisited
• Look again at retrieving profile information from ARIES “monomer channels”
• Characteristics of background errors (matrix of error covariances for temperature and humidity) very important
B-matrix Advantages Disadvantages
ECMWF well-tested in NWP inflexible, global average
“toy model” flexible may not be realistic
campaign-specific
directly applicable to case study
need good statistics
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Error covariance estimates from dropsondes and radiosondes
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Error covariance estimates from dropsondes and radiosondes
Large variance in humidity
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Error covariance estimates from dropsondes and radiosondes
Diagonal contains variances 2: level i versus level i
Off-diagonals are covariances ij: level i versus level j
© Crown copyright Met Office
Error covariance estimates from dropsondes and radiosondes
Large variance in humidity near 400 hPa
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Error covariance estimates from dropsondes and radiosondes
Can also compute T-q covariances T(level i) versus q(level j)
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ARIES B400 retrievalsTemperature
© Crown copyright Met Office
ARIES B400 retrievalsHumidity
© Crown copyright Met Office
ARIES B400 retrievalsSpectral channels used (CO2 and H2O monomer)
© Crown copyright Met Office
• So… in theory now have a better baseline profile of temperature and humidity to probe continuum channels
ARIES B400 retrievals
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ARIES B400 foreign continuum
• Obs-calc residuals are within ± 2 K for continuum-sensitive channels (with LBLRTM as simulation using MT_CKD 2.5)
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Continuum coefficientsincluding ARIES Jungfraujoch results
© Crown copyright Met Office
Continuum coefficients
ARIES nadir data from Camborne in better agreement with MT_CKD and Igor/RAL than Jungfraujoch zenith data
outliers
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Continuum coefficients
Satellite (IASI) data from Camborne and Jungfraujoch also in reasonable agreement with MT_CKD and Igor/RAL
outliers
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“CAVIAR 1.0” continuumThanks to Igor for supplying coefficients
Relatively big changes
© Crown copyright Met Office
Putting new CAVIAR continuum in LBLRTM
• Interpolate continuum coefficients to 1 cm-1 resolution (instead of 10 cm-1)
• Replace foreign-broadened and self-broadened (260 K and 296 K) coefficients in range 1280-2500 cm-1 as supplied by Igor
• Seems to run!
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ARIES B400 continuum
1950 cm-1 region stands out
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And finally… far longwave ARIES data
Positive bias < 700 cm-1
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Reference with NPL data
ARIES performance falls off < 700 cm-1
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Summary and things to do
• New profile retrievals using ARIES monomer channels, seems to produce better fit to data
• Water vapour continuum coefficients retrieved from ARIES/IASI nadir data in range 1400-2000 cm-1 are in fairly close agreement with Igor/RAL data, except around 1950 cm-1 where discrepancy is unexplained – able to compare with NPL-FTS data?
• Continuum coefficients from Jungfraujoch data are still smaller; need to reanalyse these data using ARIES retrievals (as above)
• Igor/RAL continuum coefficients included in LBLRTM at 1 cm-1 resolution, this seems to work without slowing down program
• ARIES data at extreme longwave end (overlap with TAFTS) are subject to noise/bias, need to quality control carefully
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Questions and answers
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Field campaign summary:UK (Camborne), Switzerland (Jungfraujoch)
Flight Date Weather conditions Notes
B396 19.08.08 Persistent boundary layer cloud Partial NPL data
B397 22.08.08 Persistent boundary layer cloud Partial NPL data
B400 18.09.08 Good clear sky conditions Sonde chase, good flight
B466 16.07.09 Cloud at times over Jungfraujoch Partial NPL data
B467 19.07.09 Initially thin cirrus which cleared Good NPL data
B468 20.7.09 Good clear sky conditions FLASH sonde + MetOp overpass
B469 25.07.09 Cloud at times over Jungfraujoch Partial NPL data
B470 26.07.09 Some thin cirrus encroaching Good NPL data
B471 27.07.09 Excellent clear sky conditions MetOp overpass
B472 29.07.09 Excellent clear sky conditions ARIES failure
B473 01.08.09 Excellent clear sky conditions No TAFTS
B474 04.08.09 Partial cloud over Jungfraujoch Cancelled am flight, pm only
© Crown copyright Met Office
Very preliminary analysis
© Crown copyright Met Office
“CAVIAR 1.0” continuumThanks to Igor for supplying coefficients