© Crown copyright Met Office CAVIAR ARIES water vapour continuum results Stuart Newman Reading, 6...
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Transcript of © Crown copyright Met Office CAVIAR ARIES water vapour continuum results Stuart Newman Reading, 6...
© Crown copyright Met Office
CAVIARARIES water vapour continuum resultsStuart Newman
Reading, 6 December 2010
© Crown copyright Met Office
Contents
This presentation covers the following areas
• New ARIES instrument line shape
• Monomer/continuum channel selection
• ARIES profile (water vapour) retrievals
• Continuum coefficients, compare with Igor’s data
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ARIES instrument line shapeRetrieved from high S/N nadir-viewing data
• Important to represent ILS when convolving simulation to compare with measured radiances
• ILS becomes more non-ideal towards higher wavenumbers
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Retrieval method as means of reducing profile uncertainties
• Uncertainties of order of 10% in absolute water vapour amounts are a problem when attempting to retrieve continuum strengths from ARIES data
• Bayesian retrieval of water vapour profile from a good first guess and using ARIES spectral information can potentially reduce uncertainties
• Don’t want to use same (continuum) channels in water vapour retrieval as are used to derive continuum strengths
• Therefore define set of channels in ARIES spectrum that are sensitive to H2O monomer lines but not too sensitive to H2O continuum (assumes spectroscopy errors are minor for monomer lines)
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Channel selection
Dry case, IWV = 0.5 kgm-2
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Channel selection
Moist case, IWV = 3.6 kgm-2
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Channel selection
Go ahead and use these 109 channels in retrieval
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Uplooking Jacobians
• Decreasing water vapour amount with height means all Jacobians are peaked just above the observation height
• Use Jacobians for water vapour retrieval using monomer lines only
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ARIES retrievals - results
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ARIES retrievals - results
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CAVIAR casesContinuum coeffs
• Derive continuum strength, compare to MT_CKD model in LBLRTM
• Re-do LBLRTM simulations using ARIES (monomer line) water vapour retrievals
If ARIES measures lower emission than LBLRTM/MT_CKD implies smaller continuum coefficient
If ARIES measures higher emission than LBLRTM/MT_CKD implies larger continuum coefficient
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Continuum coefficients
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Continuum coefficientsincluding ARIES Jungfraujoch results
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Need to consider self continuum?
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Self/foreign contribution
Dry case, IWV = 0.5 kgm-2
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Self/foreign contribution
Moist case, IWV = 3.6 kgm-2
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Summary and things to do
• ARIES instrument line shape has been revised for convolving simulated radiances to compare with measured radiances
• Using H2O monomer lines in ARIES spectrum to constrain/retrieve humidity profile seems to be practical way of dealing with uncertainties in profile measurements
• Foreign-broadened continuum coefficients seem to be biased low compared to Igor’s results with RAL data
• Even towards the edges of 2 band it appears that self continuum can be neglected for “high dry” Jungfraujoch cases, i.e. can fit to foreign-broadening coefficient directly
• Same approach on monomer line retrievals can be extended to other cases (B400 ARIES/IASI nadir spectra)
• Including temperature as well as humidity in ARIES retrievals may change results - priority
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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