© Crown copyright Met Office CAVIAR Update to Met Office work on field campaigns Stuart Newman Imperial College, 29 March 2011

© Crown copyright Met Office

CAVIARUpdate to Met Office work on field campaignsStuart Newman

Imperial College, 29 March 2011


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


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


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…


Very preliminary analysis

Very dry layer



Orbits to increase zenith slant path







Reduce bias with better T-dependence?


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


Error covariance estimates from dropsondes and radiosondes



Large variance in humidity



Diagonal contains variances 2: level i versus level i

Off-diagonals are covariances ij: level i versus level j



Large variance in humidity near 400 hPa



Can also compute T-q covariances T(level i) versus q(level j)


ARIES B400 retrievalsTemperature


ARIES B400 retrievalsHumidity


ARIES B400 retrievalsSpectral channels used (CO2 and H2O monomer)


• So… in theory now have a better baseline profile of temperature and humidity to probe continuum channels

ARIES B400 retrievals


ARIES B400 foreign continuum

• Obs-calc residuals are within ± 2 K for continuum-sensitive channels (with LBLRTM as simulation using MT_CKD 2.5)


Continuum coefficientsincluding ARIES Jungfraujoch results


Continuum coefficients

ARIES nadir data from Camborne in better agreement with MT_CKD and Igor/RAL than Jungfraujoch zenith data

outliers


Continuum coefficients

Satellite (IASI) data from Camborne and Jungfraujoch also in reasonable agreement with MT_CKD and Igor/RAL

outliers


“CAVIAR 1.0” continuumThanks to Igor for supplying coefficients

Relatively big changes


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!


ARIES B400 continuum

1950 cm-1 region stands out


And finally… far longwave ARIES data

Positive bias < 700 cm-1


Reference with NPL data

ARIES performance falls off < 700 cm-1


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


Questions and answers


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




“CAVIAR 1.0” continuumThanks to Igor for supplying coefficients

Documents

© Crown copyright Met Office CAVIAR Update to Met Office work on field campaigns Stuart Newman Imperial College, 29 March 2011