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CAVIAR field campaigns updateStuart Newman

UCL, 13 May 2010

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Initial continuum results from Jungfraujoch flights

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Summary of flightsFlight Date Weather conditions Comments

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

* Institute of Applied Physics in Bern launch radiosondes from Payerneequipped with RS92, Snow White and FLASH-B (Lyman-alpha) hygrometers

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Can we use FWVS data?

Dropsondes are widely recognised as most accurate source of humidity data from the aircraft

However, for runs immediately after a profile descent (e.g. 35000 ft down to 15000 ft) FWVS may be more representative

Attempt to use FWVS humidity data in LBLRTM simulations of ARIES at 15000 ft

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CAVIAR exampleB467 19-Jul-2009

• Initial run at high level for radiance measurements (here looking up)

• Spiral descent over Jungfraujoch observatory measuring in situ water vapour (rapid response FWVS probe used here)

• Subsequent run at lower level for radiance measurements (here looking up)

• Determine change in radiance due to water vapour in atmospheric path

• Derive continuum strength, compare to MT_CKD model in LBLRTM

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CAVIAR exampleB467 19-Jul-2009

• Consistent discrepancy in centre of water vapour band for channels at 1586 and 1598 cm-1 (MT_CKD continuum is relatively strong at 1586 cm-1 compared with measurements)

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Humidity information from MARSS

• Helpful to constrain humidity above the aircraft using microwave observations at 183 GHz

Microwave Airborne Radiometer Scanning System (MARSS)

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MARSS humidity channels

B467 (19/7/09)Good agreement for channel centred closest to 183 GHz line

B471 (27/7/09)Worse agreement for channel 183±1 GHz, better for 183±3 GHz

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CAVIAR exampleB471 27-Jul-2009

• Inconsistent results here, all retrieved continuum strengths < MT_CKD

• Is this because LBLRTM profile is too moist?

• Possible to use MARSS data for profile constraint?

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Preliminary resultsSelected data from flights B467-B474

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Plausible results?

Rowe PM and Walden VP: "Improved measurements of the foreign-broadened continuum of water vapor in the 6.3 mcr band at -30oC", Applied Optics , 48(7), 1358-65 (2009).

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Plausible results?

Paynter D, Ptashnik I, Shine K, Smith K, McPheat R, Williams R: "Laboratory measurements of the water vapor continuum in the 1200 - 8000 cm-1 region between 293 K and 351 K", J. Geophys. Res., 2009

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Towards a conclusion…

• Groups at Exeter, Imperial College, Reading and NPL will coordinate efforts on two flights where all have good data and atmospheric profile data are reliable

• Same profile and same underlying radiative transfer model used to ensure consistency

• Flight B400 on 18/9/2008 over Camborne

• Flight B467 on 19/7/2009 over Jungfraujoch

• Move towards “synthesis” with theoretical and laboratory studies

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Questions and answers