Page 1 TAFTS in CAVIAR Paul Green, Ralph Beeby, Alan Last, John Harries, Juliet Pickering Imperial College London Stu Newman, Jonathon UK Met. Office Eric Usadi, Tom Gardiner, Marc NPL FAAM CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 2 Introduction IC contribution to CAVIAR Far-IR science and the TAFTS instrument Radiometric calibration at NPL Summer 2009 Flight campaign Summer 2008 Flight campaign Closing remarks

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 3 IC Contribution TAFTS instrument upgrade Flight planning (lots of modelling) Instrument Calibration –Purpose built blackbody at NPL, July 2008 and May flight campaigns –Aug-Sept 2008, Camborne, UK [R Beeby next term] –July-Aug 2009, Jungfraujoch, Switzerland Synthesis of results Application of new continuum –Understanding of the impact of the new results on our understanding of present-day climate and climate change.

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 4 The TAFTS Instrument dual-input Martin-Puplett (polarizing) FTS with two spectral bands measure both nadir and zenith (+net) 4 liquid helium cooled detectors –80-300cm -1 (2 x Ge:Ga) – cm -1 (2 x Si:Sb) resolution: 0.12cm -1 (apodized) single scan: 2 secs 4 internal BB sources employs Brault sampling scheme all built in-house (J Murray + A Canas) UKMO C-130, ARA Egrett, BAe-146

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 5 Tropical Standard Atmosphere cooling rate diagram Sub-arctic winter Standard Atmosphere cooling rate diagram

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 6 Current Issues in the far-IR (0-600cm -1 ) UTH variability and far-IR cooling to space –27-35% OLR from far-IR (Sinha and Harries 1995) –Heating rate diagram (Clough et al. 1992) –Far-IR transmission act as ‘valve’ in climate change scenarios (Shaw et al. 1999) –Proposed satellite missions - CLARREO Water vapour spectroscopy –Continuum measurements down to ~400cm -1 but nothing below (Tobin et al. 1999, Serio 2008) Cirrus clouds –Mean global coverage of ~30% –Contribution coincident with peak of far-IR emission. –Cools or warms depending on altitude, thickness, optical thickness, particle size and particle shape –Cirrus presence significantly changes spectral fluxes.

History of TAFTS Flown on 3 aircraft C-130 ( ), Egrett ( ), FAAM 146 (2004+) Clear-sky campaigns EAQUATE – UK, Sept 2004 RHUBC – NSA ARM site USA, Feb-Mar 2007 CAVIAR – UK and Switzerland, Summer 2008 / 2009 Cirrus / Cloud campaigns EMERALD I/II – Australia, 2001 and 2002 WINTEX + CAESAR – UK, 2005 to 2007 CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 7

Radiometric calibration At NPL 5 th - 15 th May 2009 Pre-campaign radiometric calibration with 2 external blackbody sources. NPLxBB and ICxBB. Differential instrument, always measures the difference between two views. Temperatures viewed covers those found in flight. (+10 to -55°C) Additional runs with both external blackbodies at near-equal but cold temperatures, to isolate the instrument self-emission term – first dual input calibration and tested new beamsplitters CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 8

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 9 NPL external calibration blackbody Purpose-built traceable temperature standard calibrated BB for use by both TAFTS and ARIES [UKMO 3-16μm FTS] Alcohol cooled Temperature range –-75 to +30C Blackbody emissivity –0.996  (λ < 50 μm) –0.994  (50 μm < λ < 100 μm) – / (100 μm < λ < 200 μm) Eric Usadi, NPL

Calibration run targets (2009) RunUW BBUW temp (degC) DW BBDW temp (degC) Internal BBs hot/cold A1ICxBB-26.2NPLxBB+5, -10, -25, /20 A2ICxBB-31.8NPLxBB+5, -10, -25, -31.8, -45, /amb A3ICxBB-32.4NPLxBB+5, -10, -25, -32.4, -40, -55 amb/60(40) B1NPLxBB-10, -25, -40, -41.2, ICxBB /20 B2NPLxBB+5ICxBB-4460/amb B3NPLxBB+5, -10, -25, -40, -55 ICxBB-4070/40 CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 10

Summer flying July – 12 August 2009 Based out of Basel, Switzerland 38.5hrs over 9 flights CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 11 Courtesy: Alan Foster

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 12 Flight Campaigns instrumentation FAAM BAe-146 –SWS [shortwave] –TAFTS [far-IR] –In-situ measurements General Eastern FWVS TWC –ARIES [mid-IR] –MARSS [microwave] –Dropsondes Payerne Sonde / GPS Models (UKMO and Swiss Met) From

Jungfraujoch Mönch Jungfrau Eiger Courtesy: Stu Newman

Flight campaign instrumentation Ground-based instrumentation –Radiosonde balloons (temperature, water vapour profile, wind) –GPS (water vapour) –NPL μm sun-pointing FTS BAe-146 in-situ –Radiometers, TAFTS, ARIES, SWS –In-situ (temp, WV, wind, cloud, aerosol etc.) –Water vapour: General Eastern FPH, FWVS, TWC –Dropsondes –BBRs, surface temp, hemispherical radiance Model fields –Swiss Met Office and ECMWF model fields CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 14

CAVIAR 2009 Flight schedule DateFlightMeteorologyTAFTS performance 02/07/09B465N/ATest flight 16/07/09B466Clear (partial MC)R6-10 excellent; R1-6, 11,12 good 19/07/09B467*Some thin Ci, ↓R3-7R excellent; R1-5 good 20/07/09B468Night balloon launchR1,2,6,7 good; R3-5,8,9 ok 25/07/09B469StCu later in flightAll runs excellent 26/07/09B470*Occasional thin CiAll runs excellent 27/07/09B471*ClearR1-4 excellent; R5,6 lost chs; No R7,8 29/07/09B472ClearR1-8 excellent; No R9-13 [ARIES] 01/08/09B473ClearDid not fly - Helium 04/08/09B474*Partial MCR1-6 excellent; R7,8 lost chs; No R9-11 CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 15 MC – mountain cloud

B471 – 27/07/09 CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 16 Profile 7 ~18kft 09:58UTC Profile 7 ~20kft 09:55UTC Profile 2 ~16kft 07:40UTC

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 17 Elevation data from:

CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 18

Water Vapour profiles Each group (IC, MO, Reading) involved in the flight campaign need to know the water vapour profile (and uncertainty) to compare with measured spectra. There are a number of sources of data; dropsonde, models, aircraft in-situ, satellites. Need to be compared and combined in an intelligent manner. All participants need to be using same profiles, for better cross-comparison… Workshop in week 30 Nov – 4 Dec IC involving SN, LT and PG CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 19

Measuring Water Vapour CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 20

Measuring Water Vapour CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 21

Profile philosophy Dropsonde are most accurate measures of profile, but only occasional snap-shot. Aircraft in-situ measurements from frost-point hygrometer, fluorescence WV spectrometer and Nevzorov TWC, all have different response times and measurement characteristics. Provide profiles in ascents/descents and measure of variation along runs. ECMWF analysis model fields – 0.25° grid assimilating all available data, but produced via spherical harmonics scheme – limited detail. Swiss Met model GPS water vapour from JFJ JFJ surface measurements Satellite data (SEVIRI, IASI, AIRS etc) Microwave (MARSS) instrument on FAAM-146 And radiometer data itself – shouldn’t be forgotten. So how best to combine… CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 22

Profile philosophy Dropsondes are an accurate snap-shot, ECMWF, even if biased, should give good idea of trend, temporally and spatially. Aircraft in- situ measurements as first check of this. Initially: 1)define a few points fixed points, representative of segments of the run (Camborne – Ocean N, Camborne, Ocean S). In this case, NW-SE runs, fortuitously follows ECMWF grid diagonal. 2)Sonde drop locations, naturally cluster about these points – so attribute dropsonde data to these locations. 3)Look at time of ECMWF fields analysis/forecast, dropsonde launch and aircraft run pass. Interpolate the ECMWF fields in time between these epochs, and produce a shift in T(p),q(p) from change in ECMWF field. So, any good? CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 23

Time variance of assimilation CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 24

Comparison of ECMWF correct profiles CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 25

B471 Run 1 CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 26

B471 Run 1 CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 27

Atmospheric Profiling 2008 Pressure / hPa Water vapour / %RHTemperature / K CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009

Uncertainty in Profiles Uncertainty in atmospheric profiles is a source of uncertainty in simulated spectra – this affects comparison between simulations and TAFTS spectra Make use of Jacobians in LBLRTM to assess sensitivity of spectra to uncertainties in temperature and relative humidity Analytic Jacobians: calculate dR/dx across spectral range where R = radiance and x = atmospheric parameter Indicates the change in radiance that would be caused by a change in a given atmospheric parameter (e.g., temperature, relative humidity) CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009

Wavenumber / cm -1 Radiance / mW/m 2.sr.cm -1 dR/d log[vmr(H2O)] / mWm 2 sr.cm -1 /log[vmr]

Wavenumber / cm -1 Radiance / mW/m 2.sr.cm -1

Closing remarks Overall a very successful campaign. Best yet in terms of weather, instrument performance (TAFTS and others) and number of flights But lots to do… –Concentrate on B471. –Continue analysis of dropsonde / Payerne radiosonde data. –Determine most appropriate profile for each run – last week. –Calibrate B471 runs 2,3,4,5 and 6. –Compare with ARIES data (in cross-over region). –Uncertainty budget calculations with updated ε and ΔT from NPL-based calibration work. –LBL code updates – HITRAN2008 –Make continuum assessment, then validate with other flights. CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 32

THANK YOU CAVIAR Annual Meeting Cosener’s House,15 th Dec 2009 Page 33

Atmospheric Profiling Need to know the distribution of water vapour above and below the aircraft in order to compare TAFTS measurements with LBLRTM 1 /HITRAN 2 Aircraft performs straight, level runs (SLRs) to take measurements Collect data from different sources to produce a “best estimate” : Dropsondes released from aircraft Balloon radiosondes launched from Camborne 2-3 times daily ECMWF 3 forecast model Collaboration with Stuart Newman (Met Office) and Liam Tallis (Reading) to find best scheme for determining profile Vaisala RD93 dropsonde, courtesy