CAVIAR flying debrief (2008) Reading 25 th November 2008

TAFTS 2008NPL calibration and Summer flying

Paul Green, Ralph Beeby, Alan Last, Caroline Cox,John Harries, Juliet Pickering

Imperial College London

With many diagrams taken from Stu Newman’s report

CAVIAR flying debrief (2008)Reading 25th November 2008


Introduction

• Calibration at NPL• Summer 2008 Flight campaign• Closing remarks


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)– 300-700cm-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

Radiometric calibration

• At NPL 30th June – 18th July 2008• First radiometric calibration with 2 external blackbody

sources. • Differential instrument, always measures the

difference between two views. • First calibration with target at -55C. (Best to date is

around -40C.) • New beamsplitter (Cardiff Uni) arrived early June.

One set of measurements with original BS, and one with the new one, for comparison.



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

– -65 to +10C• Blackbody emissivity

– 0.996 0.002 (λ < 50 μm)– 0.994 0.005 (50 μm < λ

< 100 μm)– 0.990 +0.005 / -0.02 (100

μm < λ < 200 μm) Eric Usadi, NPL

Summer flying 2008

• Campaign dates: 13 Aug – 25 Sept 2008 (7 weeks)• 35 flight hours = (7x 5hr flights)• All we needed were perfect clear-sky over Camborne

in Cornwall…..


Flight campaign instrumentation

• Camborne based instrumentation– Radiosonde balloons (temperature, water vapour profile, wind)– GPS (water vapour)– Lidar backscatter (aerosol + cloud base)– Microwave retrieved water vapour and temperature (18/09/08 only)– Microtops sun photometer (aerosol optical thickness)– NPL 0.7-14μm sun-pointing FTS

• BAe-146 in-situ– Radiometers, TAFTS, ARIES, SWS– In-situ (temp, WV, wind, cloud, aerosol etc.)– Dropsondes– BBRs, surface temp, hemispherical radiance

• Model fields– MO Mesoscale model, MO and ECMWF NWP models


CAVIAR 2008 Flight schedule

Date Flight no. Meteorology Useful science

TAFTS performance

13/08/08 B394 N/A Test flight

19/08/08 B396 Persistent broken StCu, increasing late on

Yes Partial laser up to 1.5hrs

22/08/08 B397/398 Some broken StCu Yes No laser

11/09/08 B399 Too cloudy (Aborted) Good

18/09/08 B400 Excellent Yes Excellent

23/09/08 B404 Too cloudy (Aborted) Good


B396 15:00UTC B397 12:00UTC

SEVIRI images

B398 – Clear-skies?


B398 – 22/08/08 14:42UTC B398 – 22/08/08 16:27UTC

B400 synoptic chart


B400 – SEVIRI


SEVIRI image, 10:00UTC

B400 – flight track


B400 - Clouds?


B400 - Atmospheric profile data


Courtesy of R. Beeby

B400 - Preliminary data

• Entire flight dataset 3h20– 08:27:25Z – 11:46:53Z

• But concentrate on run 4• 34kft (southwards heading)• 10:25:53 -10:32:52: 7minutes • Sonde launches at:

– 10:26:04 #3– 10:28:01 #4

• Simulations: sonde #3 from 75mbar below aircraft melded with 11:00 Camborne sonde (Courtesy of R. Beeby)


Up- and downwelling radiance


B400 net radiance


B400 – other runs

Run # Altitude Time(UTC)

1 20kft 08:30

2 5.5kft 09:00

3 100ft 09:12

Balloon chase

4 34kft 10:30

5 29kft 10:45

6 14.5kft 11:10

7 5kft 11:28

8 100ft 11:40-11:45


Red dots – Camborne overpasses


Closing remarks

• NPL calibration• Campaign in UK August/September 2008

– LW data fundamentally sound… SW still to access

• Future work:– Work on NPL calibration data to determine ε and ΔT of

blackbodies– New Cardiff-made BS analysis– Final data calibration – with uncertainties– Cross-calibration with ARIES– Determination of far-IR water vapour continuum coefficients

CAVIAR flying debrief (2008) Reading 25 th November 2008

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