CAVIAR Annual MeetingCosener’s House,14th Dec 2009

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Introduction

• Calibration at NPL• Summer 2009 Flight campaign• Water vapour profiles• So preliminary data comparisons• Closing remarks

Radiometric calibration

• At NPL 5th - 15th 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.

• Additional runs with both external blackbodies at near-equal but cold temperatures, to isolate the instrument self-emission term.

CAVIAR Annual MeetingCosener’s House,14th Dec 2009

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Calibration run targets (2009)Run UW BB UW temp

(degC)DW BB DW temp

(degC)Internal BBshot/cold

A1 ICxBB -26.2 NPLxBB +5, -10, -25, -26.2

50/20

A2 ICxBB -31.8 NPLxBB +5, -10, -25,-31.8, -45, -55

60/amb

A3 ICxBB -32.4 NPLxBB +5, -10, -25, -32.4, -40, -55

amb/60(40)

B1 NPLxBB -10, -25, -40, -41.2, -42.2

ICxBB -41.2 50/20

B2 NPLxBB +5 ICxBB -44 60/amb

B3 NPLxBB +5, -10, -25, -40, -55

ICxBB -40 70/40

CAVIAR Annual MeetingCosener’s House,14th Dec 2009

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Summer flying 2009

• 13 July – 12 August 2009• Based out of Basel, Switzerland• 38.5hrs over 9 flights

CAVIAR Annual MeetingCosener’s House,14th Dec 2009

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CAVIAR 2008 Flight schedule

Date Flight Meteorology TAFTS performance

02/07/09 B465 N/A Test flight

16/07/09 B466 Clear (partial MC) R6-10 excellent; R1-6, 11,12 good

19/07/09 B467* Some thin Ci, ↓R3-7 R6-11.2 excellent; R1-5 good

20/07/09 B468 Night balloon launch R1,2,6,7 good; R3-5,8,9 ok

25/07/09 B469 StCu later in flight All runs excellent

26/07/09 B470* Occasional thin Ci All runs excellent

27/07/09 B471* Clear R1-4 excellent; R5,6 lost chs; No R7,8

29/07/09 B472 Clear R1-8 excellent; No R9-13 [ARIES]

01/08/09 B473 Clear Did not fly - Helium

04/08/09 B474* Partial MC R1-6 excellent; R7,8 lost chs; No R9-11

CAVIAR Annual MeetingCosener’s House,14th Dec 2009Page 5

MC – mountain cloud

B471 – 27/07/09

CAVIAR Annual MeetingCosener’s House,14th Dec 2009

Page 6Profile 7 ~18kft 09:58UTC

Profile 7 ~20kft 09:55UTC

Profile 2 ~16kft 07:40UTC

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Elevation data from:

http://srtm.csi.cgiar.org/

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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 2009 @ IC involving SN, LT and PG

CAVIAR Annual MeetingCosener’s House,14th Dec 2009

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Measuring Water Vapour

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Measuring Water Vapour

CAVIAR Annual MeetingCosener’s House,15th Dec 2009

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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 flight debrief (2009)Reading 16th November 2009

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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 ECMF field.

So, any good?

CAVIAR flight debrief (2009)Reading 16th November 2009

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Time variance of assimilation

CAVIAR Annual MeetingCosener’s House,14th Dec 2009

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Comparison of ECMWF correct profiles

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B471 Run 1

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B471 Run 1

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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 / Tennyson list.– Make continuum assessment, then validate with other flights.

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