CAVIAR Field Campaign Meeting, Imperial College 29/3/11

TAFTS: Water Vapour Continuum Data from the 2008 CAVIAR Field

Campaign

Ralph Beeby, Paul Green, Juliet Pickering

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Outline

• Introduction

• LBLRTM simulations

• TAFTS flight data

• LBLRTM/TAFTS comparison: Flight B400

• Continuum coefficients

• Conclusions & further work

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Introduction

• TAFTS mounted on-board UKMO/FAAM BAe-146 for CAVIAR field campaigns

• Aim: to use TAFTS spectra to measure the water vapour continuum in the far-IR

• Method: – LBLRTM uses current model of water vapour continuum to simulate

atmospheric spectra– Compare TAFTS (observed) spectra with LBLRTM (simulated) spectra– Differences between TAFTS and LBLRTM changes to continuum?

• Case study: flight B400, 18/09/2008, Camborne

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Simulating Spectra with LBLRTM

• LBLRTM takes 1-D atmospheric profile as input – need to estimate temperature and water vapour profiles from sondes and aircraft data

• Uses MT_CKD 2.5 continuum – can adjust the strength within the simulation for comparison with TAFTS data

• Below: spectrum for run 4 (34kft / 251mb) UW

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

TAFTS Spectrum

• Run 4: 34,000ft (251mb), upwelling radiances

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

TAFTS Spectrum: Windows

• Spectral features of continuum visible in windows between strong WV absorption lines

• Compare TAFTS and LBLRTM in windows to see where continuum needs adjustment

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Continuum

• Changes to continuum suggested by differences between TAFTS and LBLRTM

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Continuum (2)

• Some windows suggest correction of >100%

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Continuum (3)

• Currently large uncertainties associated with data

• Size of spread mostly due to differences between TAFTS and simulation

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Comparison

• Still parts of windows where TAFTS and LBLRTM do not agree

• Option 1: adjust TAFTS data

• Option 2: adjust simulations

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Fine-tuning

• TAFTS?• Deghosting routine• Finish uncertainty analysis: , T error

• LBLRTM?• Differences between LBLRTM and observed spectra can suggest

where T or WV profile need adjusting• 1DVar retrieval scheme performed using ARIES data (Courtesy S

Newman) - see how this affects far-IR

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

TAFTS/ARIES Inter-comparison

CAVIAR Field Campaign Meeting, Imperial College 29/3/11

Conclusions & further work

• First corrections to continuum from B400 – hope to refine these values

• Improve TAFTS data with de-ghosting routine, improve simulation with adjustments to profile – retrieval

• Repeat for other runs – are they consistent?

• Compare continuum with ARIES data