1. TAFTS: Comparison of Camborne Spectra with Simulations Ralph Beeby, Paul Green, Juliet Pickering CAVIAR Field Campaign Meeting, Reading University, 6/12/10

2. Outline Introduction LBLRTM Simulations TAFTS Flight Data (Flight B400) Comparing LBLRTM spectra with TAFTS Conclusions

3. Introduction TAFTS mounted onboard FAAM BAe-146 during CAVIAR field campaigns; Camborne (2008), Jungfraujoch (2009) Used to measure in-situ far-infrared radiances, alongside Met Office ARIES (mid-IR) Camborne data: Flight B400 (18 th September 2008) selected for case study Radiance data from TAFTS used to assess water vapour continuum Compare measured radiances with those from a simulation (LBLRTM)

4. Simulating Atmospheric Spectra LBLRTM simulates spectra for a user- defined atmospheric profile This profile defined using T and RH data from –Radiosondes (launched from Camborne) –Dropsondes (released from aircraft) –ECMWF model data Uncertainties in profiles calculated from –Instrument uncertainty –Variability over course of run (from aircraft onboard instrumentation) –Analytic Jacobian  Uncertainty in simulated radiance

5. TAFTS Flight Data 7 straight level runs performed during B400 Good TAFTS performance for first 5 runs Data calibrated for –Run 4 (34kft / 251mb), UW and DW –Run 1 (20kft / 444mb), UW –Run 2 (5.5kft / 800mb), DW Improved calibration routine removes ‘amplitude beamsplitter effect’ from spectra Spectra phase-corrected at higher resolution

6. TAFTS Spectra 34kft UW TAFTS in blue LBLRTM in red LBLRTM underestimating radiances at longer wavelengths, overestimating at shorter wavelengths  RH profile in need of adjustment?

7. Profile Analytic Jacobian for 34kft UW simulation (LBLRTM); RH profile superimposed in black Indicates sensitivity of windows to changes in water vapour concentration TAFTS / LBL comparison suggests atmosphere more opaque looking down from 250mb Sensitive to 4 significant ‘lobes’ in profile: adjust profile lobe by lobe

8. TAFTS Spectra 34kft DW (TAFTS in blue, LBLRTM in red) LBLRTM underestimating radiances  profile needs to be less opaque Jacobian suggests simulation very sensitive to changes in water vapour content

9. TAFTS Spectra Cross-comparison: 20kft UW and 5.5kft DW TAFTS in blue, LBLRTM in red TAFTS suggests atmosphere much less opaque than sim – reduce water vapour content in middle of profile?

10. Profile Distribution of RH with altitude Use 20kft UW and 5.5kft DW to constrain ‘middle section’ of profile – both suggest profile needs to be less opaque Calculate required adjustments to profile from Jacobians – do different views agree? Remaining differences after profile adjustment - continuum?

11. Conclusions TAFTS spectra from flight B400 compared with simulated spectra from LBLRTM LBLRTM spectra calculated from estimated atmospheric profiles Differences between TAFTS and LBLRTM spectra  suggest profiles need some adjustment Use Analytic Jacobians to calculate size of adjustments After adjustment, look at remaining differences between spectra – continuum?