TASK 2 Progress Meeting 1

TASK 2Progress Meeting 1 Richard Siddans, Brian Kerridge, Jane Hurley STFC Rutherford Appleton Laboratory, UK

Outline • WBS • Overview of tasks accomplished/remaining • Technical details of WP • Summary

WBS

Task overview status

Update spectroscopic database … • Current FM: • RTTOV • using RFM-derived • coefficients • HITRAN 2008 • Updated FM: • RTTOV • using LBLRTM-derived • coefficients • HITRAN 2012 • LBLRTM v12.2 instead of RFM, using AER v3.2 line parameter database rtweb.aer.com/lblrtm_frame.hmtl • CH4 and CO2 line-mixing, and fixed HDO/H2O ratio

‘Nominal’ difference LBLRTM/RFM

‘Coupling’ difference

‘Spectral’ difference

‘FM’ difference N2O F14 H2O CO2 CH4

‘HITRAN’ difference H2O CH4

Implement spectroscopic database … Impact of spectral differences δTB(ν) attributable to • the running of full nominal versions of LBLRTM and RFM (line-mixing ‘on’ + AER v3.2 vs. line-mixing ‘off’ + HITRAN 2008) • line-mixing ('on’ vs. ‘off’) • basic spectral data (AER v3.2 vs. HITRAN 2008/2012) • the forward model itself (LBLRTM vs. RFM) • the update from HITRAN 2008 to 2012 (RFM vs. RFM)

Summary • Assessed differences between LBLRTM and RFM, with intention of updating current FM with LBLRTM to include line-coupling • Differences attributable to FM, basic spectral data, line-mixing, HITRAN • Species affected = H2O and CH4, mostly • Assessed impact on retrievals by updating the FM to LBLRTM to include line-coupling • Difference in spectroscopy typically changes retrieved CH4 concentration by less than 0.5% • Since impact on retrieval is so much smaller than known issues with retrieval (4% increase in CH4 and residual fitting across-track), there will be no improvement in implementing line-mixing in updated FM

TASK 2 Progress Meeting 1