Methane Retrievals in the Thermal Infrared from IASI AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. Diane Knappett, Richard Siddans, Brian Kerridge, Jane Hurley and Alison Waterfall STFC – Rutherford Appleton Laboratory

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. TIR FTS on-board Metop-A since 2006; Metop-B since IFOV’s (each 12 km diameter at nadir) 30 views per 2200 km swath Relatively high spatial resolution measurements, day and night, over land and ocean. IASI: Infrared Atmospheric Sounding Interferometer Image: EUMETSAT

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. RAL IASI Methane Retrieval Scheme Optimal estimation retrieval scheme  Simple a priori methane field  Temperature and humidity profiles from ECMWF analysis  Surface spectral emissivity from University of Wisconsin Fits the TIR spectral range cm -1 (RMS of 0.1 K)  Scheme extracts two independent pieces of information on the methane profile Column-averaged methane of precision ppbv H 2 O, HDO, T surf, cloud fraction, cloud altitude & scale factors for two systematic fit residuals co-retrieved with methane Retrieval of effective cloud parameters achieved by fitting N 2 O, which has a well known distribution  Corrects for the effect of optically thin cloud not screened out by initial cloud filtering Scheme has been extensively compared to GOSAT, GEOSchem, TOMCAT, MACC and TCCON Paper in preparation for AMT (R.Siddans et al.)

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. RAL IASI Global Methane Dataset Key features: IASI MetOp-A (05/2007–07/2015) Processed all available days Processed one in four IASI detectors (least cloudy only) In the process of archiving with CEDA July 2007 July 2015

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. IASI Methane vs MACC – Global Monthly Mean Maps

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. IASI/MACC Time Series Comparison MACC sampled as IASI, then 2.5 x 2.5 degree monthly means produced from both – Done separately day + night (IASI generally has better sensitivity over land in the day-time) – Column average from MACC computed with / without IASI AK Monthly means binned into “TRANSCOM” regions + regions over sea MACC GHG Inversion – Up to 2012: v10-S1NOAA_ra CH 4 inversions reanalysis using only the NOAA surface observations – From 2013: v10_an CH 4 delayed-mode analysis of the GOSAT satellite and surface observations

IASI TIR – MACC GHG inversion ( )

IASI TIR – MACC GHG inversion ( ) – Anomaly

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. CH4 Anomaly Maps Dec good agreement between IASI and MACC Mar 2011 – disparity over Indonesia

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. IASI MetOp-A/-B Comparison – June 2014 Day-time difference Night-time difference Agreement within 0.5 ppbv

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. IASI-MHS T, Humidity and Surface Spectral Emissivity Standard Retrieval (June 2014) RAL has enhanced EUMETSAT’s operational IASI temperature (T) and humidity (q) processor Combines IASI with collocated microwave data from MHS and AMSU IASI-MHS T, q and emissivity being used as input to the IASI methane retrieval Eliminates errors encountered through use of ECMWF analyses and University of Wisconsin surface emissivity

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. IMS Retrieval (June 2014) IASI-MHS T, Humidity and Surface Spectral Emissivity RAL has enhanced EUMETSAT’s operational IASI temperature (T) and humidity (q) processor Combines IASI with collocated microwave data from MHS and AMSU IASI-MHS T, q and emissivity being used as input to the IASI methane retrieval Eliminates errors encountered through use of ECMWF analyses and University of Wisconsin surface emissivity

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. Summary & Future Work IASI TIR OE Retrieval Scheme Algorithm and validation paper to be published shortly (R.Siddans et al.) 8 year IASI MetOp-A methane dataset available via CEDA in Jan 2016 IASI L2 Temperature, Humidity and Emissivity IASI-MHS T, q and emissivity being used as input to the IASI methane retrieval  Improves errors from the use of ECMWF T, q and University of Wisconsin surface emissivity Development 3.7 micron Retrievals Preliminary work on 3.7 micron retrievals with a view to improving near-surface sensitivity with the solar reflected term NRT MetOp Chain Working to incorporate IASI CH4 processor (and the IASI-MHS T, q and emissivity pre-processor) into RAL’s MetOp NRT chain  Monitoring trials in ECMWF/Copernicus Atmosphere Monitoring Service

AGU Fall Meeting, 14 th -18 th December, San Francisco, USA. Current and Future IASI Instruments IASI MetOp-A 2006 IASI MetOp-B 2012 IASI MetOp-C [2017] IASI-NG MetOp-SG-A series IASI-NG MetOp-SG-B series The IASI instrument will be carried on a suite of MetOp satellites giving continuous observations up to Image: ESA - IASI [ ]