Intercalibration of AMSU-A,MHS and Update on mitigating loss of AATSR Font: Arial only Bullets: Arial round Front page slide Headline text point size 53 Subtitle text point size 20 Presenter, location and date point size 12 Divider slides Should be used to break up subjects or when changing content Headline text point size 40 Content slides Headline text size: minimum 40 First Level Bullet Points 24 Subsequent Level; Bullet Points 20 Body text size: minimum 16 Printing Please select greyscale when printing, this will remove the backgrounds and save on ink. Colour Web safe green #CFF33 (R204, G255, B51), can be used to highlight important words or phrases. Web safe red #ED2939 (R237, G41, B57), can be used to highlight severe weather warnings Campaign presentations If your presentation is part of a campaign or event then please ask the studio for assistance Intercalibration of AMSU-A,MHS and Update on mitigating loss of AATSR Roger Saunders, Pete Francis, Tom Blackmore, Brett Candy, Viju John and Tim Hewison Acknowledgements to EUMETSAT for supporting this work © Crown copyright Met Office

Goals of the project Generation of Microwave Radiance Fundamental Climate Data Records (FCDR) from the upper tropospheric water vapour channels from AMSU-B, MHS and SSM/T-2 sensors from 1994 to 2014 Generation of the Infrared Radiance FCDR from the upper tropospheric water vapour channel on HIRS from 1979 to 2014 To compare IR and MW FCDRs with simulated radiances from CMIP5 climate models and reanalyses (e.g. ERA-Interim) to ascertain deficiencies in model hydrological cycle. © Crown copyright Met Office

Something good about orbit drift! SNOs occur over all latitudes when Xing times are identical John et al 2011

Inferring radiance biases (1) SNOs For channel n on sensor 1 and channel m on sensor 2 average over all cloud-free ocean pixels within colocation area DBTnm = mean{(yn – ym)} 1 to k coincident obs k typically ~ 100 © Crown copyright Met Office

Distribution of collocations SNOs at all latitudes John et al 2011 © Crown copyright Met Office 5

Radiance dependence of bias from global SNOs N19-N18 2009-09 MA-N17 2009-05 MA-N17 2009-04 SNO – Simultaneous nadir overpass I take N19, MA, and N16 are primary satellites and N18, N17, and N15 as secondary satellites. “N” represent NOAA. “MA” represent MetOp-A Bias is calculated as primary satellite minus secondary satellite. Most of the channels show significant dependence of bias on radiance. Black symbols show dependence of bias on radiance of primary satellite. Red symbols show dependence of bias on radiance of secondary satellites. N19 Channel 3 had very high radiometric noise during this time (~7K), that is the reason why it has very large radiance dependent bias. More details in: John, V. O., G. Holl, S. A. Buehler, B. Candy, R. W. Saunders, and D. E. Parker (Accepted with minor revision, 2011), Understanding inter-satellite biases of microwave humidity sounders using global SNOs, J. Geophys. Res.. N16-N15 2008-08 John et al., (2012) Understanding inter-satellite biases of microwave humidity sounders using global simultaneous nadir overpasses, J. Geophys. Res. © Crown copyright Met Office

Scan dependent biases John et al., (submitted), Monitoring scan asymmetry of microwave humidity sounding channels using simultaneous all angle collocations (SAACs), J. Geophys. Res. © Crown copyright Met Office

Correcting for Orbit drift Equator Xing times of ascending nodes Data from 5 satellites are used to construct diurnal cycle climatology (31.25 N, 1.25 E) Channel 1 NOAA-16 channel 1 Kottayil, John, and Buehler (Submitted) Correcting diurnal cycle aliasing in microwave humidity sounder measurements, J. Geophys. Res.. © Crown copyright Met Office

Assessment of inter-calibration methods NOAA-16 – NOAA-15 John et al., (submitted), Assessment of inter-calibration methods for microwave humidity sounders, J. Geophys. Res. © Crown copyright Met Office

Summary 1 SNOs used to characterise AMSU-B/MHS biases Important to note biases change significantly with latitude so polar SNOs only tell part of story Scan biases biases vary significantly from intrument to instrument Diurnal changes can be modelled with the 5 NOAA/METOP satellites in orbit with different equator crossing times Tropical ocean appears to be best region to monitor biases © Crown copyright Met Office

Calculation of radiance biases (2) NWP as transfer standard For channel n Sensor 1: DBT(n) = mean{yn - Hn(xi)} i=1 to k obs For channel m Sensor 2: DBT(m) = mean{ym - Hm(xi)} Assume same bias? Compare DBT(n) with DBT(m) (double difference) xi atmospheric state vector for observation i © Crown copyright Met Office

AMSU-A on NOAA19 and METOP-A Chan 10 Stable but biases different for each instrument © Crown copyright Met Office

AMSU-A on NOAA19 and METOP-A Chan 8 NOAA-19 Not Stable! © Crown copyright Met Office

MHS on NOAA19 and METOP-A Chan 18 Stable but biases different for each instrument Note much higher NeDT for NOAA-19 © Crown copyright Met Office

AATSR to SLSTR ? the bridge for climate quality SST AATSR data ceased when the ENVISAT satellite failed in April 2012. It provides the high quality SST data record and well calibrated radiances useful for GSICS SLSTR is planned to be launched on Sentinel-3 in 2014? How to bridge the gap? © Crown copyright Met Office

AATSR biases © Crown copyright Met Office

HIRS SEVIRI AATSR stats over ocean 2011 © Crown copyright Met Office

HIRS SEVIRI AATSR © Crown copyright Met Office

IASI vs AATSR Can we use IASI to bridge the gap to SLSTR? © Crown copyright Met Office

IASI vs AATSR Can we use IASI to bridge the gap to SLSTR? © Crown copyright Met Office

IASI vs AATSR Can we use IASI to bridge the gap to SLSTR? © Crown copyright Met Office

Summary 2 With the failure of AATSR, METOP-A/B IASI is the best option for a stable radiometric reference in the AM orbit and AIRS in the PM orbit until Sentinel-3 is launched. The AVHRR and MODIS imagers can be used to retrieve SST but the calibration is monitored with IASI or AIRS on the same platform. A study with METOP during the overlap period with AATSR is planned © Crown copyright Met Office

Questions and answers © Crown copyright Met Office