1. Slide 1 EUMETSAT Fellow Day, 9 March 2015 Observation Errors for AMSU-A and a first look at the FY-3C MWHS-2 instrument Heather Lawrence, second-year EUMETSAT fellow, ECMWF Supervised by: Niels Bormann & Stephen English

2. Slide 2 EUMETSAT Fellow Day, 9 March 2015 AMSU-A Observation Errors

3. Slide 3 The AMSU-A Instrument 10 Temperature sounding channels EUMETSAT Fellow Day, 9 March 2015 6 satellites: good global coverage (RIP NOAA-16 June 2014) Microwave Temperature Sounder

4. Slide 4 EUMETSAT Fellow Day, 9 March 2015 Chs 9 – 14: used globally after thinning and VarQC Chs 5 – 8: also screened for cloud, orography, some sea-ice 6h metop-A, metop-B orography cloud AMSU-A current data usage: clear-sky assimilation Sea-ice, orography

5. Slide 5 EUMETSAT Fellow Day, 9 March 2015 New Observation Errors and screening part 1: channels 5 - 8 OLD METHOD orography cloud orography NEW METHOD Clear-sky forward model RTTOV Filter cloud and orography Constant observation errors Clear-sky forward model RTTOV Keep some cloud and orography Use more physical observation errors

6. Slide 6 EUMETSAT Fellow Day, 9 March 2015 Different satellite instruments have different noise terms: Instrument NedT Channel Number NedT values from Nigel Atkinson, UKMO NOAA-18 Aqua Channel Number Observation Error Aqua NOAA-18 Use different observation errors for different satellite AMSU-As: New Observation Errors and screening part 2: Satellite-dependent Observation Errors

7. Slide 7 EUMETSAT Fellow Day, 9 March 2015 New Observation Errors and Screening 1.Situation-dependent observation error model for channels 5 – 7 2.Remove first guess check for channels 6 – 8 in cloudy regions (use lwp and scatter index check) 3.Replace orography screen with observation error screen over land 4.Satellite-dependent observation errors Increased number of used data: Ch 5 - 6: orographyCh 6 – 8: over ocean ch 5: 6% ch 6: 11% ch 7: 8% ch 8: 3%

8. Slide 8 EUMETSAT Fellow Day, 9 March 2015 SUMMER: Improved fit of 12-hour forecast to ATMS improvement SUMMER: improved forecast scores Contribution to CY41R2 Impact on forecast accuracy WINTER: neutral forecast scores Normalised difference Forecast day Normalised difference Forecast day WINTER: Improved fit of 12-hour forecast to ATMS improvement 6 months of Assimilation Trials with:

9. Slide 9 FY-3C MWHS-2 EUMETSAT Fellow Day, 9 March 2015

10. Slide 10 MWTS MWHS MWRI IRAS MWTS-2 MWHS-2 IRAS MWRI GNOS See Lu et al (2011a & b), Chen et al (2014). FY-3B MWHS assimilated operationally since September 2014. EUMETSAT Fellow Day, 9 March 2015 China’s FY-3 polar orbiting satellite series FY-3A/B: launched 2008, 2012 FY-3C: launched Sep 2013

11. Slide 11 EUMETSAT Fellow Day, 9 March 2015 CMA ECMWF UKMO FY-3C collaboration Qifeng Lu, et al Bill Bell, Katie Lean, Nigel Atkinson… Regular teleconferences, feeding back findings to CMA My focus: MWHS-2

12. Slide 12 EUMETSAT Fellow Day, 9 March 2015 FY-3C MWHS-2 study Use a 6 month sample dataset to: 1.Assess data quality 2.Prepare for All-sky assimilation

13. Slide 13 EUMETSAT Fellow Day, 9 March 2015 Keep all cloud-affected data Apply higher observation errors in cloudy regions Use an all-sky forward model RTTOV-SCATT e.g. MHS channel 4 observationsMHS channel 4 observation errors All-sky Assimilation All-sky Assimilation reference: Alan Geer et al (2014), ECMWF Tech. Memo 741: http://old.ecmwf.int/publications/library/do/references/show?id=91235 AIM: Assimilate in all-sky conditions

14. Slide 14 EUMETSAT Fellow Day, 9 March 2015 MWHS-2 Instrument 5 183 GHz channels like ATMS (similar to MHS) 8 new 118 GHz channels

15. Slide 15 EUMETSAT Fellow Day, 9 March 2015 10:30 descending orbit 90 FOV (scan angles) Swath of 2700km Horizontal resolution 16 km (183 GHz) 32 km (118 GHz) MetOp-B MHS Suomi-NPP ATMS FY-3C MWHS-2 MWHS-2 Instrument

16. Slide 16 EUMETSAT Fellow Day, 9 March 2015 MWHS-2 183 GHz channels 5 183 GHz channels

17. Slide 17 EUMETSAT Fellow Day, 9 March 2015 1. Compare Observations to ECMWF background MWHS-2 Channel 13 Observation - Background The main differences are cloud features

18. Slide 18 EUMETSAT Fellow Day, 9 March 2015 2. Compare to Other Instruments MWHS-2 channel 13ATMS channel 20 Maps of observation minus background look very similar…

19. Slide 19 EUMETSAT Fellow Day, 9 March 2015 mean(o-b) stdev(o-b) MWHS-2 channel number Monthly mean and standard deviation of o-b Higher biases than ATMS and MHS Similar standard deviation MWHS-2 ATMS all-sky MHS all-sky 1 month, cloud-filtered Mean before bias correctionMean after bias correctionStandard deviation window channels High peaking Low peaking

20. Slide 20 EUMETSAT Fellow Day, 9 March 2015 183 GHz Data Quality: Summary Higher global biases for some channels (14 and 15) Most bias removed by the ECMWF Variational Bias Correction Scheme Standard deviation of background departures similar to ATMS/MHS

21. Slide 21 EUMETSAT Fellow Day, 9 March 2015 Assimilation Trials for 183 GHz channels Objective: Test the quality of the data in the full observing ECMWF system Prepare for operational assimilation Assimilation Trials: 1.Control: Full observing system T511 horizontal resolution 2.Full assimilation: Assimilate all 5 channels globally

22. Slide 22 EUMETSAT Fellow Day, 9 March 2015 Temperature: 1 – 2% change Vector Wind: 1 – 2 % change Humidity: 1 – 5 % change Assimilation Trial Results: Change in Analysis Increments 6 months data Change in root mean square (12h forecast – analysis): 0.04 0.02 -0.02 -0.04 0.00

23. Slide 23 EUMETSAT Fellow Day, 9 March 2015 Change in short-range forecasts (12-hour) Improved fits to humidity observations: AIRS IASI ATMS MHS improvement

24. Slide 24 EUMETSAT Fellow Day, 9 March 2015 Change in 1 – 10 day forecasts No significant change to forecast scores: improvement degradation e.g. geopotential and vector wind at 500hPa over Southern Hemisphere Forecast Day Normalised Difference stdev(fc – an) 6 months data

25. Slide 25 EUMETSAT Fellow Day, 9 March 2015 Summary Assimilating 183 GHz MWHS-2 channels over 6 months leads to: Increased increments of humidity, vector wind, temperature Improved fits of other observations to 12-hour forecasts (ATMS, IASI, AIRS) Neutral impact on forecast scores (days 1 – 10 forecasts)

26. Slide 26 EUMETSAT Fellow Day, 9 March 2015 FY-3C MWHS-2: 118 GHz channels

27. Slide 27 EUMETSAT Fellow Day, 9 March 2015 118 GHz: Oxygen band – Temperature sensitivity Water vapour continuum – Humidity sensitivity Cloud effects: absorption, emission, strong scattering MWHS-2 118 GHz channels 8 new 118 GHz channels

28. Slide 28 EUMETSAT Fellow Day, 9 March 2015 MWHS-2 118 GHz channel clear-sky Jacobians Channels 2 – 4: Temperature Channels 4 – 6: Temperature + cloud Channel 7: Temperature + cloud + humidity

29. Slide 29 EUMETSAT Fellow Day, 9 March 2015 Observation minus model background: Striping STRIPING observed MWHS-2 ch 3: MetOp-B AMSU-A ch 9: ATMS ch 10 (unaveraged): 1.4 K scale 5 K scale 2 K scale

30. Slide 30 EUMETSAT Fellow Day, 9 March 2015 Observation minus model background: cloud information 6 K scale 16 K scale channel 6 channel 7

31. Slide 31 EUMETSAT Fellow Day, 9 March 2015 Monthly mean observation minus background Before bias correctionAfter bias correction MWHS-2 ATMS clear-sky MetOp-B AMSU-A all-sky All AMSU-A’s all-sky 1 month, filtered for cloud:

32. Slide 32 EUMETSAT Fellow Day, 9 March 2015 Cloud-free Temperature information noisier than AMSU-A/ATMS Monthly standard deviation of observation minus background 1 month, filtered for cloud:

33. Slide 33 EUMETSAT Fellow Day, 9 March 2015 3 month All-sky Assimilation Trials: Control Assimilate channels 2 – 7 over ocean 118 GHz First Assimilation Trials Apply higher observation errors to cloud-affected data for channels 5 - 7: Channel 7 observation error

34. Slide 34 EUMETSAT Fellow Day, 9 March 2015 Mostly neutral: Small degradation of 1000hPa temperature: Results: Impact on Forecast Accuracy Work is still ongoing Forecast day

35. Slide 35 EUMETSAT Fellow Day, 9 March 2015 MWHS-2 118 GHz channels: Summary New channels with temperature, humidity, cloud sensitivity Potential for additional cloud information Temperature information more noisy than AMSU-A, striping observed On-going experimentation with 118 GHz channels – attempting to use them in all-sky (Will 4DVar be able to correctly adjust temperature, humidity increments?)

36. Slide 36 EUMETSAT Fellow Day, 9 March 2015 Summary

37. Slide 37 EUMETSAT Fellow Day, 9 March 2015 AMSU-A: New Situation-dependent observation errors: AMSU-A channels 5 - 7 Satellite-dependent observation errors: AMSU-A channels 5 – 13 Introduced more data over orography and ocean for channels 5 - 8 New observation errors and screening changes are implemented in CY41R2 with a small positive impact on short-range forecasts FY-3C MWHS-2: FY-3C MWHS-2 183 GHz data quality looks comparable to ATMS FY-3C MWHS-2 118 GHz channels have higher noise than AMSU-A but more cloud information Summary

38. Slide 38 EUMETSAT Fellow Day, 9 March 2015 Ongoing and Future work Monitor FY-3C MWHS-2 183 GHz channels and make operational (winter 2015?) Investigate further the usage of the new 118 GHz channels

39. Slide 39 EUMETSAT Fellow Day, 9 March 2015 Thank you for listening! Any questions?