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Slide 1 Initial results from the assessment of ATMS data at ECMWF Niels Bormann, Bill Bell, Anne Fouilloux, Ioannis Mallas, Nigel Atkinson, Stephen English.

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Presentation on theme: "Slide 1 Initial results from the assessment of ATMS data at ECMWF Niels Bormann, Bill Bell, Anne Fouilloux, Ioannis Mallas, Nigel Atkinson, Stephen English."— Presentation transcript:

1 Slide 1 Initial results from the assessment of ATMS data at ECMWF Niels Bormann, Bill Bell, Anne Fouilloux, Ioannis Mallas, Nigel Atkinson, Stephen English NPP ATMS SDR products review meeting, Jan 2012

2 Slide 2 Framework ATMS data have been compared passively against short- term forecasts in the ECMWF 4DVAR assimilation system. Results are based on 1 day of data (10 November 2011), obtained offline (no routine real-time data feed yet). Spatial resolution of forecast model: T511 (40 km), otherwise as in operations Radiative transfer model: RTTOV, clear-sky NPP ATMS SDR products review meeting, Jan 2012

3 Slide 3 Scan statistics: Brightness temperatures (SDRs) NPP ATMS SDR products review meeting, Jan 2012 Incorrect antenna pattern correction Data for 10 Nov 2011, over sea, no QC, no bias correction

4 Slide 4 Scan statistics: Antenna temperatures (TDRs) I NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, no bias correction

5 Slide 5 Scan statistics: Antenna temperatures (TDRs) II NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, no bias correction

6 Slide 6 Scan statistics: Antenna temperatures (TDRs) III NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, no bias correction

7 Slide 7 Comparison to AMSU-A performance Comparison to NOAA-18 AMSU-A -Comparing departure characteristics for equivalent channels at equivalent scan positions. -Raw ATMS data averaged, 3x3. -Note:  NOAA-18 data includes antenna pattern correction.  For NOAA-18, radiative transfer includes a “gamma” correction for optical depths to reduce air-mass dependent biases for AMSU-A channel 5-8. NPP ATMS SDR products review meeting, Jan 2012

8 Slide 8 Scan statistics comparison I NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, no bias correction

9 Slide 9 Scan statistics comparison II NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, no bias correction

10 Slide 10 Scan statistics comparison III NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, no bias correction

11 Slide 11 Influence of bias correction NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, scanbias removed, “bias corrected” = air-mass dependent biases removed

12 Slide 12 Histograms of Obs-FG NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, no QC, scanbias removed Channel 10, departures from NCEP Raw Averaged

13 Slide 13 Obs-FG for ATMS channel 10 NPP ATMS SDR products review meeting, Jan 2012

14 Slide 14 Channel 10 Considerable air-mass dependent biases for channel 10 for ECMWF, not seen in NCEP comparisons: -Likely explanation: pass-band specification used:  CRTM and RTTOV use idealised top-hat pass-bands:  CRTM uses 57.290344 GHz with 0.330 GHz pass-band width.  RTTOV uses 57.290344 GHz with 0.151 GHz pass-band width. -What is right? → Need measured pass-bands. NPP ATMS SDR products review meeting, Jan 2012

15 Slide 15 Humidity sounding channels NPP ATMS SDR products review meeting, Jan 2012 Data for 10 Nov 2011, over sea, “clear data”, no bias correction

16 Slide 16 Conclusions from initial assessment Noise performance of temperature sounding channels against short-term forecasts looks good: -Better than pre-launch measurements. -(At least) comparable to AMSU-A after 3x3 averaging. Scan-biases for ATMS look smoother than for AMSU-A even without an antenna pattern correction applied to ATMS data. Uncertainty about pass-band specification for channel 10: -Significant air-mass biases with RTTOV’s 151 MHz pass-band width. -NCEP results with CRTM’s 330 MHz pass-band width better. -Need pre-launch measured pass-band characteristics. No obvious problems with humidity sounding channels. NPP ATMS SDR products review meeting, Jan 2012

17 Slide 17 Outlook Further characterisation once near-realtime data stream established via EUMETSAT: -Temporal stability -Biases within an orbit -Assessment of passband parameters -Etc. Quality control, bias correction, optimised averaging, assimilation, … NPP ATMS SDR products review meeting, Jan 2012


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