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Published byGertrude Underwood Modified over 9 years ago
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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 NPP ATMS SDR products review meeting, Jan 2012
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Slide 13 Obs-FG for ATMS channel 10 NPP ATMS SDR products review meeting, Jan 2012
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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
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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
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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
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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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