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IV WMO Impact Workshop 2008

Global impact studies at the Deutscher Wetterdienst (DWD) Alexander Cress , Reinhold Hess Detlef Pingel Andreas Rhodin Heinz Werner Bitzer German Weather Service , Offenbach am Main, Germany Email: Alexander.Cress@dwd.de. Introduction Impact of satellite sounding data from ATOVS radiances

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IV WMO Impact Workshop 2008

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  1. Global impact studies at the Deutscher Wetterdienst (DWD) Alexander Cress, Reinhold Hess Detlef Pingel Andreas Rhodin Heinz Werner Bitzer German Weather Service , Offenbach am Main, Germany Email: Alexander.Cress@dwd.de • Introduction • Impact of satellite sounding data from ATOVS radiances • Quality and impact of radio occultation data • General impact of atmospheric motion vector winds • Impact of MTSAT-1R AMV wind vectors • Use of direct broadcasting MODIS winds • Use and impact of scatterometer data (ASCAT) • Summary and Outlook IV WMO Impact Workshop 2008 Alexander Cress

  2. Global Model GME • Operational NWP Model of DWD • gridpoint model, hexagonal triangular grid • 40 km mesh size, 36870 grid points/layer • 40 layers (hyprid, sigma/pressure) • prognostic variables: ps, u, v, T, qv, qc, qi, o3 • intermitient data assimilation (OI, 3-hourly) -> 3DVAR (PSAS) system • incremental digital filter initialization (P.Lynch) • At 00 UTC and 12 UTC: forecasts for 174 hours • At 18 UTC: forecasts for 48 hours IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  3. IV WMO IMPACT WORKSHOP 2008 Alexander Cress Assimilation of IFS Pseudo Temps (operational since Dec 17 2003) Profiles of IFS/4D-Var Analyses (temperature, humidity and wind) as Temps for OI/GME use of humidity profiles only above 700 hPa Assimilation one time per day for 0 UTC into Main Analysis only Data Coverage

  4. IV WMO Impact Workshop 2008 Alexander Cress • Use of Satellite Radiances (ATOVS) • AMSU-A of NOAA 15, 16, 18 and AQUA (on top of pseudo-temps) • METOP/AMSU-A in trial run • 1D-Var retrievals assimilated by OI as SATEMS (geopotential thicknesses) • (only 1D-Var analysis increments assimilated) • Tuning of background and observation errors for 1D-Var • Assimilation with reduced resolution (120km, previously 60 km) • with neutral impact • Use of IFS forecasts above GME model top (10 hPa) for RTTOV • studies with statistical linear regression from stratospheric channels • Direct Use of ATOVS radiances in 3D-VAR • AIRS/IASI: • monitoring, cloud detection, bias correction, trial runs, etc. available • work deferred for personal resources

  5. Use of AMSU-A auf NOAA-15, 16, 18 und AQUA – since 5.7.2007 Alexander Cress IV WMO Impact Workshop 2008

  6. 500 hPA ANOC, 0 UTC, for Routine, 4638 (Pseudo+1D-VAR) IV WMO Impact Workshop 2008 Alexander Cress 1D-Var (with PT) further improves compared to Routine (with PT) for 0 UTC

  7. Tuning of Covariance Matrices B and R for 1D-Var IV WMO Impact Workshop 2008 Alexander Cress Improvement of GME forecasts with tuned error statistics: Red: old R and B, Blue: tuned R and B

  8. IV WMO Impact Workshop 2008 Alexander Cress Anomaly correlation coefficient of geopotential height in 500 hPa 2007051400 – 2007053100 (18 forecasts)

  9. IV WMO Impact Workshop 2008 Alexander Cress Anomaly correlationcoefficient for 500 hPa 2008030112 – 2008032612 (26 forecasts) SH NH

  10. Use of AMSU-A Data from METOP Reinhold Hess DWD, Offenbach Offenbach, 2007

  11. Use of AMSU-A auf NOAA-15, 16, 18 und AQUA – since 5.7.2007 IV WMO Impact Workshop 2008 Alexander Cress

  12. Use of AMSU-A auf NOAA-15, 16, 18, AQUA und METOP-A (seit 21.11.07) IV WMO Impact Workshop 2008 Alexander Cress

  13. Bias correction of Metop-1: Without Bias correction IV WMO Impact Workshop 2008 Alexander Cress

  14. Bias correction of Metop-1: after Bugfix in scanangle correction IV WMO Impact Workshop 2008 Alexander Cress

  15. Use of METOP: clear positive benefit of 500hPa ANOC in SH, minor impact for EUR at 00 UTC IV WMO Impact Workshop 2008 Alexander Cress

  16. Use of METOP: small positive impact of the 500hPa ANOC in NH and EUR for 12 UTC IV WMO Impact Workshop 2008 Alexander Cress

  17. Parallelroutine: clear positive impact for all areas (00 UTC)

  18. Use of Radio Occultation data • A electromagnetic signal, transmitted by a GPS satellite, is delayed due to the presence of free electrons in the ionosphere an the refractivity of the atmosphere • The refractivity is directly linked to horizontal and vertical variation of temperature, pressure and water vapour • The refraction of the GPS signal corresponds to a shift in its phase, recorded at the receiving LEO satellite. Additionally, the signal path undergoes a bending in the atmosphere, resulting in a bending angle • Relative geometry of the GPS and LEO and the Earth changes during the occultation event, the signal path intersects the atmosphere vertically, thus providing a vertical profile of bending angle. • Observation error can be derived from the signal-noise-ratio of the amplitude of the signal • Observed quantity to be assimilated can be bending angle (DWD) or refractivity (Met Office) profiles • Benefits: High vertical resolution, independence of cloud conditions, lack of fundamental biases, uniform global coverage Measurement geometry of Radio Occultation

  19. AMV Impact Experiment • Following an initiative by Mary Forsythe and Lars Peter Riishojgaard • Data denial experiment with 3DVAR • No use of geostationary and polar AMV wind vectors • Winter period (12th Dez. 2007 – 12th January 2008) • 00 UTC and 12 UTC forecasts IV WMO Impact Workshop 2008 Alexander Cress

  20. Anomaly correlation coefficient for the Geopotential Height in 500 hPa 20071212 - 20080112 Crtl Crtll without AMVs 00 UTC 12 UTC Alexander Cress IV WMO Impact Workshop 2008

  21. RMSV Wind Vector in 200 hPa 2007121212 - 2008011212 NH SH TR Routine Routine without AMVs IV WMO Impact Workshop 2008 Alexander Cress

  22. Analysis and forecast impact of MTSAT-1R • Usage • extratropics over oceans; tropics over oceans and land • IR between 1000 and 700 hPa and above 400 hPa • QI > 85 • WVcloudy above 400 hPa • QI > 85 • WVclear is not used • VIS below 700 hPa • QI > 85 • FG check: asymmetric to remove negative OBS-FG bias • Thinning: 1 wind per pre-defined thinning box (200 km;15 vertical layers). data selection by highest noFirst Guess QI in a box • One month analysis and forecast experiment (June/July 2007) IV WMO Impact Workshop 2008 Alexander Cress

  23. OBS – FG Statistics for MTSAT-1R for July 2007 > 400 hPa QI > 80 WVcloudy IR IV WMO Impact Workshop 2008 Alexander Cress

  24. Anomaly correlation coefficent Date: 2007060912 - 2007070912 NH SH Crtl Crtl plus MTSAT-1R Crtl Crtl plus MTSAT-1R EU Crtl Crtl plus MTSAT-1R IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  25. Direct Broadcast MODIS Winds • Motivation and Usage MODIS polar winds are not available in time to be used in operational (main) run. Only available in update run Direct broadcasting winds from Tromso, McMurdo ~ 100 minutes earlier Provide only partial coverage and only Terra can be received in the NH At DWD, no MODIS winds could be used in the main runs. Using DB winds, some polar winds can be used also in the main run. Additionally, more polar winds can be used in the update cycle runs Monitoring results show same quality as conventional MODIS winds Experimental use of DB polar winds in the same way as conventional MODIS winds Experiment: 23 days in November 2007 IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  26. IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  27. Use of scatterometer data at DWD Read SCATT (25 km BUFR data) Data from data base or file or ECMWF MARS System • 10 m wind vectors (most likely wind) • QuikScat and ASCAT • Global and regional • Use of multiple wind solutions (planned) • Experiments with OI and 3DVAR Pre SCATT - read in original Bufr - data selection within analyses time window - eliminates overlapping orbits - computes KNMI rain flag; data flaging - computes direction check; data flagging - computes bias correction - data selection based on quality control - thinning - output options: Bufr; netCDF, ascii OI - Analyses - (u/v) most likely wind - coded as Pseudo-Buoy (Bufr) 3DVAR - Analyses - (u/v) more than one wind - coded as Bufr/netCDF Offline Monitoring - colloc. with GME -FG/Ana - analyses of data quality Alexander Cress IV WMO IMPACT WORKSHOP 2008

  28. Scatterometer Data Coverage 2008022500 +/- 1.5 H ASCAT (red) QuikScat (blue) IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  29. IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  30. Anomaly correlation coefficient for sea level pressure Period: 2007070812 – 2007080812 Crtl Crtl plus ASCAT Crtl Crtl plus ASCAT Southern Hemisphere Northern Hemisphere IV WMO IMPACT WORKSHOP 2008 Alexander Cress

  31. Time series of anomaly correlation coefficient for Europe Mean sea level pressure VV=72h Start of the forecasts 00 UTC ANOC Crtl Crtl plus ASCAT IV WMO IMPACT Workshop 2008 Alexander Cress

  32. Summary I • Satellite sounding data from TOVS radiances are most important data source • AMSU-A radiance data from Metop A are very import for NWP in Europe • AMV wind vectors are still a valuable observation source for NWP at DWD • Quality information of the AMV’s are very important • Positive impact of MODIS winds and MTSAT-1R after height assignment correction • Direct broadcast MODIS winds very helpful to get polar winds into main forecast run (short cut-off) IV WMO Impact Workshop 2008 Alexander Cress

  33. Summary II • ASCAT wind observations smaller bias than QuikScat. No bias correction • Scatterometer data have positive impact of single analyses/forecast • General small positive impact on forecast quality for both hemispheres predominantly on the Southern Hemisphere • Small structures are difficult to analyses due to broad scale error correlation functions • Radio occultation is a new and promising data source for NWP • Bending angles are assimilated at DWD. Benefit: High vertical resolution, independence of cloud conditions, near uniform global coverage and lack of biases • Impact on Southern Hemisphere half the impact of AMSU A radiances IV WMO Impact Workshop 2008 Alexander Cress

  34. Outlook • 3D-VAR (PSAS) assimilation system will become operational in summer 2008 • New computer platform at DWD (IBM -> NEC 9X) • Use of AMSU-B and MHS sounding profiles • Use of sounding profiles from the IASI instrument onboard of Metop • Use of wind profiler and VAD winds (USA, Europe, Japan) • New scatterometer from India (ISCAT) should become available • Investigate the impact of AVHRR polar wind vectors and AMV wind vectors from the Chinese satellite Fenyun • Use of lidar wind profiles from the ADM space mission of ESA IV WMO Impact Workshop 2008 Alexander Cress

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