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E-GVAP: EUMETNET GPS Water Vapour Programme Galina Dick (1) and Jan Dou s a ( 2 )

E-GVAP: EUMETNET GPS Water Vapour Programme Galina Dick (1) and Jan Dou s a ( 2 ) ( 1 ) GeoForschungsZentrum Potsdam, Germany ( 2 ) Geodetic Observatory Pecny, Czech Republic In collaboration with E-GVAP Team IGS Analysis Center Workshop Miami Beach, Florida, USA 2-6 June 2008.

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E-GVAP: EUMETNET GPS Water Vapour Programme Galina Dick (1) and Jan Dou s a ( 2 )

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  1. E-GVAP: EUMETNET GPS Water Vapour Programme Galina Dick (1) and Jan Dousa (2) (1) GeoForschungsZentrum Potsdam, Germany (2) Geodetic Observatory Pecny, Czech Republic In collaboration with E-GVAP Team IGS Analysis Center Workshop Miami Beach, Florida, USA 2-6 June 2008

  2. European Projects: COST, TOUGH, E-GVAP • COST-716 Action (1998-2003): • "Exploitation of Ground-Based GPS for Operational Numerical Weather Prediction and Climate Applications“ • 15 Institutions • 7 ACs • TOUGH (2003-2006): • „Targeting Optimal Use of GPS Humidity Measurements in Meteorology“ • 15 Institutions (Coordinator DMI) • 12 ACs • > 400 GPS sites E-GVAP (2006 - 2009): „The EUMETNET GPS Water Vapor Programme“ • 13 Institutions • 10 ACs • > 800 GPS sites Operational E-GVAP Network

  3. What is E-GVAP? EUMETNET GPS Water Vapour Programme EUMETNET = organisation of European national meteorological offices (West European + number of East European, enlarging) E-GVAP is a separate observing programme under EUMETNET, not all EUMETNET members are members of E-GVAP.

  4. E-GVAP Goal: prepare GPS derived ZTD/IWV for operational meteorological use Main product: ZTD/IWV of ~ 800 European sites in NRT IWV Maps Product delay: < 1h 45 min Hourly transfer to UK Met ftp-server Using for assimilation into NWP models UK MetOffice and Meteo France uses NRT ZTDs in their operational forecasts

  5. E-GVAP Members Danish Meteorological Institute (coordinator) Finnish Meteorological Institute Icelandic Meteorological Office Irish Meteorological Service Meteo Swiss Norwegian Meteorological Institute Royal Meteorological Institute of Belgium Royal Meteorological Institute of the Netherlands Spanish Meteorological Institute Meteo France Croatian Met Service Swedish Meteorological and Hydrological Institute UK Met Office Contact and information points Email address: egvap@dmi.dk Web address: http://egvap.dmi.dk

  6. GFZ Germany BKG Germany ASI Italy KNMI(1) Netherlands GOPE Czeck Rep. IEEC Spain LPT(R) Switzerland MetO FTP server METO UK BUFR BUFR Linux Workstation MetDB BUFR NGAA Sweden BUFR BUFR ROB Belgium NRT Users & mirror sites GTS Users SGN France NRT Data Flow in E-GVAP Green = nation member of E-GVAP. Blue = nation not member of E-GVAP. (IGN, Spain is currently starting as a new producer of GNSS ZTD data)

  7. Monitoring: Web Page E-GVAP Timeliness is very important for meteorological forecasting. Arrival statistics of NRT GPS ZTD data at dataserver (by Dave Offiler, UK MetOffice).

  8. Inter comparison of ZTDs from different analysis centres processing the same site, comparison with respect to NWP and radiosonde data - helps to identify optimal processing methods and helps to reject poor data. A set of 12 „supersites“ that all centres must processed has been introduced.

  9. E-GVAP Processing Strategies • PPP approach: • GFZ (EPOS) • NGAA (GIPSY) • Network approach: • ASI (GIPSY) • BKG, GOP, KNMI, LTP, ROB, METO, SGN (Bernese)

  10. Motivation for"Precise Point Positioning“ (PPP) Comparison of different adjustment approaches ==> Main reason for switching to PPP : efficient operation of large networks (>100 sites) within short computation time REQUIREMENT: GPS orbits & clocks should be given with sufficient accuracy

  11. Networks used by PPP Analysis Centres E-GVAP (~800 sites) NGAA (~360 sites): Sweden, Denmark, Finnland, Norway GFZ (~220 sites): Germany + EUREF

  12. Part 1 - Network orbit improvement: • Adjustment of precise orbits &clocks • Global network : ~20 IGS +Germansites • Input orbits: GFZ 3h Ultra Rapid (pred.) CPU (Linux PC): ~6 to 8 minutes Part 2 - PPP Analysis: • Estimation of trop. parameters • Large set of parameters possible (high sampling rate, trop. gradients) NEW: ‚slant delays‘ estimation CPU (Linux PC): <5 min for 220 sites GFZ NRT Processing Scheme GFZ EPOS Software .

  13. IWV Monitoring (Web Page of GFZ) Time series (last 2 or 7 days) Animation (selected time interval) Comparison to COSMO-DE of German Weather Service (DWD)

  14. Validation: Web Page E-GVAP (1) A feedback for ACs -ValidationwithHIRLAMmodel for each AC: Bias Example GOP Example GFZ

  15. Validation: Web Page E-GVAP (2) A feedback for ACs -ValidationwithHIRLAMmodel for each AC: StdDev Example GOP Example GFZ

  16. PPP performance (GFZ, NGAA)

  17. PPP performance (Example NGAA) • Data drop-outs is decreasing due to new routines at network operational centers e.g. SWEPOS • Occasional (2-3 hours per week) bad ZTD values delivered to EGVAP (see figure). • The reason for these “hick-ups” are related to the orbit and clock analysis which sometimes fails due to data (global data) collection problems.

  18. Comparison of different processing strategies ZIMM – one of the 12 ‘supersites’

  19. Validation with Radiosondes (example GFZ) GPS derived ZTD compared to ZTD from RS for Lindenberg, March 2008

  20. Validation with RS and WVR (example GOP)

  21. Impact of ground-based GPS measurements on forecasts Impact over Europe (Results of Meteo France, P.Poli et al.) 23 forecasts June-July 2005 Verification : radiosonde measurements Temperature RMS Diff. Wind Speed RMS Diff. Pressure (hPa) Pressure (hPa) BLUE=betterRED=worse Forecast lead time (hours) Forecast lead time (hours) Without GPS ZTD data WithGPS ZTD data

  22. E-GVAP is very thankful for the services that IGS provides the geodetic community. They are vital to the NRT GPS ZTD product that we use in meteorology. For weather forecasting the GPS ZTD data must be available fast, and of a quality which is both good and does not fluctuate strongly in time. The timeliness issue is important and clearly influences ZTD data quality. E-GVAP and IGS

  23. Conclusions/Recommendations • GPS derived ZTDs are used operationally in Europe • Due to steadily increasing number of operational GPS sites PPP strategy presents a promising outlook for future efficient GPS-meteorology. E-GVAP recommends IGS to support PPP strategy with high quality adequate products. • The 'real-time' clocks will be interesting future product for using in GPS meteorology. • For current needs E-GVAP encourages IGS to deliver clock products in ‘near-real’ time (hourly) till the ‘real-time’ IGS clocks will be available as products with sufficient quality

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