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GPS data during SOP1 & SOP2 (D4B2)

GPS data during SOP1 & SOP2 (D4B2). IODAMED meeting, 16 May 2014. Olivier Bock, LAREG IGN Pierre Bosser, ENSG IGN Contributions from : C. Champollion, E. Doerflinger (LDL) France R. Pacione (E-GEOS/ASI) Italy

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GPS data during SOP1 & SOP2 (D4B2)

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  1. GPS data during SOP1 & SOP2(D4B2) IODAMED meeting, 16 May 2014 Olivier Bock, LAREG IGN Pierre Bosser, ENSG IGN Contributions from: • C. Champollion, E. Doerflinger (LDL) France • R. Pacione (E-GEOS/ASI) Italy • J. A. Sanchez Sobrino (IGN-E), A. Seco (UPN), A. Botas (Logica), C. Sanchez Tugores (Sitibsa), L. García Pellicer (ARAGEA), Spain • M. Vasconcelos (DGT), Portugal • J. Jones, D. Offiler (UKMO), UK IODAMED meeting, 16 May 2014

  2. Outline • The operational GPS network and ZTD data flow (EGVAP -> assimilation in NWP models) • A reprocessed dataset for HYMEX SOP1+2 • Screening of ZTD data • Conversion of ZTD to IWV • Comparison of GPS IWV to AROME WMED Op An IODAMED meeting, 16 May 2014

  3. May 2012 E-GVAPEUMETNET EIG GPS Water Vapour Program • Aim: use NRT GNSS ZTD for operationalmeteorology. • EGVAP is a consortium of 13 National Weather Services working in close collaboration with11 National MappingAgencies. • GNSS network iscomposedof public & private stations and counts ~ 1500 sites. • GNSS rinex data are processed by 15 ACs in Near Real Time (NRT), i.e. latency < 1h45min. • NRT ZTD disseminated by UMKO on the GTS (BUFR files) and assimilatedin NWP models by UKMO, Meteo-France, DMI… IODAMED meeting, 16 May 2014

  4. ZTD GPS data input AROME - France 10 000 values per 3h 15 GPS ACs with different sofware and processing procedures => ZTD dataset is inhomogeneous IODAMED meeting, 16 May 2014

  5. NRT ZTD data archived on hymex DB • NRT_EGVAP_SGN (IGN/SGN, France) • Network: • - RGP (France) + reference stations (321 sites) • Processing: • BerneseGPS software • Ultra-rapidIGS orbits, fixed positions, CO=10°, no gradients, ZTD values at HH+00, 15, 30, 45, 59’ • NRT_EGVAP_IGE (IGN, Spain) • Network: • - Spain + Portugal + reference stations (288 sites) • Processing: • BerneseGPS software • Ultra-rapidIGS orbits, ZTD values: HH+00, 15, 30, 45, 59’ • NRT_EGVAP_ASI + NRT_EGVAP_ASI1 (E-GEOS/ASI, Italy) • Network: • - Italy+ reference stations (164 sites) • Processing: • GIPSY-OASIS II software • Ultra-rapidJPL orbits, fixed positions, ZTD values HH+00, 15, 30, 45’ IODAMED meeting, 16 May 2014

  6. Hymexdatabase sedoo.fr IODAMED meeting, 16 May 2014

  7. Comparison of NRT ZTD data at common sites ASI – SGN, 44 common sites, different software Mean = -3 ± 5 mm Std. = 7 mm IGE – SGN, 50 common sites, same software Std. = 7 mm Mean = 0 ± 2 mm IODAMED meeting, 16 May 2014

  8. Reprocessed network REPRO EGVAP Orphéon SGN IGE HYMEX_FR HYMEX_DE 15 networks ASI Sardinia 773 stations (3 Analysis Centres) 970 stations (2 ACs, 21 networks) IODAMED meeting, 16 May 2014

  9. Reprocessed network Homogenous reprocessing of 970 sites for period 1 Sep 2012 – 31 Mar 2013 • Reprocessing by IGN/LAREG, France • Network: 823 sites • France : RGP (349 sites) + Orphéon (182 sites) • Temporary sites : Cévennes (8 sites, Géosci. Montpellier) and Corsica (5 sites, GFZ) • Spain: 14 regions (231 sites) + IGE national network (37 sites) • Portugal: RENEP (43 sites) • North Africa: UNAVCO (5 sites) • Processing: • GIPSY-OASIS II software • Final JPL orbits & clocks, ZTD + gradients every5’, VMF1, 30 h session • Reprocessing by e-GEOS/ASI, Italy • Network: • Italy: ASI1 + new stations (Sardinia) = 147 sites • Processing: • Idem repro_LAREG IODAMED meeting, 16 May 2014

  10. Comparisonof NRT to post-proc. data IGE Mean= 0.5 ± 3 mm Std. = 8 mm SGN Mean= -0.1 ± 2 mm Std. = 6mm ASI Mean= 0.8 ± 2 mm Std. = 4 mm IODAMED meeting, 16 May 2014

  11. Screening of ZTD data 1st step Analysis of formal error for ZTD, station height, and other processing output information After Before mean 1 – 99 percentiles of ZTD formal error Std.dev. 2nd step Comparison of GPS ZTD data to ZTD data from a NWP model, rejection of data at ± 3  IODAMED meeting, 16 May 2014

  12. Conversion of ZTD to IWV accurate to 0.006% Surface pressure or NWP Analysis accurate to 0.1-1 hPa (0.01-0.1%) accurate to 0.06% accurate to 10-3 m s-2(0.01%) Principle: IWV=K(Tm)*( ZTD – ZHD ) Requires auxiliairy data accurate to 2.4 % accurate to ±3 % but k’2 = 0.047 * k3/Tm Empirical model Tm = f(Ts) or NWP Analysis Tm= 250 ± 20 K (8% variations) IODAMED meeting, 16 May 2014

  13. Uncertainty budget of GPS IWV ZTD uncertainty + ZHD uncertainty + K(Tm) uncertainty 1 mm (0.06% k1 error) + 1-2 mm (0.5-1 hPa Ps measurement error) + 1-2 mm (interpolation error) 1-2% (k2 & k3 error) + 1-2% (Tm error < 5K) 4-6 mm (IGS solution) IWV=40 kg/m2 IWV=5 kg/m2 0.3-0.5 kg/m2 0.1-1.1 kg/m2 0.6-0.9 kg/m2 GPS IWV uncertainty: bias≈ 0.2-0.8 kg/m2 random ≈ 0.2-1.5 kg/m2

  14. Comparison of GPS IWV to AROME WMED Mean= 1.5 kg m-2 Std.= 1.5 kg m-2 Slope = 0.96 Correl = 0.92 16 networks, 1 month (Sep 2012) Auxiliairy data for IWV conversion: AROME WMED (surf + T) + emp. model Tm =f(Ts) IODAMED meeting, 16 May 2014

  15. Next steps • Finalise validation of reprocessed GPS ZTD dataset • ZTD data screening (improve method, 1st step) • ZTD to IWV conversion (assess auxiliairay datasets) • Validate GPS IWV data by comparison with other data (MWR…) • Assimilation of reprocessed GPS ZTD data • AROME WMED reanalysis • Prepare data (BUFR files) and assimilation system • Test impact of assimilation, case studies • Assimilation in research models • Monitoring of radiosonde humidity biases • Validation of simulations (case studies) • Process studies (HPE) IODAMED meeting, 16 May 2014

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