Gps data during sop1 sop2 d4b2
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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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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

  • 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


Gps data during sop1 sop2 d4b2

  • 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


E gvap eumetnet eig gps water vapour program

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


Gps data during sop1 sop2 d4b2

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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

Hymexdatabase

sedoo.fr

IODAMED meeting, 16 May 2014


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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


Gps data during sop1 sop2 d4b2

  • 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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