IHOP 2002 GPS/H20 Water Vapor Investigations with Ground-Based GPS

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IHOP 2002 GPS/H20Water Vapor Investigations
with Ground-Based GPS
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Contributions

• GPS/H20 France
• J. Van Baelen, J-P. Aubagnac, CNRM, Toulouse
• O. Bock, J. Tarniewicz, SA, Paris
• A. Walpersdorf, LGIT, Grenoble
• E. Doerflinger, F. Masson, LDL, Montpellier
• Field Deployment J. Van Baelen, E.
  Doerflinger, J-P. Aubagnac, Ph. Collard,
  O. Bock
• OK Mesonet J. Basara, OU / OKmesonet team
• UCAR/GST J. Braun
• IHOP/DATA BASE JOSS, NOAA/FSL, ARM/SGP

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GPS derived IWV
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IHOP objectives for GPS/H20 teams

• Methodology Aspects
• Mapping functions and antenna modeling errors,
• Low elevation angles and slant tropospheric
  delays
• Tomographic inversion algorithms, constraints and
  resolution,
• Effect of WV heterogeneity on precise
  positionning,
• Spatial and temporal correlations in ZTDs and
  STDs and covariance matrix determination

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IHOP objectives for GPS/H20 teams

• Scientific Objectives
• GPS water vapor retrieval validation,
• Study of spatial and temporal variability and
  dynamics of IWV,
• Study of WV convergence as CI precursor,
• 3-D water vapor distribution through tomography
  both local (L1 with few L2 constraints) and
  synoptic,
• Data assimilation (slant delays),

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Field Deployment Objectives vs Logistics

• Légende
• Parc INSU
• SuomiNet
• NOAA/FSL
• ARM/CART

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GPS deployment at OKmesonet sites
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IHOP 2002 GPS deployment and observation
statistics
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IHOP 2002 GPS deployment and observation
statistics
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GPS Data Analysis Status

• Use of GAMIT / GLOBK software package
• Implemented at CNRM late fall 2002.
• First pass analysis
• Preliminary work on the 11-12 June case (!),
• 10 cut off angle, 30 seconds epochs,
• Saastamoinen hydrostatic model,
• Dry and wet Niel mapping functions,
• Three-hourly ZTD calculations and a single
  gradient per day,
• All stations non-constrained.

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GPS Data Analysis Status

• Next step
• Kalman filter to positionning and precise
  calculation of (half-)hourly ZTDs,
• Automated processing for entire campaign,
• Determination of IWV for all stations of interest
  to IHOP,
• Results provided to IHOP Data Base in final form.

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GPS Analysis Stations
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Preliminary Results June 11-12 Case Study

• ZTD and IWV Comparisons
• NOAA half-hourly ZTDs from IHOP D.B.
• French processed data (GAMIT)
• UCAR/GST processed data (Bernese)
• Combined results
• NOAA French stations IWVs
• UCAR/GST French stations ZTDs
• Field Differences

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IHOP Data Base JOSS Imagery
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French GPS Station ZTDs
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GPS vs Radiosondes ZTDs
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AIRS Campaign at CNRM (Fall 02)
Comparison IWV GPS - Radiosondes
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Conclusions

• First results of GAMIT single pass processed
  French GPS data consistent with other results,
• Addition of French GPS stations seems to provide
  finer resolution to the central area of interest
  in the 11-12 June case,
• In this case, higher humidity contents shown,
• However, all solutions appear sensitive to single
  station peculiar values gt data or artifact ?

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Ongoing Work

• Complete processing of French GPS stations and
  others of the IHOP area with GAMIT soon to be
  available with (half-)hourly ZTDs and gradients,
• Methodology and Scientific studies to be
  undertaken following the topics specified,
• Each topic is under the principal interest of
  various members of the French GPS/H2O teams, all
  of them are ready to collaborate and share their
  expertise with interested parties,
• Contact joel.van-baelen_at_meteo.fr or the
  corresponding team directly