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Tropospheric Delays

Introduction

Since June 2001, the EPN Analysis Centres operationally estimate tropospheric Zenith Path Delays (ZPD) in addition to station coordinates. These ZPD (available in daily SINEX TRO files) are used by the coordinator of the EPN troposphere product to generate each week ('wwww') the combined EPN troposphere solution containing the combined troposphere estimates with an hourly sampling rate. The coordinates, as a necessary part of this file, are taken from the EPN weekly combined SINEX file. Hence, stations without estimated coordinates in the weekly SINEX file are not included in the combined troposphere solution.

As part of the EPN reprocessing activities, an updated series of combined EPN ZPD is also computed. This was done for EPN-REPRO1 (1996-2006) and EPN-REPRO2 (1996-2014).

Download

Operational ZPD series (from GPS wk 1100 til now):

From the EUREF product directory at the BKG data centre.
Both the combined EPN troposphere solution:

  • the output file (EURwwww7.TRO)
  • a summary file (EURwwww7.TSU) with some statistics about, e.g., frequencies of the analyzed stations and accuracies of a single AC solution, providing feedback to contributing ACs (format change at GPS wk 1800!)

as well as the ZPD estimates from each AC.

EPN-REPRO1 ZPD series (from GPS wk 0834 to 1407):

From the EPN-repro1 product directory at the BKG data centre.
Both the combined EPN troposphere solution:

  • the output file (eu0wwww7.tro.Z)
  • a summary file (eu0wwww7.tsu.Z) with some statistics about, e.g., frequencies of the analyzed stations and accuracies of a single AC solution, providing feedback to contributing ACs

as well as the ZPD estimates from each AC. Note that the number and composition of the ACs in the reprocessing for each EPN station may differ from the operational EPN product.

EPN-REPRO2 ZPD series (from GPS wk 0834 to 1824):

From the EPN-repro2 product directory at the BKG data centre.
Both the combined EPN troposphere solution (Pacione, R., Araszkiewicz, A., Brockmann, E., and Dousa, J.: EPN Repro2: A reference GNSS tropospheric dataset over Europe, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-369, in review, 2016):

  • the output file (eu0wwww7.tro.Z)
  • a summary file (eu0wwww7.tsu.Z) with some statistics about, e.g., frequencies of the analyzed stations and accuracies of a single AC solution, providing feedback to contributing ACs

as well as the ZPD estimates from each AC. Note that the number and composition of the ACs in the reprocessing for each EPN station may differ from the operational EPN product.

Plots

General

Mean Zenith Path Delay biases of each AC wrt weekly EPN troposphere solution.

Stations
Zenith Path Delays extracted from weekly EPN troposphere solution Zenith Path Delay biases of each AC wrt weekly EPN troposphere solution Zenith Path Delay differences between radiosonde data and EPN troposphere solution
Updated weekly Updated weekly Updated weekly

Purpose :

  • Show time series of ZPD parameters derived from the EPN combined solution

Purpose :

  • Show the agreement of the individual EPN LACs ZPD solutions

  • Visualize potential periodic signals

  • Reflect changes in, e.g. used options, analysis procedures etc

Purpose :

  • Validate EUREF combined Zenith Path Delay (ZPD) parameters with ZPD derived from radiosonde (RS) data at co-located stations

  • Variations and differences are influenced by the horizontal distance between the two stations

  • Time series of differences reflect changes in analysis strategy

Procedure :

  • Combination of daily SINEX TRO files of the individual LACs solutions on a weekly basis

  • Weak ZPD estimates of the individual LACs solutions are excluded beforehand because of a standard deviation exceeding 15 mm

  • Outliers of the individual LACs solutions are excluded before the combination

  • Site-specific solutions of a particular LAC are eliminated for single days if the standard deviation of the series exceeds 20 mm

  • Single ZPD values of the combined solution exceeding a standard deviation of 10 mm are investigated for potential outliers

Procedure :

  • EPN LACs are delivering estimated ZPD parameters on a daily basis

  • These solutions are combined to the EPN combined (mean) solution considering the biases between the individual solutions (this way jumps will be avoided if single observations of the individual solutions are missing)

  • The resulting daily biases show the agreement of the LACs individual solutions to each other and to the mean

Procedure :

  • Download of RS data provided by EUMETNET, based on the EUREF-EUMETNET MoU

  • Processing ZPD parameters (software provided by H. Vedel, Danish Meteorological Institute (DMI))

  • Geoid undulations at co-located stations are taken into account

  • Differences at co-located stations for identical points in time