Current Network
The network of GNSS stations has been selected with the aim of achieving good spatial coverage of Luxembourg and the Greater Region.
Table 2 List of GNSS data providers Figure 3 GNSS station distribution
in Europe Figure 2 GNSS station distribution
in the Greater Region
NRT System Evaluation
The hourly NRT system has been evaluated by comparing its COST-716 format output to that of a state-of- the-art system (IES2) which is currently providing data to the E-GVAP project. For identification purpose, we call our system output as ULUX here. The figures and table below show the results of the comparison of ZTD and IWV estimates for the station CAMO (Camborne, UK) for a period of 48 hours (22-23 February 2012).
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
0 5 10 15 20 25 30 35
0:00 1:45 3:30 5:15 7:00 8:45 10:30 12:15 14:00 15:45 17:30 19:15 21:00 22:45 0:30 2:15 4:00 5:45 7:30 9:15 11:00 12:45 14:30 16:15 18:00 19:45 21:30 23:15 Difference [kg/m2]
IWM [kg/m2]
Time
IWV comparison for station: CAMO
IES2 ULUX
Difference(ULUX-IES2)
-8 -6 -4 -2 0 2 4 6 8 10 12
2340 2360 2380 2400 2420 2440 2460 2480 2500
0:00 1:45 3:30 5:15 7:00 8:45 10:30 12:15 14:00 15:45 17:30 19:15 21:00 22:45 0:30 2:15 4:00 5:45 7:30 9:15 11:00 12:45 14:30 16:15 18:00 19:45 21:30 23:15 Difference [mm]
ZTD [mm]
Time
ZTD comparison for station: CAMO
IES2 ULUX
Difference(ULUX-IES2)
Figure 4 Comparison of IWV (left) and ZTD (right) time-series obtained from ULUX and IES2 solutions (Note the different scales for the estimates and the difference)
Table 3 RMS values of the difference between ZTD and IWV estimates obtained from ULUX and IES2 for the period of 22-23 February 2012
Abstract
Since June 2011, the University of Luxembourg has started in collaboration with the University of Nottingham a PhD project entitled “The Potential of Precipitable Water Vapour Measurements using Global Navigation Satellite Systems in Luxembourg (PWVLUX)”, which is funded by the Fonds National de la Recherche (FNR) Luxembourg. The research objectives of the project are to study the potential for improvements in short-term weather forecasts and long-term climate variability for Luxembourg and the Greater Region by inclusion of the observations from Global Navigation Satellite Systems (GNSS) in the existing techniques. To achieve the research objectives, systems are being set up at the University of Luxembourg which process ground-based GNSS data for the provision of zenith total delay (ZTD) and integrated water vapour (IWV) estimates in real-time, near real-time and post-processing modes.
Through collaboration with the Administration du cadastre et de la topographie (Luxembourg) and the Service public de Wallonie (Belgium), the coverage of the available GNSS permanent networks is improved over the primary project area, although also data from other European and global networks are processed. The meteorological analysis of the PWVLUX products is supported through collaborations with the Meteorological Service of the Administration de la navigation aérienne and the EUMETNET project E-GVAP.
In this study we present the first ZTD and IWV estimates obtained from the near-real time processing systems in development at the University of Luxembourg. In a preliminary evaluation we compared their performance to some state-of-the-art systems already in operation and found that the ZTD estimates agree up to a few millimeters and the IWV estimates agree at the sub-millimeter level.
Network Region
SPSLux ( ) Luxembourg WALCORS ( ) Wallonie
(Belgium) RGP( ) France OSGB+Geonet
( )
UK
EPN ( ) Europe IGS08 ( ) Global
Conclusions
So far, two NRT processing systems to estimate ZTD and IWV with hourly and 15-minute update cycles have been developed at the University of Luxembourg. During the initial phase of the project, we have investigated the GNSS networks available to the NRT systems in order to achieve an adequate spatial coverage for Luxembourg and the Greater Region.
An evaluation of the hourly NRT system was carried out by comparing it to a similar state-of-the-art system and an agreement up to a few millimeters between the ZTD and less than 1 kg/m2 between IWV estimates was found. First preliminary results for the hourly NRT system for a frontal system crossing over Luxembourg and the Greater Region on February 23, 2012 are presented. We compared the maps of IWV with precipitation maps from weather radar data and show good agreement in the location of the foremost extent of the weather system.
Acknowledgements
This project is funded by the Fonds National de la Recherche, Luxembourg. We are also thankful to the Administration du cadastre et de la topographie, Luxembourg and the Service public de Wallonie, Belgium for provision of GNSS observation data and to the Service Météorologique de Luxembourg for support with meteorological information.
Presented at: Luxembourg Earth Observation and Integrated Applications Day, March 16, 2012 The Project
Research Objectives
• To study the impact of GNSS data on meteorological short-term forecasting.
- by incorporating GNSS data in NWM for Luxembourg
- by studying the improvement in short-term forecasting
• To investigate the climate variability using GNSS data in Luxembourg and the
Greater Region
Expected Outcomes
• Short-term Weather Forecasting:
- ZTD and IWV estimates for extreme weather periods
- 2D climatological maps of ZTD and IWV for extreme weather periods
• Climate Monitoring:
- Long-term trends/time series of ZTD and IWV - 2D climatological maps of ZTD and IWV
variations
Benefits
• The project will develop a capability (in Luxembourg) for the use of GNSS data for meteorological applications
• Improved weather forecasts for aviation and general public
• Public availability of ZTD and IWV estimates for remote sensing applications
• Improved understanding of local and regional climate and its variability
Technical Developments (at University of Luxembourg)
• A post-processing system for IWV estimation
• A near-real time (NRT) processing system for IWV estimation (completed)
• A real time (RT) processing system for IWV estimation
First Zenith Total Delay and Integrated Water Vapour Estimates from the Near Real-Time GNSS Data Processing Systems at the University of Luxembourg
Ahmed, F.(1), Teferle, F. N.(1), Bingley, R. M.(2)
1) Geophysics Laboratory, University of Luxembourg, Luxembourg
2) Nottingham Geospatial Institute, University of Nottingham, United Kingdom Contact: [email protected]
The Near Real-Time Processing Systems
Table 1 Features of the NRT processing systems at the University of Luxembourg
Figure 1 Operational Diagram of NRT processing systems at the University of Luxembourg
Processing Data & Products
Handling Database
Management
Bernese GPS Software 5.0
ZTD Estimates
Convert to IWV
IWV Estimates
Create Plots &
Animations OEDC
HD
MET
RINEX Data
Products
Meteorological Data
Download Latest Raw Data
Download Latest Products
Download Latest Meteorological Data M
a i n
t a
i n
D a
t a b a s e s
A r c h i v e
I n p u t
D a t a
A r c h i v e
O u t p u t
D a t a
Archiving System Type: Hourly NRT Sub-hourly NRT
Update Cycle 1 hour 15 minutes
Processing Engine Bernese GPS Software 5.0
Bernese GPS Software 5.0 Development
Language(s)
Perl, Python Perl, Python Input Raw Data RINEX 2.11
(hourly)
Real-time stream Input Products IGS Ultra-Rapid IGS Ultra-Rapid Antenna Calibration Absolute Absolute
Input Meteorological Data
Hourly data file from UK
MetOffice*
Sub-hourly data file from UK
MetOffice*
Outputs • ZTD estimates
• IWV estimates (COST-716)
• 2D Plots
• Animations
• ZTD estimates
• IWV estimates (COST-716)
* To be provided by Meteorological Service of Luxembourg
Daily Processes in the NRT system
• Computation of a priori coordinates for all
stations using precise point positioning
• Obtaining updated station information
• Obtaining updated antenna information
ULUX vs. IES2
RMS Difference between IWV 0.48 kg/m2 RMS Difference between ZTD 3.36 mm
Preliminary NRT Results
Figure 5 Comparison of weather radar precipitation (left), GPS IWV (center) and GPS ZTD (right)
Figure 6 3-hourly plots for IWV over the Greater Region for 20120222- 15:00UTC to 20120223-06:00UTC
0 5 10 15 20 25
15:00 15:45 16:30 17:15 18:00 18:45 19:30 20:15 21:00 21:45 22:30 23:15 0:00 0:45 1:30 2:15 3:00 3:45 4:30 5:15 6:00 6:45
BASC WALF ERPE ECHT ROUL TROI
IWV [Kg/m2]
22-Feb-2012 23-Feb-2012
Figure 7 IWV time series for 20120222-15:00UTC to 20120223-06:00UTC for SPSLux stations
From Figure 5, it is evident that the distribution of IWV is very similar to the pattern of the frontal system shown by the weather radar.
Figures 6 and 7 show the rise in the amount of IWV over Luxembourg and the Greater Region as this frontal system passes over the region.
