Using Signals Emitted by Global Navigation Satellite Systems

Transcription

1 Using Signals Emitted by Global Navigation Satellite Systems Eric Pottiaux PhD. Thesis submitted for the Degree of Doctor in Sciences Co-Promotors: Carine Bruyninx and Pascale Defraigne Université Catholique de Louvain Royal Observatory of Belgium

2 Context of the Thesis Water Vapour Weather Forecast Lack of Information about the Humidity Field Global Navigation Satellite Systems 5 November 2010 Meteoclim Eric Pottiaux 2

3 Context of the Thesis GNSS Signals Study and Observe the Neutral Atmosphere (troposphere) Provide a Product for Operational Weather Forecast On the courtesy of VTM 5 November 2010 Meteoclim Eric Pottiaux 3

4 Global Navigation Satellite Systems (GNSS) INTRODUCTION 5 November 2010 Meteoclim Eric Pottiaux 4

5 GNSS A Service to Real-time Positioning and Navigation 5 November 2010 Meteoclim Eric Pottiaux 5

6 GNSS System Design & Measurements Global navigation Satellite Systems (GNSS) Satellite constellation (altitude ~26000km) Emitting radio-signal towards the Earth (codes+carriers) Recorded by ground receivers and antennas Real-time Applications & Navigation Scientific Applications 5 November 2010 Meteoclim Eric Pottiaux 6

7 Signal or Noise? ATMOSPHERIC REFRACTION 5 November 2010 Meteoclim Eric Pottiaux 7

8 GNSS Atmospheric Refraction Troposphere: The Ionosphere: position determination is affected by errors Need Is Is a a non-dispersive to be mitigated medium medium to achieve the highest precision possible Has By frequency for in primary the position combination effect determination to change Mitigates the propagation its effects speed To decelerate the signals (measured distance > theoretical distance) Ionosphere ( km) Acceleration (carrier) Troposphere (0-80km) Decelerate 5 November 2010 Meteoclim Eric Pottiaux 8

9 GNSS-Meteorology A Simplistic View 1. If satellite s position is known 2. If station s position is known Troposphere (0-80km) 5 November 2010 Meteoclim Eric Pottiaux 9

10 GNSS-Meteorology A Simplistic View Measured Distance Theoretical Distance Tropospheric Delay The Tropospheric Delay in Short Expressed in metres or millimetres Typical values (Europe): 2.20m to 2.65m at zenith (sea level) Contains information about the atmospheric water vapour that can be used in meteorology (<20% of the total tropospheric delay) 5 November 2010 Meteoclim Eric Pottiaux 10

11 GNSS-Meteorology A Simplistic View Weather Forecasting and Nowcasting On the courtesy of RTBF 5 November 2010 Meteoclim Eric Pottiaux 11

12 Weather Forecasting in Europe THESIS OBJECTIVES GNSS-METEOROLOGY 5 November 2010 Meteoclim Eric Pottiaux 12

13 Objectives of the Thesis To Develop a State-of-the-art Methodology For estimating tropospheric delays in near real-time For weather forecasting in Europe To Provide a service to European National Meteorological Services via E-GVAP II «The EUMETNET EIG GNSS Water Vapour Program II» 5 November 2010 Meteoclim Eric Pottiaux 13

14 ANALYSIS METHODOLOGY A 2-STEP PROCESSING 5 November 2010 Meteoclim Eric Pottiaux 14

15 GNSS-Meteorology A Simplistic View 1. If satellite s position is known (IGS Orbit Products) 2. If station s position is known (computed) Troposphere (0-80km) 5 November 2010 Meteoclim Eric Pottiaux 15

16 Methodology A GNSS observation processing in 2 Steps 1st Step: Precise Position Determination 2 nd Step: Tropospheric Delay Estimations Post-processing Analysis Precise Coordinates (1.3mm N&E, 4.3mm Up) Near Real-time Analysis Coordinates fixing and Tropospheric Delay Estimation Monitoring & Validation Tropospheric Delays Precise Positions Post-Processing Tropospheric Delays Last 31 Days Current Day Time 1 st Step: Post-Processing 2 nd Step: Near Real-time Current Hour 5 November 2010 Meteoclim Eric Pottiaux 16

17 Methodology GNSS Observation Networks Network of 220+ stations IGS Network EUREF Network Belgian ROB Network German GREF Network Dutch Network French RGP Network E-GVAP Super-Sites 5 November 2010 Meteoclim Eric Pottiaux 17

18 Conclusion Methodology A GNSS observation processing in 2 Steps Methodology GNSS-Meteorology Requirements Sensitivity Tests & Optimisations Validation Precision: 4-5mm & Accuracy: < 2.5 mm) All GNSS-Meteorology Requirements are Satisfied. (Time Resolution, Spatial resolution, Precision, Accuracy, Latency) 5 November 2010 Meteoclim Eric Pottiaux 18

19 The EUMETNET EIG GNSS Water Vapour Program (E-GVAP) METHODOLOGY EUROPEAN WEATHER FORECASTS 5 November 2010 Meteoclim Eric Pottiaux 21

20 The EUMETNET EIG GNSS Water Vapour Program The Observing Network E-GVAP in Short 15 member states, including Belgium (RMI) Fruitful collaboration between meteorologists and geodesists 12 GNSS data analysis centres, including Belgium (ROB) > 1250 unique sites (+ ~200 new sites/year) ~ obs./hour ~ obs./day ~ 1.3 million obs./year 5 November 2010 Meteoclim Eric Pottiaux 22

21 Impact Studies X. Yan et al., 2009 A clear positive effect on short-range quantitative precipitation forecasts Eresmaa, 2009 The impact appears most positive in regions of Europe where GPS station density is highest 5 November 2010 Meteoclim Eric Pottiaux 23

22 Operational Assimilation within E-GVAP Since 2007, operational assimilation in the NWP models at 5 November 2010 Meteoclim Eric Pottiaux 24

23 The European GNSS-based Water Vapour Observing Network GNSS-based tropospheric delays + pressure & temperature records IWV On the courtesy of Henrik Vedel, DMI 5 November 2010 Meteoclim Eric Pottiaux 25

24 Location, extension and movement of fine structures DENSE NETWORKS OF GNSS STATIONS 5 November 2010 Meteoclim Eric Pottiaux 26

25 Multi-Cellular Thunderstorm 29 th June November 2010 Meteoclim Eric Pottiaux 27

26 Thunderstorm Case European regional network 5 November 2010 Meteoclim Eric Pottiaux 28

27 Dense GNSS Networks The Belgian Dense Network 5 November 2010 Meteoclim Eric Pottiaux 29

28 On the courtesy of Laurent Delobbe, RMI Qualitative Analysis Weather Radars Images Added-value of the dense GNSS networks? Qualitative comparison wrt. weather radars Rain OO UTC 12 UTC 24 UTC 5 November 2010 Meteoclim Eric Pottiaux 30

29 IWV(mm) Qualitative Analysis The European Network vs. Dense Network BREE DENT BRUS MEEU EIJS WARE DOUR Water Vapour and Rain IWV (mm) - 00 UTC OO UTC 12 UTC 24 UTC 5 November 2010 Meteoclim Eric Pottiaux 31

30 IWV(mm) Qualitative Analysis The European Network vs. Dense Network BREE DENT BRUS MEEU EIJS WARE DOUR Water Vapour and Rain IWV (mm) - 00 UTC OO UTC 12 UTC 24 UTC 5 November 2010 Meteoclim Eric Pottiaux 32

31 Qualitative Analysis The European Network vs. Dense Network Added-value of the dense network? Comparison wrt. Weather radar images Better resolution with the Belgian dense network Additional information appears wrt. Weather Radar images DENT BRUS DOUR BREE MEEU EIJS WARE IWV (mm) - 00 UTC IWV (mm) - 00 UTC OO UTC 12 UTC 24 UTC 5 November 2010 Meteoclim Eric Pottiaux 33

32 Quantitative Analysis Profiles through the IWV field 4 profiles through the 2-D field In the direction of the front propagation : differences ~2mm (IWV) 3 other profiles: bigger differences Maximal difference : 5.47mm (IWV) between BRUS-ERPE DENT BRUS WARE BREE DOUR European network: small structures not visible Amplitude of the small structures: 5 to 6 times what nowcasters want to see BRUS BRUS 5 November 2010 Meteoclim Eric Pottiaux 34

33 Dense GNSS Networks Location and movements of the structures The Belgian dense network allow to locate and monitor the movements of the structures Emerging zone of lower IWV density Thundery precipitation zones in the north/northeast (radar image) Zone diameters: 25-35km DENT BRUS DOUR IWV (mm) 12h30 BREE MEEU EIJS WARE OO UTC 12 UTC 24 UTC 5 November 2010 Meteoclim Eric Pottiaux 35

34 Dense GNSS Networks Location and movements of the structures The Belgian dense network allow to locate and monitor the movements of the structures Emerging zone of lower IWV density Thundery precipitation zones in the north/northeast (radar image) Zone diameters: 25-35km DENT BRUS DOUR IWV (mm) 13h30 BREE MEEU EIJS WARE OO UTC 12 UTC 24 UTC 5 November 2010 Meteoclim Eric Pottiaux 36

35 CONCLUSIONS AND PERSPECTIVES 5 November 2010 Meteoclim Eric Pottiaux 37

36 Methodology and Objectives European Level We developed a methodology to provide near real-time tropospheric delays for weather forecasting in Europe The methodology satisfies all requirements for numerical weather forecasting and nowcasting applications The methodology is used to provide an operational service to European meteorologists (E-GVAP) The tropospheric delays provided within E-GVAP enter the operational assimilation process at Météo France and U.K Met Office (more coming this autumn/winter) 5 November 2010 Meteoclim Eric Pottiaux 38

37 Methodology and Objectives Local Level We applied the methodology to study the fine structures in the 2-D water vapour field: A European network can only render the large-scale structures in the water vapour field The Belgian dense GNSS network allows to reconstruct small-scale structures (~ 20 km) and to monitor their locations and movements Significant differences up to 5.5 mm (IWV) could be observed between the 2-D water vapour fields 5 November 2010 Meteoclim Eric Pottiaux 39

38 Perspectives Meteorology and Weather Forecast Several methodology improvements are possible: Increase the spatial resolution Include more stations from dense GNSS networks Limitation: the computer power Turn the analysis into a Multi-GNSS processing GLONASS and Galileo More observations, better precision, better reliability Access to fine tropospheric structures Limitation: no precise real-time orbits for GLONASS, Galileo not ready yet 5 November 2010 Meteoclim Eric Pottiaux 40

39 Perspectives Climate Monitoring To study the applicability of the methodology to climate monitoring (Europe+Antartica) ELIS ULUX 5 November 2010 Meteoclim Eric Pottiaux 41

40 Thank you for your Attention 5 November 2010 Meteoclim Eric Pottiaux 42