Using Signals Emitted by Global Navigation Satellite Systems€¦ · MEEU BREE EIJS OO UTC 12 UTC 24 UTC 5 November 2010 36 IWV (mm) – 13h30 . CONCLUSIONS AND PERSPECTIVES 5 November

Using Signals Emitted by Global Navigation

Satellite Systems

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

Eric Pottiaux

Context of the Thesis

5 November 2010 Meteoclim 2010 - Eric Pottiaux 2

Water Vapour Weather Forecast

Lack of Information about the

Humidity Field

Global Navigation

Satellite Systems

Context of the Thesis


Provide a Product for Operational Weather Forecast

Study and Observe the Neutral Atmosphere (troposphere)

GNSS Signals

On the courtesy of VTM

INTRODUCTION

Global Navigation Satellite Systems (GNSS)


GNSS | A Service to Real-time Positioning and Navigation


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

ATMOSPHERIC REFRACTION

Signal or Noise ?


The position determination is affected by errors Need to be mitigated to achieve the highest precision possible in the position determination

Ionosphere:

Is a dispersive medium By frequency combination Mitigates its effects

Troposphere (0-80km)

GNSS | Atmospheric Refraction


Ionosphere (80-1100 km) Acceleration (carrier)

Decelerate

Troposphere:

Is a non-dispersive medium Has for primary effect to change the propagation speed To decelerate the signals (measured distance > theoretical distance)

GNSS-Meteorology | A Simplistic View



1. If satellite’s position is known 2. If station’s position is known

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)



Tropospheric Delay Theoretical

Distance Measured Distance

The Tropospheric Delay in Short…



Weather Forecasting and Nowcasting

On the courtesy of RTBF

THESIS OBJECTIVES | GNSS-METEOROLOGY

Weather Forecasting in Europe


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 »

ANALYSIS METHODOLOGY | A 2-STEP PROCESSING





1. If satellite’s position is known (IGS Orbit Products)

2. If station’s position is known (computed)

Methodology |A GNSS observation processing in 2 Steps


Time Current Day Last 31 Days

1st Step: Post-Processing 2nd Step: Near Real-time Current Hour

Precise Positions Post-Processing Tropospheric Delays

Tropospheric Delays Monitoring & Validation

2nd Step: Tropospheric Delay Estimations 1st Step: Precise Position Determination

➤ Near Real-time Analysis

➤ Coordinates fixing and Tropospheric Delay Estimation

➤ Post-processing Analysis

➤ Precise Coordinates (1.3mm N&E, 4.3mm Up)

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

Methodology |A GNSS observation processing in 2 Steps


All GNSS-Meteorology Requirements are Satisfied. (Time Resolution, Spatial resolution, Precision, Accuracy , Latency)

Co

ncl

usi

on

Sensitivity Tests & Optimisations

Methodology

Validation

GNSS-Meteorology Requirements

Precision: 4-5mm & Accuracy: < 2.5 mm)

METHODOLOGY | EUROPEAN WEATHER FORECASTS

The EUMETNET EIG GNSS Water Vapour Program (E-GVAP)


The EUMETNET EIG GNSS Water Vapour Program


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)

~ 15000 obs./hour ~ 360000 obs./day ~ 1.3 million obs./year

The Observing Network

http://egvap.dmi.dk

http://egvap.dmi.dk/

Impact Studies

Meteoclim 2010 - Eric Pottiaux 5 November 2010 23

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”

Operational Assimilation within E-GVAP


Since 2007, operational assimilation in the NWP models at

The European GNSS-based Water Vapour

Observing Network


GNSS-based tropospheric delays + pressure & temperature records IWV

On the courtesy of Henrik Vedel, DMI

DENSE NETWORKS OF GNSS STATIONS

Location, extension and movement of fine structures


Multi-Cellular Thunderstorm | 29th June 2005


Thunderstorm Case|European regional network


Dense GNSS Networks | The Belgian Dense Network


Qualitative Analysis |Weather Radars Images


Added-value of the dense GNSS networks ? Qualitative comparison wrt. weather radars

OO UTC 12 UTC 24 UTC

Rain

On

th

e co

urt

esy

of

Lau

ren

t D

elo

bb

e, R

MI

Qualitative Analysis |The European Network vs. Dense Network


BRUS

DENT

DOUR

WARE

MEEU

BREE

EIJS

IWV (mm) - 00 UTC


Water Vapour and Rain

IWV

(mm

)




BRUS

DENT

DOUR

WARE

MEEU

BREE

EIJS

IWV (mm) - 00 UTC

Water Vapour and Rain

IWV

(mm

)


Meteoclim 2010 - Eric Pottiaux

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

OO UTC 12 UTC 24 UTC 5 November 2010 33

BRUS

DENT

DOUR

WARE

MEEU BREE

EIJS

IWV (mm) - 00 UTC

IWV (mm) - 00 UTC

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 European network: small structures not visible Amplitude of the small structures: 5 to 6 times what nowcasters want to see

BRUS

BRUS BRUS

DENT

WARE BREE DOUR

BRUS

DENT

DOUR

WARE

MEEU BREE

EIJS

IWV (mm) – 12h30

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


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

BRUS

DENT

DOUR

WARE

MEEU BREE

EIJS


IWV (mm) – 13h30

CONCLUSIONS AND PERSPECTIVES


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)


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


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

To study the applicability of the methodology to climate monitoring (Europe+Antartica)

ELIS

ULUX

Perspectives| Climate Monitoring



Thank you for your Attention

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Using Signals Emitted by Global Navigation Satellite Systems€¦ · MEEU BREE EIJS OO UTC 12 UTC 24 UTC 5 November 2010 36 IWV (mm) – 13h30 . CONCLUSIONS AND PERSPECTIVES 5 November