Anticipated Event Location:
Anticipated Event Date/Timing:
22-24 November 2017
Aims and Scope:
High resolution GNSS tomography using Belgian dense network & Potential for nowcasting/forecasting.
In the 1st TOMOlab workshop organised in 2014 (Wroclaw, Poland), a focus on the interest of GNSS tomography for helping the understanding of meteorological events has been experienced. Two tomographic models (from WUELS and BIRA) have been used to retrieve the 3D field of water vapour density and of wet refractivity. Two types of severe weather situations have been studied: a first one with large scale convection and a second one with mesoscale deep convection. The mean distance between neighbouring stations (mean baseline) of the GNSS network used was about 65 km (about 85 polish stations). The tomographic grid considered was 50x50 km horizontally and 1 km vertically (surface of 600x600 km² all over Poland). Outputs from the WRF numerical weather prediction (NWP) model have been compared to tomographic retrievals showing a good potential to improve the description of the humidity field for short term forecasts (nowcasting), specially for large scale convection events.
The plan of this 2nd TOMOlab workshop contains two parts:
- GNSS tomography processing from several models and implementation of standardised products for monitoring severe weather
- Demonstrations using GNSS tomography and benefits to meteorologists (nowcasting and forecasting applications)
The collaboration of GNSS and meteorological experts has strengthened through dedicated tomography activities in the current COST Action ES1206 “Advanced Global Navigation Satellite Systems tropospheric products for monitoring severe weather events and climate” (GNSS4SWEC). Considering results and feedback from the 1st TOMOlab workshop, the application of GNSS tomography as a part of the benchmark campaign of this Action has been planned using several tomographic models from partners (e.g. WUELS, BIRA and TUW; members of TOMOlab’s programme comity). The selected area (450x450 km²) covers flat and mountain regions of Germany, Poland, Czech Republic and Austria. The mean baseline of this network is 50 km (for about 75 stations), expecting tomographic grid of 30x30 km horizontally and 0.75 km vertically. This COST Action comes to its end in May 2017.
The first part of the 2nd TOMOlab workshop is dedicated to processing. The first goal is to proceed, compare tomographic retrievals from the GNSS4SWEC benchmark campaign, and harness this close collaboration to draw benefits to the nowcasting and forecasting community. Visualisation tools of standardised products from different models will be developed.
As recommended by the 1st TOMOlab workshop, the understanding of mesoscale events requires an improvement of the horizontal resolution to properly describe deep convection and to find precursors of its initiation. The Belgian GNSS dense network and surroundings stations from France, Netherlands, Luxemburg and Germany (about 70 stations for a surface of 200x200 km² covering Belgium) has baselines ranging from 5 to 30 km (mean baseline of 20 km). The use of such a network during severe weather condition is a unique opportunity in Europe to reconstruct the 3D fields of water vapour and wet/total refractivity based on GNSS tomography with very high resolution (5x5 km horizontally and 0.5 km vertically). The second goal of this workshop is to achieve an ensemble solution of these 3D fields retrieved by GNSS tomographic models from international research scientists (a minimum of 4 models is already expected). Visualisation tools of standardised products will be assessed. The expertise in tomography of GNSS4SWEC partners is essential, and we hope for getting international contributors on board the 2nd TOMOlab workshop.
In the second part of the workshop, we would like to get expert’s hands-on experience of the usability of GNSS tomography fields in nowcasting/forecasting in order to stimulate further assimilation experiments: demonstration phase and benefits for meteorologists.
Recent assimilation experiments revealed the potential of GNSS tomography as innovative sensor for atmospheric water vapour. In order to overcome its limitations and to identify its potential for improving nowcasting/forecasting, scientists from both fields (GNSS and meteorology) are invited for
- interpreting and evaluating of the interest of standardised tomography products to describe high resolution 3D fields of water vapour and wet refractivity.
- identifying the needs of the nowcasting/forecasting community and requirements which the tomography solution has to fulfil (e.g. prototype of near-real time tomography, validation of NWP using tomography outputs, assimilation of tomography profiles)
Specific severe weather situations in Belgium (e.g. storm at Pukkelpop festival in August 2011 https://www.youtube.com/watch?v=Yim57aeDNxA, heavy rainfall in July 2014, likely pouring rains of the summer 2017) represents relevant case studies for this 2nd TOMOlab workshop. We plan to organise this meeting at the Space Pole of Brussels, Observatory/Meteorology/Aeronomy (OMA). This means a shared organisation between three Belgian federal institutes: the Royal Belgian Institute for Space Aeronomy (BIRA), the Royal Observatory of Belgium (ROB) and the Royal Meteorological Institute of Belgium (RMI). The first part of the workshop can take place at BIRA and/or ROB, and the second part at RMI with Belgian forecasters and international solicited meteorologists (participants of the workshop), and using their observation system (with our additional new observations from GNSS tomography) combined with all their nowcasting tools (e.g. Integrated Nowcasting Comprehensive Analysis – INCA-Belgium). We think this is the best way to obtain concrete results between GNSS and meteorology community (in link with NWF SAF).
We think this is the best way to obtain concrete results between GNSS and meteorology community (in link with NWF SAF).
Summary of the context and justification for the event:
The collaboration of GNSS and meteorological experts has strengthened through dedicated tomography activities (benchmark campaign) in the current COST Action ES1206 (GNSS4SWEC). This Action comes to its end in May 2017 and the 2nd TOMOlab workshop is a great opportunity to proceed, meet and compare tomographic retrievals from the GNSS4SWEC benchmark campaign. In addition, as recommended by the 1st TOMOlab workshop, the understanding of mesoscale convective events requires an improvement of the horizontal resolution of tomography products. By its low mean station inter-distances, the Belgian GNSS network is very remarkable in Europe, providing unprecedented potential for high-resolution reconstruction of the 3D water vapour field during severe weather events (frequent in Belgian Summer). Misforecasting of such past events caused a lot of damages in Belgium and casualties to the population (e.g. storm at Pukkelpop festival in August 2011). This brings a lot of motivation to improve our knowledge of the evolution of the humidity field and the detection of pre-conditions for deep convection initiation. We suggest a two steps approach: 1) 3D water vapour fields reconstruction from several tomography models (severe weather events during Summers 2011, 2014, 2017) and implementation of standardised products for monitoring severe weather monitoring 2) Demonstration phase and benefits for forecasters/meteorologists (interpretation and evaluation of interest, identification of the needs, prototype of near-real time tomography, validation of NWP using tomography outputs, perspective of assimilating tomography profiles)
The 2nd TOMOlab is a great opportunity to harness a close collaboration to draw benefits to the nowcasting and forecasting community.
Previous TOMOlab workshop:1st TOMOlab workshop on tomography and applications of GNSS observations in meteorology (2014)