Download A modern radar network for Switzerland

Federal Department of Home Affairs FDHA
Federal Office of Meteorology and Climatology MeteoSwiss
A modern radar network for Switzerland
Within the framework of the project Rad4Alp the Federal Office of Meteorology and
Climatology MeteoSwiss has been refitting and updating its radar network in line with
the latest research and technology and expanding it by adding two new radar installations in the inner-alpine regions.
Who is not familiar with the weather radar images from MeteoSwiss? They feature in television weather
programmes, on forecasts for the internet and in mobile phone applications. In preparation for a bike
ride or a mountain hike it is convenient to cast a glance at these radar images which tell users about the
areas affected and the intensity of precipitation as well as the direction it is taking. Behind these colourful images is a network of fully automated state-of-the-art radar installations that provide reliable information on precipitation in Switzerland 24 hours a day.
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One of the core duties of the national weather service, MeteoSwiss, is to observe the atmosphere and
weather developments. Precipitation and thunderstorms are events of particular importance because
they can trigger flooding, hail, strong winds and mudslides. In addition to conventional precipitation
measurements by gauges at surface weather stations, MeteoSwiss therefore now operates a network of
five weather radar stations which detect precipitation and thunderstorms over the entire territory of
Switzerland.
MeteoSwiss | Project Rad4Alp: Via ai Monti 146, 6605 Locarno-Monti, 058 460 96 85; February 2016
The sites are (see map and pictures from left to right, above Monte Lema/La Dôle) Albis near Zurich,
Monte Lema in the Canton of Ticino, La Dôle near Geneva and, the new addition, Pointe de la Plaine
Morte in the Canton of Valais and Weissfluhgipfel in the Canton of Grisons.
The three existing weather radar installations run by MeteoSwiss have been in operation for over 18
years: Monte Lema since 1993, Albis since 1994, La Dôle since 1995. They have been working
without interruption, 24 hours a day, and several components have reached the end of their life cycle.
Through the Rad4Alp project, the construction of two additional weather radars was approved with a
view to boosting the availability of overall radar information in the event of one of the other radar
stations in Switzerland failing. The extra coverage also aimed to improve warnings of heavy precipitation, storms and floods, particularly in the inner Alpine regions. These objectives have been achieved
in the form of two new radar stations in Valais and Graubünden.
What is new in technology and research?
Around the clock MeteoSwiss weather radars supply observation data for the colourful real-time radar
images that inform users via television, internet or mobile phone about the areas affected, the intensity
of precipitation and the direction it is taking.
Both the old and the new weather radars has been equipped with instruments of the latest generation,
and accordingly the data processing has been modernized. From now on all images and products will
be generated in 5-minute-intervals, also in 2.5-minute-intervals if a specific application requires it. The
spatial resolution has been enlarged from two kilometres to one kilometre and the vertical scan extended from 12 kilometres to now 18 kilometres – a substantial improvement in the context of warnings of
violent thunderstorms.
The new radar systems also enable a better distinction between rain, snow, hail and sleet; however,
substantial work still needs to be done in this area of research. Knowledge about the areas and
intensity of precipitation and its development form the basis for the assessment of dangers such as
flooding, hail, storm gusts, mudslides and avalanches. The modern radar network and the experts from
MeteoSwiss who analyse the data and continuously develop new analysis methods supply the indispensable support.
High mountains: a challenge
With its mountainous landscapes, Switzerland poses particular challenges for radar imagery, in contrast
to topographically flat countries such as The Netherlands. Alpine valleys behind mountain ranges or
peaks lie in the radar shadow, where radar beams cannot reach them, which means that no data on
precipitation in these areas can be transmitted. The two new radar stations in Valais and Graubünden
have meant that the coverage in the Alpine region has been significantly improved, and the problem of
radar shadows reduced.
MeteoSwiss | Project Rad4Alp: Via ai Monti 146, 6605 Locarno-Monti, 058 460 96 85; February 2016
High-alpine sites create a particular challenge to radar meteorologists. For instance, technical
adaptions are required to cope with the reduced air density. Also differences in altitude of about 2000
m within the radar network have to be considered when data are processed with new algorithms and
methods. MeteoSwiss can rely on a radar team which has a wealth of experience in high-alpine radar
meteorology both on the operational level and in the research and development of new applications. It
is their task to gain reliable and detailed information about rain, snow and hail from the new radar
data.
How does radar technology work?
Weather radars transmit a signal into the atmosphere. If the signal encounters rain, snow or hail, part
of the signal is back-scattered towards the radar. From the intensity of the back-scattered signal
information can be gathered about the nature and intensity of precipitation. Swiss weather radar
images are displayed in a spatial resolution of 1 km2. Within 5 minutes each radar scans the
atmosphere up to a distance of 240 km. This generates a complete three-dimensional radar image 12
times an hour.
MeteoSwiss | Project Rad4Alp: Via ai Monti 146, 6605 Locarno-Monti, 058 460 96 85; February 2016
Basis for weather forecasts and thunderstorm warnings
Weather radars provide valuable information on rain, snow, hail and other forms of precipitation. In
contrast to conventional surface weather stations which only supply information about a specific data
point, weather radar enables the overall monitoring of precipitation events. On the basis of this
information modern tools such as TRT (Thunderstorm Radar Tracking) automatically identify
dangerous storm cells and calculate their future trajectory.
Who makes use of radar data?
Radar data are useful not only to the national meteorological service MeteoSwiss, but also serve the
government authorities responsible for floods and civil protection, as well as air traffic safety in their
decision-making processes. The information is central to providing warnings and forecasts, and is also
used by privately-owned meteorological services as well as in numerous sectors such as insurance,
tourism, science etc. The Swiss population can obtain radar information via the MeteoSwiss app.
MeteoSwiss | Project Rad4Alp: Via ai Monti 146, 6605 Locarno-Monti, 058 460 96 85; February 2016