Using a novel
Hail Sensor to
Optimize
Weather Radar
Nowcasting
World’s first online network of ground-based
hail measurement combined with modern dualpolarization weather radar
by Christian Ruckstuhl1, Justin D’Atri1, Serge Mattli1, Dominik Schoen2, Martin Loeffler-Mang3,
Edgar Wetzel4, and Urs Germann5
SUMMARY
The purpose of this study is to assess the
combination of in-situ measurements with
weather radar data to validate and further
improve hail impact estimates and hail event
forecasts. A partnership of inNET Monitoring
AG and Switzerland’s national weather service,
MeteoSwiss, operates a network of automatic
online hail sensors installed in hail hotspots in
the foothills of the Swiss Alps. The in-situ
network relies entirely on the new HailSens
system developed by htw saar (University of
Applied Sciences Saarbrücken) and inNET
Monitoring AG. HailSens records individual
hail events in real-time and provides evidence
on hailstone size, event duration, event
intensity, and impact energy of individual hailstones. All data recorded locally is transmitted
to Cloud-based servers using wireless
communication. The HailSens uses eventdriven communication to ensure fast forwarding of data whenever an event is recorded. The
damage potential of hail events can then be
assessed in real time. Event-driven data
transmission and alarming functionality ensure
early warning and allow for additional reaction
time needed to take action before excessive
damage occurs. HailSens sensor networks
provide a means to optimize hail claims
processes – an advantage for both the insurer
and the insured who suffered the damage.
2015-2016 R&D Project Participants
The information provided by the HailSens can
be used as evidence of the damage potential
and can be appended to a damage claim.
Insurers and re-insurers can take advantage of
HailSens networks to improve their existing
hail climatology maps and risk models. For the
summertime hail seasons of 2015/16,
measured hail data from several hail events
has been compared with both MeteoSwiss
weather radar data and human observations
reported via the MeteoSwiss Mobile App. One
particular event is presented in the following.
MeteoSwiss5
Switzerland’s National Weather Agency
KISTERS AG4
Leading software &hardware solutions provider for
the sustainable management of energy, water & air.
HAILSENS: A NOVEL HAIL SENSOR
The size and damage potential of hailstones
are directly linked to impact energy and
momentum. The HailSens is innovative in its
ability to measure the energy physics of
individual hailstones (Loeffler et al.). Previously
existing sensors like present weather sensors
and disdrometers measure hail size optically
using a relatively small optical beam. The
larger the hailstones, the greater the distance
between individual hailstones and the higher
the probability that hailstones do not cross the
narrow optical beam. The HailSens relies on
vibration measurements and collects data on a
much larger surface thereby increasing the
probability of detecting a statistically
representative sample of a hail event.
University of Applied Sciences
Saarbrucken3
Laboratory for Optical Measurement & Laser
Technology
dimeto GmbH2
German R&D Service Provider for Intelligent Sensors
inNET Monitoring AG1
Swiss Environmental Monitoring Service Provider &
Innovative ICT Systems Integrator
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RESEARCH LOCATION & SETUP
The research project consists of 10 sensor
locations situated mainly in the hail hotspot
region of Central Switzerland (Fig. 1). In the
test region, warm continental air collides with
the high elevation snow-covered Alps.
Subsequently, meteorological conditions
favourable to the formation and development
of hail storm cells are frequently observed in
this region. All HailSens are installed on the
roofs of public buildings or at MeteoSwiss
weather monitoring stations. Each sensor is
then connected to an on-site power supply.
GSM communication is used to transmit
measurement data to the HailSens software
application running in inNET’s datacentre.
Whenever a hail event is detected, SMS alerts
are sent to the project partners and detailed
real-time hail data is shared with MeteoSwiss
in order to use the in-situ data to optimize
their radar nowcasting algorithms.
Figure 1: Location of 10 roof installed HailSens sensors
around the Central Switzerland Hail Hotspot Region
EXAMPLE HAIL EVENT RESULTS
On May 27th, 2016 a large hail event occurred
outside of Zurich, Switzerland and was detected
by a nearby HailSens sensor in the city of
Aadorf. MeteoSwiss weather radar confirmed
the presence of the large hail storm (Fig. 2), as
well a mobile phone video also documented
the large storm (Fig. 5).
Figure 2: MeteoSwiss Radar Data 27.05.16
WEATHER RADAR RESULTS (Fig. 2)
According to MeteoSwiss weather radar from
Aadorf, the estimated maximum hail size
measurements are between 3.5cm to 4.5cm at
the time of the storm.
IN-SITU HAILSENS RESULTS (Fig. 3 & 4)
Statistical processing of the data measured by
the in-situ HailSens results in a size distribution
between 0.5cm and 3.5cm, with a mean of
approx. 1.8-2.0cm.
Figure 3: HailSens Estimated Hailstone Size based on Momentum
Maximum Estimated Hailstone Size based on Radar (cm)
Figure 4: Hailstone Size Duration Profile of Aadorf Hail Event (redline is average)
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OPTIMIZATION OF RADAR
The HailSens provides new insights into
hailstorm dynamics. MeteoSwiss aims at
using this information to further optimize
its existing hail nowcasting based primarily
on weather radar data. The example results
from the large hailstorm observed in
Aadorf, Switzerland shows similar results
between the MeteoSwiss radar (hail
maximum of 3.5-4.5cm in Aadorf) and the
HailSens’ in-situ measurements (hail
maximum of 3.0-3.5cm with a 1.8-2.0cm
average). Since the estimated maximums
are similar, this suggests a promising
positive outcome for helping prove the field
accuracy of the HailSens as a viable radar
validation and optimization tool. These
results suggest that the HailSens can collect
high resolution data as a means for on-theground validation of radar measurements.
The HailSens also provides novel insights
into the average hail size, as well as
provides unique details into the duration
and intensity of the entire hail event.
Although the radar and HailSens maximum
measurements are not exactly the same, the
research team believes this can be
explained by the high local variability of hail
events, whereas the 1km grid resolution of
the radar is not able to detect the small
local differences detected by the HailSens.
The data suggests that for the Aadorf
storm, hailstones begin smaller and
infrequent initially, but after a few minutes,
their size quickly grows until reaching the
maximum average size for a few minute
plateau, and then the hailstone size begins
slowing decreasing to the smaller initial size
before transitioning completely to rain (Fig.
4). Due to the uniqueness of the duration
and intensity data, further investigation
about the characteristics of the durationintensity profile of hail events will follow
once a statistically representative number of
individual hail events, of comparable
duration and strength, have been recorded
in the test area. Based on the results
obtained so far, MeteoSwiss is confident
that the HailSens enables an enhanced
understanding of hailstorm dynamics and
subsequently will provide improved and
timelier information helping minimize the
damage caused by future hail events in the
Alps.
Figure 5: Mobile Phone Video of the large hailstorm in
Aadorf (Source: 20 Minuten)
Figure 6: MeteoSwiss Weather Radar on Plaine Morte,
2937 m above sea level.
FUTURE ROLLOUT PLANS
The research team is planning a large-scale
Hail Alarm Network in Switzerland using the
HailSens. Negotiations with additional
partners including some of the region’s
leading insurance companies and several
Swiss Federal Agencies are underway.
Moving forward, further European Weather
Agencies are also planning their own pilots
to optimize their weather radar nowcasting
capabilities and further enhance their
country's preparedness for natural hazards.
Citations:
Löffler-Mang, M., Schön, D. and Landry, M. (2011)
Characteristics of a New Automatic Hail Recorder.
Atmospheric Research, 100, 439-446
For further information, please contact:
Interested
in measuring
Hail?
Edgar Wetzel
KISTERS AG
Business Development
Manager
[email protected]
Justin D’Atri
inNET Monitoring AG
Partnership Coordinator
Let’s collaborate!
[email protected]
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