Using a novel Sensor to Optimize Nowcasting

World’s first online network of ground-based hail measurement combined with modern dual- polarization by Christian Ruckstuhl1, Justin D’Atri1, Serge Mattli1, Dominik Schoen2, Martin Loeffler-Mang3, Edgar Wetzel4, and Urs Germann5 2015-2016 R&D Project Participants SUMMARY The purpose of this study is to assess the The information provided by the HailSens can combination of in-situ measurements with be used as evidence of the damage potential weather radar data to validate and further and can be appended to a damage claim. improve hail impact estimates and hail event Insurers and re-insurers can take advantage of forecasts. A partnership of inNET Monitoring HailSens networks to improve their existing MeteoSwiss5 AG and Switzerland’s national weather service, hail climatology maps and risk models. For the Switzerland’s National Weather Agency MeteoSwiss, operates a network of automatic summertime hail seasons of 2015/16, online hail sensors installed in hail hotspots in measured hail data from several hail events the foothills of the Swiss Alps. The in-situ has been compared with both MeteoSwiss network relies entirely on the new HailSens weather radar data and human observations KISTERS AG4 system developed by htw saar (University of reported via the MeteoSwiss Mobile App. One Leading software &hardware solutions provider for Applied Sciences Saarbrücken) and inNET particular event is presented in the following. the sustainable management of energy, water & air. Monitoring AG. HailSens records individual hail events in real-time and provides evidence HAILSENS: A NOVEL HAIL SENSOR The size and damage potential of hailstones on hailstone size, event duration, event are directly linked to impact energy and University of Applied Sciences intensity, and impact energy of individual hail- momentum. The HailSens is innovative in its Saarbrucken3 stones. All data recorded locally is transmitted ability to measure the energy physics of to -based servers using wireless Laboratory for Optical Measurement & Laser individual hailstones (Loeffler et al.). Previously communication. The HailSens uses event- Technology existing sensors like present weather sensors driven communication to ensure fast forward- and disdrometers measure hail size optically ing of data whenever an event is recorded. The using a relatively small optical beam. The damage potential of hail events can then be dimeto GmbH2 larger the hailstones, the greater the distance assessed in real time. Event-driven data German R&D Service Provider for Intelligent Sensors between individual hailstones and the higher transmission and alarming functionality ensure the probability that hailstones do not cross the early warning and allow for additional reaction narrow optical beam. The HailSens relies on time needed to take action before excessive vibration measurements and collects data on a damage occurs. HailSens sensor networks much larger surface thereby increasing the inNET Monitoring AG1 provide a means to optimize hail claims probability of detecting a statistically Swiss Environmental Monitoring Service Provider & processes – an advantage for both the insurer representative sample of a hail event. Innovative ICT Systems Integrator and the insured who suffered the damage.

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RESEARCH LOCATION & SETUP Figure 1: Location of 10 roof installed HailSens sensors The research project consists of 10 sensor around the Central Switzerland Hail Hotspot Region 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 -covered Alps. Subsequently, meteorological conditions favourable to the formation and development of hail 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.

EXAMPLE HAIL EVENT RESULTS Figure 2: MeteoSwiss Radar Data 27.05.16 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 video also documented the large storm (Fig. 5).

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 Maximum Estimated Hailstone Size based on Radar (cm) between 0.5cm and 3.5cm, with a mean of approx. 1.8-2.0cm. Figure 3: HailSens Estimated Hailstone Size based on Momentum Figure 4: Hailstone Size Duration Profile of Aadorf Hail Event (redline is average)

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OPTIMIZATION OF RADAR maximum average size for a few minute Figure 5: Mobile Phone Video of the large hailstorm in The HailSens provides new insights into plateau, and then the hailstone size begins Aadorf (Source: 20 Minuten) hailstorm dynamics. MeteoSwiss aims at slowing decreasing to the smaller initial size using this information to further optimize before transitioning completely to (Fig. its existing hail nowcasting based primarily 4). Due to the uniqueness of the duration on weather radar data. The example results and intensity data, further investigation from the large hailstorm observed in about the characteristics of the duration- Aadorf, Switzerland shows similar results intensity profile of hail events will follow between the MeteoSwiss radar (hail once a statistically representative number of maximum of 3.5-4.5cm in Aadorf) and the individual hail events, of comparable HailSens’ in-situ measurements (hail duration and strength, have been recorded maximum of 3.0-3.5cm with a 1.8-2.0cm in the test area. Based on the results average). Since the estimated maximums obtained so far, MeteoSwiss is confident Figure 6: MeteoSwiss Weather Radar on Plaine Morte, are similar, this suggests a promising that the HailSens enables an enhanced 2937 m above sea level. positive outcome for helping prove the field understanding of hailstorm dynamics and accuracy of the HailSens as a viable radar subsequently will provide improved and validation and optimization tool. These timelier information helping minimize the results suggest that the HailSens can collect damage caused by future hail events in the high resolution data as a means for on-the- Alps. ground validation of radar measurements. The HailSens also provides novel insights FUTURE ROLLOUT PLANS into the average hail size, as well as The research team is planning a large-scale provides unique details into the duration Hail Alarm Network in Switzerland using the and intensity of the entire hail event. HailSens. Negotiations with additional Although the radar and HailSens maximum partners including some of the region’s measurements are not exactly the same, the leading insurance companies and several research team believes this can be Swiss Federal Agencies are underway. explained by the high local variability of hail Moving forward, further European Weather events, whereas the 1km grid resolution of Agencies are also planning their own pilots the radar is not able to detect the small to optimize their weather radar nowcasting local differences detected by the HailSens. capabilities and further enhance their The data suggests that for the Aadorf country's preparedness for natural hazards. storm, hailstones begin smaller and Citations: infrequent initially, but after a few minutes, Löffler-Mang, M., Schön, D. and Landry, M. (2011) their size quickly grows until reaching the Characteristics of a New Automatic Hail Recorder. Atmospheric Research, 100, 439-446

For further information, please contact: Interested Edgar Wetzel in measuring KISTERS AG Business Development Hail? Manager [email protected]

Justin D’Atri inNET Monitoring AG Partnership Coordinator [email protected] Let’s collaborate!

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