Preprints
https://doi.org/10.5194/amt-2023-68
https://doi.org/10.5194/amt-2023-68
12 Apr 2023
 | 12 Apr 2023
Status: this preprint is currently under review for the journal AMT.

How observations from automatic hail sensors in Switzerland shed light on local hailfall duration and compare with hailpads measurements

Jérôme Kopp, Agostino Manzato, Alessandro Hering, Urs Germann, and Olivia Martius

Abstract. Measuring hailstorms is a difficult task due to the rarity and mainly small spatial extent of the events. Especially, hail observations from ground-based time-recording instruments are scarce. We present the first study of extended field observations made by a network of 80 automatic hail sensors from Switzerland. The main benefits of the sensors are the live recording of the hailstone kinetic energy and the precise timing of the impacts. Its potential limitations include a diameter dependent dead time which results in less than 5 % of missed impacts, and the possible recording of impacts not due to hail which can be filtered using a radar reflectivity filter. We assess the robustness of the sensors measurements by doing a statistical comparison of the sensor observations with hailpads observations and we show that despite their different measurement approaches, both devices measure the same hail size distributions. We then use the timing information to measure the local duration of hail events, the cumulative time distribution of impacts and the time of the largest hailstone during a hail event. We find that 75 % of local hailfalls last just a few minutes (from less than 4.4 min to less than 7.7 min, depending on a parameter to delineate the events) and that 75 % of impacts occurs in less than 3.3 min to less than 4.7 min. This time distribution suggests that most hailstones, including the largest, fall during a first phase of high hailstone density, while a few remaining and smaller hailstones fall in a second low density phase.

Jérôme Kopp et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2023-68', Andrew Heymsfield, 30 Apr 2023
  • RC2: 'Comment on amt-2023-68', Julian C. Brimelow, 25 May 2023

Jérôme Kopp et al.

Model code and software

sensors_observations Jérôme Kopp https://github.com/jekopp-git/sensors_observations

Jérôme Kopp et al.

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Short summary
We present the first study of extended field observations made by a network of 80 automatic hail sensors from Switzerland. The sensors record the exact timing of hailstone impacts, providing valuable information about the local duration of hailfall. We found that the majority of hailfalls last just a few minutes and that most hailstones, including the largest, fall during a first phase of high hailstone density, while a few remaining and smaller hailstones fall in a second low density phase.