RMI Seminar: Citizen weather reports at RMIB and their use for radar-based hail detection verification

Seminar by Dr. Laurent DELOBBE & Dr. Maarten REYNIERS

Title: Citizen weather reports at RMIB and their use for radar-based hail detection verification


The detection and prediction of very local weather effects, like wind gusts, fog or hail storms, remains a challenging issue in meteorology. One of the difficulties in making progress here is the lack of ground truth data: in many cases only fragmentary observations are available, e.g., through a climatological network or through (social or conventional) media. In particular, there is a lack of ground observations of precipitation type and related quantities like hailstone dimensions and snow depth. Hydrometeor classification schemes based on dual-pol radar data can contribute to this verification, but these algorithms inherently suffer from the limitation that they can only provide information on hydrometeor type at the measurement height of the radar and that they rely on an indirect identification of the precipitation type. The rise of mobile devices like smartphones, connected cars and all kinds of IoT sensors, opens up new opportunities to collect in-situ meteorological information which can contribute to verify existing nowcasting/forecasting schemes or to develop new ones. One promising approach is the collection of citizen weather reports through smartphones. In August 2019, the Royal Meteorological Institute of Belgium (RMIB) added such a reporting feature in its smartphone app. Currently the database of citizen reports holds more than two million records. Since May 2022, the app users are also able to add a photo to their observation.


In this presentation, we describe the general concept of the app feature and how the quality control of the reports and the filtering of the photos are organised. Then, we give some general statistics of the aggregated dataset. The data collected have already been exploited in several use cases at RMIB, such as the verification of the official weather warnings and the forecasts per commune as sent out by the weather office, and the validation of an experimental fog prediction algorithm, by using fog reports. Specifically in this presentation, we will focus on the verification of the operational radar-based hail detection algorithm used at RMIB. Among all reported observations, 23 % concern precipitation (rain, snow or hail) and 0.7 % hail. We will examine the extent to which such a dataset allows evaluating the performance of the algorithm in terms of probability of correct and false detections. Such an unconventional observation system brings uncommon sources of uncertainties and biases related to the human nature of the observations. However, we will show that citizen weather reports prove to be an extremely valuable new source of very localised information for many applications in research and operations at RMIB.

When: December 8, 2022 at 2 PM

Where: Conference room at RMI and online

Join Zoom Meeting
Meeting ID: 810 5145 2090
Passcode: 481801


Thursday, December 8, 2022 - 14:00 to 16:00

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