Radar and lightning detection
Crowdsourced and opportunistic observations
Next to conventional observation systems like satellites, ground weather stations, weather radars or lightning detection networks, alternative sources of observations are increasingly used in meteorology.
Crowdsourced observations
A huge amount of weather observations is collected every year from the users of the RMI smartphone app. Additionally, RMI is collecting data from private stations owned and operated by weather amateurs within the international WOW network . These novel data sources offer new research opportunities. For example, citizen observations from the smartphone app can be used for the verification of radar-based precipitation type identification.
Another example of crowdsourcing is the use of car sensor data for extracting weather information. In the SARWS project, the use of such data for improving road safety has been investigated.
Rainfall observations from underground gravity measurements
The Royal Observatory of Belgium operates a superconducting gravimeter to monitor the real-time variations in g, the Earth's gravity. The gravimeter is installed in Membach (Eastern Belgium), 48 m underneath the surface, at 85 km distance from the RMI Wideumont radar. An increase of water mass at ground level due to precipitation results in a decrease in underground measured gravity. The comparison of radar and gravity time series over 15 years shows that short-duration intense rainfall events cause a rapid decrease in the measured gravity. Rainfall amounts can be derived from this decrease. The gravimeter allows capture of rainfall at a much larger spatial scale than a traditional rain gauge. It can be seen as huge rain gauge.
The use of a gravimeter for estimating rainfall is a typical example of opportunistic sensing. A gravimeter is not designed to measure rainfall. Still, very useful information on rainfall can be found in the data. Another example of opportunistic sensing is the use of weather radar observations for monitoring bird migrations.
The superconducting gravimeter at Membach (Royal Observatory of Belgium). On the right, one can see the hollow sphere that levitates in a persistent magnetic field (picture: E. Coveliers).
Temporal evolution of the residual gravity measured by the gravimeter (top), radar reflectivity (middle) and cumulative rainfall from radar and from gravimeter (bottom) on 24 July 2017.