Mobilizing Citizen Science for Hail Research: Motivations, Challenges, and Outcomes

Abstract Since 2016, a citizen science project focused on natural hailstone collection has been initiated, aiming to bridge the gap in hailstorm observations and increase the understanding of the effect of aerosols during hailstone formation. In this project, 3063 effective fallen hailstones from 15 provinces in China were successfully gathered by 100 volunteers. The online platform WeChat was leveraged to broadcast collection needs, engage the public, and provide detailed sample collection instructions. Freshly fallen hailstones were collected by volunteers after hailstorms and properly stored until delivery for further laboratory analysis. After preprocessing, the chemical composition of the collected hailstones was analyzed, including water-soluble ions, insoluble particles, and stable isotopes from inner nuclei to outer shells. The analysis results revealed that the water-soluble ions and insoluble particles in hailstones have significant correlation with local surface aerosols, and diverse properties of ice-nucleating particles in hailstones, as well as varying hailstone vertical growth trajectories were observed. The results provide insights into hailstone formation and highlight the importance of atmospheric chemistry in predicting hailstorms in the future. Various strategies were adopted in initiating this citizen science project to encourage public engagement, acknowledge achievement, and gather feedback. Surveys indicated that most of the responding volunteers (79%) were primarily motivated by the opportunity to contribute to science, with favorable scientific literacy achieved via general education and science outreach efforts. Notably, 67% of the respondents reported motivation originating from direct experience of hail damage. The widespread use of smartphones and social media is crucial for extending information networks and increasing citizen science project mobilization. Significance Statement Hailstorms are mesoscale deep convection events with high social impacts and low predictability. It is difficult for researchers to collect natural hailstones before they melt. To bridge this gap from observation to research, a citizen science demonstration project was launched in 2016 under the High-Impact Weather Project (HIWeather) of the World Weather Research Programme (WWRP). Leveraging social networks and public engagement, 3063 effective fallen hailstones from 15 provinces in China have been collected in this project. These diverse geospatial samples provide a foundation to better understand hailstone growth and interactions with aerosols. A survey of participants revealed motivations driven by educational and interest backgrounds, as well as their personal experiences with hail damage. This project offers valuable insight into the potential of citizen science in China.