An Evaluation of Thunderstorm Observations in Southern Ontario Using Automated Lightning Detection Data

Abstract

igh-impact weather events, such as thunderstorms and their associated hazards, are aspects of a changing climate that are likely to have an adverse effect on society. Southern Ontario is Canada?s most populated region as well as the region of Canada that receives the most thunderstorms. Before completing climatological studies of thunderstorms in southern Ontario, it is important to determine whether historical thunderstorm data are reliable. Archived thunderstorm data are available from eight 24-h-staffed weather stations across southern Ontario. The data may be subject to observer bias. This study compared the manual observations of thunderstorms with automated data from the Canadian Lightning Detection Network. It was found that the data that are based on the manual observations are reliable enough that any significant trends in thunderstorm occurrence over time should be apparent. Because of the small-scale nature of thunderstorms, however, the data may only be valid for small distances (up to 10 km) around each weather station. A diurnal bias was also discovered, with manual thunderstorm observations being slightly better at night.