An Accumulated Winter Season Severity Index

Indices and scales exist to aid in the ranking and classification of a number of weather and climate events, including tornadoes, hurricanes, northeastern United States winter storms, and droughts. The ranking and classification systems facilitate the communication of particular hazards to the public, allowing the collection of multiple factors into one scale that is calibrated to describe the risk or impact from that hazard. Winter seasons have significant societal impacts across all sectors, with impacts that range from direct human health and mortality to commerce, transportation, and education.

In this study, point-based winter season severity is calibrated based on temperature and precipitation (snowfall) thresholds for several sites across the central United States. Daily scores are calculated based on the thresholds, and values are accumulated through the winter season, allowing a running total of winter severity in the midst of a season as well as a final, cumulative value representing the full season. At an individual site, the values across multiple seasons can be compared to determine the relative severity of a winter season in the context of the climatology of that site. Additionally, the values at each site can be normalized by an averaging period to represent a scaled severity index, allowing comparison among sites.