Relationships between Environmental Parameters and Storm Observations in Po Valley: Are They Climate Change Invariant?

For climate models, forecasting environmental parameters has usually been easier than explicitly predicting storm activity, including lightning, hail at ground, and accumulated convective rainfall. It is common to identify -on past data- some statistical relationships between environmental parameters that favor storm occurrence or intensification and storm-related observations. Then, these relationships are applied to future model scenarios. In this study, many environmental parameters derived from radiosounding observations in northeastern Italy are studied during the 1992–2022 convective seasons (April–September), and their changes in this 31-yr period are assessed. For instance, the temperature (averaged across different mandatory levels) shows an increase of approximately 0.53°C every 10 years, while the precipitable water exhibits a positive trend of about 13% (°C)^-1. Most of the examined indices, particularly those linked to water content and potential instability, are characterized by a noticeable upward trend that should potentially favor the storm formation and intensification.

However, upon studying corresponding storm-related observations, similar trends do not clearly emerge. In fact, from data recorded over FVG plain, there is: i) no statistically significant incrase in rain; ii) a tendency towards less hailstorms using data collected from a hailpad network; iii) no trend of CG (cloud-to-gound) lightnings in the Great Alpine Region (GAR) using EUCLID data.

In conclusion, finding a statistical relationship between more favorable environmental parameters and the observed convective events is not straightforward. In fact, the development of storms is a highly complex phenomenon and simple statistical relationships with average environmental conditions could miss some of the underlying mechanisms. At the local scale of northeastern Italy, the relationships between environmental parameters and storm development are not climate change invariant. This sheds new light on the estimation of future storms in the perspective of global warming.