Changes in Northern Hemisphere Winter Storm Tracks and Extreme Precipitation, Attributed to the 1.5C and 2C Levels of Global Warming

The observed hydro-climate in the Northern Hemisphere is closely tied to the large-scale atmospheric circulation over the Northern Atlantic and Pacific Ocean. Several studies have shown that recent changes in these circulation patterns (e.g. North Atlantic Oscillation/Arctic Oscillation) correspond with stronger activity of cyclones, which supply heat and moisture to the large parts of Europe and North America. Therefore, future changes in storminess will likely contribute to changes in a wide range of weather extremes (e.g. surges, extreme precipitation and winds).

Future scenarios, simulated with GCMs, indicate a poleward expansion of Hadley Cell and associated with it northward/north-eastward shift of storms. However, many derived characteristics of future storms remain inconsistent, due to model deficiencies in representing realistic features of storm's tracks and intensity, as well as sensitivity of analysis to the storm identification methods.

This study advances understanding of differential climate impacts between 1.5C and 2C levels of global warming by analyzing daily output of the high-resolution HAPPI simulations. We are presenting analysis of large ensemble runs to infer about changes in winter large–scale circulation, their impact on characteristics of extratropical storms and extreme precipitation events in the Northern Hemisphere. The analysis corroborates the fact that in many regions (e.g. California) precipitation extremes do not necessarily scale with the mean hydro-climate change. This underlines importance of high spatial and temporal resolution in climate simulations to derive information about a future weather, relevant for the local communities.