Dynamical and thermodynamic changes responsible for a tripling of Alaskan convective storms in future climate

Abstract:

Organized convective systems produce heavier downpours and can become more intense with climate change. Such changes could be further amplified in high-latitudes since the Arctic is warming faster than any other region in the world and subsequently moistening. However, little attention has been paid to climate change impacts on intense thunderstorms in the pan-Arctic, where they can produce flash flooding, landslides, or ignite wildfires.

We use a convection-permitting model to simulate Alaska’s climate under current and end of the century high emission scenario conditions. The current climate simulation is able to capture hourly precipitation statistics compared to rain gauge data. We apply a precipitation tracking algorithm to identify intense, organized convective systems, which are projected to triple in frequency and extend to the northernmost regions of Alaska under future climate conditions. Peak rainfall rates in the core of the storms will intensify by 37% in line with atmospheric moisture increases.

The physical reasons for this rapid increase in organized convection are investigated. In a future climate, more moisture originates from Arctic marine basins and relative humidity over continental Alaska is projected to increase due to sea ice loss. This favors the development of organized convection through more unstable thermodynamic environments, increased low-level buoyancy, and weaker downdrafts.

We show that these changes are consistent with analytical considerations based on basic physical laws, which suggests that organized thunderstorms might become more frequent in other pan-Arctic continental regions highlighting their unique vulnerability to climate change.