Kilometer-scale modeling projects a tripling of Alaskan convective storms in future climate

Abstract

Convective storms produce heavier downpours and become more intense with climate change. Such changes could be even 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 the impact of global warming on intense thunderstorms in high latitude continental regions, where they can produce flash flooding or ignite wildfires. We use a model with kilometer-scale grid spacing to simulate Alaska’s climate under present and end of the century high emission scenario conditions. The current climate simulation is able to capture the frequency and intensity of hourly precipitation 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. These results could have severe impacts on Alaska’s economy and ecology since floods are already the costliest natural disaster in central Alaska and an increasing number of thunderstorms could result in more wildfires ignitions.

Dynamic and Thermodynamic Impacts of Climate Change on Organized Convection in Alaska

“…We know from observations that organized convective systems are present but rare in the pan-Arctic [Жукова et al, 2018, Punkka andBister, 2015]. In a predecessor study [Poujol et al, 2020] we showed that organized convective storms are projected to triple by the end of the century in Alaska under a high emission scenario as a result of anthropogenic climate change. These results are supported by observational studies in Siberia [Chernokulsky et al, 2011] that report a strong increase in the frequency of deep convective clouds during the period 1991-2010.…”

“…We are interested in convective storms in the Interior, Western and Northern Alaska. As in [Poujol et al, 2020], we define continental Alaska as the five climate regions shown in Figure 1a, which were defined by [Bieniek et al, 2012]. The North Slope has an Arctic climate and convective storms are rarely observed in this region [Grice and Comiskey, 1976].…”

“…Therefore, it has a continental climate and this is where convective activity is strongest [Grice andComiskey, 1976, Reap, 1991]. A more detailed description of the domain can be found in [Poujol et al, 2020]. The full description of the model parameters is available in [Monaghan et al, 2018].…”

“…The model accurately represents interannual variability and precipitation maxima. Also, hourly precipitation in the model was evaluated against precipitation stations hourly data and the model was found to produce a correct annual cycle, and to have a diurnal cycle delayed by 0-3 hours depending on the stations [Poujol et al, 2020]. This last study showed that the model is able to reproduce correctly the distribution of CAPE and CIN as observed by weather balloons in Fairbanks, and also showed that the model reasonably represents organized convective storms compared to the few radar and satellite observations that are available.…”

“…The increased open ocean areas in future climates provide an additional source of moisture [Bintanja and Selten, 2014], which causes Pan-Arctic Title Suppressed Due to Excessive Length 5 climate change to be uniquely different from climate change in other parts of the globe. This study investigates the causes for the threefold increase of Alaskan organized convective storms presented in [Poujol et al, 2020] by analysing changes in moisture advection patterns and changes in dynamic and thermodynamics of convective systems and their environments.…”