Map of RoS events across Alaska.

Rain and snow are typical features of the Alaska landscape, but rain-on-snow events present specific and unique hazards to both infrastructure and wildlife. A paper published by CASC researchers in 2018 used dynamical downscaling to create a new set of data which helps us better understand the past and future of these rain-on-snow events. Now, the data is available for download through CASC partners, the Scenarios Network for Alaska and Arctic Planning.

The paper Assessment of Alaska Rain-on-Snow Events Using Dynamical Downscaling was published in the Journal of Applied Meteorology and Climatology in August of 2018. It used downscaling techniques to address issues with the frequency and distribution of the Alaska weather observation network. The data suggests an increasing frequency of rain-on-snow events can be expected in northern and interior areas of the state, while southern coastal regions (where these events are currently most common) are likely to see the frequency of these events decline. Understanding and predicting these events can be critical as icing on the surface of deep snow can prevent wildlife from accessing sources of food under the snow, changing the subsistence patterns of both the animals and the communities which rely on them. The icing that results from rain-on-snow events can also persist on roadways and other infrastructure for long periods of time in Alaska, presenting transportation and other hazards.

This is due not primarily to shifts in precipitation patterns, but shifts in temperature which make that rain more likely to fall as water before icing in the north, and more likely to fall as rain where temperatures are above freezing in the south. The movement of large amounts of warm water through the oceans in a process known as ‘advection’ may also be a primary driver of heavy precipitation events, particularly in northern Alaska. Relatively small shifts in climate patterns such as storm strengths or high-pressure systems can lead to precipitation falling as rain in cold areas.

The rain-on-snow event data can now be accessed and explored by other researchers who study extreme climate events as well as other decision-makers across the state. Peter Bieniek, Alaska CASC scientist and lead author on the paper, points out that rain-on-snow events have become a common topic lately. “I imagine the data will be useful to land managers and wildlife managers,” said Bieniek, “but also the Alaska Department of Transportation, emergency managers, and even school district administrators could find the data useful in planning.”

The data is now available through the Scenarios Network for Alaska and Arctic Planning’s data portal and covers the entire state of Alaska.