Atmospheric River Risk Communication within Western U.S. Water Utilities

Atmospheric river characteristics are changing, making them more intense. What can science users, such as water managers respond? How do we as a science team produce results that are not only useful, but actually used and implemented into practice?

Here we take the approach of knowledge co-production, partnering with Seattle Public Utilities, a major west coast urban water utility. Our goal is to increase their ability to adapt to extreme rainfall events, producing research that is not only useful, but used. To this goal of enhancing adaptive capacity, we are focusing in on communication as a major building block in the adaptation cycle.

How are utility workers communicating about extreme rainfall risk? What changes do they anticipate? What do they need to enhance their capacity to effectively respond?

This work is in progress, and we are currently employing mixed methods to understand SPU's needs in their internal climate risk communications. The next phase of the project will develop interventions, including enhanced crew training resources, and mechanisms to evaluate the project outputs' long-term efficacy.

Recent warming of US West Coast Atmospheric Rivers

Are US West Coast atmospheric rivers getting warmer? If so, this could potentially alter the critical rain/snow balance in snowpack-dependent watersheds and cause precipitation at higher elevations to fall as rain rather than snow. Not only would warmer, primarily rain-producing atmospheric rivers greatly affect snow accumulation, but they might also increase the intensity of runoff, the potential for flooding, and the occurrence of rain-on-snow events.

We assess trends in cool season atmospheric river temperatures that occurred 1980-2016 over the Pacific Coast states of California, Oregon, and Washington. We also compare atmospheric river temperature trends to regional background temperature trends and trends in along-track atmospheric river temperature. We find overall atmospheric river warming over this period and particularly robust warming in October, November, and March atmospheric rivers. Atmospheric river warming appears to not be solely scaling to either local background temperature or along-track trends.

Gonzales et. al., (2019) Journal of Geophysical Research - Atmospheres

Flavors of Atmospheric Rivers:

Moisture or wind dominated?

Left: Atmospheric rivers event conditions on the wind (x-axis) and moisture (y-axis) spectrum, colored by "Moisture Dominance". Right: Precipitation composite of wet vs. windy high-IVT ARs.

Gonzales et al., (2020), Geophysical Research Letters

Strong integrated vapor transport (IVT) has been recognized as the defining characteristic of AR intensity, with AR strength often categorized by an event’s IVT and storm impacts often scaling close to IVT. However, ARs associated with similar IVT may yield very different impacts due to subtle but important differences in other AR characteristics. We quantify the relative distribution of moisture-dominated vs. wind-dominated (“wet” vs. “windy”) ARs across the west coast of North America. We quantify the seasonal and geographic distribution of AR types, and assess the relative impacts of wet vs. windy ARs upon landfall. We also investigate pre-landfall characteristics that govern the resulting AR flavor, including source regions and pathways of ARs.