Atmospheric rivers draw moisture from oceans and can help replenish regional water supplies on the west coasts of major continents around the world. Unfortunately, they can also bring massive amounts of moisture that can cause damaging and costly storms, and climate change is intensifying the effects.
Atmospheric rivers are long, narrow bands of moisture in the atmosphere that can transport massive amounts of moisture to the westerns coasts of major continents. As all the moisture moves inland, it provides rain and snowfall that can help replenish snowpacks and benefit regional water supplies.
California and other western states rely on the snowpack to provide water resources for agriculture, energy, manufacturing and municipal uses. These so called “Pineapple Express” storms that often originate off the coast of Hawaii can be beneficial and a welcome relief to the West Coast, as it increasingly struggles with drought and resultant wildfires.
Unfortunately, the storms can often be overly generous and bring too much of a good thing. A new systematic analysis from a team of researchers from Scripps Institution of Oceanography and the Army Corps of Engineers found that “while many of these events are benign, the largest of them cause most of the flooding damage in the western United States.”
Conclusions from the analysis include:
- Atmospheric rivers caused an average of $1.1 billion in flood damages yearly in the western U.S.
- More than 80 percent of all flooding damages in the West in the years studied were associated with atmospheric rivers.
- In some areas, such as coastal northern California, these systems caused over 99 percent of damages.
- In an average year, about 40 atmospheric rivers made landfall along the Pacific coast somewhere between Baja California and British Columbia – most events were benign; about half caused no insured losses.
- Damaging billion-dollar storms occurred every three to four years.
Climate change is expected to intensify existing weather patterns that change where and how we want precipitation to fall. This means enhanced cycles of drought and deluge that will have significant impacts on infrastructure and water resources. The analysis of atmospheric rivers confirms these expectations and prior research that found “atmospheric rivers are predicted to grow longer, wetter and wider in a warming climate.”
This means that, in addition to extended periods of drought, the heavy damaging rains people in western states have experienced in recent years could become a regular part of life.