The winter of 2022 saw California being struck by 11 atmospheric rivers, marking an exceptionally wet season for the state. These weather phenomena have both positive and negative impacts, influencing water supply and causing potential damage via floods and landslides. With climate change looming, it’s expected that the frequency and intensity of these atmospheric rivers will increase in some regions around the world.
Understanding Atmospheric Rivers
Atmospheric rivers are long, narrow regions situated in the atmosphere that function like invisible rivers in the sky. They are responsible for transporting most of the water vapor residing outside of the tropics. A famous example of an atmospheric river is the “Pineapple Express.” This weather phenomenon collects warm, moist air near Hawaii and, upon reaching land in the Western United States and Canada, can cause heavy rain and snowfall. In California, it is capable of producing up to 5 inches of rain within a single day.
Common locations for atmospheric rivers include the extratropical North Pacific/Atlantic, Southeastern Pacific, and South Atlantic oceans. These atmospheric rivers frequently make landfall on the west coasts of North and South America. Other areas that experience atmospheric river landfalls include Greenland, Antarctica, and the south-central United States.
Formation of Atmospheric Rivers
Atmospheric rivers predominantly form over tropical regions. The process commences with warm temperatures causing ocean water to evaporate and ascend into the atmosphere. From there, strong winds assist in carrying the water vapor throughout the atmosphere. As the atmospheric rivers move over land, the vapor rises even higher, before cooling into water droplets and falling as precipitation.
Impacts of Atmospheric Rivers
Heavy rainfall from atmospheric rivers can lead to flooding, landslides, and mudslides. These weather phenomena can also disrupt water supplies and generate drought-like conditions. However, not all atmospheric rivers result in damage. Most are weak systems that often bring much needed rain or snow, which play crucial roles in replenishing water supplies.
Atmospheric Rivers and Climate Change
Climate change is anticipated to enhance the frequency and intensity of atmospheric rivers in certain parts of the world, particularly within the mid-latitudes. This increase could have substantial implications for water resources management, flood control, and various other public policy aspects. As we grapple with these changes, understanding and adapting to the unpredictable nature of atmospheric rivers will become increasingly important.