Atmospheric rivers are tubes or ribbons of water vapor that evaporate from the equator and surge up over the ocean and into the atmosphere. Meteorologist Ben Kirtman explains how atmospheric rivers affect climate in the Western United States.

via The University of Miami

Since atmospheric rivers are typically most active in the winter, they also coincide with other climate patterns that can impact global weather—the El Niño/La Niña effect. These phenomena can have a major influence on the number of atmospheric rivers that develop, Kirtman said. Currently, meteorologists believe we are experiencing a La Niña pattern for a second consecutive year. La Niña years are typically characterized by less rainfall and more drought conditions, which means winters in the southern half of the United States are drier and often warmer. In contrast, the upper half of the country experiences more precipitation, cooler temperatures, and fewer atmospheric rivers during a La Niña winter.

Here, Kirtman elaborates on the characteristics of atmospheric rivers, and explains how La Niña and climate change could impact them.

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