El Niño-Induced Winter Precipitation

A careful examination of how mountains impact precipitation changes during El Niño and La Niña events in western North America could be the key to developing more informed water conservation plans along the Colorado River, according to new research.

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A consideration of how mountains influence El Niño and La Niñainduced precipitation change in western North America may be the ticket to more informed water conservation planning along the Colorado River, new research suggests. The study, coinciding with a recent shift from a strong La Niña to a strong El Niño, brings a degree of precision to efforts to make more accurate winter precipitation predictions in the intermountain West by comparing 150 years of rain and snow data with historic El Niño-Southern Oscillation patterns.

Overall, the analysis shows increasing winter precipitation trends in the north and decreasing trends in the south, particularly during the latter part of the 20th century. It also sheds light on how mountains both amplify and obstruct precipitation, leading to heavier rainfall to their west and lower levels of precipitation to their east.

The more accurate estimate of where and how much winter precipitation has been driven by El Niños of the past may help guide future management of resources in western North America, one of the most water-stressed parts of the world, researchers say. “Because of the seasonality of precipitation in the West, most of it falls during the winter. If you can predict how much precipitation you’ll have in the winter, you’ll have a good sense of what your summer dry period will look like in terms of your water allocation,” said James Stagge, lead author of the study and an assistant professor of civil, environmental and geodetic engineering at The Ohio State University.