Study Explains if Recent Drought is a Result of us being in the Second Winter of a Double-Dip La Niña

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Drought across much of the U.S. Credit:

You might have noticed that it has been quite dry over much of the U.S. this winter, with drought expanding across several regions, particularly in the south.

As we are currently fully immersed in the second winter of a “double-dip” La Niña, you might wonder if these dry conditions are typical in the second winter of a double-dip La Niña?  And are there any differences in how the atmosphere responds to La Niña in the second winter relative to the first?  Well if either of those questions ever crossed your mind, then you’re in luck!

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Average precipitation anomalies (mm/day) for November–April for the first (left) and second (right) extended winters of all multi-year La Niñas since 1900. Anomalies are compared to the 1900-2012 average, with the linear trend removed. figure from GPCC data and adapted from Okumura et al. (2017).

ENSO blog recently published the results of a study led by Dr. Yuko Okumura of the University of Texas at Austin, which addressed how the impacts of La Niña may change from the first winter to the second for double-dip La Niñas like this one.

Double-dip La Niñas actually are pretty common. Including the current event, we have experienced eight instances in which La Niña conditions in the first winter were followed by La Niña in the subsequent winter.

Spoiler alert: Dr. Okumura and colleagues found evidence that U.S. drought and the North Pacific atmospheric circulation anomalies strengthen in the second winter of a double-dip La Niña.

For the full study, and to geek out on the science, stats, graphs, and maps, go to the website. Super interesting!

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