Amplified Madden-Julian Oscillation impacts in Pacific-North America region
The Madden-Julian Oscillation (MJO)—a tropical rainfall pattern—excites atmospheric waves that can substantially impact on extratropical weather. However, little is known about future changes in this “teleconnection” pattern. Here we show that the MJO teleconnection pattern in boreal winter will likely extend further eastward over the North Pacific, leading to amplified impacts on California rainfall variabilities.
The eastward-extended teleconnection allows the MJO to exert a larger impact in the Northeast Pacific and along the west coast of North America. The enhanced sub-seasonal variability poses acute challenges on regional resource management and extreme weather preparation.
The Madden-Julian Oscillation (MJO) is a slow-moving tropical mode that produces a planetary-scale envelope of convective storms. By exciting Rossby waves, it creates teleconnections with far-reaching impacts on extratropical circulation and weather. While recent studies have investigated the MJO's response to anthropogenic warming, not much is known about potential changes in MJO teleconnection patterns. Here we show that the MJO teleconnection pattern in boreal winter will likely extend further eastward over the North Pacific. This is due primarily to an eastward shift in the exit region of the subtropical jet, on which the teleconnection pattern is anchored, and additionally contributed by an eastward extension of the MJO itself. The eastward-extended teleconnection allows the MJO to exert a greater impact downstream on the Northeast Pacific and North American west coast. Over California specifically, the multi-model mean projects a ~54% increase in MJO-induced precipitation variability by 2100 under a high emission scenario.