Tropical Forcing of Atmospheric River Events in the North Pacific: Implications for Southern California

The prolonged drought in California has by now largely subsided due to the large
number of land falling atmospheric rivers in the 2016-2017 winter season. Here we
explore intraseasonal, interannual and decadal variabilities in winter AR activity
along the California coast, especially in Southern California, with a special focus on
the leading modes of covariance between tropical SSTs and the 200-hPa
geopotential height in the Northern Hemisphere and an understanding of how the
tropical related teleconnections modulate the AR activity in the North Pacific. This
new approach explores a path towards improved intra-seasonal to seasonal
predictions of climate variability in Southern California and may help explain how
the most recent winter, which is not the anomalously strong el Niño as that in the
last winter, brought California out of drought. Finally, we will suggest a way
forward to better understand the causes of the recent drought over Southern
California and how we may improve projections of its future change.