Influence of the Autumn SST in the Southern Pacific Ocean on Winter Precipitation in the North American Monsoon Region

Previous investigations have reported that the impacts of the preceding climate signal in the Southern Hemisphere can extend to Northern Hemisphere middle latitudes during the following season. This study suggests that the positive (negative) boreal autumn south Pacific Ocean dipole (SPOD) sea surface temperature anomalies are usually followed by reduced (increased) precipitation in the following winter over the North American monsoon (NAM) region. The positive autumn SPOD has the potential to regulate the southward fluctuation of the eddy-driven westerly jet in the southern Pacific Ocean, and exert the Rossby wave train stretching across the Pacific Ocean to transport the related energy into the NAM region. This finally results in anomalous high pressure in the troposphere over the NAM region. The related sinking motion and the water vapor conditions further affect the precipitation variability in these regions. This entire process can be referred to as a "coupled oceanic-atmospheric bridge", in which the "oceanic bridge" is the SPOD and the "atmospheric bridge" is the response of atmospheric circulation in the Pacific Ocean.