Spatial and temporal characteristics of the decadal abrupt changes of global atmosphere-ocean system in the 1970s

Abstract

Using NOAA extended reconstruction SST (ERSST.v2) and NCEP/NCAR reanalysis, a moing t test technique is employed to detect the decadal abrupt change years (DACYs) in the time series of several atmosphere-ocean variables. The decadal abrupt changes (DACs) existed widely in the ocean-atmosphere system in 1973-1978. In the ocean, the decreased DACs (DDACs, the variable decreases after the DACY) occurred in the North and South Pacific and the increased DACs (IDACs, the variable increases after the DACY) mainly took place in the eastern Pacific, southern South Pacific and South Indian Ocean. In the atmosphere, the IDACs happened over the Eastern Hemispheric tropics and subtropics in the low troposphere and over the global tropics and subtropics in the middle and upper troposphere and stratosphere. The higher pressure levels, the larger the DAC regions and the later the DACYs generally. The initial oceanic DACs in the 1970s cannot be explained by the DACs of wind stress, which happened 2 years (a) later than the original oceanic DACs. In addition, the tropical influence through atmosphere and ocean cannot explain the initial DDACs of SST and atmosphere of the North Pacific, which occurred about 2 a in advance of tropical warming. The DDACs in the 1970s of the North Pacific cannot interpret that of other oceanic regions, because they were not the initial oceanic DACs in the 1970s. These findings suggest that the DACs in the 1970s may initially originate from the ocean and a coupled atmosphere-ocean decadal interaction mechanism existed in the winter of the North Pacific. Copyright 2007 by the American Geophysical Union.