Dependence of the structure of the Northern Hemisphere annular mode on the polarity of ENSO

[1] The structure of the Northern Hemisphere annular mode (NAM) is shown to be significantly different during warm and cold winters of the ENSO cycle. During warm winters the Arctic center of action of the annular mode is more prominent and extends deeper into Siberia, its related surface air temperature signal is stronger, and the compensating outer ring in the sea-level pressure field is much broader, encompassing the entire tropics. During cold winters the NAM signature is much more pronounced over the Pacific sector: the sea-level pressure pattern exhibits a North Pacific center of action, positively correlated with the Atlantic center, and pronounced deflections of the storm track are also evident. It is suggested that the former features are associated with the equatorward displacement of the jet stream and the storm tracks during warm winters of the ENSO cycle and the latter is related to the the more pronounced break in the subtropical jet stream over the Pacific sector during cold winters.