Interdecadal unstationary relationship between NAO and east China's summer precipitation patterns

Based on a 120-year Chinese station rainfall dataset and historical NAO indices, the interdecadal unstationary relationship between the North Atlantic Oscillation (NAO) and east China's summer precipitation patterns is revealed for the period 1880-1999. It is shown that on the interannual timescale, the March NAO is closely related to the first leading precipitation mode which exhibits an outof-phase variation of the precipitation between the Yangtze River Valley and Southeast China, and the January NAO is closely related to the third leading mode which depicts the anomalous rainfall in North China and its out-of-phase variation in the Yangtze River Delta. Both of the two relationships are characterized by clear and consistent interdecadal variations, with almost the same transition points occurring in about 1905, 1925 and 1950, respectively. Further analyses imply that these interdecadal changes of the relationship are possibly associated with the SSTA in North Pacific and North Atlantic. Copyright 2009 by the American Geophysical Union.