Characteristics of atmospheric circulation patterns over East Asia and their impacts on precipitation in summer

摘要

We investigated 3 summer atmospheric circulation patterns over the mid-latitudes of East Asia—the monopole (MOP), East Asia?Pacific (EAP) and southeast?northwest out-of-phase dipole (EWD)—and their impacts on precipitation in eastern China. Our results show that an increase in the frequency of the positive MOP pattern enhances precipitation in northeastern China, while a longer persistence of this pattern induces above-average precipitation in the midto-lower reaches of the Yangtze River valley (MLRYR). For the negative MOP pattern, a higher frequency of this pattern leads to below-average precipitation in northeastern and southern China, while its persistence has insignificant influences on precipitation in eastern China. In - creases in the frequency and persistence of the positive EAP pattern intensify precipitation in the MLRYR. For the negative EAP pattern, increases in the frequency and persistence of the pattern reduce precipitation in the MLRYR, and a higher frequency of this pattern markedly intensifies precipitation in northern China. Regarding the positive EWD pattern, an increase in its frequency favors below-average precipitation in northern China, and an increase in its persistence clearly intensifies precipitation in the MLRYR. Increases in the frequency and persistence of the negative EWD pattern produce below- (above-)average precipitation in the MLRYR (north eastern China), with a longer persistence of this pattern especially reducing precipitation in the MLRYR. These results indicate that the frequency and persistence of each pattern have different impacts on precipitation in eastern China.