Seasonal Responses of Precipitation in China to El Nino and Positive Indian Ocean Dipole Modes

Using composite, regular, and partial regression analyses in the six consecutive seasons from spring of the El Nino-Southern Oscillation (ENSO)-/Indian Ocean Dipole (IOD)-developing year through summer following the ENSO/IOD mature phase, the individual and combined impacts of El Nino and positive Indian Ocean Dipole (pIOD) on the evolution of precipitation in China are diagnosed for the period 1950-2013. It is shown that the seasonal responses of precipitation in China to El Nino and pIOD events, and their relationship with the large-scale atmospheric circulations, differ from one season to another. For the pure El Nino years, there is a seasonal reversal of precipitation over southeastern and northwestern China, with deficient precipitation occurring in these two regions before the onset of anomalous wet conditions in the developing autumn. Meanwhile, North China tends to be drier than normal in the developing seasons, but wetter than normal in the decaying seasons. For the pure pIOD events, southern China suffers a precipitation deficit (surplus) in the developing spring (summer and autumn). Furthermore, both North China and northwestern China experience excessive precipitation in the developing autumn and decaying summer. In addition, there is reduced precipitation in northeastern China during both the developing and decaying summers, whereas increased precipitation occurs in the developing autumn and decaying winter. For the combined years, southern China experiences enhanced moisture supply and suffers from increased precipitation from the developing summer through the subsequent spring, but reduced precipitation in the developing spring and decaying summer. Similar to the pure El Nino, northwestern (North) China becomes wetter than normal after the developing summer (autumn) in the combined years. In general, the ENSO/IOD-related precipitation variability could be explained by the associated anomaly circulations.