Intraseasonal variability of summer monsoon rainfall over the lower reaches of the Yangtze River basin

摘要

This work investigates the boreal-summer intraseasonal variability (ISV) of the precipitation over the lower reaches of the Yangtze River basin (LYRB) during 1979–2016, based on daily Climate Prediction Center global precipitation data. The ISV of the summer monsoon rainfall over the LYRB is mainly dominated by the lower-frequency 12–20-day variability and the higher-frequency 8–12-day variability. The lower-frequency variability is found to be related to the northwestward-propagating quasi-biweekly oscillation (QBWO) over the western North Pacific spanning the South China Sea (SCS) and Philippine Sea, while the higher-frequency variability is related to the southeastward propagating midlatitude wave train (MLWT). Moreover, not each active QBWO (MLWT) in the SCS (East Asia) can generate ISV components of the precipitation anomaly over the LYRB. The QBWO can change the rainfall significantly with the modulation of mean state precipitation, while the quasi-11-day mode mainly depends on the intensity of the MLWT rather than the mean precipitation change. These findings should enrich our understanding of the ISV of the East Asian summer monsoon and improve its predictability.