Interannual Variation of the Quasi-biweekly Oscillation Intensity of Diabatic Heating over the Tibetan Plateau during Boreal Summer and Its Relationship with Rainfall Anomaly over Eastern China

Using China’s high-resolution grid rainfall data as well as the National Centers for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) and ERA-Interim reanalysis data from 1979 to 2018, the relationship between the interannual variation of the main mode (southern concentrated pattern) of the quasi-biweekly oscillation (QBWO) of diabatic heating over the Tibetan Plateau (TP) during boreal summer and rainfall anomaly over eastern China is investigated. When the interannual intensity of QBWO over TP is strong, a significant positive correlation exists between the summer rainfall anomaly in the south of the Yangtze River and QBWO over southern TP. In the weak years, rainfall anomalies in the Jianghuai region and South China characterize a dipole pattern. Additionally, in the strong (weak) years, the low-latitude intraseasonal signal originating in the Northwest Pacific region mainly shows a westward (northwestward) propagation, and the mid-high-latitude quasi-barotropic intraseasonal signal mainly shows a southward (southwestward) propagation. The combined effect of signals from low latitudes propagating westward (northwestward) and mid-to-high latitudes propagating southward (southwestward) cause different abnormal rainfall patterns in China. The low-latitude QBWO signal propagating westward (northwestward) weakens and disappears after reaching the Arabian Sea (southeast of TP). The southward (southwestward) signal in the mid-high-latitude converges with the westward (northwestward) signal in the low-latitude, continues propagating westward, and finally weakens and disappears.