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Spring precipitation in southeastern China and Bengal, occurring during the transitional phase from winter to summer monsoons, serves as a critical window into the dynamics of large-scale circulations and the subsequent summer monsoon. While many studies have analyzed spring precipitation in southeastern China and Bengal, their interconnections and implications for the summer monsoon have remained relatively under explored. We utilized the Empirical Orthogonal Function of spring precipitation to reveal Synchronous Spring Precipitation (SSP) in southeastern China and Bengal. This synchronicity is bridged by the East Asian Subtropical Jet (EASJ) that extends from Bengal to southeastern China. The EASJ was predominantly correlated with precipitation in southeastern China prior to the 1990s, while it developed a more profound connection with precipitation in Bengal after the 1990s. Notably, SSP anomalies occurred during the developing phase of the El Niño-Southern Oscillation (ENSO). The predictive capacity of SSP for the Indian summer monsoon (ISM) amplifies during periods of the intensified SSP-ENSO correlations and positive phase of the North Pacific Meridional Mode. Tree-ring based reconstructions spanning the past two centuries further corroborate the persistent linkages among the SSP, ISM, and ENSO. Our research sheds light on the intricate interplay of these factors and their significance in understanding and predicting the monsoon dynamics in the region.

Hydroclimatic change across China has received considerable attention due to its vital significance for regional ecosystem stability and economic development, yet the spatiotemporal dynamics of its nonlinear trends and complexity have not been fully understood. Herein, the spatiotemporal evolution of Dai’s self-calibrating Palmer drought severity index (scPDSI) trends in China during the period from 1951 to 2014 is diagnosed using the ensemble empirical mode decomposition (EEMD) method. A persistent and noticeable drying has been identified in North and Northeastern China (NNEC) since the 1950s. Significant wetting in the north of the Tibetan Plateau (TP) and the south of the western parts of Northwestern China (WNWC) started sporadically at first and accelerated until around 1980. A slight wetting trend was found in Southwest China (SC) before 1990, followed by the occurrence of a dramatic drying trend over the following decades. In addition, we have found that the scPDSI variations in WNWC and the TP are more complex than those in NNEC and SC based on our application of Higuchi’s fractal dimension (HFD) analysis, which may be related to complex circulation patterns and diverse geomorphic features.