A dry-wet teleconnection between southwestern and northeastern China in winter and early spring

Global climate change has led to more frequent and intense dry and wet extremes, causing considerable socio-economic losses, but whether these extremes in distant regions are linked and what mechanisms are driving their changes remain unclear. Based on the standardized precipitation-evapotranspiration index and ERA5 reanalysis data, this study reveals a dry-wet teleconnection between southwestern China (SWC) and northeastern China (NEC) from January to April: when SWC was extremely dry, NEC tended to be anomalously wet, and vice versa. Although the seesawing teleconnection is most significant on interannual time scales, it also experienced interdecadal changes, with wet SWC and dry NEC in 1979–1998 and 2019-present and dry SWC and wet NEC in 1999–2018. Further investigations suggest that the pattern of dry SWC and wet NEC is related to anomalous anticyclones (cyclones) over SWC (NEC), which lead to significant changes in surface temperature and total precipitation in the respective regions. The dryness in western (eastern) SWC is mainly influenced by the changes in temperature (precipitation), while the NEC wetness is affected mainly by the changes in temperature. Observational and modeling studies further suggest that the pressure anomalies over SWC and NEC are caused by zonally and meridionally propagating Rossby wave trains, triggered by the North Atlantic Oscillation and the enhanced Indo-Pacific convection, respectively. These wave trains further lead to hydroclimatic extremes in North America, southern Europe, and the Middle East by regulating the atmospheric circulation anomalies over these regions.