The Role of the Meridional Rossby wave for Extreme Heatwaves Over East Asia

The North Pacific High is a dominant circulation system that governs the weather in the East Asian region during the summer, and its western boundary serves as a waveguide for the propagation of Rossby waves from the equatorial to mid-latitudes. The deep convection over the equatorial western Pacific usually creates Rossby waves that propagate northward along this waveguide. This meridional Rossby wave, known as the Pacific-Japan (PJ) pattern, is the dominant teleconnection pattern in the vicinity of East Asia, and it often accompanies Heatwaves.

In this study, the circulation and thermodynamic characteristics of the PJ pattern were investigated based on a daily timescale to better understand their relationship with the likelihood of heatwaves in East Asia. According to thermodynamic budget calculations, horizontal heat advection crossing the climatological flow pattern is the key factor for the observed surface air warming. The circulation pattern associated with a PJ pattern largely explains the enhanced warm advection. The overall findings of this study provide valuable insights into the development mechanisms of heatwaves on an intraseasonal timescale.