Propagation and influence on tropical precipitation of intraseasonal variation over mid-latitude East Asia in boreal winter

The authors investigate the characteristics of propagation and the influence on tropical precipitation of 9–29-day intraseasonal variation over midlatitude East Asia during boreal winter, and find that the intraseasonal wind signal can propagate both eastward and southward. In the case of eastward propagation, the intraseasonal wind signal is mainly confined to the midlatitudes, featuring eastward migration of anomalous cyclones and anticyclones. In the case of southward propagation, intraseasonal meridional wind perturbations may extend from the mid to the low latitudes, and even the equatorial region. The accompanying wind convergence/divergence induces anomalous precipitation in the near-equatorial regions, forming a north–south dipole precipitation anomaly pattern between the southern South China Sea and the eastern China–Japan region. An anomalous meridional overturning circulation plays an important role in linking tropical and midlatitude intraseasonal wind and precipitation variations.