Associations between China monsoon rainfall and tropospheric jets

Abstract

AbstractStrong associations, in both the annual cycle and interannual variations, between east China monsoon rainfall and tropospheric jets are established with the use of observations and general‐circulation model simulations. Two distinct systems dominate regional rainfall: the east Asian jet stream (EAJ) in the north and the Hadley cell in the south. The EAJ is associated with Mei‐Yu and polar fronts as well as vigorous jet‐transverse circulations, whereas the Hadley cell is allied to tropical upper‐level easterlies and intertropical convergence zone convection. An equatorward EAJ displacement causes precipitation to increase over south‐central (south) China during June‐August (January‐March). Conversely, a poleward shift of the summer (winter) EAJ brings heavier precipitation over north (central‐north) China. On the other hand, over the South China Sea the Hadley cell influence prevails and, consequently, increased rainfalls concur with enhanced lower‐level westerlies. Furthermore, the EAJ fluctuations are strongly coupled with southern oscillation variations. Their interactions tend to precede (follow) El Niño phenomena during October through May (summer). The EAJ related flow anomalies also have potential skill to predict China rainfall interannual variability. To conclude, a realistic China monsoon simulation requires accurate representation of the EAJ and Hadley cell. Both features link regional rainfall to tropical and extratropical planetary‐scale circulations and, in turn, to global surface characteristics.