The Madden-Julian Oscillation and Extratropical Teleconnection over East Asia during the Northern Winter in IPCC AR4 Climate Models

摘要

The reproducibility of the extratropical teleconnection in East Asia associated with the Madden-Julian Oscillation (MJO) during the boreal winter is evaluated in the 20th century experiment (20C3M) outputs from 16 global climate models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). It is revealed that five of the models (BEST models) realistically simulate the MJOextratropical convection teleconnection. These models successfully represent the MJO convective signals better than the other models. Through analysis of the wave activity flux and Rossby wave source (RWS), the upper-level extratropical wave train induced by MJO convection is demonstrated to propagate northeastward along the Asian jet with its reinforcement, which eventually affects the convective variability in East Asia. The BEST models pronouncedly reproduce the extratropical wave train and RWS. However, the other models produce unrealistic or no extratropical wave trains due to unrealistically produced RWSs, although all models realistically exhibit the climatological absolute vorticity over the Asian jet as a waveguide. Furthermore, only the BEST models reproduce the low-level moisture transport with southerlies from the tropics into East Asia, which are associated with realistically reproduced anticyclonic circulation over the North Pacific, that is largely formed as a Rossbywave response to the cooling anomaly with meaningful suppressed convection over tropical western and central Pacific. In summary, correctly simulating the intensity of the MJO convection and its eastward propagation into the Pacific is necessary in order to predict the wintertime climate variability over East Asia.