麻豆AV

Tropical Subseasonal Variability and Its Teleconnection in Canadian EC GEM

According to the past studies, the analysis of observations indicates the tropical convection anomaly may have impacts on the pressure distribution in higher latitude with Rossby wave train. Aimed at improving the Madden-Julian Oscillation (MJO) in Global Environmental Multiscale Model developed by Environment Canada (EC GEM) and the prediction of the wintertime weather in North America, the convection structure of MJO and the teleconnection in the north hemisphere from GEM are assessed.聽 In general, the significant convective features of MJO can be reproduced by GEM and the signal is also more intense than observation. In the 23 model years, the outgoing longwave radiation (OLR) and the precipitation distribution in the tropics from our simulation is able to represent the eastward propagation of the convection system and to capture the corresponding locations of convection in each phase of MJO. Based on the MJO index defined by Wheeler and Hendon, the same method is applied here for the further analysis of the linkage between the tropical subseasonal variability and the teleconnection in the Northern Hemisphere.聽 Since the MJO index can be considered as the convection signal, the lag composite analysis of the geopotential height with the index depicts the distribution after the convection. After MJO phase 3, the convection occurance in the Indian Ocean, the 500hPa geopotential height anomaly draws a positive-North Atlantic Oscillation (NAO) like pattern. While after the convection reaches the Western Pacific Ocean, MJO Phase 7, the 500hPa geopotential height anomaly behaves like negative NAO pattern. Reversely, the lag composite of NAO index in GEM with respect to each MJO phase also has the statistic significant correlation to phase 3 and 7, which is similar to the former research that reveals the connection between the NAO and the MJO. Results in this study suggest the understanding of MJO may provide an access to the better forecast of the wintertime weather in North America.