The Modulation and Decadal Change of Madden-Julian Oscillation on Tropical Cyclone in the Western North Pacific Ocean
Friday, 19 December 2014
This study focuses on the climatological relationship between the Modden-Julian Oscillation (MJO) and Tropical Cyclone (TC) activity in the Western North Pacific (WNP) and its decadal variability. Based on the knowledge of the modulation of MJO on TC in WNP, a set of data including the RMM(Real-time Multivariate MJO)index from RMRC(bureau of meteorology)of the Centre for Australian Weather and Climate Research,the best tracks from the Navy Joint Typhoon Warming Center(JTWC),daily data of the NCEP/NCAR reanalysis and the ECMWF ERA-interim reanalysis were used.The result shows that TC frequency in WNP exhibited a statistically significant decrease during the period of 1998-2010, comparing to the period of 1979-1997.The decrease on TC frequency in WNP mainly occured during MJO active phases 4,5,6,and 7. In further investigation on comparison of cycle days of MJO, duration of MJO active phases (4,5,6,and 7),low-frequency wind at 850hPa, large-scale convection circulation and vatiability of Surface Sea Temperatures (SST) and Outgoing Longwave Radiation (OLR) in MJO active phases between 1979-1997 and 1998-2010, we found that: during 1998-2010,cycle days of MJO and duration of MJO active phases exhibited a significant decrease; low-frequency wind at 850hPa showed an eastern-wind transition; convective areas in MJO active phases decreased and anormaly of its SST were more negative. These may be reasons of difference of TC frequency in the period of 1979-1997 and 1998-2010.