Influences Of Madden-julian Oscillation On The Surface Air Temperature Changes Over The Antarctic

Although the West Antarctic and Antarctic Peninsula have experienced the most significant warming over the world,a decreasing trend of surface air temperature(SAT)was observed on the East Antarctic(EA,30°W–150°E,66.5°–90°S)during the austral summer(DJF)of 1979–2014 with the global warming of climate.The cause for this cooling of SAT over the East Antarctic is uncertain.Previous highlighted the effects of higher latitude dynamics and the tropical SST forcing on the SAT trends in the Antarctic area.In this thesis,we found that the decadal changes in Madden-Julian Oscillation(MJO)also contribute to the cooling trend in EA via atmospheric teleconnection,based on the reanalysis diagnosis and modeling experiments.The analysis and diagnosis of large-scale circulation and associated SAT budget equation show that MJO convective activities over the equatorial Indian Ocean(western Pacific)can induce warm(cold)advection and adiabatic warming(cooling)anomalies over the EA through exciting the anomalous circulations related to the poleward-propagating Rossby wave train.Compared to the earlier decade(1979–1996),the austral summer MJO events over the Indian Ocean(western Pacific)tend to occur less(more)frequently in the recent epoch of 1997–2014,SAT over the East Antarctic resulting in a net cooling effect over the EA through tropicalextratropical teleconnection.When we extended the data including the second half of the 20 th century(1957-2010),the multi-decadal changes of DJF SAT in EA appear to be tightly connected with MJO convective activities over the tropics based on the SVD analysis.The influence of equatorial MJO on EA SAT was also confirmed by designing and conducting the sensitivity experiments using the NOAA/GFDL Low Ocean Atmosphere Resolution(LOAR)of Coupled Model 2.5(CM2.5).This model well simulates the equatorial MJO features with the maximum intensity over the Indian ocean warm pool.Once the equatorial MJO signals over the tropical region were removed from the model simulation by nudging the prognostic variables toward their annual cycle and longer period components(> 90 days)derived from the control experiment,the EA SAT decreases.When only the Indian ocean MJO was removed,the EA SAT shows a more significant decrease.These modeling results support the observational finding about the influences of MJO on the EA SAT.