Future change in the Madden-Julian oscillation using CMIP5 simulations

Abstract:

Future changes in the Madden-Julian oscillation (MJO) have been examined using CMIP5 simulations. To represent future MJO change, historical experiment data from 1979 to 2005 and representative concentration pathway 8.5 (RCP 8.5) run data from 2071 to 2100 are compared. Several changes and associated processes are investigated: 1) MJO will strengthen. For this, the following three aspects are presented. First, in wavenumber-frequency power spectrum analysis for 30-90 days filtered precipitation over [15°S-15°N], spectral power tends to increase significantly. Second, the explained variance of combined EOF1 and EOF2 using 30-90 days filtered zonal winds at 200 and 850 hPa and OLR increases from 46% to 54%. Lastly, the days of MJO index (defined as the amplitude of PC1 and 2 in combined EOF) that is larger than 1.0 increase. 2) Changes in the MJO phase speed are unclear, because different models in CMIP5 show different results. The main process for controlling the phase speed of the MJO will be examined using two and half layer model. Other characteristics of the MJO will be discussed through the moist static energy and moisture budget analyses.