A Composite Study of the Madden-Julian Oscillation
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
Pagination or Media Count:
A composite based on the phase of the 30-60 day oscillation referred to here as the Madden-Julian Oscillation or MJO is used to examine kinematic and thermodynamic fields over the equatorial western Pacific Ocean for three Northern Hemisphere winter seasons 1986-89. The composite is based on Outgoing Longwave Radiation OLR data from NOAA polar-orbiting satellites plotted in time versus longitude diagrams. Eastward propagation of low OLR inferred deep convection values associated with the trough of the MJO wave was clearly visible in these Hovmoller diagrams. These diagrams were used to construct a four convective phase composite. The composite is then applied to the OLR and model analysis data from the European Center for Medium Range Weather Forecasts ECMWF and the National Meteorological Center NMC. Large scale heat and moisture budgets are calculated and compared to other tropical budget studies. Emphasis is placed on inter-phase variability and the role of El Nino-Southern Oscillation ENSO as a modulator of convective activity. The OLR composite reveals that during the two warm years 1986-87 and 1987-88 the main convective activity was centered between the 2.5 deg S and 5.0 deg S. It shifted to between 10.0 deg S and 15.0 deg S during the cold year 1988-89. The OLR data also indicated that the convection was stronger in the warm years than in the cold year. The eastward propagation of the convection was also evident.