MM5 Modeling of the Madden–Julian Oscillation in the Indian and West Pacific Oceans: Implications of 30–70-Day Boundary Effects on MJO Development

Abstract The results of an experiment designed to isolate the initiation phase of the Madden–Julian oscillation (MJO) from 30–70-day boundary effects is presented. The technique used to accomplish this involves employing the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5), as first presented in the companion paper to this paper. Two runs, each 2 yr long, are integrated forward from 1 June 1990. The first run, called the control, uses the unmodified National Centers for Environmental Prediction (NCEP)–NCAR reanalysis (NRA) dataset for boundary conditions. The second run, called the notched, uses the same NRA dataset for the boundary conditions, with the exception that all signals with periodicities in the 30–70-day range have been removed. Any signals in the 30–70-day range subsequently generated by the notched run are then solely due to signals generated from within the model domain or from signals entering through the domain boundar...