Investigating MJO Precursors and Initial Stages with Multivariate Principal Oscillation Analysis

Abstract:

We have applied Principal Oscillation Pattern (POP) analysis to minimally filtered gridded analyses of several variables which can be used as markers of Madden-Julian Oscillation (MJO) initiation. One of the resulting modes is MJO-like, with an 11-pentad period and a 3-pentad decay time. We have separately used a variety of criteria to identify several MJO events during boreal winters 1998-2012 for individual examination. Here we explore how the MJO-like mode evolves during these cases in multiple ways. We track the contributions to that mode by upper- and lower-level zonal winds and latent heating (as proxied by Outgoing Longwave Radiation, OLR), as well as the contributions made by mid-tropospheric temperature (T400) and sea-level pressure (SLP) in the pre-cursor and early stages of the events. We also examine the stochastic forcing of these cases using diagnostics based on fluctuation-dissipation theory, and compare the characteristics of this forcing during the early stages of several MJO events.