Air-sea Interaction and Island Geography Impacts on Madden-Julian Oscillation (MJO) Initiation and Propagation Through the MAritime Continent

Colorado State University, Fort Collins CO

Investigators

Abstract

Results of this research will benefit the weather forecasting and model development communities, and promote collaboration with other scientists. The project supports one full-time student. Research results will be documented in peer-reviewed publications and shared through participation in national and international workshops and conferences. The Madden-Julian oscillation (MJO) is a large-scale intraseasonal (30-50 day) tropical disturbance with coupled convection and circulation anomalies that propagate eastward at about 5 m/s. The MJO impacts tropical weather across the globe, and influences weather at higher latitudes via teleconnections. The extratropical impacts are especially pronounced when MJO heating is centered over the Maritime Continent and West Pacific. Most state-of-the-art general circulations models (GCMs) struggle to simulate eastward-propagating MJO convection, and those that do typically have difficulty with its propagation across and beyond the Maritime Continent. Coupling an atmosphere-only GCM to an interactive ocean model often improves the magnitude, periodicity, and propagation characteristics of its MJO simulation, but there is no consensus as to why this is true. This research will advance our understanding of the roles of air-sea interaction and Maritime Continent geography on the simulation of the MJO. Expected outcomes of this research are 1) improved understanding of processes critical to MJO initiation and propagation and 2) new insights into why so many GCMs struggle to simulate an eastward propagating MJO capable of translating the Maritime Continent. The objectives of this project are 1) to understand the mechanisms of air-sea interaction on MJO convective development and its impact on moist static energy and 2) to understand the relative influences of air-sea coupling and Maritime Continent geography on MJO propagation. Reanalysis and model output from the super-parameterized Community Atmosphere Model (SPCAM) will be analyzed to assess the mechanisms of air-sea interaction on MJO convective development in coupled and uncoupled simulations, and for MJO events that do and do not propagate across the Maritime Continent. A series of modeling exercises using idealized island geography will be performed to test existing hypotheses concerning the Maritime Continent's impact on MJO convection and its propagation. Analysis methods will be applied to a limited set of coupled climate models to examine the extent to which results are model dependent.