Mechanism and Impacts of Intensifying Madden-Julian Oscillations

Yale University, New Haven CT

Investigators

Abstract

The Madden-Julian Oscillation (MJO) is a large-scale convective and circulation system that propagates slowly eastward over the equatorial Indian and West Pacific Oceans. It modulates tropical cyclones, monsoons, the surface wind stress on equatorial oceans, and atmospheric rivers of moisture that can cause mid-latitude flooding. The research involves using recently developed dynamical analysis techniques and a novel Lagrangian model to study the mechanism of the MJO and how its impacts are likely to change as the climate warms. The work will help warn society about potential changes to the MJO and associated impacts that might be missed by conventional climate models. The work includes the training and education of a graduate student. A variety of observations indicate that the MJO has intensified in the last century, especially in the latter half. Most climate models suggest MJO rainfall will continue to become heavier in the future, but models are divided on the question of whether MJO circulations will further intensify. This is a critical question, because many of the MJO's impacts are related to the perturbations it causes to wind patterns. In this proposal, the researchers plan to: 1) Develop a new observational composite MJO dynamical structure that is centered on its convective envelope; 2) Partition composite observed and modeled MJO circulations into Kelvin and Rossby wave components and relate them to the mechanism of the MJO; and 3) Simulate MJO changes and associated impacts for the next century using a novel Lagrangian modeling system. This work will help to clarify the dynamics of the MJO in nature and in models, provide an explanation for why some models predict intensifying MJO circulations and others do not, and assess potential impacts from a changing MJO. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.