Collaborative Research: Evaluating the Roles of Factors Critical to MJO Simulations Using the NCAR CAM3 with Deterministic and Stochastic Convection Parameterization Closures

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The Madden-Julian Oscillation (MJO) is a large-scale pattern of precipitation and atmospheric circulation anomalies which forms over the Indian Ocean and propagates slowly eastward towards the central equatorial Pacific Ocean. Impacts of the MJO are felt over much of the earth, and the presence of the MJO in the central equatorial Pacific Ocean exerts a strong modulation of hurricane activity in the Gulf of Mexico. Work conducted under this grant is intended to improve the representation of the MJO in global climate models (GCMs), particularly the National Center for Atmospheric Research Community Atmosphere Model (CAM). The questions addressed in the research focus on specific factors believed to be essential to a successful MJO simulation: 1) How important is convective momentum transport [CMT, occurring in cumulus clouds] in the MJO simulation? The objective of addressing this question is to understand what role convective momentum transport plays in westerly wind bursts accompanying MJOs. 2) What are the roles of convective versus stratiform heating, shallow versus deep convection, and stochastic versus deterministic convection closure in the MJO simulation? The objective is to determine how each of the processes affects the MJO simulation [here stratiform refers to the flat, upper-level "anvils" associated with deep cumulus clouds]. 3) How do these roles depend on the MJO phases in the MJO development process? The objective of answering this question is to understand what role each process plays during different stages of the MJO evolution. Motivation for the work comes from the difficulty in simulating and predicting the MJO using weather and climate models.The work has broader impacts due to the many worldwide impacts of the MJO on weather and climate, as better representation of the MJO in models is a first step in generating useful MJO forecasts. In addition, the MJO is an important test case for the parameterization of convection and cloud processes in climate models, which would increase our confidence in predictions and projections of climate change. Beyond these broader impacts, the project also promotes science education through undergraduate teaching and outreach activities to high schools.