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Towards an Improved Understanding of the Initiation and Propagation of the Madden-Julian Oscillation

The Madden-Julian Oscillation (MJO) exerts significant influences on global climate and weather, and serves as a critical basis of the “Seamless Prediction” concept by bridging the forecasting gap between medium- to long-range weather forecasts and short-term climate prediction. However, our understanding of the essential MJO physics is still elusive. The MJO remains poorly represented in current climate models, which leaves us greatly disadvantaged in undertaking climate change studies, particularly in projecting future changes in extreme events that are significantly modulated by the MJO.

Motivated by exciting recent developments in MJO observations (the DYNAMO field campaign), modeling (the MJO Task Force/GEWEX GASS MJO Inter-comparison Project), and theories (e.g., the “moisture mode”), and by taking advantage of the availability of these unprecedented datasets, we propose to form a climate process team to expedite investigations on key physical processes responsible for initiation and propagation of the MJO. This team is built upon strong expertise in MJO studies among research groups from UCLA/JPL (Jiang and Waliser, co-organizers of the MJO Task Force/GEWEX GASS global MJO evaluation project, with expertise in observational and modeling diagnosis and MJO sciences), GFDL (Zhao and Lin, members of the core GFDL model development team, with expertise in model development), UH (Wang, with expertise in MJO theories) and CSU (Johnson, one of the lead PI of the DYNAMO field campaign, with expertise in in-situ observations). The proposed work will entail observational studies, in particular by utilizing the DYNAMO in-situ and satellite observations, 27 climate model datasets from the MJO Task Force/GASS MJO Project especially with the unique model output of physical tendency terms, as well as extensive experiments based on a newly developed state-ofthe- art GCM at the NOAA GFDL (HIRAM3.5) which exhibits superior MJO skill. We will thoroughly investigate critical physical processes for the MJO instability and propagation, with a primary focus on feedbacks between environmental moisture and convection, convection and its induced circulation, and cloud-induced radiative heating and convection. This study will significantly promote our understanding of the key model physics for realistic MJO simulations, thus leads to reduction of model biases in representing the MJO, which provides a major source of global predictability on the sub-seasonal time scale.

This proposal is strongly relevant to one of the NOAA NGSP’s long-term goal, “toward an improved scientific understanding of the changing climate system”, by advancing core capabilities in “understanding and modeling” and “predictions and projections”, as well as societal challenges in “climate impacts on water resources” and “changes in extremes of weather and climate”. In particular, this research directly addresses CVP program’s FY2015 calls for “Understanding Processes Affecting Madden-Julian Oscillation Initiation and Propagation” through a climate process team with expertise on observational diagnoses, theoretical understanding, modeling of the MJO. This proposed study is also in concert with one of the main goals of the WWRP/WCRP’s recently launched Sub-seasonal to Seasonal prediction (S2S) initiative, “to improve forecast skill and understanding of the sub-seasonal to seasonal timescale”, and greatly contributes to efforts in MJO process-oriented diagnoses led by the WGNE MJO Task Force.

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