The Simulated Organization of Deep Convection during MJO

It has been hypothesized that the initiation and propagation of the Madden-Julian Oscillation (MJO) are related to the organization of convective clouds that make up the larger-scale convective envelopes. The preferred organizational pattern and process of such clouds, on the other hand, can also be significantly affected by environmental conditions that may vary across the MJO life cycle. Although the existence of different degrees of the convective organization during various phases of the MJO is well documented in observations, the mechanisms responsible for such differences are yet to be fully understood. Since dense and massive convective scale cold pools are generated by rain droplets evaporating, we hypothesize that these cold pools can excite new convection at their edges by dynamic lifting, thermal fueling, or even colliding with each other, to help organize convective systems in the MJO active phase. Here, this problem is approached following a modeling perspective, using a combination of Eulerian and Lagrangian numerical models. First, observational data from the Dynamics of the MJO (DYNAMO) campaign is used to validate high-resolution model simulations obtained using the Weather Research and Forecasting (WRF) and the System for Atmospheric Modeling (SAM) models. Then, different organizational indices diagnosing convective organization in the model simulation during different phases of the MJO are discussed. Finally, Lagrangian diagnostic tools are used to investigate at a process level how cold pools modulate the degree of organization at different stages of the MJO by determining the most preferred distances between updrafts and clusters as particular organized patterns within MJO. This analysis demonstrates the importance of the environmental conditions affected by the MJO and the smaller-scale convective dynamics to vary tropical convective organization that will be useful for better understanding the two-way feedback between MJO and convective organization.