MJO theory in relation to comprehensive models and observations

Abstract:

I will describe some recent thinking on the fundamental physics of the MJO. Much recent work portrays the MJO as some form of “moisture mode” – meaning that the prognostic variable of greatest importance is moisture or a conserved variable closely related to it, such as moist static energy or moist entropy – and I will argue for this line of thinking, presenting evidence in favor of it, as well as unresolved problems.

I will focus on the relationship between theory, numerical modeling at a range of scales, and observations. We have reached a new phase in the study of the MJO: the phenomenon has been described in great detail from an observational point of view, and perhaps even more importantly, the best numerical models can now simulate it well. I will argue that in this situation, theory is most compelling when its core assumptions can be specifically defended using both observations and comprehensive numerical models. I will make connections between the moisture mode view and results from several different types of numerical models: numerical weather prediction models, global climate models, and small-domain high-resolution cloud resolving models.