293 The Role of Tropical Cyclones in Maintaining or Disrupting MJO Circulations

Monday, 8 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Lawrence C. Gloeckler, SUNY, Albany, NY; and P. E. Roundy

As a fundamental part of the global circulation, the Madden–Julian oscillation (MJO) influences the evolution of large-scale circulation patterns proximate to and far from its convective envelope. Tropical cyclones (TCs) also modulate large-scale circulation patterns across the globe, especially following their recurvature and interaction with mid- and high-latitude circulations. Consequently, TCs that occur in conjunction with active MJO events often modify circulation outcomes associated with the MJO and possibly contribute to particular patterns of forecast error in different parts of the globe.

A temporal linear decomposition of the zonal momentum budget is performed to quantify the extent to which TCs contribute to the maintenance or disruption of circulation patterns that evolve in conjunction with the MJO. Each component in the budget equation is linearly decomposed into background (greater than 100-day), intraseasonal (20−100-day), and transient (less than 20-day) time scales, and components that significantly contribute to the intraseasonal zonal wind tendency are retained. Composites are organized by TC type (i.e., recurving and non-recurving) without regard for MJO activity, and relative to different Real-time Multivariate MJO (RMM) phases. Background and intraseasonal horizontal advection terms are shown to dominate feedbacks between TCs and circulations associated with the MJO. Curvature and the meridional advection of transient zonal wind by transient meridional wind, among other terms, are also demonstrated to be important contributors to the budget. Results suggest that, in the context of this budget, feedbacks between TCs and circulations that evolve in conjunction with the MJO are most sensitive to TC trajectory (whether or not the TC recurves).

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