A dynamical-system description of precipitation over the tropics and the midlatitudes

Yano, Jun-Ichi ; Ambaum, Maarten H. P. ; Dacre, Helen F. ; Manzato, Agostino

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A dynamical-system approach is proposed to describe the relationship between precipitation and a chosen predictor. This is done by constructing a two dimensional phase space spanned by predictor and predictant. This study uses two sounding data sets from the Tropical Western Pacific and Friuli Venezia Giulia (FVG) over North-East Italy as representatives of the tropics and midlatitudes, in addition to a basin-scale average over the winter-period North Atlantic from global re-analysis data. In contrast to conventional correlation-based approaches, the proposed approach depicts periodic cycles, as well as discharge-recharge cycles as its nonlinear extension. Discharge-recharge cycles for tropical convection are identified by using both the convective available potential energy (CAPE) and the column-integrated water vapor (CIW) as predictors, as well as the baroclinicity for the winter-period North-Atlantic rain. On the other hand, the midlatitude rain, as seen over FVG as well as the winter-period North Atlantic, does not constitute a well-defined periodic cycle either with CAPE or CIW as a predictor. The inferred phase-space trajectories are more deterministic at peripheries of dense data areas rather than at a middle in the phase space. Data-dense areas in phase space, where traditional approaches primarily focus, are associated with more prediction uncertainties in our analysis due to more phase-velocity fluctuations.</p>

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