Author: fferaco

Article by R. Marino and F. Feraco on the cover page of JGR (Machine Learning and Computation) Vol. 1 (3)

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New Publication on JGR (Machine Learning and Computation) Vol. 1 (3): Augmented four-dimensional Mesosphere and Lower Thermosphere wind field reconstruction via the Physics-Informed Machine Learning approach HYPER

J.M. Urco, F. Feraco, J.L. Chau, R. Marino

The mesosphere and lower thermosphere (MLT) is a fluid framework whose multiscale dynamics is determined by a superposition of non-linear processes and by the interplay of gravity waves and turbulent motions. A thorough comprehension of this atmospheric region requires substantial observational infrastructure, needed to resolve and disentangle its complex dynamics. State-of-the-art observational methods struggle to accurately capture mesoscale dynamics due to the inherent difficulty to perform observations at MLT altitudes. A majority of the observational methods rely on assumptions such as homogeneity, smoothness of the prognostic fields, or zero vertical wind velocities, which may not hold in the upper atmosphere at the mesoscales. In this study, we introduce a novel machine learning-based approach HYPER (HYdrodynamic Point-wise Environment Reconstructor), designed to characterize MLT dynamics. HYPER utilizes a physics-informed neural network to project sparse Doppler meteor detections into four-dimensional time-series arrays containing the Cartesian components of the velocity field. This method combines meteor radar observations with the physics prescribed by the Navier-Stokes equations. The validation of HYPER was conducted through a series of benchmarks on numerical data and the application of our algorithm on actual meteor radar observations, all of which yielded realistic approximations of the reconstructed physical fields. This innovative approach represents a significant step toward an accurate characterization of the MLT dynamics, overcoming the limitations of existing methods, and providing valuable insights into the behavior of this poorly accessible region of the atmosphere.

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New Publication on Science, Vol. 383 (6686), p. 1005-1009: Large-scale self organization in dry turbulent atmospheres

A. Alexakis, R. Marino, P.D. Mininni, A. Van Kan, R. Foldes, F. Feraco

How turbulent convective fluctuations organize to form larger-scale structures in planetary atmospheres remains a question that eludes quantitative answers. The assumption that this process is the result of an inverse cascade was suggested half a century ago in two-dimensional fluids, but its applicability to atmospheric and oceanic flows remains heavily debated, hampering our understanding of the energy balance in planetary systems. We show using direct numerical simulations with spatial resolutions of 12288² × 384 points that rotating and stratified flows can support a bidirectional cascade of energy, in three dimensions, with a ratio of Rossby to Froude numbers comparable to that of Earth’s atmosphere. Our results establish that, in dry atmospheres, spontaneous order can arise through an inverse cascade to the largest spatial scales.

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New Publication on Science Advances, Vol. 8 (41), p. 033801: Direct observational evidence of an oceanic dual kinetic energy cascade and its seasonality

D. Balwada, J.H Xie, R. Marino, F. Feraco

The ocean’s turbulent energy cycle has a paradox; large-scale eddies under the control of Earth’s rotation transfer kinetic energy (KE) to larger scales via an inverse cascade, while a transfer to smaller scales is needed for dissipation. It has been hypothesized, using simulations, that fronts, waves, and other turbulent structures can produce a forward cascade of KE toward dissipation scales. However, this forward cascade and its coexistence with the inverse cascade have never been observed. Here, we present the first evidence of a dual KE cascade in the ocean by analyzing in situ velocity measurements from surface drifters. Our results show that KE is injected at two dominant scales and transferred to both large and small scales, with the downscale flux dominating at scales smaller than ∼1 to 10 km. The cascade rates are modulated seasonally, with stronger KE injection and downscale transfer during winter.