A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

SCALING PROPERTIES OF EXTREME VALUES, INTERMITTENCY, ANDLYAPUNOV EXPONENTS OF WIND AND TEMPERATURE DYNAMICSOF CENTRAL AMAZONIAGermán Poveda, Jorge M. Ramírez, Carlos D. Hoyos, John F. Mejía.Posgrado en Aprovechamiento de Recursos HidráulicosUniversidad Nacional de Colombia, Sede Medellínjramirez@hidraulica.unalmed.edu.coAbstractWe use high resolution (60 Hz) wind velocity and temperature data gathered duringMay 1999 at Rodonia (central Amazonia) as part of LBA field campaigns, to studydiverse features of turbulence in and over the canopy. Our analyses are aim todetermining scaling properties of the extreme events of wind velocity over a broadrange of timescales. The scaling relation between the tails of the probability densityfunction (PDF) are calculated for different time scales, and upon these relations,predictions are made for the PDF at any particular timescale. Secondly, we applywavelet transforms to detect intermittency features in the energy dissipation rates.Intermittency is a fundamental issue that is brought about to explain the insufficiency ofKolmogorov’s theory to describe the sample structure function and the non-Gaussiannature in the dynamics of turbulent signals. Also, we use ideas pertaining non-lineardynamical systems to artificially reconstruct the attractor in phase space. Towards thatend, we use the methods of “false neighbours” and the Shannon mutual information,and then we estimate the largest Lyapunov exponent of the reconstructed attractor. Ourresults indicate the exponential divergence trajectories in phase space, thus suggestingthe existence of a strange attractor in the dynamics of the turbulent atmosphericboundary layer over Central Amazonia.