Growth of (finite) Perturbations in Spatiotemporal Systems. Application to Ensemble Weather Forecasting

Modern meteorology is concerned with the nonlinear dynamics of the atmosphere and ocean (ensemble prediction, etc.). However, although low dimensional chaos is nowadays well known, much less is understood about spatiotemporal systems with a large number of degrees of freedom, as those describing the atmosphere-ocean evolution. The nonlinear effects that drive the dynamics of finite perturbations are a key factor for the understanding of error growth and ensemble prediction in these systems. However, most of the methods used currently in meteorology rely on findings from the low dimensional world and do not take into account the interactions between space and time inherent of these systems. In this talk we focus on the singular features of spatiotemporal chaos, as opposed to low-dimensional dynamics, paying attention to the interplay between spatial and temporal dynamics. To this aim we consider not only infinitesimal dynamics (characterized by the Lyapunov spectrum), but also the properties of finite growth in the edge of predictability. A recent analogy introduced with the scaling (fractal) growth of rough interfaces (such as the propagation of a fire interface in a sheet of paper) provides a framework for the analysis and characterization of the spatial and temporal dynamics of these systems, and their interplay.


As an illustrative example we analyze data from the DEMETER project, an state-of-the-art ensemble forecast system for seasonal forecasting, which includes multiple models and initial conditions.


More details in http://www.meteo.unican.es/en/research/spatiotemporal_chaos



Herrera, S., Pazó, D., Fernández, J., Rodríguez, M.A., (2012) Tellus A. In press.


Herrera, S., Fernández, J., Rodríguez, M. A. and Gutiérrez, J.M., (2010) Nonlin. Processes Geophys. 17, 329–337.


Fernández, J., Primo, C., Cofiño, A.S., Gutiérrez, J.M., Rodríguez, M.A., (2009) Climate Dynamics, 33, 233-243.