ATMOSPHERIC TURBULENCE

Author: LÓPEZ GONZÁLEZ-NIETO PILAR.
Year: 2003.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS.

Summary: The fluid systems are capable of developing a phenomenon of nature that is unpredictable turbulence because these dynamic systems are governed by nonlinear equations of motion. Este régimen flulido también es propio de los fluidos geofísicos como la atmósfera y el océano. The turbulence in fluids arises as a result of the evolution of an unstable laminar flow initially. Such instability is supported by the increased speed, the presence of obstacles or viscosity or density of the fluid itself. The fluid turbulence is facilitated by the presence of hydrodynamic instabilities of various kinds. Our interest is in the lower atmosphere, which is a fluid geogísico stratified and moving prodiminantemente in turbulent regime. The atmospheric turbulence is the primary responsibility of the transfer processes of the various physical quantities important in the study of atmósera such as humidity, heat, the time or the concentration of any pollutant. The buoyancy forces are directly related to the presence of stratification in a fluid and are the result of the action of gravity on density variations exist, generating a wide variety of fluid movements and caused directly influenced by them. In particular, it highlights the fluid phenomena resulting from an unstable density subsumed under the name of convection by buoyancy, which are the object of study of this work. The main objective of this report is the modeling and experimental study of turbulent mixing generated under conditions of unstable stratification in the fluid system built for that purpose. Thus, attempts to perform a modeling experimental mixing turbulent convective-type result of a volatile stratification could be regarded as if it were home heat despite the fact that the experimental procedure does not make any use of thermal variations, but variations salt concentration. The pilot raised assembly generates a set of plumes turbulent axilsimétricos that stand out as producers mixture under unstable conditions in a stratified fluid. The process of mixing turbulent generated experimentally analyzed globally through the study of the efficiency of mixing and the height of the mixed layer, which are values that consider only the initial state and the end of the system fluid. In addition, it conducts a study of the temporal evolution of the process of turbulent mixing.

Author: PÉREZ LANDA GORKA.
Year: 2005.
University: PAÍS VASCO [www.ehu.es].
Place of defense: E.T.S. DE INGENIEROS DE BILBAO.
Place of preparation: E.T.S. DE INGENIERÍA DE BILBAO.

Summary: The mesoscale atmospheric circulations, often determine the conditions of transport in regions of complex topography. Their study is needed on the characterization of the behavior of tracer interest in these areas. In Southern Europe, various research projects have shown the non-local nature of these processes, interactions at different scales, appearing so often, the least for half of the year (April-September). This paper shows how the combined application of experimental techniques suited to these scales and models of mesoscale weather allows in-depth analysis of these circulations and the mechanisms of transport and accumulation of pollutants during episodic situations: applications are submitted studies relevant made in the north and east coast of the Iberian Peninsula. Moreover, the study of the spatial variability of CO2 in the region of Valencia, allows draw conclusions that may have implications in the methodologies currently used in the study of the behavior of CO2 worldwide overall. Thus, the vertical and horizontal gradients (tierra-mar) CO2 simulated in the region of Valencia to high-resolution mesoscale model, can not be solved with models globally. This implies that in regions with similar characteristics, the results of the models currently used in the study of CO2 on a global scale can present significant divergence.