Geophysical and Astrophysical Fluid Dynamics

Abstract:

A new general circulation model (GCM) of Venus is being developed at Oxford. Venus presents unique numerical and physical challenges because of its thick atmosphere, slow underlying solid body rotation, and super-rotating atmosphere. Preliminary results from a GCM with simplified physical parameterizations are discussed. The current model uses linearized cooling and friction schemes, and spans five decades of pressure (0-90 km). The model is able to demonstrate significant global super-rotation, and although not yet fully realistic, future plans include more detailed representation of the Venusian atmosphere, such as the planetary boundary layer (PBL) scheme. The use of the model is discussed in supporting and interpreting data from future missions to Venus. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Abstract:

We study the interannual variability of dust storms on Mars in an assimilation of thermal profiles and dust opacity observations into a general circulation model for the Martian atmosphere. The observations have been provided by the thermal emission spectrometer aboard the Mars Global Surveyor spacecraft during the scientific mapping phase over more than two complete Martian years, which include three dusty seasons in southern spring. A comparison between dust seasons which are characterized only by regional storms and the global, planet-encircling dust storm of 2001 is performed, focusing on the meteorological conditions which can trigger the onset and development of the global storm, and its effects on the global circulation. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Abstract:

The banded patterns of cloud and wind are among the most striking features of the atmospheres of Jupiter and Saturn, but their dynamical origin remains poorly understood. Most approaches towards understanding zonation so far (also in the terrestrial oceans) have used highly idealized models to show that it might originate from dynamical anisotropy in a shallow turbulent fluid layer due to the planetary β-effect. Here we report the results of laboratory experiments, conducted on a 14-m diameter turntable, which quantitatively confirm that multiple zonal jets may indeed be generated and maintained by this mechanism in the presence of deep convection and a topographic β-effect. At the very small values of Ekman number (≤2 × 10-5) and large local Reynolds numbers (≥2000, based onjet scales) achieved, the kinetic energy spectra suggest the presence of both energy-cascading and enstrophy-cascading inertial ranges in addition to the zonation near twice the Rhines wave number. Copyright 2004 by the American Geophysical Union.