Simulation of Venus' general circulation

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Wednesday, 20 January 2010: 4:15 PM
B314 (GWCC)
Christopher Lee, California Institute of Technology, Pasadena, CA

Rotating over 200 times slower than the Earth, Venus is in a different dynamical regime to that of the Earth. Observations from spacecraft as early as the 1970's showed a significant superrotation of the atmosphere relative to the solid body of the planet. Being in such an extremely different regime, Venus provides a tempting target for the testing of general circulation models and investigation of eddy driven phenomena.

However, the modeling of the atmospheric circulation on Venus is greatly complicated by the mass of the atmosphere that is 90 times larger than the atmosphere of Earth. A massive Carbon Dioxide atmosphere produces a surface pressure of 9.2 MPa and a surface temperature exceeding 750K, more than 400K above the black body equilibrium temperature. The tremendous thermal mass and optical depth greatly complicates fast and accurate radiative modeling of the atmosphere compared to other terrestrial planets.

Despite these problems, some progress has been made in understanding how the atmospheric super-rotation is maintained in the Venus atmosphere and what mechanisms are involved in creating the observed structures in the cloudy atmosphere. Approaches using linearized forcing and friction are able to produce Venus-like circulations with significant equatorial super-rotation. Simulations generally confirm the hypothesis that atmospheric instabilities induce equatorial convergence of momentum from the mid-latitude jets.

Problems still exist with these models insofar as they apply heating in a way that does not properly capture radiative exchange within the atmosphere and also do not impose heating with the correct time scales. One of the major activities in which we are currently engaged is the development of a radiative heating scheme that is both efficient enough to be used in a GCM model, but yet provides a more realistic treatment of the radiative heating.