------------------------------ HR: 15:55h AN: U32A-05 TI: Simple Tests of Simple Climate Models AU: * Withers, P EM: withers@lpl.arizona.edu AF: University of Arizona, Lunar and Planetary Laboratory University of Arizona, Tucson, AZ 85721 United States AU: Lorenz, R EM: rlorenz@lpl.arizona.edu AF: University of Arizona, Lunar and Planetary Laboratory University of Arizona, Tucson, AZ 85721 United States AB: Planetary climate predictions are generally made with general circulation models. These models take years to develop and almost as long to run on a supercomputer. A simple model for predicting some elementary parameters of planetary climate would have great utility. The complexity and non-linearity of planetary climate systems make it challenging to identify a useful and appropriate simple model, yet many complex systems can be characterized, in the broadest sense, by simple models. The terrestrial climate has been studied by a variety of simple models. Some models have assumed that the terrestrial climate system is operating in such a way as to maximize efficiency, some have used analogies to heat diffusion, and some have considered the entropy production within the system. Here, we test some simple climate models on more than one planet. A simple climate model than works for only one planet is unlikely to be applicable in the general case; conversely, a simple climate model that works for several planets is likely to be applicable in the general case. We focus on latitudinal variations on Venus, Earth, and Mars in annually-averaged temperature and outgoing thermal radiation. We also examine seasonal averages to establish what the appropriate timescale is for applying these simple models. Depending on our progress, we hope to examine fluid planets in addition to solid surface planets. The simple model considering entropy production predicts that the outgoing thermal radiation at a given latitude is proportional to the square root of the incoming solar radiation at that latitude. Hence, a seasonal timescale is inappropriate for this model as it predicts no outgoing thermal radiation at all from the polar night. This model predicts annually-averaged temperatures on Venus and Earth that are surprisingly close to their observed values and are significantly better than zeroth-order predictions with no latitudinal heat transport. Acknowledgement: Jonathon Lunine DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707) DE: 3309 Climatology (1620) DE: 3319 General circulation DE: 3346 Planetary meteorology (5445, 5739) DE: 5409 Atmospheres--structure and dynamics SC: U MN: 2001 Spring Meeting