Climate Model Code Final Report


The following represents the final written report for the climate model module of the Team 3 Term Project. Here we address the climate model code results, the parameters used in the simulation and conclusions drawn from this climate model portion of our project.
As noted in a previous report related to the execution and validation of the climate model code, this code ran successfully on the CSI SGI under the FORTRAN'77 compiler. Also noted in yet another previous report was the underlying paradigms used in implementing the code. Since not all of the paradigms noted were actually implemented, we will review here the implemented code and the results, also comparing our results with known measurements from the Viking Landers.

The physical characteristics of Mars as used by our climate code can be displayed by executing the code itself, yielding the diameter of Mars in kilometers, its radius, its mass, its density, the length of a Martian day in seconds, the obliquity of Mars in degrees, the Martian orbital eccentricity, the solar orbital period in Earth days, the Martian albedo and the semi-major axis of Mars in kilometers.

The Viking Landers provide a modicum of comparison for our results from this code. The Viking Lander 1 was close to the equator and its measured temperatures during a 24 hour period approximately ranged from -93 to -3 degrees Celsius. Execution of our code produces temperatures at the equator for the current epoch to be on the order of -37 degree Celsius.

The Viking Lander 2 was closer to the polar region and its measurements during a 24 hour period approximately ranged from -123 to -8 degrees Celsius. Execution of our code produces temperatures at the polar region for the current epoch to be on the order of -112 degrees Celsius.

We have discovered that the orbital eccentricity of Mars itself is a mojor factor in the changing Martian surface temperature. Variability of the temperature on the surface of Mars is also influenced by the obliquity of the Martian axis.

Published reports (Ward, 1973) confirm the variability of the Martian obliquity and established two periodicities in the obliquity that would contribute to the variability of the Martian surface temperature. One of these periodicities occurs over a time of about 120,000 Earth years and the other occurs at a period of about 1.2 million Earth years.

Our final computer climate model as implemented does not take into account the transmission coefficient of the Martian atmosphere. Others (de Vaucouleurs, 1954) have investigated the theoretical surface temperature of Mars using similar approaches and we have plots of these results. These atmospheric results from the model can be compared to the Viking Lander measurements. It should be noted that if one wishes to extrapolate to the time of the origin of the planet's surface itself (about 4.5 billion years ago) then a thicker atmosphere must be considered.

Another factor that must be considered in the examination of the surface temperature is the relationship between the temperature and pressure of carbon dioxide, the major constituent of the atmosphere. Thus reports (Leighton and Murray, 1966) have been able to link the vapor pressure over the polar regions to the temperature. Basically, if the temperature at the poles would increase, the atmospheric pressure globally would increase.

One might also be tempted to link the greenhouse effect of ozone to the temperature at the Martian surface. In two reports (Lindner, 1991 and Espenak et al., 1991) it was demonstrated that ozone is of minor consequence on Mars.

We believe that the major contributor to the surface temperature of Mars is the solar radiation, and thus while we failed to implement all paradigms that we had originally hoped to implement, we believe that our temperature model of the surface is a reasonable first approximation.

Some of our preliminary results are depicted in the following graphics. The first graphic here depicts the color legend for the images.

The following images depict the surface temperature over a five billion year span beginning at the current epoch and proceeding back 1 billion years for each image (i.e. 0, 1, 2, 3, 4, and 5 billion years ago).

Our "projections" of the surface temperature of Mars back to the formation of the planet, are based on the published assumptions that there was a significant increased source of energy, perhaps from the planet itself, collisions from other bodies or some other mechanism. Unfortunately, the increase in the Martian temperature back in time does not take into account the stellar astrophysics evolution.

The sun is a star and as such goes through an evolutionary process itself. If our current theories about stellar evolution are correct, then our own sun should have been significantly cooler (on the order of about 30%) some 5 billion years ago. This creates a dilemma, often called the hot sun dilemma, in which case would lead to a simulation with a change in the solar constant, leaving the surface temperature of Mars, still averaging below the freezing point of water. This has consequences for the feasibility of any life on the surface of the planet.