A Systems Approach to Venus Climate Modeling

We propose to develop a unique approach to an understanding of the various factors that have shaped Venus’ climate. We plan to numerically simulate the planetary climate system by developing a set of interconnected modules, each representing one component of Venus’ climate. The first modules that we will develop are numerical models for atmospheric radiative transfer, surface/atmosphere interactions, surface volatile sources, and tropospheric chemistry. These will be followed by parameterized models for exospheric escape processes, atmospheric chemistry and cloud physics, photochemistry, and global circulation. Climate feedback loops result from interconnections between modules, in the form of the parameters pressure, temperature, and atmospheric mixing ratios. The model will utilize a wide range of existing data on Venus, from laboratory and ground and spacecraft based measurements, to define the current state of the Venus climate system. A pilot model has been completed in order to illustrate the feasibility and usefulness of such an approach. A simple atmospheric radiative transfer numerical model was developed and coupled to a number of plausible surface mineral buffering reactions. Using this approach, equilibrium climate regimes were sought. The results of the pilot model showed that under current conditions, the climate of Venus is at or near an unstable equilibrium point. Without sources, the system spontaneously evolved to a cooler, lower pressure state. The construction of a set of interconnected computer programs to model the climate of Venus will enable us to explore several important issues regarding the evolution and stability of the Venus climate system. In particular, we will be able to calculate the possible feedback effects of surface mineral buffering of volatiles on the stability of the greenhouse effect. The climatic implications of volcanic sources of key radiatively active species such as CO2, H2O, and SO2 will also be explored using the model. We will seek equilibrium climate states predicted by the model, possible steady state climates, and characteristic mechanisms and time scales for climate evolution.