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Project Progress

We have updated Kasting’s radiative-convective climate model by including a new routine for calculating infrared fluxes from Mlawer et al., J. Geophys. Res. 102, 16663-16682, 1997. This routine uses 16-term correlated-k coefficient sums to parameterize absorption by CO₂ and H₂O. The k’s are spaced so that they give good resolution of the Doppler cores of absorption lines. This allows us to calculate improved temperature profiles in the stratosphere. This climate code grew out of work carried out last year for the NASA Ames NAI group.

As input to this new modeling effort, Martin Cohen (U.C. Berkeley) has provided realistic spectra for an F2V and K2V star using International Ultraviolet Explorer (IUE) spectra (short- and long-wavelength ultraviolet (UV)) and Kurucz model spectra (photospheric spectra for the visible through far infrared wavelength range). Kasting and his undergraduate research aide, Kara Krelove (Penn.State), have used this input to their new coupled chemical-climate model to calculate the evolution of atmospheric ozone as a function of O₂ for a range of Earth-like planets around stars of different spectral type. Using the calculated equilibrium atmospheres from the coupled chemical-climate model, Dave Crisp and Vikki Meadows at the Jet Propulsion Laboratory (JPL) are using radiative transfer tools currently under development for the Virtual Planetary Laboratory to generate high-resolution synthetic spectra. These spectra were generated for realistic, balanced clear and cloudy radiative/chemical equilibrium model atmospheres. These simulations have provided significant insight into the combined effects of temperature and trace gas distributions on the detectability of biosignatures, and have potential future uses for the interpretation of data from the planned Terrestrial Planet Finder (TPF) mission. A paper should be submitted by the end of this summer ('02).