Photochemical and Climate Models

Developed by Dr. James Kasting, colleagues and students

There are three models available:

- 1D Radiative/Convective Climate Model

- 1D Photochemical Model for High O₂ Atmospheres

- 1D Photochemical Model High CO₂/High CH₄ Atmospheres

RADIATIVE/CONVECTIVE CLIMATE MODEL

General characteristics of this model:

This model uses the RRTM (www.rtweb.aer.com) code for the infrared. It can give accurate solutions only for low CO₂ atmospheres (up to 100 the present level of CO₂ that is a mixing ratio of 3.55x10^-2)

HIGH O₂ PHOTOCHEMICAL MODEL
General characteristics of this model:

This model works coupled with the climate model or stand alone. It has been adapted from the original version that ran in a Cray system to run in the Sun system.

STELLAR FLUXES

The Sun and three other stars can be used as an input for the high O2 photochemical model and the climate model. The spectra of these stars were gathered and coadded by Martin Cohen (U. California at Berkeley) for the Virtual Planetary Laboratory (VPL), a project of the NASA Astrobiology Institute.

The stars are:

Sun
HD128167: F2V star, sigma Bootis
HD22049: K2V star, epsilon Eridani
GJ 388: M4.5V star, AD Leo

The codes have already been set up to read the spectra of these stars. The spectra read by the models are binned to match the format required by the codes. The high resolution spectra of these stars can be found on the VPL Stellar Spectra Pages

HIGH CO₂/HIGH CH₄ PHOTOCHEMICAL MODEL

General characteristics of this model:

For high CO₂-high CH₄/low O₂ atmospheres: It does not work in couple mode. The version provided runs in the Sun system. The code is on the file HighCO2.tar (This version was developed by Pushker Kharecha and James Kasting)

TO GET THE MODELS

IMPORTANT INSTRUCTIONS, PLEASE DOWNLOAD AND READ BEFORE USING THE CODES

The codes are in fortran 77 with some fortran 90 features.

Presently, this version runs in unix, but we hope to have a version for linux soon.

Radiative/Convective Climate and High O2 Photochemical models files:

The climate and the high O₂ version of the photochemical models are in the file CHEMCLIM_O2.tar, save the file CHEMCLIM_O2.tar and write:

tar xvf CHEMCLIM_O2.tar
The directory CHEMCLIM_O2 will be created. It will contain a subdirectory named CLIMA where the climate model resides and another called ATMCHEM with the photochemical model. The main program to run both models (coupled or stand alone) is couple.f.

There is a readme file in every subdirectory with a short description of what is in that specific subdirectory.

The readme file that is VERY important to read BEFORE compiling the codes is README.first under the directory CHEMCLIM_O2, also, it is recommended to read the headers of the climate (CHEMCLIM_O2/CLIMA/clima.f) and the photochemical code (CHEMCLIM_O2/ATMCHEM/atm_chem.f).

CHEMCLIM_O2.tar

High CO2 photochemical model files:

To extract the files for the high CO₂ photochemical model, save the file HighCO2.tar and write:

tar xvf HighCO2.tar
The directory HighCO2 will be created. Read the file README.Archean_photocode for instructions of how to compile, run the code and set up boundary conditions for it. Questions about this code may be addressed to Dr. James Kasting (kasting@essc.psu.edu)

HighCO2.tar

ACKNOWLEDGEMENTS

The models were originally developed by Dr. James Kasting. The present models are the result of the work of several students and colleagues: Michael Mischna, Alex Pavlov, Kara Krelove, Hilary Justh, Pushker Kharecha, Irene Schneider, Patrick Kasting, Jacob Haqq-Misra, and Antigona Segura (I am sure I am forgetting somebody, please let me know).

Special thanks to Philip von Paris and Lee Grenfell who invested a lot of time improving these codes.

REFERENCES

(papers available here)

** Kasting, J.F. and Ackerman, T.P. (1986) Climatic consequences of very high CO₂ levels in the earth s early atmosphere. Science 234, 1383-1385.
** Mlawer, E.J., Taubman, S.J., Brown, P.D., Iacono, M.J., and Clough, S.A. (1997) Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model of the longwave. J. Geophys. Res. 102, 16663 -16682.
** Pavlov, A.A. and Kasting, F. (2002) Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere. Astrobiology 2, 27-41.
** Pavlov, A.A., Kasting, J.F., Brown, L.L., Rages, K.A., and Freedman, R. (2000) Greenhouse warming by CH4 in the atmosphere of early Earth. J. Geophys. Res. 105, 11981-11990.
** Segura, A.; K. Krelove, J. F. Kasting, D. Sommerlatt V. Meadows, D. Crisp, M. Cohen and E. Mlawer (2003) Ozone Concentrations and Ultraviolet Fluxes on Earth-like Planets Around Other Stars. Astrobiology, 3(4), 689-708.

** Antigona Segura, James F. Kasting, Victoria Meadows, Martin Cohen, John Scalo, David Crisp, Rebecca A.H. Butler and Giovanna Tinetti . Biosignatures from Earth-Like Planets Around M Dwarfs. Astrobiology, 5(6), 706-725. 2005.

** Kharecha, P., Kasting, J.F., and Siefert, J.L (2005) A coupled atmosphere-ecosystem model of the early archean Earth. Geobiology 3, 53-76.

Have fun!!

Edited by Antigona Segura. August, 2006
Please send feedback, corrections, requests, etc. to naivpl@uw.edu