A circulation model for paleoclimate studies: Model description and first applications Gerrit Lohmann (MPI) , Frank Lunkeit (University of Hamburg), K. Fraedrich, Mojib Latif     Apart from the red spectrum of climate variability there is enhanced variability due to glacial-interglacial cycles during the Quaternary. In order to simulate the last glacial cycle, an atmospheric general circulation model has been constructed to be applied for paleoclimate studies. The dynamical part of the model is based on the primitive equations model PUMA in T21L5 resolution, which has been extended by relatively simple radiation and precipitation schemes. The model contains representations of subgrid scale fluxes, snow, and vegetation. The required CPU time for the atmospheric model is less than 6 min per year on the present Cray C90 in Hamburg. Because of the low computational costs, the model can be also used for sensitivity studies and ensemble integrations. The atmospheric model is able to reproduce the present day's climate reasonably well. Sensitivity experiments are performed in order to evaluate the model's response to SST anomalies and variations in external forcing. An experiment with the solar insolation 115,000 years before present shows an increase in the number of snow days on the Northern Hemisphere (NH), and a weakened Indian summer monsoon compared with present day's climate. This is consistent with reduced NH summer insolation enabling snow accumulation. Snow accumulation could therefore initiate a glacial climate. The atmospheric model has been coupled to the ocean model LSG. Besides the exchange of mass, heat, and momentum, the coupled system has a variable orography and land-sea distribution. This makes the model applicable for climate variations on the very long geological timescale, when other than today's land-sea distribution were present.     Fraedrich, K., E. Kirk, F. Lunkeit, 1998: PUMA (DKRZ Report 16) plain PostScript file Lohmann, G., 1998: The influence of a near-bottom transport on the sensitivity of the thermohaline circulation. J. Phys. Oceanogr. 28, 2095-2103. Maier-Reimer, E., U. Mikolajewicz, and K. Hasselmann, 1993: Mean circulation of the Hamburg LSG OGCM and its sensitivity to the thermohaline surface forcing. J. Phys. Oceanogr., 23, 731-757.     go to Paleoclimate variability go to Gerrit Lohmann's home page Author:Gerrit Lohmann Webmaster:Dietmar Dommenget (Last update: July 2000)