IMPACT OF PARAMETERIZATIONS ON SIMULATED WINTER MIDHOLOCENE AND LAST GLACIAL MAXIMUM CLIMATIC CHANGES IN THE NORTHERN-HEMISPHERE

Within the Paleoclimate Modeling Intercomparison Project, we have perf ormed simulations of the present-day, mid-Holocene (MH), and Last Glac ial Maximum (LGM) climates with two versions of the LMD (Laboratoire d e Meterologie Dynamique, CNRS, Paris) atmospheric general circulation model which differ in their horizontal resolution and some parameteriz ations of the surface processes. This work focuses on the winter simul ated climatic changes in northern midlatitudes, and we use energy budg et analyses to diagnose the impact of the parameterizations on the cli matic sensitivity. The dependency of the surface transfer coefficients on the air stability is shown to play a key role for the climatic sen sitivity over regions of stable conditions: the northern Atlantic whic h is sea-ice covered at LGM, and the midlatitude continents during MH. For the MH we use a simple mathematical projection method to extract the climatic change signal from its interannual variability.