Stefan Liess Research Scientist Ph.D., 2002, University of Hamburg, Germany/Max-Planck Institute for Meteorology E-mail: liess@umn.edu Climate modeling, tropical climate dynamics.

Research Interests

My research interests focus on the simulation of atmospheric dynamics and climate change with general circulation models (GCM), especially the ECHAM GCM. This GCM is based on the European Center for Medium Weather Forecast model and modified at the Max-Planck Institute for Meteorology in order to adapt the model for climate simulations.

Currently, I am assessing the capabilities of the GCM to simulate and forecast tropical intraseasonal variability, especially the Madden-Julian Oscillation (MJO). I perform sensitivity studies to point out the mechanisms, that are important for the evolution of the MJO. The predictability study focuses on time scales of a few weeks, which is longer than numerical weather prediction. One goal is to predict the active and break phases of the Asian summer monsoon. I create ensemble forecast experiments with the ECHAM5 GCM and compare them to control simulations and satellite observations. In order to obtain useful initial conditions for the forecasts, I utilize the breeding method that allows large model uncertainties to grow and small uncertainties to be damped. I also carry out forecast skill experiments for observed events. For this the prognostic variables of the model are “nudged” toward the observations. The nudging mechanism is a powerful tool to direct the model close enough toward the observations but small enough to let the model develop its own physical mechanisms.

Additionally, I am interested in exploring the interactions of climate and vegetation, especially the impacts of deforestation and afforestation on the climate in different regions. In an earlier work I conducted GCM experiments, with predicted and observed vegetation changes. I found that the simulated local climate change due to deforestation in humid regions is dominated by changes in evaporation, whereas the change in arid regions is dominated by reflectivity.

I am maintaining the SPARC (Stratospheric Processes and Their Role in Climate) Data Center at http://www.sparc.sunysb.edu and use the available high-resolution data for studies of the impacts of tropopause characteristics on tropical convection.

Selected Publications

Liess, S., D. E. Waliser, S. D. Schubert and I. Kirchner, 2006: Forecasting observed boreal summer intraseasonal variability. J. Atmos. Sci., in preparation.

Liess, S., D. E. Waliser and S. D. Schubert, 2005: Predictability studies of the intraseasonal oscillation with the ECHAM5 GCM. J. Atm. Sci., 62, 3320-3336.

Liess, S. and L. Bengtsson, 2004: The intraseasonal oscillation in ECHAM4. Part II: sensitivity studies. Climate Dynamics, 22, 671-688.

Liess, S., L. Bengtsson and K. Arpe, 2004: The intraseasonal oscillation in ECHAM4. Part I: coupled to a comprehensive ocean model. Climate Dynamics, 22, 653-669.

Liess, S. and L. Gates, 2004: Impacts of land use changes (in German). Promet, 30, 134-140.

Dümenil Gates, L. and S. Liess, 2001: Impacts of deforestation and afforestation in the Mediterranean region as simulated by the MPI atmospheric GCM. Global and Planetary Change, 30, 305-324.