Free and forced atmospheric responses to sea surface temperatures using a GCM with idealized topography
This study reports results from an investigation of the individual and modified responses of the atmospheric circulation to SST anomalies in the North Atlantic in a series of experiments using the CESM 1.0.5 suite of models. In these experiments, three different configurations are used. The first is an all ocean (i.e., the “aquaplanet”) and is used to determine the free response of the atmosphere to the SST anomaly. The second configuration includes simple land and is used to determine how land-ocean configuration impacts the original response of the atmospheric circulation to the SST anomaly. The third configuration includes idealized Rocky Mountains, Alps and the Tibetan Plateau. This configuration allows for determining modulation on the atmospheric response by additional influence from the major orography of the continents. In all the three configurations, three SST experiments are done; a control (i.e., zonally symmetric) and cold and warm zonally asymmetric experiments. The zonally asymmetric experiments use a monopole anomaly of 4°C centered in the latitude and longitude of the realistic North Atlantic Ocean. These experiments allow for breakdown of the free and modulated atmospheric responses to the SST anomaly and land as well as orography configurations. In addition, these results can aid our understanding of why the atmosphere responds stronger in certain regions than others.