Studying regional climate change based on uncertainty in climate parameters using CAM3
In order to investigate future regional climate impacts, the MIT IGSM2.3 is coupled to the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 3 (CAM3). For linkages between the IGSM2.3 and CAM3, the 3-D atmospheric model is driven by the IGSM2.3 SST anomalies with a climatological annual cycle taken from an observed dataset, instead of the full IGSM2.3 SSTs, to provide a better SST annual cycle and more realistic features between the ocean and atmospheric components. This approach yields a consistent regional distribution and climate change over the 20th century as compared to observational datasets. For each emissions scenario, an ensemble member of the IGSM2.3 SST/SIC probabilistic distribution drives CAM3 to span the multi-dimensional space of uncertainty in climate parameters. For consistency, for each set of IGSM2.3/CAM3 runs, the trace gas concentrations calculated by the atmospheric chemistry component of the IGSM2.3 is used to force CAM3. The cloud adjustment scheme used in the IGSM2.3 was implemented in CAM3, which allows modifying its climate sensitivity to match that of the IGSM2.3 setup that generates the SST field used to drive CAM3.
With this approach, regional climate impacts can be assessed under various emissions scenarios based on probability distributions of climate parameters. In this paper, preliminary results from these ensemble simulations are presented. A particular focus is placed on the distribution of extreme events. For example, the frequency, duration and intensity of extreme events such as heat waves, floods and droughts, precipitation and storm activities can be investigated, as well as other dynamical features such as jet stream modulation.