Evaluating the Inverse Relationship Between Aggregate Tropical Cyclone Activity and Subsequent Winter Climate within Uncoupled ECHAM Simulations

A recent observational/reanalysis- based-study by Hart [2011] examined a striking statistical relationship between the northern hemisphere tropical cyclone (TC) activity (evaluated using both TC count and power dissipation [Emanuel, 2007]) and the subsequent winter climate. Those results show that there exists a moderately strong inverse relationship between the amount of poleward TC power-dissipation (e.g., recurving TCs) and the 500-hPa stationary eddy-temperature flux within the extra-tropics. This relationship was found to be optimized for western Pacific recurving typhoons and extended across several reanalysis datasets for winter climate. Further this predictor of aggregate TC activity was the variable that explained the most variance of the aforementioned winter climate.

We will present results from a non-coupled modeling study that examines the robustness of this relationship when extended to simulations. A 30-year 20-member ensemble of simulations has been performed using a T159 horizontal resolution of the Max-Planck-Institut für Meteorologie ECHAM5 atmosphere model. The ECHAM5 ensemble is defined by perturbations to the respective atmospheric states and each member of the ensemble has an identical temporally evolving sea-surface temperature (SST). Model generated storms, with TC characteristics, have been identified and tracked in these simulations. The modeled relationship between TC activity and the subsequent winter's circulation will be presented, with potential physical bases for this relationship explored.