Inconsistencies in future changes in tropical cyclone statistics between CMIP5-class models and state of the art high resolution atmospheric models

Abstract:

High resolution simulations of the Community Atmospheric Model, CAM5.1 under idealized experimental protocols of future climate change respond entirely differently than do simulations of the same model at resolutions comparable to the CMIP5 models. At 25km, the model produces fewer total tropical cyclones but more of the most intense storms in the warmer configurations. Direct tracking of tropical storms in the 100km version of the model produces an increase in the total number of tropical storms in the warmer configurations. This inconsistency cannot be rectified by relaxing the tracking criteria to follow more storms. Furthermore, the standard forms of tropical storm Genesis Potential Indices, based on monthly averages of large scale climatological fields fail to describe the change in the actual cyclogenesis of tracked storms in the high resolution model. Hence, we conclude that conclusions about future changes in tropical cyclone statistics drawn from the CMIP5 database of climate model simulations must be interpreted with extreme caution.