Investigating the Ability of Global Climate Models to Simulate MJO Modulation of Tropical Cyclone Activity in the Pacific Basin

Globally, the impact of climate change on tropical cyclones (TCs) is relatively well understood – overall frequency is expected to decrease while average intensity increases. This consensus on the average response, however, masks significant uncertainty at the basin scale, much of which can be linked to deficiencies in global climate models (GCMs). The cost of climatological simulations with high enough resolution to explicitly resolve TCs has been limiting, as has the inability of models to simulate modes of tropical variability such as the Madden-Julian Oscillation (MJO), which is important for cyclogenesis. In addition, climate change simulations have suggested a strengthened MJO in the future, but the impact of this amplification on TCs has not yet been explored. Here, we present the first steps towards filling this gap. We investigate the potential of a dynamical downscaling approach developed by Kerry Emanuel to capture the MJO’s observed modulation of cyclogenesis in the Northwest and Northeast Pacific Oceans when driven by reanalysis input. The method allows for a robust sample of MJO- and seasonally-dependent TC statistics without incurring excessive computational cost. We will then select a subset of CMIP5 models that are best able to resolve the MJO to determine if a similar relationship is present in modern GCMs. If so, it paves the way for examining the role of MJO amplification on future TC genesis modulation and associated human impacts.