Simulated Impacts of Two Types of El Nino on the Tropical Cyclone Activity over Northwest Pacific

Recently the phenomenon about the existence of two different types of El Nino occurred in tropical Pacific have attracted many studies on the topics and intensive debates.  Following these works, whether there are also distinct impacts to global climate from the Eastern-Pacific (EP) and Central-Pacific (CP) El Nino had drawn  lots of studies to revisit the ENSO influences.  For example, it has been demonstrated that tropical cyclone (TC) frequency in the Northwest Pacific is correlated well with CP El Nino index during boreal summer despite the lack of correlation with EP El Nino index due to cancellation between enhanced and reduced TC activity in different domains.

Our study aims at not only the examination on the model capability in reproducing the findings from limited observed events in the past few decades, but also try to investigate the main physical processes that cause their different impacts on the seasonal TC activity over Northwest Pacific.  We use the composites of SST distribution and evolution under the typical EP and CP El Nino as well as the normal condition for the boundary conditions to drive the Max Plank Institute global climate model (ECHAM5) in this study.  To assess the uncertainty of model simulation, 10 ensemble members in each experiments are performed.  The result will also be compared with composite of EP and CP El Nino events sampled from the century long AMIP-type simulation from ECHAM5 to understand the possible interaction with decadal variability over the North Pacific.