Simulation of the Present and Future Projection of Seasonal Northwest Pacific Tropical Cyclone Activities with a Regional Climate Model

Simulation of the Present and Future Projection of Seasonal Northwest Pacific Tropical Cyclone Activities with a Regional Climate Model

Teng-Ping Tzeng¹, Chi-Chieh Lee¹, Hsin-Chien Liang², Cheng-Ta Chen¹, Yuqing Wang³

¹National Taiwan Normal University, Department of Earth Sciences

²Research Center for Environmental Change, Academia Sinica

³ International Pacific Research Center, University of Hawaii at Manoa

The majority of current approach for using dynamical model to project future seasonal tropical cyclone (TC) activity involves counting the number of TC-like vortices simulated in the model.  Nevertheless, such approach requires vigorous test on the reliability of model to capture the TC-Climate Interactions.  Recent studies on seasonal TC activity with dynamical forecast system over Atlantic basin show promising results. They are able to reproduce some aspects of the observed climatology, interannual variability, and the long-term trend of seasonal TC activity.  Our study aims on using regional climate model as a key component to explore the feasibility of dynamical downscaling of TC activities over Northwest Pacific.  In particular, we will examine how the model simulated TC activities in response to the large-scale climate forcing, such as seasonal cycle and ENSO variability before applying the anthropogenic climate change condition.

Using the ERA-interim reanalysis data and observed SSTs to forced our regional climate model over Northwest Pacific, we found that model can reasonably capture the main characteristics of seasonal evolution of TC activities and their interannual variability.  Interestingly, when we forced the regional model with NCAR CCSM4 historical simulation from CMIP5 data archive for the present-day condition, the simulated TC activities further improved from the run forced by reanalysis.  The detailed review on the large scale environmental conditions for TC genesis from the forcing data and simulation indicated that the more active convective activities and mid-tropospheric moisture are the main contributions to the improved simulation.   These TC genesis favorite conditions further prevail in the future climate projection run under RCP8.5 scenario and lead to significant increase of TC activities during the typhoon season despite the more stable atmospheric thermal structure in the future.