Tropical Cyclone Activity in Regional and Grid-Refined Global Simulations

Abstract:

Most electric power and transmission facilities in Japan operate for half a century or more, so it is important to ensure against general fatigue and damage from extreme weather and climate events. There is therefore a critical demand for useful assessments of the present weather and accurate predictions of future weather and climate.

Tropical Cyclones (TCs) are among the most destructive weather phenomenon to the industry. This study compares simulated TC activity in regional climate simulations using the Weather Research and Forecasting (WRF) model and global climate simulations using the Model for Prediction Across Scales (MPAS) specifically to identify the benefits of global variable resolution simulation. Horizontal refinement to approximately 20km grid spacing over the Northwest Pacific is achieved through nesting for WRF and MPAS uses a variable resolution mesh. The ability of these two simulation approaches to capture TC activity is examined in single-year continuous simulations from May 2005 to April 2006.

Compared to surface station and satellite derived rainfall datasets, tropical precipitation patterns are reproduced reasonably well by both models, but the annual precipitation totals are overestimated. Similarly, using an automated TC identification and tracking algorithm, results show that both models reproduce well TC genesis regions, tracks, wind-pressure relationships, and intensification rate, but TC frequencies are overestimated by both models. These results indicate that global variable resolution simulation is a suitable tool to study regional climate and TC activity. Future work will use MPAS to simulate longer periods of current and future climate to provide a unique view of the future change TC activity over Japan, tailored to the needs of the electric power industry.