Evaluation of tropical cyclones over the South China Sea simulated by the 12 km MetUM regional climate model

Abstract

The ability of a newly developed non-hydrostatic regional climate model (RCM) based on the Unified Model of the UK Met Office (MetUM) at a resolution of 12 km is examined for the simulation of tropical cyclone (TC) activity affecting the South China Sea and is compared with the current version of the MetUM RCM at the resolution of 25 km. The results show that both the 25 and 12 km models can reasonably simulate the TC-associated large-scale environments, while the 12 km model has a better ability to simulate the South Asian monsoon. Compared with the 25 km model, the 12 km model generally improves the simulation of track density and the radial wind structure of TCs. However, the annual cycle of simulated TCs show that both models tend to overestimate the TC frequency in May and November–January while underestimating the frequency in June–September. Compared with the 25 km model, the 12 km model produces fewer intense TCs with 10 m maximum wind speeds >30 m s−1. It is also found that both the 12 and 25 km models reproduce the observed modulation of TC activity associated with different phases of the El Niño/Southern Oscillation (ENSO) such as the reduced track density and accumulated cyclonic energy during El Niño events, while the 12 km model better captures the TC–ENSO response including the track density and the large-scale environments than the 25 km model.