Projections of tropical cyclones affecting Vietnam under climate change: downscaled HadGEM2‐ES using PRECIS 2.1

Abstract

The potential changes in tropical cyclone (TC) activity, and the associated large‐scale environmental conditions, for Vietnam and the South China Sea, posed by climate change, are examined using a high‐resolution regional climate model system, PRECIS 2.1, to downscale the Met Office Hadley Centre CMIP5 model, HadGEM2‐ES, to a resolution of 25 km (PRECIS_Had2). The ERA‐Interim reanalysis is also downscaled to the same resolution (PRECIS_ERAI) for comparison. An objective algorithm is used to identify and track the TCs. The PRECIS_Had2 is evaluated for the period of 1990–2005 by comparing with the PRECIS_ERAI and the observed best‐track data of TCs. Compared to PRECIS_ERAI, PRECIS_Had2 represents the TC‐associated large‐scale environments reasonably well but shows stronger vertical wind shear over the South China Sea and during the summer southwesterly monsoon. For TCs, PRECIS_Had2 is capable of capturing the TC distribution but shows a notable underestimation of very intense TCs. The analysis of the influence of global warming on the TC activity reveals that PRECIS_Had2 simulates a pronounced seasonal shift of TC activity in a warmer climate for both the RCP4.5 and RCP8.5 scenarios, with an increase in TC activity during winter related to the more favourable large‐scale conditions, while a decrease in TCs associated with less favourable large‐scale conditions is projected in summer.