Response of Southwest Pacific storminess to changing climate

Abstract

Mid-latitude island nations of the Southwest Pacific (SWP) region like New Zealand not only host winter mid-latitude storms but also tropical storms that develop during summer and autumn. In recent decades, perhaps under the influence of a changing global climate, such tropical storms are observed to travel longer distances towards the southern mid latitudes. The aim of the current study is to estimate likely changes in future storminess in the SWP region during summer and autumn. It uses a new set up of a regional coupled atmosphere-ocean model (integrated over five years each under historical, 1960-1964, and projected future, 2095-2099, boundary conditions) as a tool that allows for frequent air-sea interaction at a mean horizontal resolution of about 25 km. The role of observed changes in large-scale environmental variables in causing recent changes in storminess is illustrated, and a relationship between the two is established by multiple linear regression. This relationship is used to construct scenarios of likely changes in future storminess using the simulated (projected future minus historical) differences in large-scale environmental conditions.