No abstract

No abstract

In this article, the ability of the Met Office Unified Model to simulate the severe weather over the South Island of New Zealand, on 8 January 2004 is investigated. Simulations were run at horizontal resolutions of between 60 and 1 km. The modelled broad-scale rainfall and wind features, most notably the area-averaged accumulated rainfall, were found to converge with resolution. At the highest resolutions, all the observed rainfall and wind features of this event were captured well by the model. Even the 12-km-resolution model is able to resolve the broad elongated ridge-like structure of the Southern Alps and qualitatively capture the main features of the rainfall and wind fields.

Abstract:A regional climate model (RCM) for New Zealand has been developed. The RCM is embedded within a GCM and both models are run under pre-industrial conditions. Seasonal mean output of the RCM is compared against NCEP data and the New Zealand national climate database. Regional and seasonal aspects of modelled surface temperature and precipitation are to a large extent simulated correctly. The main anomalies are related to the difficulty of incorporating New Zealand's orography appropriately and to the initial and lateral boundary conditions, which were supplied by the GCM. The largest anomalies occur over the Southern Alps, where the modelled temperatures are too low and where the amount of precipitation is too high. Many parts of the east coasts in both the North and South Island are too warm and too dry. Correlation patterns of temperature and precipitation with mean sea-level pressure differ considerably from the equivalent patterns constructed from NCEP data, but do show in general the dominant relationships between wind direction and temperature and precipitation.