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Synoptic weather regimes over Aoteaora New Zealand
  • Jonny Williams,
  • James Renwick
Jonny Williams
NIWA

Corresponding Author:[email protected]

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James Renwick
Victoria University of Wellington
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Abstract

This work provides an updated set of 12 dominant geopotential height fields - or ‘regimes’ - over Aotearoa New Zealand. These regimes were initially produced by Kidson (2000) and have provided the basis for many other subsequent studies. These maps provide a guide to the prevailing weather due to the broad equivalence of 1000hPa geopotential height and mean-sea-level pressure. The results presented here are broadly in agreement with previous work but with some important differences. The most notable of these being the need to average two blocking regimes together to provide good agreement between this work and Kidson (2000). These differences are attributed to the software used, improvements to the underlying dataset itself and to the ‘mixing’ of statistically indistinguishable empirical orthogonal functions - EOFs - in different linear combinations. All data and code used in this work is publicly accessible and it is hoped that this will provide a catalyst for open discussions on this topic, particularly with relation to future perturbations to these regimes under climate change.