Synoptic weather regimes over Aoteaora New Zealand

Williams, J. ORCID: https://orcid.org/0000-0002-0680-0098 and Renwick, J. (2021) Synoptic weather regimes over Aoteaora New Zealand. Weather & Climate, 41. pp. 2-17.

Abstract/Summary

This work provides an updated set of 12 dominant geopotential height fields over Aotearoa New Zealand defined using NCEP/NCAR reanalyses and provides an initial analysis of the same using a state of the art dataset with increased temporal and spatial resolution; ERA5. 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 strong relationships between circulation patterns and surface climate in New Zealand. The results presented here using the NCEP/NCAR reanalysis are broadly in agreement with previous work but with some important differences. The most notable of these differences is the need to average two regimes together to provide good agreement between this work and Kidson (2000). These differences are attributed to differences in software used, improvements to the underlying dataset itself and to the ‘mixing’ of statistically indistinguishable empirical orthogonal functions in different linear combinations. Using ERA5 data results in sets of weather types which are analogous in some ways to previous work but with some important differences, especially over mountainous regions. Use of ERA5 noticeably improves the ratio of intra- to inter-regime variance; a measure of the ‘quality’ of the cluster analyses. 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. The mathematical methods used in this study are widely used in the New Zealand weather and climate community and it is hoped that this work will prove useful as a resource for future studies.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/124980
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Meteorological Society of New Zealand
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