Speaker
Benjamin Pohl
Institute
Time & Place
Thu, 29 Jun 2023 16:00:00 NZST in BT 236
Abstract
Weather types and weather regimes are commonly used to analyze climate variability at multiple timescales, and their local impacts at regional and fine spatial scales. One of their main limitations, due to their discretization of continuous variability patterns, is that they only explain a moderate proportion of the total variability, especially for low-frequency timescales. Part of interannual, decadal and long-term changes occurs within the types, thereby modifying their intrinsic properties, rather than between the types, modifying their occurrence. Here, we develop a series of continuous descriptors that monitor the location and intensities of the atmospheric centers of action (ACAs: atmospheric highs and lows) associated with the weather types, in order to further explore and explain the part of climate variability that was neglected in previous studies, that is, the diversity among the days ascribed to a given weather type. Our methodology is tested and applied to the 12 types identified by Kidson (2000) over Aotearoa New Zealand (ANZ).
We first show that large-scale modes of climate variability like ENSO and the SAM significantly modulate the ACAs within the types, and these relationships are even stronger than those previously identified with type occurrence. Next, we also show that a given weather type is likely to produce temperature or precipitation anomalies over ANZ that can be of opposite sign, and this is mostly driven by the location and strength of the corresponding ACAs. Finally, we analyze co-occurrences between these types and atmospheric rivers (AR) making landfall over ANZ, in order to assess the synoptic configurations leading to AR development and/or daily precipitation extremes.
Biography
Presenter: Benjamin Pohl (Centre de Recherches de Climatologie, Biogéosciences, Dijon, France).
People involved: Benjamin Pohl (CNRS, France), Andrew Sturman (UC); Hervé Quénol (CNRS); Andrew Lorrey (NIWA); James Renwick (VUW); Nicolas Fauchereau (NIWA); Julien Pergaud (CNRS); Hamish Prince, Daniel Kingston, Nicolas Cullen (U Otago).
