15 Jul 2022
15 Jul 2022
Status: this preprint is currently under review for the journal WCD.

The three-dimensional structure of fronts in mid-latitude weather systems as represented by numerical weather prediction models

Andreas Alexander Beckert1, Lea Eisenstein2, Annika Oertel2, Timothy Hewson3, George C. Craig4, and Marc Rautenhaus1 Andreas Alexander Beckert et al.
  • 1Visual Data Analysis Group, Regional Computing Centre, Universität Hamburg, Hamburg, 20146, Germany
  • 2Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany
  • 3European Centre for Medium-Range Weather Forecasts, Reading, RG2 9AX, United Kingdom
  • 4Meteorological Institute, Ludwig-Maximilians-University Munich, Munich, 80333, Germany

Abstract. Atmospheric fronts are a widely used conceptual model in meteorology, most encountered as two-dimensional (2-D) front lines on surface analysis charts. The three-dimensional (3-D) dynamical structure of fronts has been studied in the literature by means of “standard” 2-D maps and cross-sections and is commonly sketched in 3-D illustrations of idealized weather systems in atmospheric science textbooks. However, only recently the feasibility of objective detection and visual analysis of 3-D frontal structures and their dynamics within numerical weather prediction (NWP) data has been proposed, and such approaches are not yet widely known in the atmospheric science community. In this article, we investigate the benefit of objective 3-D front detection for case studies of extratropical cyclones and for comparison of frontal structures between different NWP models. We build on a recent gradient-based detection approach, combined with modern 3-D interactive visual analysis techniques, and adapt it to handle data from state-of-the-art NWP models including those run at convection-permitting kilometer-scale resolution. The parameters of the detection method (including data smoothing and threshold parameters) are evaluated to yield physically meaningful structures. We illustrate the benefit of the method by presenting two case studies of frontal dynamics within mid-latitude cyclones. Examples include joint interactive visual analysis of 3-D fronts and warm conveyor belt (WCB) trajectories, and identification of the 3-D frontal structures characterising the different stages of a Shapiro-Keyser cyclogenesis event. The 3-D frontal structures show agreement with 2-D fronts from surface analysis charts and augment the surface charts by providing additional pertinent information in the vertical dimension. A second application illustrates the effect of convection on 3-D cold front structure by comparing data from simulations with parameterised and explicit convection and shows that convection could strengthen the cold front. Finally, we consider “secondary fronts” that commonly appear in UK Met Office surface analysis charts. Examination of a case study shows that for this event the secondary front is not a temperature-based but purely a humidity-based feature. We argue that the presented approach has great potential to be beneficial for more complex studies of atmospheric dynamics and for operational weather forecasting.

Andreas Alexander Beckert et al.

Status: open (until 28 Aug 2022)

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Andreas Alexander Beckert et al.

Video supplement

Development of 3-D frontal structures, jet stream and WCB trajectories of Vladiana Andreas A. Beckert, Lea Eisenstein, Annika Oertel, Tim Hewson, George C. Craig, Marc Rautenhaus

Comparison of objectively 725 detected 3-D fronts in wet-bulb potential temperature and potential temperature Andreas A. Beckert, Lea Eisenstein, Annika Oertel, Tim Hewson, George C. Craig, Marc Rautenhaus

Interactive front analysis of storm Friederike using the open-source meteorological 3-D visualization framework "Met. 3D" Andreas A. Beckert, Lea Eisenstein, Annika Oertel, Tim Hewson, George C. Craig, Marc Rautenhaus

Andreas Alexander Beckert et al.


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Short summary
This study revises and extends a previously presented 3-D objective front detection method and demonstrates its benefits to analyse weather dynamics in numerical simulation data. Based on two case studies of extratropical cyclones, we demonstrate the evaluation of conceptual models from dynamic meteorology, illustrate the benefits of our interactive analysis approach by comparing fronts in data with different model resolutions, and study the impact of convection on fronts.