The three-dimensional structure of fronts in mid-latitude weather systems in numerical weather prediction models
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...
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Veröffentlicht in: | Geoscientific Model Development 2023-08, Vol.16 (15), p.4427-4450 |
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Zusammenfassung: | 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 has the feasibility of the objective detection and visual analysis of 3-D
frontal structures and their dynamics within numerical weather prediction
(NWP) data 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 extra-tropical
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 kilometre-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, as well as
identification of the 3-D frontal structures characterizing 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 relation between convection
and 3-D cold-front structure by comparing data from simulations with
parameterized and explicit convection. 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-dominated but a humidity-dominated 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. |
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ISSN: | 1991-9603 1991-959X 1991-962X 1991-9603 1991-962X |
DOI: | 10.5194/gmd-16-4427-2023 |