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Medientyp:
E-Artikel
Titel:
A novel method for objective identification of 3-D potential vorticity anomalies
Beteiligte:
Fischer, Christoph;
Fink, Andreas H.;
Schömer, Elmar;
van der Linden, Roderick;
Maier-Gerber, Michael;
Rautenhaus, Marc;
Riemer, Michael
Erschienen:
Copernicus GmbH, 2022
Erschienen in:
Geoscientific Model Development, 15 (2022) 11, Seite 4447-4468
Sprache:
Englisch
DOI:
10.5194/gmd-15-4447-2022
ISSN:
1991-9603
Entstehung:
Anmerkungen:
Beschreibung:
Abstract. Potential vorticity (PV) analysis plays a central role in studying atmospheric dynamics and in particular in studying the life cycle of weathersystems. The three-dimensional (3-D) structure and temporal evolution of the associated PV features, however, are not yet fully understood. Anautomated technique to objectively identify 3-D PV features can help to shed light on 3-D atmospheric dynamics in specific case studies as well asfacilitate statistical evaluations within climatological studies. Such a technique to identify PV features fully in 3-D, however, does not yetexist. This study presents a novel algorithm for the objective identification of PV anomalies along the dynamical tropopause in gridded data, ascommonly output by numerical simulation models. The algorithm is inspired by morphological image processing techniques and can be applied to bothtwo-dimensional (2-D) and 3-D fields on vertically isentropic levels. The method maps input data to a horizontally stereographic projection andrelies on an efficient computation of horizontal distances within the projected field. Candidates for PV anomaly features are filtered according toheuristic criteria, and feature description vectors are obtained for further analysis. The generated feature descriptions are well suited forsubsequent case studies of 3-D atmospheric dynamics as represented by the underlying numerical simulation. We evaluate our approach by comparisonwith an existing 2-D technique and demonstrate the full 3-D perspective by means of a case study of an extreme precipitation event that wasdynamically linked to a prominent subtropical PV anomaly. The case study demonstrates variations in the 3-D structure of the detected PV anomaliesthat would not have been captured by a 2-D method. We discuss further advantages of using a 3-D approach, including elimination of temporalinconsistencies in the detected features due to 3-D structural variation and elimination of the need to manually select a specific isentropic levelon which the anomalies are assumed to be best captured. These advantages, as well as the suitability of the implementation to process big data sets,also open applications for climatological analyses. The method is made available as open-source for straightforward use by the atmosphericcommunity.