Abstract
Jet streams are fast three-dimensional coherent air flows that interact with other atmospheric structures such as warm conveyor belts (WCBs) and the tropopause. Individually, these structures have a significant impact on the mid-latitude weather evolution, and the impact of their interaction is still subject of research in the atmospheric sciences. A first step towards a deeper understanding of the meteorological processes is to extract the geometry of jet streams, for which we develop an integration-based feature extraction algorithm. Thus, rather than characterizing jet coreline purely as extremal line structure of wind magnitude, our coreline definition includes a regularization to favor jet corelines that align with the wind vector field. Based on the line geometry, proximity-based filtering can automatically detect potential interactions between WCBs and jets, and results of an automatic detection of split and merge events of jets can be visualized in relation to the tropopause. Taking ERA5 reanalysis data as input, we first extract jet stream corelines using an integration-based predictor-corrector approach that admits momentarily weak air streams. Using WCB trajectories and the tropopause geometry as context, we visualize individual cases, showing how WCBs influence the acceleration and displacement of jet streams, and how the tropopause behaves near split and merge locations of jets. Multiple geographical projections, slicing, as well as direct and indirect volume rendering further support the interactive analysis. Using our tool, we obtained a new perspective onto the three-dimensional jet movement, which can stimulate follow-up research.
Highlights
Jet streams are fast three-dimensional coherent air flows that interact with other atmospheric structures such as warm conveyor belts (WCBs) and the tropopause
Jet streams can interact with the tropopause as well as with outflows of warm conveyor belts (WCBs), which are strongly slantwise and coherently ascending air streams within extratropical cyclones that diverge at the tropopause (Madonna et al, 2014)
Jet streams are three-dimensional meteorological flow features that can interact with other atmospheric structures such as warm conveyor belts and the tropopause
Summary
Meteorologists face the challenge of making sense out of highly complex atmospheric data, which is large, three-dimensional, time-dependent and contains multiple fields. We aim for an explicit extraction of jet stream coreline geometry, which enables automatic detection of proximity to WCBs and allows for the automatic extraction of split and merge events, around which the tropopause is expected to show highly three-dimensional structures. Instead, we extract the jet stream as an instantaneous flow feature from the atmospheric data using a predictor-corrector approach (Banks and Singer, 1994) that follows the flow and corrects the trajectories towards the ridge lines of the wind magnitude field. This way, we can balance between two.
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