Lagrangian Coherent Structures and Vortex Formation in High
Spatiotemporal-Resolution Satellite Winds of an Atmospheric Kármán
Vortex Street
Abstract
Recent advances in geostationary imaging have enabled the derivation of
high spatiotemporal-resolution cloud-motion winds for the study of
mesoscale unsteady flows. Due to the general absence of ground truth,
the quality assessment of satellite winds is challenging. In the current
limited practice, straightforward plausibility checks on the smoothness
of the retrieved wind field or tests on aggregated trends such as the
mean velocity components are applied for quality control. In this paper,
we demonstrate additional diagnostic tools based on feature extraction
from the retrieved velocity field. Lagrangian Coherent Structures (LCS),
such as vortices and transport barriers, guide and constrain the
emergence of cloud patterns. Evaluating the alignment of the extracted
LCS with the observed cloud patterns can potentially serve as a test of
the retrieved wind field to adequately explain the time-dependent
dynamics. We discuss the suitability and expressiveness of direct,
geometry-based, texture-based, and feature-based flow visualization
methods for the quality assessment of high spatiotemporal-resolution
winds through the real-world example of an atmospheric Kármán vortex
street and its laboratory archetype, the 2D cylinder flow.