Vortex Delight

September 1, 2010 · 0 comments

This Monday at the AMS Conference on Mountain Meteorology, Rieke Heinze of the Institut für Meteorologie und Klimatologie at the Leibniz Universität Hannover presented this very cool looking simulation of von Kármán vortex streets, which sometimes show up in satellite images of clouds in the lee of isolated mountain islands. The nifty thing about Heinze’s simulation project is that it shows the vortices retaining a warm core from bottom to top in the flow (cross section not shown here).

On her project web site (where you can download the video), Heinze writes:

Atmospheric vortex streets consist of two rows of counterrotating mesoscale eddies with vertical axis in the wake of large islands. They resemble classical Kármán vortex streets which occur in laboratory experiments behind a cylinder. Usually, atmospheric vortex streets can be found in the stratocumulus capped mixed layer over the ocean when there is a strong elevated inversion well below the island top.

In the animations the island consists of a single Gaussian shaped mountain with a height of about 1.3 km and a base diameter of about 12km. Particles are released in one layer and act as passive tracers. Their vertical motion is disabled. The colour of the particles reflects the difference between the temperature at the respective particle position and the mean temperature, horizontally averaged over the total domain. Blue/red colours represent a relatively low/high temperature. The animation shows that the cores of the eddies are warmer than the environment. The length of the animation corresponds to about 14h real time.