David Murakis interests include numerical methods for atmospheric research and fluid dynamics. He is a faculty member at the Department of Mathematics at Simon Fraser University, Canada.

This talk is in Collaboration with the WPI.

When: Monday May 7th, 3pm

Where: Room 8.135, Faculty of Mathematics, Oskar-Morgenstern-Platz 1

Abstract:

A holepunch cloud is a curious and rare atmospheric feature where an aircraft, descending or ascending through a thin cloud layer, leaves behind a growing circular hole of clear air. Observed since the early days of aviation, only in 2011 was this holepunch phenomenon simulated in a full-physics numerical weather model. Although the initiation process has long been explained by ice crystal formation, the continued growth of the hole, even up to an hour after its birth, remained a bit of a fluid dynamical mystery.

We begin by excluding some of the "obvious" reasons by tweaking the physics in the numerical simulations (fake weather!). We then attribute the expansion of the hole to the presence of an expanding wavefront. The leading edge of this wave is a front of phase change, where cloudy air is continually evaporated and so expands the hole. Our explanation has led us towards the development of a more general theory for an understanding of how atmospheric waves can evolve the shape of clouds.

This work is in collaboration with R. Rotunno (NCAR), H. Morrison (NCAR), R. Walsh (SFU) and H. Lynn (SFU).