Joint Seminar: Objects are closer than they appear: diurnal gravity waves as a probe of hurricanes’ internal structure

Satellite observations of cloudy hurricane canopies have shown a universal, daily, wave-like feature that propagates radially outward, as far as 600 km. Daytime solar heating of a hurricane’s upper eyewall is surely responsible, but the mechanism for the wave was previously unknown. I will discuss numerical experiments that suggest these waves are internal inertia-gravity waves, and in fact propagate through (almost!) the entire depth of the hurricane. Their structure is similar to the classical “St. Andrew’s cross” pattern response to a bobbing cylinder in a quiescent fluid. Due to the hurricane’s flow field, diurnal waves can only begin to propagate well beyond the storm core, though the anticyclonic outflow region is more receptive to near-core diurnal propagation. The prohibited region is highly sensitive to a disruptive process called an eyewall replacement cycle (ERC), in which the original eyewall breaks down and is replaced by a larger, contracting eyewall. Results suggest that a hurricane's size can reach at least 1000 km radially, even in the upper troposphere.




13:30 Uhr


Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg


Morgan O'Neill, Weizmann Institute of Science


Bjorn Stevens

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