NOAA/National Severe Storms Laboratory


Hypothesis (Rasmussen-1) concerning morphology/role of mesoscale vortices for convective initiation

Erik Rasmussen on May 1, 2000 at 14:40:00:

Background: Several researchers have noted the existence of coherent km-scale kinematic structures along boundaries. We recently have obtained high-resolution surface data from a mobile mesonet that shows that vortices exist in the DCVZ and some drylines with scales of 100-1000 m. Our observations show that these vortices redistribute near-ground water vapor, and visual observations show there may be an association between cumulus growth and the existence of a vortex.

Hypothesis: Vortices (~vertical) in boundaries have similar structure aloft as at the ground, extend through the same depth as the boundary itself, and are associated with local horizontal maxima in virtual temperature.

NOTE: This is a "first-step" hypothesis. Note that we are not attempting to explain the forcing of the vortices, nor their role in convection initiation. Instead, we seek only to document their existence and the fact that they are playing a role in vertical transport of heat and moisture. Note also that the sampling strategy should provide enough data to do preliminary investigation, and hypothesis-generation, concerning the forcing of the vortices and role in convection initiation.

Locate vortices with mobile dual-Doppler and airborn pseudo-dual-Doppler radar. Sample them with mobile dual-Doppler, mobile and airborne mesonets, and mobile soundings, and compare these samplings with thermodynamic fields retrieved from dual-Doppler wind syntheses.
Ground-detected vortices weaken/disappear with height below the boundary top/inversion. Virtual temperature perturbations aloft are not correlated with the existence of ground-detected vortices.

The following appear in order; discussion points may directly refer to one or more comments preceeding it.


Click here to comment on this hypothesis. Please reference: RASMUSSEN-1.