10B.1 A Systematic Methodology for Assessing the Ability of Atmospheric Bores and Solitons to Initiate Elevated Deep Convection

Wednesday, 25 January 2017: 1:30 PM
Conference Center: Tahoma 3 (Washington State Convention Center )
Steven E. Koch, NOAA/NSSL, Norman, OK

The ability of bores and solitons to raise conditionally unstable air parcels to their Level of Free Convection (LFC) is examined.  Numerous lidar and radar profiling systems are used, in conjunction with ultra-high resolution numerical models, to examine this question.  Profiling instrumentation used includes thermodynamic measurements from ground-based AERI and microwave radiometer systems; wind measurements from Doppler wind lidar, Doppler weather radars, FM-CW radar, and boundary layer wind profilers; aerosol measurements from backscatter lidar; and moisture measurements from airborne Differential Absorption Lidar.

It will be demonstrated that these observing systems can readily detect the presence of bores and their attendant vertical circulations.  Furthermore, these data can be quite useful in diagnosing the necessary and sufficient conditions for: bore generation, maintenance, strengthening and type (including undular vs. turbulent bores, and their evolution into solitons).  Thus, quantities such as the Froude Number, the Scorer parameter profile, the “mu” factor, and other theoretical parameters governing bore dynamics from hydraulic theory can be computed with high precision.  Results repeatedly show that bores waft moist air up to the middle troposphere and weaken any capping inversion, thus reducing inhibition to deep convection development.  Application of parcel displacement profiles derived from the Doppler lidar and wind profiler analyses and the predictive models to representative pre-bore soundings obtained from the other thermodynamic profiling systems permit assessments to be made of the direct effects of the bore on a given atmosphere.   It is found that in some cases, this lifting is sufficient to raise parcels to their LFC and generate deep convection, but in other cases, even strong lifting may not be sufficient to trigger deep convection if the lifting is confined to too shallow a layer, is of insufficient duration, and/or the pre-bore environment contains a very strong capping inversion with limited moisture.

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