Identification

Title

Development and forcing of the rear inflow jet in a rapidly developing and decaying squall line during BAMEX

Abstract

This study examines the development, structure, and forcing of the rear inflow jet (RIJ) through the life cycle of a small, short-lived squall line over north-central Kansas on 29 June 2003. The analyses were developed from airborne quad-Doppler tail radar data from the NOAA and NRL P-3 aircraft, obtained over a 2-h period encompassing the formation, development, and decay of the squall line during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The strengthening of the system-relative rear inflow to 17 m s(-1) was concurrent with the formation of a bow echo, an increased dynamic pressure gradient beneath the rearward-tilted updraft, and two counterrotating vortices at either end of the bow. The later weakening of the RIJ to 8 m s(-1) was concurrent with the weakening of the bow, a decreased dynamic pressure gradient at midlevels behind the bow, and the weakening and spreading of the vortices. In a modeling study, Weisman quantified the forcing mechanisms responsible for the development of an RIJ. This present study is the first to quantitatively analyze these mechanisms using observational data. The forcing for the horizontal rear inflow was analyzed at different stages of system evolution by evaluating the contributions of four forcing mechanisms: 1) the horizontal pressure gradient resulting from the vertical buoyancy distribution (delta P-B), 2) the dynamic pressure gradient induced by the circulation between the vortices (delta P-V), 3) the dynamic irrotational pressure gradient (delta P-I), and 4) the background synoptic-scale dynamic pressure gradient (delta P-S). During the formative stage of the bow, delta P-I was the strongest forcing mechanism, contributing 50% to the rear inflow. However, during the mature and weakening stages, delta P-I switched signs and opposed the rear inflow while the combination of delta P-B and delta P-V accounted for at least 70% of the rear inflow. The delta P-S forced 4%-25% of the rear inflow throughout the system evolution.

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document

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http://n2t.net/ark:/85065/d7kp837q

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eng

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geoscientificInformation

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title

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publication

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2016-01-01T00:00:00Z

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publication

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2009-04-01T00:00:00Z

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Copyright 2009 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

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opensky@ucar.edu

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http://opensky.ucar.edu/

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