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Title

Observations of the 9 June 2002 dryline during IHOP 2002 -- A null case for convection initiation

Abstract

The detailed analysis of the three-dimensional structure of a dryline observed over the Oklahoma panhandle during the International H2O Project (IHOP_2002) on 11 June 2002 is presented. High-resolution observations obtained from the National Center for Atmospheric Research Electra Doppler Radar (ELDORA), S-band dual-polarization Doppler radar (S-Pol), water vapor differential absorption lidar (DIAL) Lidar pour l'Etude des Interactions Aérosols Nuages Dynamique Rayonnement et du Cycle de l'Eau (LEANDRE II; translated as Lidar for the Study of Aerosol–Cloud–Dynamics–Radiation Interactions and of the Water Cycle) as well as Learjet dropsondes are used to reveal the evolution of the dryline structure during late afternoon hours when the dryline was retreating to the northwest. The dryline reflectivity shows significant variability in the along-line direction. Dry air was observed to overrun the moist air in vertical cross sections similar to a density current. The updrafts associated with the dryline were 2–3 m s−1 and were able to initiate boundary-layer-based clouds along the dryline. The formation of this dryline was caused by high equivalent potential temperature air pushing northwestward toward a stationary front in the warm sector. Middle-level clouds with radar reflectivity greater than 18 dBZe near the dryline were detected by ELDORA. A roll boundary, which was associated with larger convergence and moisture content, was evident in the S-Pol data. It is found that the instability parameters most favorable for convection initiation were actually associated with the roll boundary, not the dryline. A storm was initiated near the roll boundary probably as a result of the combination of the favorable instability parameters and stronger upward forcing. It is noted that both the 11 June 2002 dryline and the roll boundary presented in this paper would not be identified if the special datasets from IHOP_2002 were not available. Although all model runs [fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5), Meso Eta, and Rapid Update Cycle (RUC)] suggested deep convection over the Oklahoma panhandle and several cloud lines were observed near the dryline, the dryline itself did not initiate any storms. The reasons why the dryline failed to produce any storm inside the IHOP_2002 intensive observation region are discussed. Both synoptic-scale and mesoscale conditions that were detrimental to convection initiation in this case are investigated in great detail.

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http://n2t.net/ark:/85065/d7pr7xjx

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eng

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publication

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2016-01-01T00:00:00Z

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2006-01-01T00:00:00Z

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Copyright 2006 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

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UCAR/NCAR - Library

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