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ROLLS, STREETS, WAVES, AND MORE

A Review of Quasi-Two-Dimensional Structures in the Atmospheric Boundary Layer

George S. Young
,
David A. R. Kristovich
,
Mark R. Hjelmfelt
, and
Ralph C. Foster

The atmospheric boundary layer is home to a number of horizontally elongated quasi-two-dimensional phenomena including cloud streets, roll vortices, thermal waves, and surface layer streaks. These phenomena, their dynamics, and their interactions are explored via a review of the literature. Making a clear distinction between the various quasi-two-dimensional phenomena allows improved synthesis of previous results and a better understanding of the interrelationships between phenomena.

Full access
April Hiscox
,
Sudheer Bhimireddy
,
Junming Wang
,
David A. R. Kristovich
,
Jielun Sun
,
Edward G. Patton
,
Steve P. Oncley
, and
William O. J. Brown

Abstract

Stable boundary layers are still a relatively problematic component of atmospheric modeling, despite their frequent occurrence. While general agreement exists that Monin–Obukhov similarity is not applicable in the stable boundary layer (SBL) due to the nonhomogeneous, nonstationary flow, no universal organizing theory for the surface SBL has been presented. The Stable Atmospheric Variability and Transport (SAVANT) field campaign took place in the fall of 2018 to explore under what conditions shallow drainage flow is generated. The campaign took place in an agricultural setting and covered the period of both pre- and postharvest, allowing for not only a basic exploration of the boundary layer but also a robust dataset for applied agricultural understanding of aerosol dispersion and impacts of changes in surface cover on drainage flows. This article provides a description of the field campaign. Examples of publicly available data products are presented, as well as examples of shallow drainage flow and corresponding lidar measurements of dispersion. Additionally, the field campaign was used to provide educational opportunities for students from several disciplines, and the outcomes of these joint educational ventures are discussed as models for future collaborations.

Open access
David A. R. Kristovich
,
Richard D. Clark
,
Jeffrey Frame
,
Bart Geerts
,
Kevin R. Knupp
,
Karen A. Kosiba
,
Neil F. Laird
,
Nicholas D. Metz
,
Justin R. Minder
,
Todd D. Sikora
,
W. James Steenburgh
,
Scott M. Steiger
,
Joshua Wurman
, and
George S. Young

Abstract

Intense lake-effect snowstorms regularly develop over the eastern Great Lakes, resulting in extreme winter weather conditions with snowfalls sometimes exceeding 1 m. The Ontario Winter Lake-effect Systems (OWLeS) field campaign sought to obtain unprecedented observations of these highly complex winter storms.

OWLeS employed an extensive and diverse array of instrumentation, including the University of Wyoming King Air research aircraft, five university-owned upper-air sounding systems, three Center for Severe Weather Research Doppler on Wheels radars, a wind profiler, profiling cloud and precipitation radars, an airborne lidar, mobile mesonets, deployable weather Pods, and snowfall and particle measuring systems. Close collaborations with National Weather Service Forecast Offices during and following OWLeS have provided a direct pathway for results of observational and numerical modeling analyses to improve the prediction of severe lake-effect snowstorm evolution. The roles of atmospheric boundary layer processes over heterogeneous surfaces (water, ice, and land), mixed-phase microphysics within shallow convection, topography, and mesoscale convective structures are being explored.

More than 75 students representing nine institutions participated in a wide variety of data collection efforts, including the operation of radars, radiosonde systems, mobile mesonets, and snow observation equipment in challenging and severe winter weather environments.

Full access
David A. R. Kristovich
,
George S. Young
,
Johannes Verlinde
,
Peter J. Sousounis
,
Pierre Mourad
,
Donald Lenschow
,
Robert M. Rauber
,
Mohan K. Ramamurthy
,
Brian F. Jewett
,
Kenneth Beard
,
Elen Cutrim
,
Paul J. DeMott
,
Edwin W. Eloranta
,
Mark R. Hjelmfelt
,
Sonia M. Kreidenweis
,
Jon Martin
,
James Moore
,
Harry T. Ochs III
,
David C Rogers
,
John Scala
,
Gregory Tripoli
, and
John Young

A severe 5-day lake-effect storm resulted in eight deaths, hundreds of injuries, and over $3 million in damage to a small area of northeastern Ohio and northwestern Pennsylvania in November 1996. In 1999, a blizzard associated with an intense cyclone disabled Chicago and much of the U.S. Midwest with 30–90 cm of snow. Such winter weather conditions have many impacts on the lives and property of people throughout much of North America. Each of these events is the culmination of a complex interaction between synoptic-scale, mesoscale, and microscale processes.

An understanding of how the multiple size scales and timescales interact is critical to improving forecasting of these severe winter weather events. The Lake-Induced Convection Experiment (Lake-ICE) and the Snowband Dynamics Project (SNOWBAND) collected comprehensive datasets on processes involved in lake-effect snowstorms and snowbands associated with cyclones during the winter of 1997/98. This paper outlines the goals and operations of these collaborative projects. Preliminary findings are given with illustrative examples of new state-of-the-art research observations collected. Analyses associated with Lake-ICE and SNOWBAND hold the promise of greatly improving our scientific understanding of processes involved in these important wintertime phenomena.

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