scholarly journals Nocturnal Elevated Convection Initiation of the PECAN 4 July Hailstorm

2018 ◽  
Vol 146 (1) ◽  
pp. 243-262 ◽  
Author(s):  
J. W. Wilson ◽  
S. B. Trier ◽  
D. W. Reif ◽  
R. D. Roberts ◽  
T. M. Weckwerth
Keyword(s):  
Gravity Waves ◽  
University Of Wyoming ◽  
Cloud Base ◽  
Doppler Lidar ◽  
Convective Storms ◽  
Multiple Observations ◽  
Western Side ◽  
Convection Initiation ◽  
The University ◽  
Advance Knowledge

AbstractDuring the Plains Elevated Convection at Night (PECAN) experiment, an isolated hailstorm developed on the western side of the PECAN study area on the night of 3–4 July 2015. One of the objectives of PECAN was to advance knowledge of the processes and conditions leading to pristine nocturnal convection initiation (CI). This nocturnal hailstorm developed more than 160 km from any other convective storms and in the absence of any surface fronts or bores. The storm initiated within 110 km of the S-Pol radar; directly over a vertically pointing Doppler lidar; within 25 km of the University of Wyoming King Air flight track; within a network of nine sounding sites taking 2-hourly soundings; and near a mobile mesonet track. Importantly, even beyond 100 km in range, S-Pol observed the preconvection initiation cloud that was collocated with the satellite infrared cloud image and provided information on the evolution of cloud growth. The multiple observations of cloud base, thermodynamic stability, and direct updraft observations were used to determine that the updraft roots were elevated. Diagnostic analysis presented in the paper suggests that CI was aided by lower-tropospheric gravity waves occurring in an environment of weak but persistent mesoscale lifting.

scholarly journals Evolution and Vertical Structure of an Undular Bore Observed on 20 June 2015 during PECAN

2017 ◽  
Vol 145 (9) ◽  
pp. 3775-3794 ◽  
Author(s):  
Dana Mueller ◽  
Bart Geerts ◽  
Zhien Wang ◽  
Min Deng ◽  
Coltin Grasmick
Keyword(s):  
Life Cycle ◽  
University Of Wyoming ◽  
Cold Pool ◽  
Undular Bore ◽  
Wave Trapping ◽  
Hydraulic Theory ◽  
The University ◽  
Second Wave ◽  
Scorer Parameter ◽  
Equal Amplitude

This study documents the evolution of an impressive, largely undular bore triggered by an MCS-generated density current on 20 June 2015, observed as part of the Plains Elevated Convection at Night (PECAN) experiment. The University of Wyoming King Air with profiling nadir- and zenith-viewing lidars sampled the south-bound bore from the time the first bore wave emerged from the nocturnal convective cold pool and where updrafts over 10 m s−1 and turbulence in the wave’s wake were encountered, through the early dissipative stage in which the leading wave began to lose amplitude and speed. Through most of the bore’s life cycle, its second wave had a higher or equal amplitude relative to the leading wave. Striking roll clouds formed in wave crests and wave energy was detected to about 5 km AGL. The upstream environment indicates a negative Scorer parameter region due to flow reversal at midlevels, providing a wave trapping mechanism. The observed bore strength of 2.4–2.9 and speed of 15–16 m s−1 agree well with values predicted from hydraulic theory. Surface and profiling measurements collected later in the bore’s life cycle, just after sunrise, indicate a transition to a soliton.

First Doppler lidar and cloud radar measurements of orographic convection initiation from a mountain observatory in the Al Hajar Mountains of the United Arab Emirates.

2021 ◽  
Author(s):  
Oliver Branch ◽  
Andreas Behrendt ◽  
Osama Alnayef ◽  
Florian Späth ◽  
Thomas Schwitalla ◽  
...  
Keyword(s):  
United Arab Emirates ◽  
Sea Breeze ◽  
Doppler Lidar ◽  
Cloud Seeding ◽  
Low Level ◽  
Cloud Radar ◽  
Orographic Convection ◽  
Radar Measurements ◽  
Convection Initiation ◽  
Convective Cells

<p>We present exciting Doppler lidar and cloud radar measurements from a high-vantage mountain observatory in the hyper-arid United Arab Emirates (UAE) - initiated as part of the UAE Research Program for Rain Enhancement Science (UAEREP). The observatory was designed to study the clear-air pre-convective environment and subsequent convective events in the arid Al Hajar Mountains, with the overarching goal of improving understanding and nowcasting of seedable orographic clouds. During summer in the Al Hajar Mountains (June to September), weather processes are often complex, with summer convection being initiated by several phenomena acting in concert, e.g., interaction between sea breeze and horizontal convective rolls. These interactions can combine to initiate sporadic convective storms and these can be intense enough to cause flash floods and erosion. Such events here are influenced by mesoscale phenomena like the low-level jet and local sea breeze, and are constrained by larger-scale synoptic conditions.</p><p>The Doppler lidar and cloud radar were employed for approximately two years at a high vantage-point to capture valley wind flows and observe convective cells. The instruments were configured to run synchronized polar (PPI) scans at 0°, 5°, and 45° elevation angles and vertical cross-section (RHI) scans at 0°, 30°, 60, 90°, 120°, and 150° azimuth angles. Using this imagery, along with local C-band radar and satellite data, we were able to identify and analyze several convective cases. To illustrate our results, we have selected two cases under unstable conditions - the 5 and 6 September 2018. In both cases, we observed areas of low-level convergence/divergence, particularly associated with wind flow around a peak 2 km to the south-west of the observatory. The extension of these deformations are visible in the atmosphere to a height of 3 km above sea level. Subsequently, we observed convective cells developing at those approximate locations – apparently initiated because of these phenomena. The cloud radar images provided detailed observations of cloud structure, evolution, and precipitation. In both convective cases, pre-convective signatures were apparent before CI, in the form of convergence, wind shear structures, and updrafts.</p><p>These results have demonstrated the value of synergetic observations for understanding orographic convection initiation, improvement of forecast models, and cloud seeding guidance. The manuscript based on these results is now the subject of a peer review (Branch et al., 2021).</p><p> </p><p>Branch, O., Behrendt, Andreas Alnayef, O., Späth, F., Schwitalla, Thomas, Temimi, M., Weston, M., Farrah, S., Al Yazeedi, O., Tampi, S., Waal, K. de and Wulfmeyer, V.: The new Mountain Observatory of the Project “Optimizing Cloud Seeding by Advanced Remote Sensing and Land Cover Modification (OCAL)” in the United Arab Emirates: First results on Convection Initiation, J. Geophys. Res.  Atmos., 2021. In review (submitted 23.11.2020).</p>

A Case Study of Gravity Waves–Convective Storms Interaction: 9 May 1979

1983 ◽  
Vol 40 (12) ◽  
pp. 2804-2830 ◽  
Author(s):  
James G. Stobie ◽  
Franco Einaudi ◽  
Louis W. Uccellini
Keyword(s):  
Gravity Waves ◽  
Convective Storms

scholarly journals Elk Ranch Determination of Eligibility for the National Register of Historic Places

2011 ◽  
Vol 33 ◽  
pp. 37-46
Author(s):  
Mary Humstone
Keyword(s):  
National Park ◽  
Cultural Landscape ◽  
Historical Analysis ◽  
University Of Wyoming ◽  
National Register ◽  
Grand Teton National Park ◽  
Jackson Hole ◽  
History Of ◽  
Landscape Survey ◽  
The University

During summer 2010, the University of Wyoming American Studies Program conducted an intensive cultural landscape survey and historical analysis of the Elk Ranch in Grand Teton National Park. Led by Research Scientist Mary Humstone, students documented the ranch landscape and remaining buildings. They conducted research in local archives to uncover the history of the ranch and determine its significance in the history of Jackson Hole and Grand Teton National Park. The team determined that the property is eligible for the National Register of Historic Places, with significance in agriculture and conservation.

HYDROPTILIDAE (TRICHOPTERA) FROM SOUTHERN UNITED STATES

1947 ◽  
Vol 79 (1) ◽  
pp. 12-20 ◽  
Author(s):  
Donald G. Denning
Keyword(s):  
United States ◽  
New Species ◽  
University Of Wyoming ◽  
Southern United States ◽  
Southern States ◽  
The Past ◽  
Caddis Flies ◽  
The University ◽  
Made In

During the past several years a number of interesting collections of Hydroptilidae were made in the southern states, particularly in Louisiana, Georgia and Florida. These collections have now been examined and found to contain several new species and new distributional records of this little known family of “micro” caddis flies.Unless designated otherwise types of new species described herein are in the author's collection at the University of Wyoming.

scholarly journals Environmental Analysis of GOES-R Proving Ground Convection-Initiation Forecasting Algorithms

2015 ◽  
Vol 54 (7) ◽  
pp. 1637-1662 ◽  
Author(s):  
Jason M. Apke ◽  
Daniel Nietfeld ◽  
Mark R. Anderson
Keyword(s):  
Environmental Variables ◽  
Environmental Influences ◽  
Principal Component ◽  
University Of Alabama ◽  
Algorithm Performance ◽  
University Of Wisconsin ◽  
Improve Algorithm ◽  
Convection Initiation ◽  
The University

AbstractEnhanced temporal and spatial resolution of the Geostationary Operational Environmental Satellite–R Series (GOES-R) will allow for the use of cloud-top-cooling-based convection-initiation (CI) forecasting algorithms. Two such algorithms have been created on the current generation of GOES: the University of Wisconsin cloud-top-cooling algorithm (UWCTC) and the University of Alabama in Huntsville’s satellite convection analysis and tracking algorithm (SATCAST). Preliminary analyses of algorithm products have led to speculation over preconvective environmental influences on algorithm performance. An objective validation approach is developed to separate algorithm products into positive and false indications. Seventeen preconvective environmental variables are examined for the positive and false indications to improve algorithm output. The total dataset consists of two time periods in the late convective season of 2012 and the early convective season of 2013. Data are examined for environmental relationships using principal component analysis (PCA) and quadratic discriminant analysis (QDA). Data fusion by QDA is tested for SATCAST and UWCTC on five separate case-study days to determine whether application of environmental variables improves satellite-based CI forecasting. PCA and significance testing revealed that positive indications favored environments with greater vertically integrated instability (CAPE), less stability (CIN), and more low-level convergence. QDA improved both algorithms on all five case studies using significantly different variables. This study provides an examination of environmental influences on the performance of GOES-R Proving Ground CI forecasting algorithms and shows that integration of QDA in the cloud-top-cooling-based algorithms using environmental variables will ultimately generate a more skillful product.

Impact of Convectively Generated Low-Frequency Gravity Waves on Evolution of Mesoscale Convective Systems

2020 ◽  
Vol 77 (10) ◽  
pp. 3441-3460
Author(s):  
Rebecca D. Adams-Selin
Keyword(s):  
Gravity Waves ◽  
Low Frequency ◽  
Mesoscale Convective Systems ◽  
Cloud Base ◽  
Mature Stage ◽  
First Order ◽  
Convective Systems ◽  
Stratiform Region ◽  
Mesoscale Convective ◽  
Wave Modes

AbstractIdealized numerical simulations of mesoscale convective systems (MCSs) over a range of instabilities and shears were conducted to examine low-frequency gravity waves generated during initial and mature stages of convection. In all simulations, at initial updraft development a first-order wave was generated by heating extending through the depth of the troposphere. Additional first-order wave modes were generated each time the convective updraft reintensified. Each of these waves stabilized the environment in advance of the system. As precipitation descended below cloud base, and as a stratiform precipitation region developed, second-order wave modes were generated by cooling extending from the midlevels to the surface. These waves destabilized the environment ahead of the system but weakened the 0–5 km shear. Third-order wave modes could be generated by midlevel cooling caused by rear inflow intensification; these wave modes cooled the midlevels destabilizing the environment. The developing stage of each MCS was characterized by a cyclical process: developing updraft, generation of n = 1 wave, increase in precipitation, generation of n = 2 wave, and subsequent environmental destabilization reinvigorating the updraft. After rearward expansion of the stratiform region, the MCSs entered their mature stage and the method of updraft reinvigoration shifted to absorbing discrete convective cells produced in advance of each system. Higher-order wave modes destabilized the environment, making it more favorable to development of these cells and maintenance of the MCS. As initial simulation shear or instability increased, the transition from cyclical wave/updraft development to discrete cell/updraft development occurred more quickly.

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