Surface In Situ Observations within the Outflow of Forward-Flank Downdrafts of Supercell Thunderstorms

2006 ◽  
Vol 134 (5) ◽  
pp. 1422-1441 ◽  
Author(s):  
Christopher J. Shabbott ◽  
Paul M. Markowski
Keyword(s):  
Three Dimensional ◽  
Thermodynamic Characteristics ◽  
Streamwise Vorticity ◽  
Low Level ◽  
Thermodynamic Conditions ◽  
Supercell Thunderstorm ◽  
In Situ Observations ◽  
Supercell Thunderstorms ◽  
Negative Buoyancy

Abstract In the long-standing conceptual model of a supercell thunderstorm, the forward-flank downdraft (FFD) and its associated negative buoyancy originate from precipitation loading and the latent chilling of air due to the melting and evaporation of precipitation. The horizontal buoyancy gradient within the outflow of the FFD has been identified as an important source of low-level, streamwise vorticity in three-dimensional numerical simulations of supercells. These simulations have demonstrated that the formation of low-level mesocyclones is critically dependent on the baroclinic generation of horizontal vorticity within the FFD outflow. Despite the implied dynamical importance of the FFD outflow in the evolution of supercell thunderstorms, only a very limited number of thermodynamic observations have been obtained within FFD outflow. The range of thermodynamic conditions within FFD outflow is not well known, nor is it known whether any systematic relationship exists between the thermodynamic characteristics of FFD outflow and the intensity of low-level mesocyclones and/or tornadogenesis. In this paper, in situ observations obtained at the ground by a mobile mesonet within FFD outflow are used to investigate whether any relationship exists between the thermodynamic characteristics of the outflow and low-level mesocyclogenesis and/or tornadogenesis. The data were obtained within both tornadic and nontornadic supercells (12 cases total) during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) from 1994 to 1995, and in smaller field campaigns during the 1997–99 period.

scholarly journals Development of a three-dimensional growth prediction model for the Japanese scallop in Funka Bay, Japan, using OGCM and MODIS

2015 ◽  
Vol 72 (9) ◽  
pp. 2684-2699 ◽  
Author(s):  
Yang Liu ◽  
Sei-Ichi Saitoh ◽  
Yu Ihara ◽  
Satoshi Nakada ◽  
Makoto Kanamori ◽  
...  
Keyword(s):  
Prediction Model ◽  
Three Dimensional ◽  
Temperature Data ◽  
Japanese Scallop ◽  
Growth Prediction ◽  
Chl A ◽  
Funka Bay ◽  
Dimensional Growth ◽  
In Situ Observations

Abstract The Japanese scallop (Patinopecten (Mizuhopecten) yessoensis) is an important commercial species in Funka Bay, Japan, where it is farmed using the hanging culture method. Our study was based on 6 years (from 2006 to 2011) of monthly in situ observations of scallop growth at Yakumo station. To produce a basic spatial distribution dataset, we developed an interpolation solution for the shortage of Chl-a concentration data available from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Additionally, we integrated four-dimensional variational (4D-VAR) assimilation water temperature data from ocean general circulation models (OGCMs), with four vertical levels (6, 10, 14, and 18 m) from the sea surface. Statistical models, including generalized additive models (GAMs) and generalized linear models, were applied to in situ observation data, satellite data, and 4D-VAR data to identify the influence of environment factors (interpolated Chl-a, temperature, and depth) on the growth of scallops, and to develop a three-dimensional growth prediction model for the Japanese scallops in Funka Bay. We considered three methods to simulate the growth process of scallops (accumulation, summation, and product), and used them to select the most suitable model. All the interpolated Chl-a concentrations and 4D-VAR temperature data were verified by shipboard data. The results revealed that GAM, using an accumulation method that was based on a combination of integrated temperature, integrated log Chl-a, depth, and number of days, was best able to predict the vertical and spatial growth of the Japanese scallop. The predictions were verified by in situ observations from different depths (R2 = 0.83–0.94). From the distribution of three-dimensional predicted scallop growth maps at each depth, it was suggested that the growth of the Japanese scallop was most favourable at 6 m and least favourable at 18 m, although variations occurred in each aquaculture region in different years. These variations were probably due to the ocean environment and climate variation.

scholarly journals Three-dimensional in situ observations of short fatigue crack growth in magnesium

2011 ◽  
Vol 59 (17) ◽  
pp. 6761-6771 ◽  
Author(s):  
A. King ◽  
W. Ludwig ◽  
M. Herbig ◽  
J.-Y. Buffière ◽  
A.A. Khan ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Three Dimensional ◽  
Short Fatigue Crack ◽  
In Situ Observations

scholarly journals Terrain Trapped Airflows and Precipitation Variability during an Atmospheric River Event

2020 ◽  
Vol 21 (2) ◽  
pp. 355-375 ◽  
Author(s):  
Ju-Mee Ryoo ◽  
Sen Chiao ◽  
J. Ryan Spackman ◽  
Laura T. Iraci ◽  
F. Martin Ralph ◽  
...  
Keyword(s):  
Wrf Model ◽  
Wind Fields ◽  
Low Level ◽  
Atmospheric River ◽  
Gap Flow ◽  
Period 2 ◽  
Modeling Systems ◽  
In Situ Observations ◽  
Aircraft Data

AbstractWe examine thermodynamic and kinematic structures of terrain trapped airflows (TTAs) during an atmospheric river (AR) event impacting Northern California 10–11 March 2016 using Alpha Jet Atmospheric eXperiment (AJAX) aircraft data, in situ observations, and Weather and Research Forecasting (WRF) Model simulations. TTAs are identified by locally intensified low-level winds flowing parallel to the coastal ranges and having maxima over the near-coastal waters. Multiple mechanisms can produce TTAs, including terrain blocking and gap flows. The changes in winds can significantly alter the distribution, timing, and intensity of precipitation. We show here how different mechanisms producing TTAs evolve during this event and influence local precipitation variations. Three different periods are identified from the time-varying wind fields. During period 1 (P1), a TTA develops during synoptic-scale onshore flow that backs to southerly flow near the coast. This TTA occurs when the Froude number (Fr) is less than 1, suggesting low-level terrain blocking is the primary mechanism. During period 2 (P2), a Petaluma offshore gap flow develops, with flows turning parallel to the coast offshore and with Fr > 1. Periods P1 and P2 are associated with slightly more coastal than mountain precipitation. In period 3 (P3), the gap flow initiated during P2 merges with a pre-cold-frontal low-level jet (LLJ) and enhanced precipitation shifts to higher mountain regions. Dynamical mixing also becomes more important as the TTA becomes confluent with the approaching LLJ. The different mechanisms producing TTAs and their effects on precipitation pose challenges to observational and modeling systems needed to improve forecasts and early warnings of AR events.

Processes Preventing the Development of a Significant Tornado in a Colorado Supercell on 26 May 2010

2020 ◽  
Vol 148 (5) ◽  
pp. 1753-1778
Author(s):  
Shawn S. Murdzek ◽  
Paul M. Markowski ◽  
Yvette P. Richardson ◽  
Robin L. Tanamachi
Keyword(s):  
Small Radius ◽  
Future Research ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Far Field ◽  
Streamwise Vorticity ◽  
Low Level ◽  
Precipitation Region ◽  
Negative Buoyancy

Abstract A supercell produced a nearly tornadic vortex during an intercept by the Second Verification of the Origins of Rotation in Tornadoes Experiment on 26 May 2010. Using observations from two mobile radars performing dual-Doppler scans, a five-probe mobile mesonet, and a proximity sounding, factors that prevented this vortex from strengthening into a significant tornado are examined. Mobile mesonet observations indicate that portions of the supercell outflow possessed excessive negative buoyancy, likely owing in part to low boundary layer relative humidity, as indicated by a high environmental lifted condensation level. Comparisons to a tornadic supercell suggest that the Prospect Valley storm had enough far-field circulation to produce a significant tornado, but was unable to converge this circulation to a sufficiently small radius. Trajectories suggest that the weak convergence might be due to the low-level mesocyclone ingesting parcels with considerable crosswise vorticity from the near-storm environment, which has been found to contribute to less steady and weaker low-level updrafts in supercell simulations. Yet another factor that likely contributed to the weak low-level circulation was the inability of parcels rich in streamwise vorticity from the forward-flank precipitation region to reach the low-level mesocyclone, likely owing to an unfavorable pressure gradient force field. In light of these results, we suggest that future research should continue focusing on the role of internal, storm-scale processes in tornadogenesis, especially in marginal environments.

scholarly journals Three-dimensional in situ observations of compressive damage mechanisms in syntactic foam using X-ray microcomputed tomography

2017 ◽  
Vol 52 (17) ◽  
pp. 10186-10197 ◽  
Author(s):  
M. E. Kartal ◽  
L. H. Dugdale ◽  
J. J. Harrigan ◽  
M. A. Siddiq ◽  
D. Pokrajac ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Syntactic Foam ◽  
Microcomputed Tomography ◽  
Damage Mechanisms ◽  
X Ray ◽  
In Situ Observations ◽  
Compressive Damage

The Influence of Environmental Low-Level Shear and Cold Pools on Tornadogenesis: Insights from Idealized Simulations

2013 ◽  
Vol 71 (1) ◽  
pp. 243-275 ◽  
Author(s):  
Paul M. Markowski ◽  
Yvette P. Richardson
Keyword(s):  
Heat Sink ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Heat Sinks ◽  
Streamwise Vorticity ◽  
Near Surface ◽  
Low Level ◽  
Cold Pools ◽  
Cyclonic Vortex ◽  
Negative Buoyancy

Abstract Idealized, dry simulations are used to investigate the roles of environmental vertical wind shear and baroclinic vorticity generation in the development of near-surface vortices in supercell-like “pseudostorms.” A cyclonically rotating updraft is produced by a stationary, cylindrical heat source imposed within a horizontally homogeneous environment containing streamwise vorticity. Once a nearly steady state is achieved, a heat sink, which emulates the effects of latent cooling associated with precipitation, is activated on the northeastern flank of the updraft at low levels. Cool outflow emanating from the heat sink spreads beneath the updraft and leads to the development of near-surface vertical vorticity via the “baroclinic mechanism,” as has been diagnosed or inferred in actual supercells that have been simulated and observed. An intense cyclonic vortex forms in the simulations in which the environmental low-level wind shear is strong and the heat sink is of intermediate strength relative to the other heat sinks tested. Intermediate heat sinks result in the development (baroclinically) of substantial near-surface circulation, yet the cold pools are not excessively strong. Moreover, the strong environmental low-level shear lowers the base of the midlevel mesocyclone, which promotes strong dynamic lifting of near-surface air that previously resided in the heat sink. The superpositioning of the dynamic lifting and circulation-rich, near-surface air having only weak negative buoyancy facilitates near-surface vorticity stretching and vortex genesis. An intense cyclonic vortex fails to form in simulations in which the heat sink is excessively strong or weak or if the low-level environmental shear is weak.

scholarly journals Understanding the Impact of Radar and In Situ Observations on the Prediction of a Nocturnal Convection Initiation Event on 25 June 2013 Using an Ensemble-Based Multiscale Data Assimilation System

2018 ◽  
Vol 146 (6) ◽  
pp. 1837-1859 ◽  
Author(s):  
Samuel K. Degelia ◽  
Xuguang Wang ◽  
David J. Stensrud ◽  
Aaron Johnson
Keyword(s):  
Data Assimilation ◽  
Great Plains ◽  
Cold Pool ◽  
Radar Observations ◽  
Low Level ◽  
In Situ Observations ◽  
Outflow Boundary ◽  
Convection Initiation ◽  
The Impact

The initiation of new convection at night in the Great Plains contributes to a nocturnal maximum in precipitation and produces localized heavy rainfall and severe weather hazards in the region. Although previous work has evaluated numerical model forecasts and data assimilation (DA) impacts for convection initiation (CI), most previous studies focused only on convection that initiates during the afternoon and not explicitly on nocturnal thunderstorms. In this study, we investigate the impact of assimilating in situ and radar observations for a nocturnal CI event on 25 June 2013 using an ensemble-based DA and forecast system. Results in this study show that a successful CI forecast resulted only when assimilating conventional in situ observations on the inner, convection-allowing domain. Assimilating in situ observations strengthened preexisting convection in southwestern Kansas by enhancing buoyancy and locally strengthening low-level convergence. The enhanced convection produced a cold pool that, together with increased convergence along the northwestern low-level jet (LLJ) terminus near the region of CI, was an important mechanism for lifting parcels to their level of free convection. Gravity waves were also produced atop the cold pool that provided further elevated ascent. Assimilating radar observations further improved the forecast by suppressing spurious convection and reducing the number of ensemble members that produced CI along a spurious outflow boundary. The fact that the successful CI forecasts resulted only when the in situ observations were assimilated suggests that accurately capturing the preconvective environment and specific mesoscale features is especially important for nocturnal CI forecasts.

scholarly journals An Investigation of the Goshen County, Wyoming, Tornadic Supercell of 5 June 2009 Using EnKF Assimilation of Mobile Mesonet and Radar Observations Collected during VORTEX2. Part II: Mesocyclone-Scale Processes Affecting Tornado Formation, Maintenance, and Decay

2016 ◽  
Vol 144 (9) ◽  
pp. 3441-3463 ◽  
Author(s):  
James Marquis ◽  
Yvette Richardson ◽  
Paul Markowski ◽  
Joshua Wurman ◽  
Karen Kosiba ◽  
...  
Keyword(s):  
Life Cycle ◽  
Ensemble Kalman Filter ◽  
Vertical Structure ◽  
Spatial Scales ◽  
Near Surface ◽  
Low Level ◽  
Structure Changes ◽  
In Situ Observations ◽  
Negatively Buoyant

Storm-scale and mesocyclone-scale processes occurring contemporaneously with a tornado in the Goshen County, Wyoming, supercell observed on 5 June 2009 during the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) are examined using ensemble analyses produced by assimilating mobile radar and in situ observations into a high-resolution convection-resolving model. This paper focuses on understanding the evolution of the vertical structure of the storm, the outflow buoyancy, and processes affecting the vertical vorticity and circulation within the mesocyclone that correspond to changes in observed tornado intensity. Tornadogenesis occurs when the low-level mesocyclone is least negatively buoyant relative to the environment, possesses its largest circulation, and is collocated with the largest azimuthally averaged convergence during the analysis period. The average buoyancy, circulation, and convergence within the near-surface mesocyclone (on spatial scales resolved by the model) all decrease as the tornado intensifies and matures. The tornado and its parent low-level mesocyclone both dissipate surrounded by a weakening rear-flank downdraft. The decreasing buoyancy of parcels within the low-level mesocyclone may partly be responsible for the weakening of the updraft surrounding the tornado and decoupling of the mid- and low-level circulation. Although the supply of horizontal vorticity generated in the forward flank of the storm increases throughout the life cycle of the tornado, it is presumably less easily tilted and stretched on the mesocyclone-scale during tornado maturity owing to the disruption of the low-level updraft/downdraft structure. Changes in radar-measured tornado intensity lag those of ensemble Kalman filter (EnKF) mesocyclone vorticity and circulation.

scholarly journals A Model for Coronal Inflows and In/Out Pairs

2021 ◽  
Author(s):  
Benjamin Lynch
Keyword(s):  
Solar Wind ◽  
White Light ◽  
Mass Density ◽  
Three Dimensional ◽  
Solar Wind Plasma ◽  
Slow Solar Wind ◽  
Intrinsic Variability ◽  
Density Depletion ◽  
In Situ Observations

<div> <div> <div> <p>We present a three-dimensional (3D) numerical magnetohydrodynamics (MHD) model of the white-light coronagraph observational phenomena known as coronal inflows and in/out pairs. Coronal inflows in the LASCO/C2 field of view (approximately 2–6 Rs) were thought to arise from the dynamic and intermittent release of solar wind plasma associated with the helmet streamer belt as the counterpart to outward-propagating streamer blobs, formed by magnetic reconnection. The MHD simulation results show relatively narrow lanes of density depletion form high in the corona and propagate inward with sinuous motion that has been characterized as "tadpole-like" in coronagraph imagery. The height–time evolution and velocity profiles of the simulation inflows and in/out pairs are compared to their corresponding observations and a detailed analysis of the underlying magnetic field structure associated with the synthetic white-light and mass density evolution is presented. Understanding the physical origin of this structured component of the slow solar wind’s intrinsic variability could make a significant contribution to solar wind modeling and the interpretation of remote and in situ observations from Parker Solar Probe and Solar Orbiter.</p> </div> </div> </div>

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