scholarly journals Structure and Evolution of a Possible U.S. Landfalling Tropical Storm in 2006

2010 ◽  
Vol 138 (1) ◽  
pp. 265-278 ◽  
Author(s):  
Zachary Gruskin
Keyword(s):  
Air Force ◽  
Cross Sections ◽  
Closed Surface ◽  
Tropical Storm ◽  
Doppler Velocity ◽  
Velocity Data ◽  
Warm Core ◽  
Surface Circulation ◽  
Convective Process ◽  
Surface Observations

Abstract A tropical disturbance made landfall near Morehead City, North Carolina, on 27 June 2006. Surface observations, Air Force reconnaissance, and Doppler velocity data suggest that the disturbance had a closed surface circulation at landfall, with maximum 1-min surface winds >18 m s−1, the threshold of tropical storm strength. A cyclostrophic wind calculation using Doppler velocity data and surface observations indicates that the circulation of the disturbance likely caused the tropical storm force winds observed, rather than an environmental pressure gradient or short-lived convective process. Doppler velocity cross sections of the disturbance further suggest that the disturbance was warm core, and an analysis of the disturbance’s environment reveals that latent heat of condensation was likely a large source of energy for the disturbance, though there was some baroclinic forcing. These observations and analyses make a compelling case for the upgrade of the disturbance to a tropical storm in the best-track database.

Using Drifter Velocity Measurements to Assess and Constrain Coarse-Resolution Ocean Models

2021 ◽  
Author(s):  
Mengnan Zhao ◽  
Rui M. Ponte ◽  
Ou Wang ◽  
Rick Lumpkin
Keyword(s):  
Time Variable ◽  
Ocean Dynamics ◽  
Careful Examination ◽  
Velocity Data ◽  
Velocity Measurements ◽  
Data Errors ◽  
Coarse Resolution ◽  
Surface Circulation ◽  
Ocean Models ◽  
Data Constraints

AbstractProperly fitting ocean models to observations is crucial for improving model performance and understanding ocean dynamics. Near-surface velocity measurements from the Global Drifter Program (GDP) contain valuable information about upper ocean circulation and air-sea fluxes on various space and time scales. This study explores whether GDP measurements can be used for usefully constraining the surface circulation from coarse-resolution ocean models, using global solutions produced by the consortium for Estimating the Circulation and Climate of the Ocean (ECCO) as an example. To address this problem, a careful examination of velocity data errors is required. Comparisons between an ECCO model simulation, performed without any data constraints, and GDP and Ocean Surface Current Analyses Real-time (OSCAR) velocity data, over the period 1992–2017, reveal considerable differences in magnitude and pattern. These comparisons are used to estimate GDP data errors in the context of the time-mean and time-variable surface circulations. Both instrumental errors and errors associated with limitations in model physics and resolution (representation errors) are considered. Given the estimated model-data differences, errors and signal-to-noise ratios, our results indicate that constraining ocean state estimates to GDP can have a substantial impact on the ECCO large-scale time-mean surface circulation over extensive areas. Impact of GDP data constraints on the ECCO time-variable circulation would be weaker and mainly limited to low latitudes. Representation errors contribute substantially to degrading the data impacts.

scholarly journals Velocity and concentration profiles of saline and turbidity currents flowing in a straight channel under quasi-uniform conditions

2014 ◽  
Vol 2 (1) ◽  
pp. 167-180 ◽  
Author(s):  
M. Stagnaro ◽  
M. Bolla Pittaluga
Keyword(s):  
Cross Sections ◽  
Longitudinal Velocity ◽  
Fixed Bed ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Turbidity Currents ◽  
Straight Channel ◽  
Densimetric Froude Number ◽  
Vertical Coordinate ◽  
Dimensionless Velocity

Abstract. We present a series of detailed experimental observations of saline and turbidity currents flowing in a straight channel. Experiments are performed by continuously feeding the channel with a dense mixture until a quasi-steady configuration is obtained. The flume, 12 m long, is characterized by a concrete fixed bed with a uniform slope of 0.005. Longitudinal velocity profiles are measured in ten cross sections, 1 m apart, employing an ultrasound Doppler velocity profiler. We also measure the density of the mixture using a rake of siphons sampling at different heights from the bottom in order to obtain the vertical density distributions in a cross section where the flow already attained a quasi-uniform configuration. We performed 27 experiments changing the flow discharge, the fractional excess density, the character of the current (saline or turbidity) and the roughness of the bed in order to observe the consequences of these variations on the vertical velocity profiles and on the overall characteristics of the flow. Dimensionless velocity profiles under quasi-uniform flow conditions were obtained by scaling longitudinal velocity with its depth averaged value and the vertical coordinate with the flow thickness. They turned out to be influenced by the Reynolds number of the flow, by the relative bed roughness, and by the presence of sediment in suspension. Unexpectedly, the densimetric Froude number of the current turned out to have no influence on the dimensionless velocity profiles.

scholarly journals A Study of the Vibrational Excitation of H2 by Measurements of the Drift Velocity of Electrons in H2−Ne Mixtures

1988 ◽  
Vol 41 (4) ◽  
pp. 573 ◽  
Author(s):  
JP England ◽  
MT Elford ◽  
RW Crompton
Keyword(s):  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Excitation Cross Section ◽  
Vibrational Excitation ◽  
Pure Hydrogen ◽  
Velocity Data ◽  
Highly Sensitive ◽  
Hydrogen Mixtures ◽  
Made In

Measurements of electron drift velocities have been made in 1�160% and 2�892% hydrogen-neon mixtures at 294 K and values of EI N from 0�12 to 1�7 Td. The measurements are highly sensitive to the region of the threshold of the v = 0 → 1 vibrational excitation cross section for hydrogen and have enabled more definitive tests of proposed cross sections to be made than was possible using drift velocity data for H2−He and H2−Ar mixtures. The theoretical v = 0 → 1 vibrational excitation cross section of Morrison et al. (1987) is shown to be incompatible with the present measurements. A new set of hydrogen cross sections has been derived from the available electron swarm measurements in pure hydrogen and hydrogen mixtures.

scholarly journals Warm-Core Formation in Tropical Storm Humberto (2001)

2012 ◽  
Vol 140 (4) ◽  
pp. 1177-1190 ◽  
Author(s):  
Klaus Dolling ◽  
Gary M. Barnes
Keyword(s):  
Energy Content ◽  
Early Stage ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Mesoscale Convective System ◽  
Tropical Storm ◽  
Central Pressure ◽  
Convective System ◽  
Warm Core ◽  
Mesoscale Convective

At 0600 UTC 22 September 2001, Humberto was a tropical depression with a minimum central pressure of 1010 hPa. Twelve hours later, when the first global positioning system dropwindsondes (GPS sondes) were jettisoned, Humberto’s minimum central pressure was 1000 hPa and it had attained tropical storm strength. Thirty GPS sondes, radar from the WP-3D, and in situ aircraft measurements are utilized to observe thermodynamic structures in Humberto and their relationship to stratiform and convective elements during the early stage of the formation of an eye. The analysis of Tropical Storm Humberto offers a new view of the pre-wind-induced surface heat exchange (pre-WISHE) stage of tropical cyclone evolution. Humberto contained a mesoscale convective vortex (MCV) similar to observations of other developing tropical systems. The MCV advects the exhaust from deep convection in the form of an anvil cyclonically over the low-level circulation center. On the trailing edge of the anvil an area of mesoscale descent induces dry adiabatic warming in the lower troposphere. The nascent warm core at low levels causes the initial drop in pressure at the surface and acts to cap the boundary layer (BL). As BL air flows into the nascent eye, the energy content increases until the energy is released from under the cap on the down shear side of the warm core in the form of vigorous cumulonimbi, which become the nascent eyewall. This series of events show one possible path in which a mesoscale convective system may evolve into a warm-cored structure and intensify into a hurricane.

scholarly journals Tropical Transition of an Unnamed, High-Latitude, Tropical Cyclone over the Eastern North Pacific

2016 ◽  
Vol 144 (2) ◽  
pp. 713-736 ◽  
Author(s):  
Alicia M. Bentley ◽  
Nicholas D. Metz
Keyword(s):  
Life Cycle ◽  
Tropical Cyclone ◽  
Cross Sections ◽  
North Pacific ◽  
Lower Troposphere ◽  
Sea Surface ◽  
The West ◽  
Warm Core ◽  
Cold Core ◽  
North Pacific Basin

Abstract In early November 2006, an unnamed tropical cyclone (TC) formed via the tropical transition (TT) process at 42°N over the eastern North Pacific. An extratropical cyclone (EC), developing downstream of a thinning upper-tropospheric trough over the eastern North Pacific, served as the precursor disturbance that would ultimately undergo TT. The TT of the unnamed TC was extremely unusual—occurring over ~16°C sea surface temperatures in a portion of the eastern North Pacific basin historically devoid of TC activity. This paper 1) identifies the upper- and lower-tropospheric features linked to the formation of the EC that transitions into the unnamed TC, 2) provides a synoptic overview of the features and processes associated with the unnamed TC’s TT, and 3) discusses the landfall of the weakening cyclone along the west coast of North America. As observed in previous studies of TT, the precursor EC progresses through the life cycle of a marine extratropical frontal cyclone, developing a bent-back warm front on its northern and western sides and undergoing a warm seclusion process. Backward air parcel trajectories suggest that air parcels isolated in the center of the transitioning cyclone were warmed in the lower troposphere via sensible heating from the underlying sea surface. Vertical cross sections taken through the center of the cyclone during its life cycle reveal its transformation from an asymmetric, cold-core, EC into an axisymmetric, warm-core, TC during TT. Ensemble reforecasts initialized after TT highlight the relatively low forecast skill associated with the landfall of the weakening cyclone.

Genesis of Pre–Hurricane Felix (2007). Part II: Warm Core Formation, Precipitation Evolution, and Predictability

2010 ◽  
Vol 67 (6) ◽  
pp. 1730-1744 ◽  
Author(s):  
Zhuo Wang ◽  
M. T. Montgomery ◽  
T. J. Dunkerton
Keyword(s):  
Initial Conditions ◽  
Numerical Technique ◽  
Transformation Process ◽  
Tropical Storm ◽  
Convective Precipitation ◽  
Moist Convection ◽  
Near Surface ◽  
Warm Core ◽  
Stratiform Precipitation ◽  
Deep Moist Convection

Abstract This is the second of a two-part study examining the simulated formation of Atlantic Hurricane Felix (2007) in a cloud-representing framework. Here several open issues are addressed concerning the formation of the storm’s warm core, the evolution and respective contribution of stratiform versus convective precipitation within the parent wave’s pouch, and the sensitivity of the development pathway reported in Part I to different model physics options and initial conditions. All but one of the experiments include ice microphysics as represented by one of several parameterizations, and the partition of convective versus stratiform precipitation is accomplished using a standard numerical technique based on the high-resolution control experiment. The transition to a warm-core tropical cyclone from an initially cold-core, lower tropospheric wave disturbance is analyzed first. As part of this transformation process, it is shown that deep moist convection is sustained near the pouch center. Both convective and stratiform precipitation rates increase with time. While stratiform precipitation occupies a larger area even at the tropical storm stage, deep moist convection makes a comparable contribution to the total rain rate at the pregenesis stage, and a larger contribution than stratiform processes at the storm stage. The convergence profile averaged near the pouch center is found to become dominantly convective with increasing deep moist convective activity there. Low-level convergence forced by interior diabatic heating plays a key role in forming and intensifying the near-surface closed circulation, while the midlevel convergence associated with stratiform precipitation helps to increase the midlevel circulation and thereby contributes to the formation and upward extension of a tropospheric-deep cyclonic vortex. Sensitivity tests with different model physics options and initial conditions demonstrate a similar pregenesis evolution. These tests suggest that the genesis location of a tropical storm is largely controlled by the parent wave’s critical layer, whereas the genesis time and intensity of the protovortex depend on the details of the mesoscale organization, which is less predictable. Some implications of the findings are discussed.

Analysis of ultrasonic Doppler velocity data obtained in models of stenosed carotid bifurcations with irregular lesion surface

1997 ◽  
Vol 5 (3) ◽  
pp. 199-206 ◽  
Author(s):  
K. Kaluzynski ◽  
B. Lesniak ◽  
K. Mikolajczyk ◽  
D. Liepsch
Keyword(s):  
Doppler Velocity ◽  
Velocity Data

scholarly journals Comments on “Structure and Evolution of a Possible U.S. Landfalling Tropical Storm in 2006”

2010 ◽  
Vol 138 (1) ◽  
pp. 279-281 ◽  
Author(s):  
John L. Beven ◽  
Lixion A. Avila ◽  
Eric S. Blake ◽  
Hugh D. Cobb ◽  
Richard J. Pasch
Keyword(s):  
Tropical Cyclone ◽  
Companion Paper ◽  
Closed Surface ◽  
Conclusive Evidence ◽  
Eastern United States ◽  
Kinematic Parameters ◽  
System A ◽  
Surface Circulation ◽  
Surface Data ◽  
National Hurricane Center

Abstract The Best Track Change Committee of the National Hurricane Center evaluates proposed changes to the Hurricane Database (HURDAT) in the Atlantic and eastern North Pacific basins. In the companion paper, Gruskin documents a possible tropical cyclone that affected portions of the eastern United States on 27–28 June 2006 and proposes that it be added to HURDAT. The committee reviewed the aircraft, radar, rawinsonde, satellite, and surface data available on this system and found it to be a challenging and complex system. A reconnaissance aircraft flying in the system in real time failed to find a closed circulation before landfall, and kinematic parameters suggest the system was more likely to have the structure of an open wave, with any surface circulation at best being poorly defined. Because of the lack of conclusive evidence regarding the existence of a closed surface circulation before landfall, the committee has decided not to add this system to HURDAT as a tropical cyclone.

scholarly journals Momentum Transfer Cross Section for Electrons in Krypton Derived from Measurements of the Drift Velocity in H2?Kr Mixtures

1988 ◽  
Vol 41 (5) ◽  
pp. 701 ◽  
Author(s):  
JP England ◽  
MT Elford
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Personal Communication ◽  
Electron Drift ◽  
Velocity Data ◽  
The Cross ◽  
Momentum Transfer Cross Section ◽  
Made In

Measurements of electron drift velocities have been made in 0�4673% and 1�686% hydrogenkrypton mixtures at 293 K and values of E/ N from 0�08 to 2�5 Td with an estimated uncertainty of <�0�7%. The data have been used in conjunction with the H2 cross sections of England et aL (1988) to derive the momentum transfer cross section for krypton over the energy range 0�05 to 6�0 eV. The drift velocity data have also been used to test the Kr momentum transfer cross sections of Koizumi et aL (1986) and Hunter (personal communication 1988). The cross section of Koizumi et aL is clearly incompatible with the present measurements while the cross section of Hunter has been used to predict these measurements to within 1% to 3%.

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