scholarly journals Investigating effects of force and pressure centre signals on stabilogram analysis

2019 ◽  
Vol 13 (9) ◽  
pp. 1305-1310
Author(s):  
Egehan Cetin ◽  
Suleyman Bilgin
Keyword(s):  
Pressure Centre

scholarly journals Synoptic climatological approach associated with three recent summer heatwaves in the Canadian Arctic

2020 ◽  
Vol 11 (S1) ◽  
pp. 233-250 ◽  
Author(s):  
Farahnaz Fazel-Rastgar
Keyword(s):  
Sea Ice ◽  
Canadian Arctic ◽  
Arctic Region ◽  
Low Pressure ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
The North ◽  
Pressure Centre ◽  
Temperature Records ◽  
Arctic Temperature

Abstract The observed unusually high temperatures in the Arctic during recent decades can be related to the Arctic sea ice declines in summer 2007, 2012 and 2016. Arctic dipole formation has been associated with all three heatwaves of 2007, 2012 and 2016 in the Canadian Arctic. Here, the differences in weather patterns are investigated and compared with normal climatological mean (1981–2010) structures. This study examines the high-resolution datasets from the North American Regional Reanalysis model. During the study periods, the north of Alaska has been affected by the low-pressure tongue. The maximum difference between Greenland high-pressure centre and Alaska low-pressure tongue for the summers of 2012, 2016 and 2007 are 8 hPa, 7 hPa and 6 hPa, respectively, corresponding and matching to the maximum summer surface Canadian Arctic temperature records. During anomalous summer heatwaves, low-level wind, temperatures, total clouds (%) and downward radiation flux at the surface are dramatically changed. This study shows the surface albedo has been reduced over most parts of the Canadian Arctic Ocean during the mentioned heatwaves (∼5–40%), with a higher change (specifically in the eastern Canadian Arctic region) during summer 2012 in comparison with summer 2016 and summer 2007, agreeing with the maximum surface temperature and sea ice decline records.

scholarly journals Present temperature, precipitation and rain-on-snow climate in Svalbard

2020 ◽  
Author(s):  
Siiri Wickström ◽  
Marius O. Jonassen ◽  
John Cassano ◽  
Timo Vihma ◽  
Jørn Kristiansen
Keyword(s):  
Weather Prediction ◽  
Open Water ◽  
Low Pressure ◽  
Numerical Weather Prediction Model ◽  
The Arctic ◽  
Pressure Center ◽  
Climate Conditions ◽  
Temperature And Precipitation ◽  
Pressure Centre ◽  
Local Variability

<p>Potentially high-impact warm and wet winter conditions have become increasingly common in recent decades in the arctic archipelago of Svalbard. In this study, we document present 2m temperature, precipitation and rain-on-snow (ROS) climate conditions in Svalbard and relate them to different atmospheric circulation (AC) types. For this purpose, we utilise a set of observations together with output from the high resolution numerical weather prediction model AROME-Arctic. We find that 2m median temperatures vary the most across AC types in winter and spring, and the least in summer. Southerly and southwesterly flow is associated with 10th percentile 2m temperatures above freezing in all seasons. In terms of precipitation, we find the highest amounts and intensities with onshore flow over open water. Sea ice appears to play a strong role in the local variability in both 2m temperature and precipitation. ROS is a frequent phenomenon in the study period, in particular below 250 m ASL. In winter, ROS only occurs with AC types from the southerly sector or during the passage of a low pressure centre or trough. Most of these events occur during southwesterly flow, with a low pressure center west of Svalbard.</p><p> </p>

scholarly journals Assessment of the Balance and Dizziness Objectification in Patients with Vestibular Bilous Headache

Doctor Ru ◽  
2021 ◽  
Vol 20 (9) ◽  
pp. 17-20
Author(s):  
E.M. Illarionova ◽  
◽  
N.P. Gribova ◽  
◽  
Keyword(s):  
Visual Stimulation ◽  
Control Group ◽  
Frequency Spectra ◽  
Study Objective ◽  
Study Materials ◽  
Study Results ◽  
Pressure Centre ◽  
Group 2 ◽  
International Headache Classification ◽  
Primary Frequency

Study Objective: To study the balance in patients with vestibular bilious headache (BH) and possible use of a special comprehensive stabilometrical program for dizziness objectification in them. Study Design: open comparative study. Materials and Methods. The study included 188 patients. Group 1 were 94 patients with confirmed BH (according to the International Headache Classification). Group 2 were 94 patients with common migraine. The stabilometrical control group included 94 healthy subjects. The balance and dizziness objectification were assessed using a special comprehensive method comprising a set of stabilometrical tests. Study Results. The most marked changes in stabilometrical parameters were recorded in patients with BH. Primary frequency spectra of these patients were in a range of 0.3 Hz and above 2 Hz, showing the dysfunction of the postural system and vestibular component in particular. The rate of pressure centre deviation and statokinesigram area were increased in the patients from group 2 vs controls; however, statistically significant differences were noted only in opticokinetic test, sensory and vestibular, and closed-eye tandem results. Comparison of the two clinical groups demonstrates significant differences in basic stabilometrical parameters of all challenge tests. Visual control exclusion as well as substandard visual stimulation had significant impact on changes in the analysed parameters. Conclusion. The use of special stabilometrical tests (opticokinetic stimulation, sensory and vestibular and tandem tests) described in this article allows assessing the balance, quantifying vestibular dysfunction in patients with BH, and objectifying dizziness. Keywords: dizziness, balance, vestibular migraine, computer-aided stabilometry.

Control of the Hydrofoil Ship

1967 ◽  
Vol 20 (03) ◽  
pp. 292-303 ◽  
Author(s):  
P. Magini ◽  
J. Burroughs
Keyword(s):  
Relative Position ◽  
Water Surface ◽  
Hydrodynamic Pressure ◽  
Inertial Space ◽  
Pressure Centre ◽  
Sea Transportation ◽  
The Subject ◽  
The Moment ◽  
Control Surfaces ◽  
Righting Moment

Modern hydrofoil ships have evolved in response to the need for a fast reliable means of sea transportation which is capable of operating in all sea conditions. It is the purpose of this paper to describe how the application of modern stabilization and navigation technology to hydrofoil ships has contributed to the achievement of these goals.First, consider the subject of stability. In particular, consider the source of roll stability in three types of ships: a displacement ship; a surface piercing hydrofoil and a submerged-foil hydrofoil. A roll disturbance of each of the ships is depicted in Fig. 1. In both the displacement ship and in the surface piercing hydrofoil, the righting moment is produced entirely by the change in attitude of the ship relative to the water surface. In the case of the displacement ship, the righting moment is due to the shift of the centre of buoyancy. For the surface piercing hydrofoil, the moment occurs due to the shift of the hydrodynamic pressure centre of the foils. However, for the submerged-foil hydrofoil, no righting moment is produced by the change of the relative position of the water surface. The righting moment for this ship must be produced by underwater control surfaces in response to the change of ship attitude relative to inertial space, as sensed by a vertical gyro. It is this transfer of stability reference from the water surface to an inertial reference that leads to the superior seakeeping capabilities of the submerged foil hydrofoil.

scholarly journals Storm Tilo over Europe in November 2007: storm surge and impacts on societal and energy infrastructure

2019 ◽  
Vol 49 ◽  
pp. 187-196 ◽  
Author(s):  
Anthony James Kettle
Keyword(s):  
Water Level ◽  
Storm Surge ◽  
North Sea ◽  
Tide Gauge ◽  
Winter Storms ◽  
Energy Infrastructure ◽  
The North ◽  
Short Period ◽  
Pressure Centre ◽  
The North Sea

Abstract. Storm Tilo on 8–9 November 2007 ranks among the serious winter storms in northern Europe over the past 30 years. Its low pressure centre passed across the northern North Sea, and this led to a cold air outbreak in northwest Europe. Strong north winds across the North Sea contributed to a high storm surge that was serious for coastal regions in eastern England, the Netherlands and Germany. Storm winds and unusually high waves caused shipping accidents and damage to some offshore energy infrastructure. This report presents an outline of the met-ocean conditions and a short overview of storm impacts on societal and energy infrastructure. The progress of the storm surge around the North Sea is analysed using data from the national tide gauge networks. A spectral analysis of the water level data is used to isolate the long period storm surge and short period oscillations (i.e., <4.8 h) from the tidal signal. The calculated skew surge is compared with literature reports for this storm and also with another serious North Sea storm from 31 October–1 November 2006 (Storm Britta). The short period oscillations are compared with the platform and shipping incident reports for the 2 d storm period. The results support previous reports of unusual wave and water level dynamics during some severe regional winter storms.

scholarly journals ENSO variability in the deuterium-excess record of a coastal Antarctic ice core from the McMurdo Dry Valleys, Victoria Land

2005 ◽  
Vol 41 ◽  
pp. 140-146 ◽  
Author(s):  
N.G. Patterson ◽  
N.A.N. Bertler ◽  
T.R. Naish ◽  
U. Morgenstern
Keyword(s):  
Southern Oscillation ◽  
Ice Core ◽  
Moisture Flux ◽  
Low Pressure ◽  
Dry Valleys ◽  
Deuterium Excess ◽  
Amundsen Sea ◽  
Ross Ice Shelf ◽  
West Antarctic ◽  
Pressure Centre

AbstractThe El Niño–Southern Oscillation (ENSO) signal in coastal Antarctic precipitation is evaluated using deuterium-excess data measured from an ice core located at Victoria Lower Glacier (VLG) Dome, McMurdo Dry Valleys. Recent studies suggest that interannual variations in the intensity and position of the Amundsen Sea low, a low-pressure centre that controls moisture flux in the West Antarctic sector, is modulated by the ENSO. Deuterium-excess values from the VLG ice core, which serve as a proxy for changes in regional moisture flux, exhibit oscillations of equivalent duration to those observed in the Southern Oscillation Index (SOI). Results of cross-spectral analyses show that temporal fluctuations in deuterium excess and the SOI covary and are coherent at ~4.9, 3.6, 3.0, 2.6, 2.4 and 2.0 year frequencies between 1950 and 2000. We ascribe this covariance to shifts in the source and transport pathway of precipitation that is deposited in coastal Victoria Land as a consequence of ENSO’s influence. High values of deuterium excess are consistent with increased meridional flow carrying warm, moist air southward across the Ross Sea when the low-pressure centre is positioned to the north of the Ross Ice Shelf (La Niña mode). Low deuterium-excess values, which reflect a more westerly to southerly flow across the West Antarctic ice sheet and Ross Ice Shelf leading to cooler and drier en-route conditions, occur when the low-pressure centre is positioned above the Amundsen Sea (El Niño mode).

scholarly journals Analysis of hourly precipitation characteristics in Kraków, southern Poland, using a classification of circulation types

2009 ◽  
Vol 40 (6) ◽  
pp. 553-563 ◽  
Author(s):  
Robert Twardosz
Keyword(s):  
Atmospheric Circulation ◽  
Circulation Type ◽  
Exceedance Probability ◽  
Maximum Precipitation ◽  
Southern Poland ◽  
Hourly Precipitation ◽  
Circulation Types ◽  
Precipitation Characteristics ◽  
Pressure Centre ◽  
Precipitation Events

This paper investigates the relationship between maximum precipitation in Kraków and types of atmospheric circulation in southern Poland, as classified by Niedźwiedź. Three characteristics were used to define this relationship: maximum precipitation (Pmax), its duration (d) and probability of exceedance (p). The input data came from Kraków's uniquely long and homogenous pluviographic record spanning the period 1886–2007. Hourly precipitation values for the maximum precipitation events were identified and arranged in 1–24 hour intervals. They were then processed using the generalized extreme value (GEV) distribution to produce quantiles of maximum precipitation totals in each of the intervals and broken down by the corresponding circulation type. Differences between the development mechanisms are manifested in relationships between precipitation characteristics and their measure of randomness, i.e. exceedance probability. This paper demonstrates that maximum precipitation events depend on their duration d and atmospheric circulation. The maximum short-duration (one-hour) events occur primarily in either of two circulation types: (i) cyclonic with advection from the east and from the southeast or (ii) low-pressure centre and cyclonic trough. Maximum long-duration precipitation events (24 hour), on the other hand, occur in the cyclonic type of circulation with advection from the north and from the northeast.

scholarly journals A process-based anatomy of Mediterranean cyclones: From baroclinic lows to tropical-like systems

2020 ◽  
Author(s):  
Emmanouil Flaounas ◽  
Suzanne L. Gray ◽  
Franziska Teubler
Keyword(s):  
Latent Heat ◽  
Wrf Model ◽  
Lower Troposphere ◽  
Mature Stage ◽  
Atmospheric Processes ◽  
Mediterranean Cyclones ◽  
Pressure Centre ◽  
Diabatic Processes ◽  
Diabatic Forcing ◽  
A Minor

Abstract. In this study, we address the question of the atmospheric processes that turn Mediterranean cyclones into severe storms. Our approach applies on-line potential vorticity (PV) budget diagnostics and piecewise PV inversion to WRF model simulations of the mature stage of 100 intense Mediterranean cyclones. We quantify the relative contributions of different processes to cyclone development and therefore deliver, for the first time, a comprehensive insight into the variety of cyclonic systems that develop in the Mediterranean from the perspective of cyclone dynamics. In particular, we show that all 100 cyclones are systematically influenced by two main PV anomalies: a major anomaly in the upper troposphere, related to the baroclinic forcing of cyclone development, and a minor anomaly in the lower troposphere, related to diabatic processes and momentum forcing of wind. Among the diabatic processes, latent heat is shown to act as the main PV source (reinforcing cyclones), being partly balanced by PV sinks of temperature diffusion and radiative cooling (weakening cyclones). Momentum forcing is shown to have an ambiguous feedback, able to reinforce and weaken cyclones while in certain cases playing an important role in cyclone development. Piecewise PV inversion shows that most cyclones develop due to the combined effect of both baroclinic and diabatic forcing, i.e. due to both PV anomalies. However, the stronger the baroclinic forcing, the less a cyclone is found to develop due to diabatic processes. Several pairs of exemplary cases are used to illustrate the variety of contributions of atmospheric processes to the development of Mediterranean cyclones: (i) cases where both baroclinic and diabatic processes contribute to cyclone development; (ii) cases that mainly developed due to latent-heat release; (iii) cases developing in the wake of the Alps; and (iv) two unusual cases, one where momentum forcing dominates cyclone development and the other presenting a dual surface pressure centre. Finally, we focus on ten medicane cases (i.e. tropical-like cyclones). In contrast to their tropical counterparts – but in accordance with most intense Mediterranean cyclones – most medicanes are shown to develop under the influence of both baroclinic and diabatic processes. In discussion of medicane driving processes, we highlight the need for a physical definition of these systems.

scholarly journals A process-based anatomy of Mediterranean cyclones: from baroclinic lows to tropical-like systems

2021 ◽  
Vol 2 (1) ◽  
pp. 255-279
Author(s):  
Emmanouil Flaounas ◽  
Suzanne L. Gray ◽  
Franziska Teubler
Keyword(s):  
Latent Heat ◽  
Wrf Model ◽  
Lower Troposphere ◽  
Mature Stage ◽  
Atmospheric Processes ◽  
Mediterranean Cyclones ◽  
Pressure Centre ◽  
Diabatic Processes ◽  
Diabatic Forcing ◽  
A Minor

Abstract. In this study, we address the question of the atmospheric processes that turn Mediterranean cyclones into severe storms. Our approach applies online potential vorticity (PV) budget diagnostics and piecewise PV inversion to WRF model simulations of the mature stage of 100 intense Mediterranean cyclones. We quantify the relative contributions of different processes to cyclone development and therefore deliver, for the first time, a comprehensive insight into the variety of cyclonic systems that develop in the Mediterranean from the perspective of cyclone dynamics. In particular, we show that all 100 cyclones are systematically influenced by two main PV anomalies: a major anomaly in the upper troposphere, related to the baroclinic forcing of cyclone development, and a minor anomaly in the lower troposphere, related to diabatic processes and momentum forcing of wind. Among the diabatic processes, latent heat is shown to act as the main PV source (reinforcing cyclones), being partly balanced by PV sinks of temperature diffusion and radiative cooling (weakening cyclones). Momentum forcing is shown to have an ambiguous feedback, able to reinforce and weaken cyclones while in certain cases playing an important role in cyclone development. Piecewise PV inversion shows that most cyclones develop due to the combined effect of both baroclinic and diabatic forcing, i.e. due to both PV anomalies. However, the stronger the baroclinic forcing, the less a cyclone is found to develop due to diabatic processes. Several pairs of exemplary cases are used to illustrate the variety of contributions of atmospheric processes to the development of Mediterranean cyclones: (i) cases where both baroclinic and diabatic processes contribute to cyclone development; (ii) cases that mainly developed due to latent-heat release; (iii) cases developing in the wake of the Alps; and (iv) two unusual cases, one where momentum forcing dominates cyclone development and the other presenting a dual-surface pressure centre. Finally, we focus on 10 medicane cases (i.e. tropical-like cyclones). In contrast to their tropical counterparts – but in accordance with most intense Mediterranean cyclones – most medicanes are shown to develop under the influence of both baroclinic and diabatic processes. In discussion of medicane-driving processes, we highlight the need for a physical definition of these systems.

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