scholarly journals Cyclones of Subtropical Origin in the Southwest Pacific: a Climatology and Aspects of Movement and Development

2021 ◽  
Author(s):  
◽  
Susanne Sandra Schroder
Keyword(s):  
New Zealand ◽  
Tropical Cyclones ◽  
Development Process ◽  
Extratropical Cyclones ◽  
Extratropical Transition ◽  
Southwest Pacific ◽  
Baroclinic Waves ◽  
Upper Level ◽  
Type 3

<p>A comprehensive study on cyclones of subtropical origin (STCs) in the Southwest Pacific is carried out. A brief history of the damage caused by STCs in New Zealand between 1990 and 2005 is given. It shows that approximately 2 to 3 times a year STCs come into the vicinity of New Zealand, mostly affecting the North Island and causing predominantly flood damage. A climatology is compiled with a cyclone track database covering 21 years, providing an overview of the behaviour and characteristics of STCs in this region. Distinct annual and seasonal patterns in frequency, tracks and intensity are revealed. Some of these patterns resemble those of tropical cyclones, in particular those undergoing extratropical transition, while others resemble those of extratropical cyclones in this region. In addition, it is shown that there is a significant increase in the number of summer STCs, which coincides with an increase in sea surface temperatures in the area. The structure and processes involved in the development of STCs are investigated in more detail using data from the United Kingdom Meteorological Office (UKMO) global model spanning 5 years (1999 to 2003). An analysis of the upper-level flow shows that STCs are steered into midlatitudes by upper-level baroclinic waves, m general through interaction with an upper-level trough. Differences in the structure and development of STCs can be attributed to the fact that upper-level baroclinic waves are able to propagate far into the sub tropics in this region. This is also the reason for the existence of three types of STCs, when differentiating by characteristics of their development process. Type 1 STCs are very similar to extratropical cyclones in structure and development. The structure and the development process of Type 3 STCs resemble more those of tropical cyclones. The initial development of Type 2 STCs is similar to that of Type 3, but they then undergo a transition, found to be very similar to that of tropical cyclones undergoing extratropical transition. Interseasonal variations in the upper-level flow over the Southwest Pacific are reflected in the behaviour and characteristics of STCs and subsequently the occurrence of the three types of STCs. During the colder seasons baroclinic waves frequently propagate relatively far into the subtropics in this region. This means STCs not only have a high chance of being picked up by an upper-level trough and undergoing extratropical transition, they are also able to actually form in the vicinity of a trough. Thus, during that time most STCs tend to be either Type 1 or 2. On the other hand, during summer, when baroclinic waves only occasionally propagate into the subtropics, there is a higher frequency of Type 3 STCs. In terms of weather-related threats to New Zealand, the interaction with an upperlevel trough is the cause for STCs coming into the vicinity of New Zealand, while the high rain rates that accompany them, and that are the cause for the extensive, mostly flood-related, damage, are attributed to their place of origin.</p>

scholarly journals Cyclones of Subtropical Origin in the Southwest Pacific: a Climatology and Aspects of Movement and Development

2021 ◽  
Author(s):  
◽  
Susanne Sandra Schroder
Keyword(s):  
New Zealand ◽  
Tropical Cyclones ◽  
Development Process ◽  
Extratropical Cyclones ◽  
Extratropical Transition ◽  
Southwest Pacific ◽  
Baroclinic Waves ◽  
Upper Level ◽  
Type 3

<p>A comprehensive study on cyclones of subtropical origin (STCs) in the Southwest Pacific is carried out. A brief history of the damage caused by STCs in New Zealand between 1990 and 2005 is given. It shows that approximately 2 to 3 times a year STCs come into the vicinity of New Zealand, mostly affecting the North Island and causing predominantly flood damage. A climatology is compiled with a cyclone track database covering 21 years, providing an overview of the behaviour and characteristics of STCs in this region. Distinct annual and seasonal patterns in frequency, tracks and intensity are revealed. Some of these patterns resemble those of tropical cyclones, in particular those undergoing extratropical transition, while others resemble those of extratropical cyclones in this region. In addition, it is shown that there is a significant increase in the number of summer STCs, which coincides with an increase in sea surface temperatures in the area. The structure and processes involved in the development of STCs are investigated in more detail using data from the United Kingdom Meteorological Office (UKMO) global model spanning 5 years (1999 to 2003). An analysis of the upper-level flow shows that STCs are steered into midlatitudes by upper-level baroclinic waves, m general through interaction with an upper-level trough. Differences in the structure and development of STCs can be attributed to the fact that upper-level baroclinic waves are able to propagate far into the sub tropics in this region. This is also the reason for the existence of three types of STCs, when differentiating by characteristics of their development process. Type 1 STCs are very similar to extratropical cyclones in structure and development. The structure and the development process of Type 3 STCs resemble more those of tropical cyclones. The initial development of Type 2 STCs is similar to that of Type 3, but they then undergo a transition, found to be very similar to that of tropical cyclones undergoing extratropical transition. Interseasonal variations in the upper-level flow over the Southwest Pacific are reflected in the behaviour and characteristics of STCs and subsequently the occurrence of the three types of STCs. During the colder seasons baroclinic waves frequently propagate relatively far into the subtropics in this region. This means STCs not only have a high chance of being picked up by an upper-level trough and undergoing extratropical transition, they are also able to actually form in the vicinity of a trough. Thus, during that time most STCs tend to be either Type 1 or 2. On the other hand, during summer, when baroclinic waves only occasionally propagate into the subtropics, there is a higher frequency of Type 3 STCs. In terms of weather-related threats to New Zealand, the interaction with an upperlevel trough is the cause for STCs coming into the vicinity of New Zealand, while the high rain rates that accompany them, and that are the cause for the extensive, mostly flood-related, damage, are attributed to their place of origin.</p>

scholarly journals Vitreopapillary Tractions

2018 ◽  
pp. 244-248
Keyword(s):  
Optic Disc ◽  
Development Process ◽  
Pigment Epithelium ◽  
Posterior Vitreous Detachment ◽  
Fiber Layer ◽  
Visual Functions ◽  
Previous Trauma ◽  
Type 3

Vitreo-papillary tractions develop in the posterior vitreous detachment (PVD) development process that vitreous cannot pass the separation process from the papilla. Distortion of the nerve fiber layer and microvascular structures in the papillae by the posterior hyaloid traction causes deterioration of visual functions. Conditions causing local ocular anatomic variations, such as small crowded papillae, previous trauma, intraocular surgery, intraocular inflammations, intraocular vascular problems may be predisposing for abnormal PVD. Vitreopapillary tractions (VPT) can be classified as primary if there is no other ocular pathology that can lead to abnormal PVD, and secondary, if there is a concurrent pathology that can lead to abnormal PVD. Three types of VPT's are defined according to the Optical coherence tomography (OCT) based classification. Type 1: vitreous band traction on the optic disc Type 2: prominent vitreous condensation at the optic disc surface and cup, Type 3: elevation of the anterior optic disc cup border above the level of the retina pigment epithelium/Bruch's membrane. Diagnosis is made by clinical examination ultrasonography and OCT findings. Vitrectomy is performed in situations that threaten visual functions in the treatment.

scholarly journals Evidence of small-scale quasi-isentropic mixing in ridges of extra-tropical baroclinic waves

2019 ◽  
Author(s):  
Daniel Kunkel ◽  
Peter Hoor ◽  
Thorsten Kaluza ◽  
Jörn Ungermann ◽  
Björn Kluschat ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Transition Layer ◽  
Static Stability ◽  
Life Cycles ◽  
Small Scale ◽  
Extratropical Cyclones ◽  
Helmholtz Instability ◽  
Extratropical Transition ◽  
Air Masses ◽  
Baroclinic Waves

Abstract. Stratosphere–troposphere exchange within extratropical cyclones provides the potential for anthropogenic and natural surface emissions to rapidly reach the stratosphere as well as for ozone from the stratosphere to penetrate deep into the troposphere, even down into the boundary layer. The efficiency of this process directly influences the surface climate, the chemistry in the stratosphere, the chemical composition of the extratropical transition layer, and surface pollution levels. Here, we present evidence for a mixing process within extratropical cyclones which has gained only little attention so far and which fosters the transport of tropospheric air masses into the stratosphere in ridges of baroclinic waves. We analyzed airborne measurement data from a research flight of the WISE (Wave driven isentropic exchange) campaign over the North Atlantic in autumn 2017 supported by forecasts from a numerical weather prediction model and trajectory calculations. Further detailed process understanding is obtained from experiments of idealized baroclinic life cycles. The major outcome of this analysis is that air masses mix in the region of the tropopause and potentially enter the stratosphere in ridges of baroclinic waves at the anti-cyclonic side of jet without changing their potential temperature drastically. This quasi-isentropic exchange occurs above the outflow of warm conveyor belts, in regions which exhibit enhanced static stability in the lower stratosphere and a Kelvin–Helmholtz instability across the tropopause. The enhanced static stability is related to radiative cooling below the tropopause and the presence of small scale waves. The Kelvin–Helmholtz instability is related to vertical shear of the horizontal wind associated to small scale waves at the upper edge of the jet-stream. The instability leads to the occurrence of turbulence and consequent mixing of trace gases in the tropopause region. While the overall relevance of this process has yet to be assessed, it has the potential to significantly modify the chemical composition of the extratropical transition layer in the lowermost stratosphere in regions which have previously gained only little attention in terms of mixing in baroclinic waves.

scholarly journals Evidence of small-scale quasi-isentropic mixing in ridges of extratropical baroclinic waves

2019 ◽  
Vol 19 (19) ◽  
pp. 12607-12630 ◽  
Author(s):  
Daniel Kunkel ◽  
Peter Hoor ◽  
Thorsten Kaluza ◽  
Jörn Ungermann ◽  
Björn Kluschat ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Transition Layer ◽  
Static Stability ◽  
Life Cycles ◽  
Small Scale ◽  
Extratropical Cyclones ◽  
Helmholtz Instability ◽  
Extratropical Transition ◽  
Air Masses ◽  
Baroclinic Waves

Abstract. Stratosphere–troposphere exchange within extratropical cyclones provides the potential for anthropogenic and natural surface emissions to rapidly reach the stratosphere as well as for ozone from the stratosphere to penetrate deep into the troposphere, even down into the boundary layer. The efficiency of this process directly influences the surface climate, the chemistry in the stratosphere, the chemical composition of the extratropical transition layer, and surface pollution levels. Here, we present evidence for a mixing process within extratropical cyclones which has gained only a small amount of attention so far and which fosters the transport of tropospheric air masses into the stratosphere in ridges of baroclinic waves. We analyzed airborne measurement data from a research flight of the WISE (Wave-driven ISentropic Exchange) campaign over the North Atlantic in autumn 2017, supported by forecasts from a numerical weather prediction model and trajectory calculations. Further detailed process understanding is obtained from experiments of idealized baroclinic life cycles. The major outcome of this analysis is that air masses mix in the region of the tropopause and potentially enter the stratosphere in ridges of baroclinic waves at the anticyclonic side of the jet without changing their potential temperature drastically. This quasi-isentropic exchange occurs above the outflow of warm conveyor belts, in regions which exhibit enhanced static stability in the lower stratosphere and a Kelvin–Helmholtz instability across the tropopause. The enhanced static stability is related to radiative cooling below the tropopause and the presence of small-scale waves. The Kelvin–Helmholtz instability is related to vertical shear of the horizontal wind associated with small-scale waves at the upper edge of the jet stream. The instability leads to the occurrence of turbulence and consequent mixing of trace gases in the tropopause region. While the overall relevance of this process has yet to be assessed, it has the potential to significantly modify the chemical composition of the extratropical transition layer in the lowermost stratosphere in regions which have previously gained a small amount of attention in terms of mixing in baroclinic waves.

scholarly journals The Extratropical Transition of Tropical Cyclone Edisoana (1990)

2014 ◽  
Vol 142 (8) ◽  
pp. 2772-2793 ◽  
Author(s):  
Kyle S. Griffin ◽  
Lance F. Bosart
Keyword(s):  
Tropical Cyclones ◽  
Polar Front ◽  
Lower Latitude ◽  
Extratropical Transition ◽  
Southwest Indian Ocean ◽  
Half Wavelength ◽  
Lower Amplitude ◽  
Upper Level ◽  
Jet Streaks ◽  
Upper Level Jet

Abstract Documentation of southwest Indian Ocean (SWIO) tropical cyclones (TCs) and extratropical transition (ET) events is sparse in the refereed literature. The authors present a climatology of SWIO TC and ET events for 1989–2013. The SWIO averages ~9 tropical cyclones (TCs) per year in this modern era. Of these TCs, ~44% undergo extratropical transition (ET), or ~four per year. A case study of TC Edisoana (1990), the most rapidly intensifying SWIO post-ET TC between 1989 and 2013, shows that extratropical interactions began when an approaching trough embedded in the subtropical jet stream (STJ) induced ET on 7 March. As Edisoana underwent ET, a subtropical ridge downstream amplified in response to poleward-directed positive potential vorticity (PV) advection associated with diabatically (convectively) driven upper-level outflow from TC Edisoana. This amplifying lower-latitude ridge phased with a lower-amplitude higher-latitude ridge embedded in the polar front jet (PFJ), resulting in the merger of the two jets. This ridge phasing and jet merger, combined with the approach of an upstream trough embedded in the PFJ, resulted in a decrease in the half-wavelength between the approaching trough and the downstream phased ridges and provided extratropical cyclone Edisoana with a prime environment for rapid reintensification (RI). Poleward-directed positive PV advection into the phased ridge strengthened the upper-level jet downstream of Edisoana, which provided the primary baroclinic forcing throughout the RI phase. A backward trajectory analysis suggests that strong diabatic heating enhanced favorable synoptic-scale forcing for ascent from the upstream and downstream jet streaks and played a crucial role in the deepening of Edisoana through the ET and RI periods.

scholarly journals Large-Scale Conditions for Reintensification after the Extratropical Transition of Tropical Cyclones in the Western North Pacific Ocean

2020 ◽  
Vol 33 (23) ◽  
pp. 10039-10053
Author(s):  
Wataru Yanase ◽  
Udai Shimada ◽  
Nao Takamura
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
North Pacific Ocean ◽  
Japan Meteorological Agency ◽  
Horizontal Gradient ◽  
Extratropical Transition ◽  
Planetary Scale ◽  
Upper Level

AbstractTropical cyclones that complete extratropical transition (ETTCs) in the western North Pacific are statistically analyzed to clarify the large-scale conditions for their reintensification. A dataset of ETTCs is grouped into intensifying, dissipating, and neutral classes based on the best track data documented by the Japan Meteorological Agency during the period 1979–2018. Intensifying ETTCs are most frequent in September–October, whereas dissipating ETTCs are most frequent in the later season, October–November. Intensifying ETTCs occur at higher latitudes than dissipating ETTCs, where the upper levels are characterized by high potential vorticity (PV) and a steep horizontal gradient of PV. The composite analysis demonstrates that intensifying ETTCs are associated with deep upper-level troughs to their northwest, intense ridge building to their northeast, and strong updrafts to their north associated with vorticity advection and warm-air advection. These results statistically support the findings of previous studies. Furthermore, an analysis using a time filter demonstrates the relationship between planetary-scale environments and synoptic-scale dynamics in the upper levels. The high PV to the northwest of ETTCs is attributed not only to eastward-moving troughs, but also to the environmental PV. The low PV to the northeast of ETTCs results from the negative PV formation associated with ridge building, which almost cancels the environmental PV. Thus, the environmental PV at relatively high latitudes enhances the intensity of positive PV to the northwest of ETTCs, and increases the upper limit of the magnitude of ridge building to the northeast.

FUNCTIONAL STATUS AND ADAPTIVE POTENTIAL IN FOREIGN STUDENTS WITH DIFFERENT TYPES OF VEGETATIVE REGULATION DURING TUITION

2020 ◽  
pp. 118-126
Author(s):  
A.M. Satarkulova
Keyword(s):  
Heart Rate ◽  
Foreign Students ◽  
Autonomic Regulation ◽  
The Body ◽  
Functional Changes ◽  
Different Types ◽  
Type 3 ◽  
Adaptive Abilities

The assessment and dynamic control over students’ status is a very important task. It allows timely detection of prenosological status prior to pathology and health maintenance in students. The objective of the paper is to assess the adaptive abilities of the body, to analyze changes in heart rate variability indicators in students with various types of autonomic regulation, to identify prenosological status and precursory pathological symptoms. Materials and Methods. The study enrolled 302 students from India, aged 21.54±1.43. Programming complex «Psychophysiologist» was used to register the main HRV parameters within 5 minutes. Health status was evaluated according to the index of functional changes and the scale of functional states. Results. N.I. Shlyk (2009) distinguished two groups of students with different types of autonomic regulation: type 1 (53 %) with moderate and type 2 (5 %) with marked characteristics of central regulation profile, type 3 (35 %) with moderate and type 4 (7 %) with marked characteristics of autonomous regulation profile. Main parameters of HRV and adaptation potential were defined for each student.All the parameters characterized functional and health status. Conclusions. It was shown that 82 % of trial subjects (type 1), 53 % (type 2), 94 % (type 3) and 95 % (type 4) demonstrated satisfactory adaptation and their physiological processes were at an optimal level. 18 % of students (type 1) demonstrated reduced adaptive abilities of the body. Moreover, they were under moderate stress. 47 % of subjects (type 2) were also under a significant stress, which was proven by excessively high SI, low SDNN and TP, and an increased index of functional changes. 5 % of students (type 4) revealed dysfunctional characteristics in the heart rhythm, peculiar to pathology. Keywords: foreign students, heart rate variability, types of autonomic regulation, adaptation potential, functional status. Оценка состояния студентов и динамический контроль за ним является важной задачей, поскольку позволяет своевременно выявлять у студентов донозологические состояния, предшествующие патологии, и способствовать сохранению здоровья. Цель. Оценка адаптивных возможностей организма, анализ изменений показателей вариабельности сердечного ритма у студентов с различными типами вегетативной регуляции, выявление донозологических состояний и ранних признаков патологии. Материалы и методы. В исследовании участвовало 302 студента в возрасте 21,54+1,43 года из Индии. Регистрировались основные параметры ВСР в течение 5 мин с использованием программно-аппаратного комплекса «Психофизиолог». Состояние и уровень здоровья оценивались по индексу функциональных изменений и шкале функциональных состояний. Результаты. По способу, предложенному Н.И. Шлык, выделены группы студентов с различными типами вегетативной регуляции: I (53 %) и II типы (5 %) – с умеренным и выраженным преобладанием центрального контура регуляции соответственно, III (35 %) и IV типы (7 %) – с умеренным и выраженным преобладанием автономного контура регуляции соответственно. У каждого из студентов определены основные параметры ВСР и адаптационного потенциала, характеризующие функциональное состояние и уровень здоровья. Выводы. Показано, что для 82 % обследуемых с I типом, 53 % со II типом, 94 % c III типом и 95 % с IV типом регуляции характерно состояние удовлетворительной адаптации, физиологические процессы сохраняются на оптимальном уровне. В группе студентов I типа у 18 % студентов адаптивные возможности организма снижены, выявлено состояние умеренного напряжения. У 47 % обследуемых II типа также зафиксировано состояние резко выраженного напряжения, индикатором которого является чрезмерно высокое значение SI, низкие величины SDNN и ТP, повышенное значение индекса функциональных изменений. В группе студентов с IV типом у 5 % учащихсяв регуляции ритма сердца выявлены дисфункциональные признаки, характерные для патологии. Ключевые слова: иностранные студенты, вариабельность сердечного ритма, типы вегетативной регуляции, адаптационный потенциал, функциональное состояние.

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