DOCSLIB.ORG

The Separate Roles of Geostrophic Vorticity and Deformation in the Midlatitude Occlusion Process

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Separate Roles of Geostrophic Vorticity and Deformation in the Midlatitude Occlusion Process 2404 MONTHLY WEATHER REVIEW VOLUME 127 The Separate Roles of Geostrophic Vorticity and Deformation in the Midlatitude Occlusion Process JONATHAN E. MARTIN Department of Atmospheric and Oceanic Sciences, University of WisconsinÐMadison, Madison, Wisconsin (Manuscript received 19 June 1998, in ®nal form 30 October 1998) ABSTRACT Separate vector expressions for the rate of change of direction of the potential temperature gradient vector resulting from the geostrophic vorticity and geostrophic deformation, referred to as QVR and QDR, respectively, are derived. The evolution of the thermal structure and forcing for quasigeostrophic vertical motion in an occluded cyclone are investigated by examining the distributions of QVR and QDR and their respective convergences. The dynamics of two common structural transformations observed in the evolution of occluded cyclones are revealed by consideration of these separate forcings. First, the tendency for the sea level pressure minimum to deepen northward and/or westward into the cold air west of the triple point is shown to be controlled by the convergence of QVR, which is mathematically equivalent to thermal wind advection of geostrophic vorticity, a well-accepted mechanism for forcing of synoptic-scale vertical motion. Second, the lengthening of the occluded thermal ridge and surface occluded front are forced by the nonfrontogenetic geostrophic deformation, which rotates the cold frontal zone cyclonically while it rotates the warm frontal zone anticyclonically. The net result is a squeezing together of the two frontal zones along the thermal ridge and a lengthening of the occluded thermal ridge. The associated convergence of QDR along the axis of the the thermal ridge also forces vertical motion on a frontal scale. This vertical motion accounts for the clouds and precipitation often observed to extend from the triple point westward to the sea level pressure minimum in the northwest quadrant of occluding cyclones. 1. Introduction expressions involved the along- and across-isentrope Extratropical cyclones are often accompanied by components of the Q-vector (Hoskins et al. 1978) and frontal baroclinic zones, usually a cold front and a warm so could be directly related to forcings for vertical mo- front. The thermal evolution of these cyclones repre- tion through the Q±G omega equation. sents a central component of their overall structural evo- In a recent study of the dynamics of occluded cy- lution. This thermal evolution involves changes in the clones, Martin (1999) employed a similar partitioning vigor of the individual frontal zones and in their ori- of the Q-vector into its along- and across-isentrope com- entation with respect to one anotherÐboth of which ponents (Qs and Qn, respectively). He showed that the occur throughout the cyclone life cycle. The dynamical predominant forcing for upward vertical motions in the processes that control these two components of the ther- occluded sector of midlatitude cyclones was associated mal evolution of cyclones are also responsible for pro- with convergence of Qs. It was further shown that the ducing secondary circulations to which the character- differential rotation of =u implied by the convergent istic cloud and precipitation distribution in cyclones can ®eld of Qs was responsible for the production of the be accurately ascribed. characteristic occluded thermal ridge. Recent work by Keyser et al. (1988) and Keyser et In that study it was noted that Qs was the sum of al. (1992), hereafter referred to as K88 and K92, has contributions from both the geostrophic vorticity and examined the Lagrangian tendency of the potential tem- deformation (a point ®rst made by K88). These two perature gradient vector. K88 derived expressions for forcings were not, however, investigated separately. In the rates of change of both the magnitude and direction this paper, we extend our investigation of the rotational (i.e., Q ) component of Q by partitioning it into separate of =u and called them Fn and Fs, respectively. K92 s demonstrated that the corresponding quasigeostrophic vector expressions representing the rates of change of direction of =u produced by the geostrophic vorticity and deformation, respectively. The results of this anal- ysis shed new light on the Q±G dynamics of the occlu- Corresponding author address: Dr. Jonathan E. Martin, Depart- ment of Atmospheric and Oceanic Sciences, University of Wiscon- sion process by suggesting different, but complemen- sinÐMadison, 1225 W. Dayton St., Madison, WI 53706. tary, roles are played by the geostrophic vorticity and E-mail: [email protected] deformation in forcing the thermal evolution, and cloud q 1999 American Meteorological Society OCTOBER 1999 MARTIN 2405 and precipitation distribution, of the postmature phase ]]2 V midlatitude cyclone. s¹122f v 2 f g ´ =z (2a) oog2 ø The analysis begins with a brief review of the various 12]p ]p forms of the Q±G omega equation in section 2. We then on an f-plane except in frontal±jet streak regions where offer a derivation of the separate vorticity and defor- the neglected deformation term [term B in (2)] is usually mation contributions to Qs (the rotational component of large (Wiin-Nielsen 1959). In his examination of the the Q±G vector frontogenesis function) in section 3. importance of the deformation term throughout the life Examples of the separation of these two rotational com- cycle of a typical midlatitude cyclone, Martin (1998a) ponents in the three cyclones investigated by Martin has recently offered the more general statement that the (1999) will also be given there. The evolution of these deformation term is large in regions where ®rst-order separate forcings throughout the life cycle of one of discontinuities in temperature are coincident with re- these occluding cyclones will be given in section 4. A gions of nonzero ®rst derivatives in the geostrophic wind discussion of the occlusion process in light of this anal- ®eld. Such regions are not constrained to be frontal in ysis as well as the development of a dynamic conceptual nature; in fact, he showed that the thermal ridge com- model of the occlusion process are given in section 5. monly associated with the occluded quadrant of cy- Finally, in section 6 conclusions are offered along with clones is an example of a nonfrontal region in which suggested future directions. the deformation term is large in the midtroposphere. An alternative version of the Q±G omega equation on an f-plane was given by Hoskins et al. (1978) as 2. The quasigeostrophic omega equation ]2 The traditional form of the Q±G omega equation is 22 s¹1f o v 522= ´ Q, (3) given by (Holton 1992) 12]p2 where Q is given by ]2 s¹122f v o ]p2 ]V ]V 12 Q 5 f g 2 gg´ =u i,à 2 ´ =u jˆ o []1212]x ]y ]]f 2 5 f [V ´ =(z 1 f )] 2¹ V ´ = , (1) c /c og g g with g 5 (R/fP )(P /P) y p . Thus, the divergence of the ]p []12]p oo Q vector describes the complete forcing for the Q±G 2 2 2 2 2 2 where ¹ 5] /]x 1] /]y , zg 5 (1/ f o)¹ f, and ]f/]p omega equation. Another important physical meaning 52RT/p. It is tempting to consider the two terms on of the Q vector is that it represents the rate of change the rhs of (1) as representations of separate physical of =u following the geostrophic ¯ow [i.e., Q 5 processes; however, a convincing argument against such f og(d/dtg)=u, where d/dtg 5]/]t 1 Ug ]/]x 1 Vg ]/]y]. a practice was made by Trenberth (1978) and Hoskins As such, Q describes changes in the magnitude of =u et al. (1978). Upon carrying out the derivatives on the as well as changes in the direction of =u. For this reason, rhs of (1), Trenberth (1978) found that some cancellation Q represents the Q±G analog of the vector frontogenesis existed between the two terms. By neglecting the so- function, F, introduced by K88. called ``deformation term'' (Wiin-Nielsen 1959) he con- Following a suggestion made by K88, K92 partitioned cluded that the rhs of (1) could be approximated by the Q vector into along- and across-isentrope compo- considering the advection of geostrophic absolute vor- nents and investigated the vertical motion forcings de- ticity by the column thermal wind, a result similar to scribed by each component in an idealized model sim- that produced by Sutcliffe (1947). The Trenberth (1978) ulation. Barnes and Colman (1993) and Kurz (1997) expression of (1) is given by offer recent examples of this partitioning in observed cases. We adopt a natural coordinate system in which ]2 nà is directed along =u and sà is 908 counterclockwise s¹122f v o 2 from nà (slightly different from that used by K88 and 12]p K92). In such a coordinate system the across- and along- isentrope components of Q (Q and Q , respectively) ]Vg n s 5 2 f og´ =(z 1 f ) are given by ]p A Q ´ =u =u Q 55Q nà (4a) nn|=u||=u| ]Vgggg]U ]V ]V [] 1 2 f ´ = 2 ´ = , (2) o []]y 12]p ]x 12]p and B Q ´(kˆ 3 =u)(kˆ 3 =u) Q 55Q sÃ. (4b) which is approximately equal to ss|=u||[]=u| 2406 MONTHLY WEATHER REVIEW VOLUME 127 K92 found that bands of Q forcing distributed parallel half of the approximate Trenberth forcing for Q±G ver- to the baroclinic zones within their idealized cyclone tical motion (2a). Martin (1999) noted that this fact (physically reminiscent of frontal circulations) were en- accounts for the considerable similarity in distribution tirely accounted for by convergence of the across-is- that generally exists between regions of Trenberth forc- entrope component, Qn.
Load more

Recommended publications
  • The Social Life of Climate Change Models Routledge Studies in Anthropology
    The Social Life of Climate Change Models Routledge Studies in Anthropology 1 Student Mobility and Narrative 8 The Social Life of Climate in Europe Change Models The New Strangers Anticipating Nature Elizabeth Murphy-Lejeune Edited by Kirsten Hastrup and Martin Skrydstrup 2 The Question of the Gift Essays across Disciplines Edited by Mark Osteen 3 Decolonising Indigenous Rights Edited by Adolfo de Oliveira 4 Traveling Spirits Migrants, Markets and Mobilities Edited by Gertrud Hüwelmeier and Kristine Krause 5 Anthropologists, Indigenous Scholars and the Research Endeavour Seeking Bridges Towards Mutual Respect Edited by Joy Hendry and Laara Fitznor 6 Confronting Capital Critique and Engagement in Anthropology Edited by Pauline Gardiner Barber, Belinda Leach and Winnie Lem 7 Adolescent Identity Evolutionary, Cultural and Developmental Perspectives Edited by Bonnie L. Hewlett The Social Life of Climate Change Models Anticipating Nature Edited by Kirsten Hastrup and Martin Skrydstrup NEW YORK LONDON First published 2013 by Routledge 711 Third Avenue, New York, NY 10017 Simultaneously published in the UK by Routledge 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN Routledge is an imprint of the Taylor & Francis Group, an informa business © 2013 Taylor & Francis The right of Kirsten Hastrup and Martin Skrydstrup to be identified as the authors of the editorial material, and of the authors for their individual chapters, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers.
    [Show full text]
  • MASARYK UNIVERSITY BRNO Diploma Thesis
    MASARYK UNIVERSITY BRNO FACULTY OF EDUCATION Diploma thesis Brno 2018 Supervisor: Author: doc. Mgr. Martin Adam, Ph.D. Bc. Lukáš Opavský MASARYK UNIVERSITY BRNO FACULTY OF EDUCATION DEPARTMENT OF ENGLISH LANGUAGE AND LITERATURE Presentation Sentences in Wikipedia: FSP Analysis Diploma thesis Brno 2018 Supervisor: Author: doc. Mgr. Martin Adam, Ph.D. Bc. Lukáš Opavský Declaration I declare that I have worked on this thesis independently, using only the primary and secondary sources listed in the bibliography. I agree with the placing of this thesis in the library of the Faculty of Education at the Masaryk University and with the access for academic purposes. Brno, 30th March 2018 …………………………………………. Bc. Lukáš Opavský Acknowledgements I would like to thank my supervisor, doc. Mgr. Martin Adam, Ph.D. for his kind help and constant guidance throughout my work. Bc. Lukáš Opavský OPAVSKÝ, Lukáš. Presentation Sentences in Wikipedia: FSP Analysis; Diploma Thesis. Brno: Masaryk University, Faculty of Education, English Language and Literature Department, 2018. XX p. Supervisor: doc. Mgr. Martin Adam, Ph.D. Annotation The purpose of this thesis is an analysis of a corpus comprising of opening sentences of articles collected from the online encyclopaedia Wikipedia. Four different quality categories from Wikipedia were chosen, from the total amount of eight, to ensure gathering of a representative sample, for each category there are fifty sentences, the total amount of the sentences altogether is, therefore, two hundred. The sentences will be analysed according to the Firabsian theory of functional sentence perspective in order to discriminate differences both between the quality categories and also within the categories.
    [Show full text]
  • Moderating the Impact of Climate Change
    Cities, Seas, and Storms Managing Change in Pacific Island Public Disclosure Authorized Economies Public Disclosure Authorized Public Disclosure Authorized Volume IV Adapting to Climate Change November 30, 2000 PAPUA NEW GUINEA AND PACIFIC ISLANDS COUNTRY UNIT • THE WORLD BANK in collaboration with Public Disclosure Authorized Environment and Conservation Division ·I·G·C·I· SPREP Kiribati PICCAP Copyright © 2000 The International Bank for Reconstruction And Development/ THE WORLD BANK 1818 H Street, N.W. Washington, D.C. 20433, U.S.A. All rights reserved Manufactured in the United States of America First printing November 13, 2000 Second printing November 30, 2000 World Bank Country Study Reports are among the many reports originally prepared for internal use as part of the continuing analysis by the Bank of the economic and related conditions of its developing member countries and of its dialogues with the governments. Some of the reports are published in this series with the least possible delay of the use of the governments and the academic, business and financial, and development communities. The typescript of this paper therefore has not been prepared in accordance with the procedures appropriate to formal printed texts, and the World Bank accepts no responsibility for errors. Some sources cited in this paper may be informal documents that are not readily available. The World Bank does not guarantee the accuracy of the data included in this publication and accepts no responsibility whatsoever for any consequence of their use. The boundaries, colors, denominations, and other information shown on any map in this volume do not imply on the part of the World Bank Group any judgment on the legal status of any territory or the endorsement or acceptance of such boundaries.
    [Show full text]
  • Manuscript with All Authors Reviewing and Contributing in Various Proportion to Sections
    A dynamic and thermodynamic analysis of the 11 December 2017 tornadic supercell in the Highveld of South Africa Lesetja E. Lekoloane1,2, Mary-Jane M. Bopape1, Gift Rambuwani1, Thando Ndarana3, Stephanie Landman1, Puseletso Mofokeng1,4, Morne Gijben1, and Ngwako Mohale1 1South African Weather Service, Pretoria, 0001, South Africa 2Global Change Institute, University of the Witwatersrand, Johannesburg, 2050, South Africa 3Department of Geography, Geoinformatics and Meteorology, University of Pretoria, Pretoria, 0001, South Africa 4School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, 2050, South Africa Correspondence: Lesetja Lekoloane ([email protected]) Abstract. On 11 December 2017, a tornadic supercell initiated and moved through the northern Highveld region of South Africa for 7 hours. A tornado from this supercell led to extensive damage to infrastructure and caused injury to and displacement of over 1000 people in Vaal Marina, a town located in the extreme south of the Gauteng Province. In this study we conducted an analysis in order to understand the conditions that led to the severity of this supercell, including the formation 5 of a tornado. The dynamics and thermodynamics of two configurations of the Unified Model (UM) were also analysed to assess their performance in predicting this tornadic supercell. It was found that this supercell initiated as part of a cluster of multicellular thunderstorms over a dryline, with three ingredients being important in strengthening and maintaining it for 7 hours: significant surface to mid-level vertical shear, an abundance of low-level warm moisture influx from the tropics and Mozambique Channel, and the relatively dry mid-levels (which enhanced convective instability).
    [Show full text]
  • Plantation Forests, Climate Change and Biodiversity
    Biodivers Conserv (2013) 22:1203–1227 DOI 10.1007/s10531-013-0458-8 ORIGINAL PAPER Plantation forests, climate change and biodiversity S. M. Pawson • A. Brin • E. G. Brockerhoff • D. Lamb • T. W. Payn • A. Paquette • J. A. Parrotta Received: 9 November 2011 / Accepted: 15 February 2013 / Published online: 13 March 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Nearly 4 % of the world’s forests are plantations, established to provide a variety of ecosystem services, principally timber and other wood products. In addition to such services, plantation forests provide direct and indirect benefits to biodiversity via the provision of forest habitat for a wide range of species, and by reducing negative impacts on natural forests by offsetting the need to extract resources. There is compelling evidence that climate change is directly affecting biodiversity in forests throughout the world. These impacts occur as a result of changes in temperature, rainfall, storm frequency and mag- nitude, fire frequency, and the frequency and magnitude of pest and disease outbreaks. However, in plantation forests it is not only the direct effects of climate change that will impact on biodiversity. Climate change will have strong indirect effects on biodiversity in plantation forests via changes in forest management actions that have been proposed to mitigate the effects of climate change on the productive capacity of plantations. These include changes in species selection (including use of species mixtures), rotation length, thinning, pruning, extraction of bioenergy feedstocks, and large scale climate change S. M. Pawson (&) Á E. G. Brockerhoff Scion (New Zealand Forest Research Institute), Forestry Rd, Ilam, P.O.
    [Show full text]
  • Again, the Air Mass Thunderstorm Is the “Garden Variety” One… to Get More the More Organized, Longer Lived Severe Thunders
    Again, the air mass thunderstorm is the “garden variety” one… To get more the more organized, longer lived severe thunderstorms, we need a combination of more ingredients Ingredients for severe thunderstorms INGREDIENT 1: CONDITIONAL INSTABILITY Needs to be through the depth of the troposphere Make the atmosphere more conditionally unstable by: Warming and moistening near the surface Cooling and drying aloft INGREDIENT 2: WIND SHEAR Change in horizontal wind speed through a vertical depth. If the wind speed changes direction as well that’s even better! Why is wind shear a necessary ingredient for severe thunderstorms? CUMULUS STAGE MATURE STAGE Updraft only Updraft + downdraft NO WIND SHEAR MOST WITH FAVORABLE WIND FOR GROWTH SHEAR (Bluestein) Wind shear allows the updraft to be maintained in the cloud and not get choked off by the downdraft—so the thunderstorm keeps receiving the warm, moist air it needs to keep growing. Where to look for severe thunderstorms (in central and eastern U.S.) In the vicinity of a mid-latitude cyclone Strong upper level winds from the north and west Surface winds from the south to southeast (a low-level jet) Fronts, particularly in front of and at a cold front in the warm sector Drylines: transition zone between dry cT air and moist mT air Very common in the southern Great Plains. THESE CAN ENHANCE: 1. THE VERTICAL WIND SHEAR 2. CONDITIONAL INSTABILITY (i.e. CAPE) More Organized Severe Thunderstorm Types In approximate order of severity Multicell thunderstorms Less severe Squall lines Mesoscale Convective Complexes Supercells Most severe Multicell Thunderstorms In moderate shear, thunderstorms can get a bit more organized, numerous and have longer lifetimes.
    [Show full text]
  • Stakeholder Involvement in Value Co-Destruction: a Case Of
    ASSOCIATION FOR CONSUMER RESEARCH Labovitz School of Business & Economics, University of Minnesota Duluth, 11 E. Superior Street, Suite 210, Duluth, MN 55802 Stakeholder Involvement in Value Co-Destruction: a Case of Promoting Condoms in India Samanthika Gallage, Nottingham University Business School Sameer Deshpande, Griffith University This paper explores the reasons for low condom usage in India by elucidating the stakeholder involvement in the value creation and delivery process. Data was collected from non-profit organisations in India and findings suggested that value co-destruction resulted from cultural incongruencies amplified by stakeholders [to cite]: Samanthika Gallage and Sameer Deshpande (2020) ,"Stakeholder Involvement in Value Co-Destruction: a Case of Promoting Condoms in India", in NA - Advances in Consumer Research Volume 48, eds. Jennifer Argo, Tina M. Lowrey, and Hope Jensen Schau, Duluth, MN : Association for Consumer Research, Pages: 758-757. [url]: http://www.acrwebsite.org/volumes/2661294/volumes/v48/NA-48 [copyright notice]: This work is copyrighted by The Association for Consumer Research. For permission to copy or use this work in whole or in part, please contact the Copyright Clearance Center at http://www.copyright.com/. Sociomaterial Performativity of the Surveillant Assemblage on Healthcare Platforms Handan Vicdan, Emlyon Business School, France EXTENDED ABSTRACT technologies (Orlikowski and Scott, 2008; Kjellberg and Helgesson, This conceptual paper proposes a sociomaterial lens for under- 2006) that enact performances (Barad, 2003) at micro/meso/macro standing how surveillance functions and produces outcomes in plat- levels, and how these outcomes reshape existing practices and trans- form organizations, and draws attention to this performative process form power dynamics among market actors (Cecez-Kecmanovic et of knowledge generation in healthcare.
    [Show full text]
  • 1 9.1 High-Shear, Low-CAPE Environments
    9.1 High-shear, low-CAPE environments: What we know and where to go next Keith D. Sherburn* and Matthew D. Parker Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 1. Introduction al. 2008), as shown in Figure 1. Additionally, moisture is * abundant in the low-levels and often throughout much of As noted by numerous operational case studies the troposphere, contributing to low LCLs. Though (e.g., Cope 2004; Lane and Moore 2006; Clark 2009), instability is limited, it is often (but not necessarily) environments associated with low instability and strong focused in the low levels, leading to enhanced values of deep-layer wind shear vector magnitudes [high-shear, 0-3 km CAPE (e.g., Lane 2008). In addition to strong low-CAPE (HSLC) environments] pose a unique deep-layer shear vector magnitude, low-level winds and challenge to forecasters due to their compact spatial shear are intense, with low-level jets (LLJs) commonly dimensions (e.g., McCaul 1987; Davies 1990; Kennedy reaching 25-30 m s-1 (e.g., Lane and Moore 2006). et al. 1993; Davis and Parker 2014), rapid intensification Lightning can be limited or nonexistent in these of rotation (e.g., Cope 2004), relatively low ratio environments, owing to the lack of instability within the between severe weather reports and environmental clouds’ mixed-phase region (van den Broeke et al. hours (e.g., Dean et al,. 2009), and prevalence during 2005). the cool season and overnight (Sherburn and Parker 2014a). However, literature on severe HSLC b. Radar presentation and signatures environments remains sparse, leading to numerous gaps in the knowledge base, particularly related to the The most common convective modes in HSLC dynamics and predictability of severe HSLC convection.
    [Show full text]
  • Proposed Loan and Technical Assistance Grant Cyclone
    Report and Recommendation of the President RRP: COO 39118 Report and Recommendation of the President to the Board of Directors on a Proposed Loan and Technical Assistance Grant to the Cook Islands for the Cyclone Emergency Assistance Project June 2005 CURRENCY EQUIVALENTS (as of 14 April 2005) Currency Unit – New Zealand dollar (NZ$) NZ$1.00 = US$0.726 $1.00 = NZ$1.376 ABBREVIATIONS ADB – Asian Development Bank AusAID – Australian Agency for International Development CIIC – Cook Islands Investment Corporation CIMS – Cook Islands Meteorological Services GDP – gross domestic product IEE – initial environmental examination km2 – square kilometer kph – kilometers per hour MFEM – Ministry of Finance and Economic Management NZAid – New Zealand Aid PMU – project management unit PSC – project steering committee TA – technical assistance US – United States GLOSSARY Tropical cyclones, typhoons, or hurricanes are names given to the same phenomenon in different parts of the world. They are weather systems with strong winds that circulate anticlockwise around low-pressure areas in the northern hemisphere and clockwise in the southern hemisphere. They are capable of causing massive destruction in three ways: by high winds, heavy rainfall causing inland flooding; and storm-surge flooding. Tropical cyclones form near the equator near the open sea where the surface temperature is at least 26° Celsius. They may last with destructive power for 2 weeks or more. The warm sea provides the overlying atmosphere with a continuous supply of energy and moisture, first to generate a tropical cyclone and then to maintain its destructive violence as it moves forward. The diameter of a tropical storm, called the eye, may have a diameter ranging from 20–150 kilometers (km) The source of energy is cut off when the storm crosses a coastline and moves inland, thus reducing its destructive power.
    [Show full text]
  • Characteristics of Extratropical Cyclones That Cause Tornadoes in Italy: a Preliminary Study
    atmosphere Article Characteristics of Extratropical Cyclones That Cause Tornadoes in Italy: A Preliminary Study Eigo Tochimoto 1 , Mario Marcello Miglietta 2,* , Leonardo Bagaglini 3 , Roberto Ingrosso 4 and Hiroshi Niino 5 1 National Research Institute for Earth Science and Disaster Resilience, 3-1, Tennodai, Tsukuba 305-0006, Ibaraki, Japan; [email protected] 2 National Research Council of Italy—Institute of Atmospheric Sciences and Climate (CNR-ISAC), 35127 Padua, Italy 3 National Research Council of Italy—Institute of Atmospheric Sciences and Climate (CNR-ISAC), 00133 Rome, Italy; [email protected] 4 Department of Earth and Atmospheric Sciences, University of Quebec in Montreal, Montreal, QC H3C 3P8, Canada; [email protected] 5 Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan; [email protected] * Correspondence: [email protected] Abstract: Characteristics of extratropical cyclones that cause tornadoes in Italy are investigated. Tornadoes between 2007 and 2016 are analyzed, and statistical analysis of the associated cyclone structures and environments is performed using the JRA-55 reanalysis. Tornadoes are distributed sporadically around the cyclone location within a window of 10◦ × 10◦. The difference in the cyclone tracks partially explains the seasonal variability in the distribution of tornadoes. The highest number of tornadoes occur south of the cyclone centers, mainly in the warm sector, while a few are observed Citation: Tochimoto, E.; Miglietta, along the cold front. Composite mesoscale parameters are examined to identify the environmental M.M.; Bagaglini, L.; Ingrosso, R.; conditions associated with tornadoes in different seasons.
    [Show full text]
  • Updating Knowledge of Cyclonic Wave Hazard for Tahiti and Moorea Islands
    Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Open Access Nat. Hazards Earth Syst. Sci. Discuss., 2, 725–756, 2014 Natural Hazards www.nat-hazards-earth-syst-sci-discuss.net/2/725/2014/ and Earth System doi:10.5194/nhessd-2-725-2014 NHESSD © Author(s) 2014. CC Attribution 3.0 License. Sciences Discussions 2, 725–756, 2014 This discussion paper is/has been under review for the journal Natural Hazards and Earth Updating knowledge System Sciences (NHESS). Please refer to the corresponding final paper in NHESS if available. of cyclonic wave hazard for Tahiti and Updating knowledge of cyclonic wave Moorea Islands hazard for Tahiti and Moorea Islands S. Lecacheux et al. (French Polynesia) through a probabilistic Title Page approach Abstract Introduction S. Lecacheux, T. Bulteau, and R. Pedreros Conclusions References BRGM, 3 Avenue Claude Guillemin Cedex 2, BP 6009, 45060 Orléans, France Tables Figures Received: 18 December 2013 – Accepted: 8 January 2014 – Published: 23 January 2014 J I Correspondence to: S. Lecacheux ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. J I Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion 725 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract NHESSD This paper intends to reevaluate cyclonic wave scenarios used for hazard studies for two French Polynesian Islands (Tahiti and Moorea) with a combination of expertise and 2, 725–756, 2014 probabilistic analysis. The method
    [Show full text]
  • Supercell Thunderstorm
    Thunderstorm Basics Section 2 Features Indicating Strong/Severe Storms Anvil: The anvil is the elongated cloud at the top of the storm that spreads downwind with upper level steering winds. The anvil will appear solid, not wispy, and will have sharp, well defined edges. Overshooting Top: The overshooting top is the dome of cloud directly above the main storm updraft tower and the anvil. If the overshooting top is persistent and lasts for 10 minutes or longer, it is generally a sign of a very strong thunderstorm updraft. Shown is a severe thunderstorm in the distance with a visible thick anvil and large overshooting top. Photo by Gene Rhoden. Main Storm Tower: The “trunk” of the storm is the visible updraft of the storm from its base near the ground to just below the anvil. This part of the storm can show: Vertically oriented tower, with sharp, well defined edges Solid, cauliflower appearance Visible rotation of the middle and lower levels, and possibly striations evident in the clouds Rain-free Base: The area below the main storm tower. It is generally on the south or southwestern flank of a storm. 19 Spotter’s Field Guide SEVERE LOCAL STORMS Wall Cloud: A wall cloud is an isolated lower cloud attached to the rain- free base and below the main storm tower. Wall clouds often are on the trailing side of a storm. For example, with a storm that is moving to the north or northeast, the wall cloud typically is on the south or southwest side of the storm. With some storms, the wall cloud area may be obscured by precipitation.
    [Show full text]