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A Cluster Analysis of Tropical Cyclone A CLUSTER ANALYSIS OF TROPICAL CYCLONE TRAJECTORIES IN THE SOUTH INDIAN OCEAN: THE INFLUENCES OF THE EL NINO-SOUTHERN OSCILLATION AND THE SUBTROPICAL INDIAN OCEAN DIPOLE By KEVIN D. ASH A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010 1 © 2010 Kevin D. Ash 2 To the Captain of the cargo vessel in the Indian Ocean who did not listen to my advice and motivated me to learn more. 3 ACKNOWLEDGMENTS I would like to first extend thanks to my parents and my brother for their love and support. I am also grateful to Ann Foster and the United States Geological Survey for employing me during my first year in Gainesville and affording me the opportunity to earn a decent paycheck while in graduate school. I am appreciative as well to the Department of Geography for funding and the opportunity to work as a Teaching Assistant during my second year. I am grateful to the Poehling family and all who graciously supported the establishment of a new fellowship this year in memory of their son, Ryan. Many thanks as well to my thesis committee members Peter Waylen and Tim Fik for their valuable advice. Finally, thank you to my committee chair and advisor Corene Matyas for her dedication and wisdom in challenging and guiding me during the last two years. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 8 LIST OF ABBREVIATIONS ........................................................................................... 10 ABSTRACT ................................................................................................................... 11 CHAPTER 1 INTRODUCTION .................................................................................................... 13 2 LITERATURE REVIEW .......................................................................................... 21 Tropical Cyclones of the South Indian Ocean ......................................................... 21 Introduction ....................................................................................................... 21 Brief History and Early Research ..................................................................... 21 Basic Tropical Cyclone Climatology ................................................................. 23 A Climatologically Favorable Environment ....................................................... 24 El Niño-Southern Oscillation ................................................................................... 27 Introduction ....................................................................................................... 27 ENSO Influences in the South Indian Ocean .................................................... 28 Tropical Cyclones and El Niño-Southern Oscillation ............................................... 31 Subtropical Indian Ocean Dipole ............................................................................ 35 Tropical-Temperate Troughs .................................................................................. 37 Conclusion .............................................................................................................. 39 3 A CLUSTER ANALYSIS OF SOUTH INDIAN OCEAN TROPICAL CYCLONE TRAJECTORIES .................................................................................................... 49 Introduction ............................................................................................................. 49 Tropical Cyclone Data and Study Area Definition ................................................... 50 Cluster Analysis in Tropical Cyclone Research ...................................................... 52 The Clustering Procedure ....................................................................................... 54 Discussion .............................................................................................................. 58 Eastern Formation Region: C1 and C6 ............................................................ 58 Central Formation Region: C2 and C7 ............................................................. 59 Western Formation Region: C3 and C4 ........................................................... 59 Far West/Mozambique Channel: C5 ................................................................ 60 Conclusion .............................................................................................................. 60 5 4 THE INFLUENCES OF EL NINO-SOUTHERN OSCILLATION AND THE SUBTROPICAL INDIAN OCEAN DIPOLE .............................................................. 71 Introduction ............................................................................................................. 71 Data and Methods .................................................................................................. 75 Results .................................................................................................................... 78 Kruskal-Wallis ANOVA Results ........................................................................ 78 Multiple Comparisons and SST Anomaly Composites ..................................... 78 Discussion .............................................................................................................. 85 Conclusion .............................................................................................................. 89 5 CONCLUSIONS ................................................................................................... 108 APPENDIX TROPICAL CYCLONES ANALYZED IN THE PRESENT STUDY .............................. 113 LIST OF REFERENCES ............................................................................................. 119 BIOGRAPHICAL SKETCH .......................................................................................... 131 6 LIST OF TABLES Table page 1-1 Tropical cyclone close passes in the South Indian Ocean. ................................. 20 3-1 Seven main clusters of SIO TCs. ........................................................................ 62 3-2 Frequency of TC genesis by month for C1-C7. .................................................. 62 4-1 P-values for KW ANOVA and Modified-Levene Equal-Variance Tests. .............. 92 4-2 Standardized median anomalies for N3.4, N1.2, N4, and SDI. ........................... 92 4-3 Multiple comparison tests for Niño-3.4 stratified by clusters.. ............................. 92 4-4 Multiple comparison tests for Niño-1.2 stratified by clusters. .............................. 93 4-5 Multiple comparison tests for Niño-4 stratified by clusters. ................................. 93 4-6 Multiple comparison tests for SDI stratified by clusters.. .................................... 93 4-7 Tropical cyclones by cluster and combined ENSO/SDI phases.......................... 94 7 LIST OF FIGURES Figure page 1-1 South Indian Ocean region map.. ....................................................................... 20 2-1 Annual frequencies of South Indian Ocean tropical cyclones. ............................ 41 2-2 Monthly frequencies of South Indian Ocean tropical cyclones. .......................... 42 2-3 South Indian Ocean tropical cyclone trajectories. ............................................... 43 2-4 Indian Ocean Sea Surface Temperatures, averaged from 1979-2008.. ............. 44 2-5 Indian Ocean Outgoing Longwave Radiation, averaged from 1979-2008. ......... 45 2-6 Difference of El Niño and La Niña SST patterns in the SIO. ............................... 46 2-7 Difference of El Niño and La Niña SLP patterns in the SIO. ............................... 47 2-8 Difference of El Niño and La Niña 500 hPa zonal wind patterns in the SIO. ...... 48 3-1 Dendrogram of SIO TCs when clustered by initial longitude. ............................. 63 3-2 Map of five cluster solution of SIO TCs when clustered by initial longitude.. ...... 64 3-3 Dendrogram of central region SIO TCs when clustered by final latitude and longitude. ............................................................................................................ 64 3-4 Dendrogram of western region SIO TCs when clustered by final latitude and longitude. ............................................................................................................ 65 3-5 Dendrogram of eastern region SIO TCs when clustered by final latitude and longitude. ............................................................................................................ 66 3-6 Tropical cyclone trajectories in Cluster 1 (C1) .................................................... 67 3-7 Tropical cyclone trajectories in Cluster 6 (C6) .................................................... 67 3-8 Tropical cyclone trajectories in Cluster 2 (C2). ................................................... 68 3-9 Tropical cyclone trajectories in Cluster 7 (C7). ................................................... 68 3-10 Tropical cyclone trajectories in Cluster 3 (C3) .................................................... 69 3-11 Tropical cyclone trajectories in Cluster 4 (C4) ...................................................
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