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4.7. Predicting Tropical Cyclone Intensification

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4.7. Predicting Tropical Cyclone Intensification The Association of Tall Eyewall Convection with Tropical Cyclone Intensification A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at George Mason University By Owen A. Kelley Master of Science George Mason University, 1997 Bachelor of Arts St. John's College, 1993 Director: Michael Summers, Professor Department of Physics and Astronomy Spring Semester 2008 George Mason University Fairfax, VA Copyright 2008 Owen A. Kelley ii ACKNOWLEDGEMENTS Over the past four years, a number of people have discussed with me the ideas in this dissertation. They include Tom Bell, Natalie Blades, Craig Bohren, Scott Braun, Daniel Cecil, Jeff Halverson, Bart Kelley, Genevieve Demos Kelley, John Kwiatkowski, Chris Landsea, Chuntao Liu, David Marks, Daniel Melendez, Mike McCumber, Bob Meneghini, Bill Olson, Dave Silberstein, Joanne Simpson, Erich Stocker, John Stout, and Ed Zipser. The above mentioned people do not necessarily agree with the conclusions of this dissertation, nor are they responsible for any errors. Section 3.9 contains unpublished research from a collaboration with John Stout. The TRMM Science Data and Information System (TSDIS) provided computational facilities. The dissertation was strengthened by suggestions from my adviser Michael Summers and my dissertation committee, which includes Jim Beall, Jeff Halverson, and Menas Kafatos. Various organizations and individuals provided the data used in this dissertation. NASA/JAXA/NICT provided TRMM data. Many TRMM subsets were downloaded from the JAXA Tropical Cyclone Database. NCDC provided ground radar data. The National Hurricane Center (NHC) and the Joint Typhoon Warning Center (JTWC) provided world-wide best track wind intensity estimates. Scott Braun provided output from his simulation of Hurricane Bonnie (1998). Mark DeMaria provided his database of intensity predictors from the Statistical Hurricane Intensity Prediction Scheme (SHIPS). Klaus Hoinka provided the tropopause climatology. NLDN data provided by Nicholas Demetriades of Vailsala Thunderstorm. GOES data provided by Ray Zehr. NOAA provided radiosonde profiles (http://raob.fsl.noaa.gov). Looking back ten years, several courses at George Mason University and at the University of Maryland prepared me to conduct atmospheric research. Those courses were taught by Michael Summers, John Wallin, Daniel Carr, Cliffon Sutton, Bob Atlas, and Eugenia Kalnay. During the same period, I developed my research skills at the Naval Research Laboratory (NRL). At NRL, my work was directed by Michael Picone, Daniel Melendez, Robert Meier, Ken Dymond, and Bob McCoy. Looking back further, I am grateful to my parents for giving me a sense of curiosity about the world and a full measure of tenacity. iii TABLE OF CONTENTS Page List of tables...................................................................................................................... vii List of figures..................................................................................................................... ix List of abbreviations ......................................................................................................... xii List of symbols...................................................................................................................xv Abstract..............................................................................................................................xx 1. Introduction.....................................................................................................................1 2. Literature review ...........................................................................................................13 2.1. Tall convective cells in tropical cyclone eyewalls ..........................................13 2.1.1. History of tall eyewall cell observations...........................................13 2.1.2. Tall eyewall cells as a mixture of air and water................................17 2.1.3. Discussion of CAPE in tall eyewall cells .........................................19 2.1.4. Updraft speed in tall eyewall cells....................................................21 2.1.5. Surface rain rate of tall eyewall cells................................................22 2.1.6. Other properties of tall eyewall cells ................................................22 2.1.7. Tropical climatological freezing height............................................23 2.1.8. Tropical cyclone wind intensity........................................................24 2.2. The thermodynamic importance of water in the atmosphere ..........................25 2.3. Satellite observations.......................................................................................29 2.3.1. Techniques for observing precipitation ............................................29 2.3.2. Revisit time .......................................................................................36 2.4. Ground-based observations .............................................................................39 2.5. Radar reflectivity.............................................................................................44 2.5.1. Mathematical derivation of radar reflectivity ...................................48 2.5.2. Calculating the precipitation rate from radar reflectivity .................55 2.5.3. Hydrometeor fall speed.....................................................................57 2.6. Future instrumentation ....................................................................................62 2.7. Dynamics of tall convection............................................................................63 2.7.1. Parcel theory of convective updrafts.................................................63 iv 2.7.2. Vertical distribution of temperature and pressure.............................66 2.7.3. Mathematical derivation of vertical CAPE.......................................71 2.7.4. Circulation set up by a tall convective cell .......................................77 2.8. Dynamics of tropical cyclones ........................................................................80 2.8.1. Gradient wind balance ......................................................................81 2.8.2. Dissipative forces..............................................................................82 2.8.3. Eye subsidence..................................................................................83 2.8.4. The eye's thermal anomaly and wind intensity.................................86 2.8.5. Energy conversion ratios...................................................................94 2.8.6. Eyewall vorticity stretching ..............................................................98 2.9. Wave motion ...................................................................................................99 2.9.1. Static stability and inertial stability.................................................101 2.9.2. Gravity waves.................................................................................103 2.9.3. Rossby radius of deformation .........................................................106 2.9.4. Rossby waves..................................................................................111 2.10. Maximum potential intensity of a tropical cyclone.....................................112 2.11. Factors affecting the actual intensity of a tropical cyclone .........................119 3. Correlation examined with satellite observations.......................................................133 3.1. Preparatory calculations ................................................................................134 3.2. Height calculation..........................................................................................139 3.3. Case selection................................................................................................145 3.4. Choosing a radar reflectivity threshold .........................................................148 3.5. Choosing a radar height threshold.................................................................152 3.6. Choosing thresholds for other instruments....................................................156 3.7. Association with current tropical cyclone intensification .............................164 3.8. Predicting future tropical cyclone intensification .........................................171 3.9. Extremely tall cells and tropical cyclones.....................................................176 3.9.1. Locating extremely tall cells...........................................................178 3.9.2. External properties of extremely tall cells ......................................180 3.9.3. Internal properties of extremely tall cells .......................................182 3.9.4. Discussion.......................................................................................190 4. Correlation examined with ground-based observations..............................................194 4.1. Calculating height, area, and eyewall location..............................................197 4.2. The agreement between coincident satellite and ground radar observations ...................................................................................................202 v 4.3. Time-azimuth plots........................................................................................207 4.4. Case study of one tropical cyclone................................................................209
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