Institute of Geography University of Fribourg, Switzerland S@G6UDPITCDQ 7@UX@@I C6DGA6GG DIU@ITDU` 6I9 C6DG 96H6B@ PI BSPVI9 9@U@SHDI@9 7` S696S 6I9 GDBCUIDIB P7T@SW6UDPIT THESIS Presented to the faculty of Science of the University of Fribourg for obtaining the grade of 'RFWRUUHUXPQDWXUDOLXP presented by ROMAN MARCO HOHL born June 14, 1971 citizen of Wolfhalden (AR), Switzerland THESIS No. 1357 ADAG Copy AG, Zurich, Switzerland Zurich, November 2001 Accepted by the faculty of Science of the University of Fribourg, Switzerland on the proposition of the jury: Prof. Dr. M. Beniston, University of Fribourg, Switzerland Prof. Dr. H. Richner, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland Dr. H.H. Schiesser, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland Prof. Dr. A. Weis, president of the jury, University of Fribourg, Switzerland Fribourg, 22 November 2001 The thesis director: Prof. Dr. M. Beniston The dean: Prof. Dr. A. von Zelewsky 8r Qhtr) Thunderstorm over the Jura mountains, Switzerland, during the afternoon of 19 June 1977. Picture taken by Dr. Willi Schmid, Atmospheric Science ETH, Zurich, Switzerland with permission 8r Abstract v Zusammenfassung ix Introduction 1 1.1 Outline........................................................................................................................ 1 1.2 Thunderstorm Theory ................................................................................................ 1 1.2.1 Severe Thunderstorms....................................................................................... 2 1.2.2 Hail Formation .................................................................................................. 4 1.2.3 Hail Suppression ............................................................................................... 6 1.3 Remote Detection of Hail .......................................................................................... 7 1.3.1 Ground Measurements of Hail (LQVLWX Detection)............................................ 7 1.3.2 Satellite Measurements of Hail ......................................................................... 8 1.3.3 Radar Measurements of Hail............................................................................. 9 1.3.4 Radar-Based Criteria for the Detection of Hail............................................... 11 1.3.5 Hail Kinetic Energy: Radar vs. Hailpad Data ................................................. 13 1.3.6 Hail Kinetic Energy: Radar vs. Hail Damage Data......................................... 15 1.3.7 Radar Data in Switzerland .............................................................................. 17 1.4 Hail Damage Assessment and Risk Response ......................................................... 18 1.4.1 Hail Damage Assessment................................................................................ 19 1.4.2 Response to Hail Risk ..................................................................................... 19 1.4.3 Hail Damage Data in Switzerland................................................................... 21 1.5 Prediction of Hailfall................................................................................................ 23 1.6 Lightning Activity in Severe Thunderstorms........................................................... 24 1.6.1 Lightning Discharges ...................................................................................... 24 1.6.2 Thunderstorm Electrification Processes.......................................................... 26 1.6.3 Observation of CG Lightning Activity in Severe Thunderstorms .................. 28 1.6.4 CG Lightning Data in Switzerland.................................................................. 32 1.7 Introducing the Three Articles ................................................................................. 32 i 2. The use of weather radars to estimate hail damage to automobiles: An exploratory study in Switzerland 35 2.1 Abstract .................................................................................................................... 35 2.2 Introduction.............................................................................................................. 36 2.3 Data .......................................................................................................................... 38 2.3.1 Insurance Data................................................................................................. 38 2.3.2 Radar Data....................................................................................................... 40 2.4 Methods.................................................................................................................... 42 2.4.1 Attribution of Hailfall Intensity and Damage Claims..................................... 42 2.4.2 Cross-Correlation and Storm Shifting Method ............................................... 42 2.5 Results...................................................................................................................... 45 2.5.1 Storm Scale Analyzes ..................................................................................... 45 2.5.2 The Influence of Seasonal Hailfall Intensity on Damage Variables ............... 47 2.5.3 Shifting and Correlation Analyses .................................................................. 49 2.5.4 Hailfall Intensity vs. Loss Ratios .................................................................... 50 2.5.5 Hailfall Intensity vs. Mean Damages.............................................................. 52 2.5.6 Hailfall Intensity vs. Damage Extents............................................................. 52 2.6 Discussion ................................................................................................................ 53 2.7 Conclusion ............................................................................................................... 55 3. Hailfall: The relationship between radar-derived hail kinetic energy and hail damage to buildings 57 3.1 Abstract .................................................................................................................... 57 3.2 Introduction.............................................................................................................. 58 3.3 Data .......................................................................................................................... 61 3.3.1 Radar Data....................................................................................................... 61 3.3.2 Hail Damage Claim Data ................................................................................ 63 3.4 Methods.................................................................................................................... 65 3.4.1 Cross-Correlation of Storm Intensity and Hail Damage Variables................. 65 3.4.2 Damage Functions........................................................................................... 68 3.5 Results...................................................................................................................... 69 3.5.1 Storm Variables............................................................................................... 70 3.5.2 Storm Shifting and Cross-Correlation Analyses............................................. 71 3.5.3 Radar-Derived Hail Kinetic Energy vs. Mean Damages ................................ 72 3.5.4 Radar-Derived Hail Kinetic Energy vs. Total Loss Ratios............................. 74 3.5.5 Calibration of Damage Functions for Total Loss Ratios ................................ 75 ii 3.5.6 The hailstorm of 5 July 1999 .......................................................................... 77 3.6 Discussion ................................................................................................................ 80 3.7 Conclusion ............................................................................................................... 83 4. Cloud-to-ground lightning activity in relation to the radar-derived hail kinetic energy in Switzerland 85 4.1 Abstract .................................................................................................................... 85 4.2 Introduction.............................................................................................................. 86 4.3 Data .......................................................................................................................... 87 4.3.1 Radar ............................................................................................................... 87 4.3.2 CG Lightning .................................................................................................. 88 4.4 Method and Data Correction.................................................................................... 89 4.4.1 Radar and Lightning Data Analyzes Method.................................................. 89 4.4.2 Data Correction Methods ................................................................................ 92 4.5 Results...................................................................................................................... 94 4.5.1 Storm Scale Analyzes ..................................................................................... 94 4.5.2 Hail Kinetic Energy at Upper and Lower Storm-Level .................................. 95 4.5.3 Total Hail Kinetic Energy vs. Total