Weather and Climate Extremes in a Changing Climate. Regions of ...

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TABLE OF CONTENTS
3 .......................................................................................................................................................................... 81
Causes of Observed Changes in Extremes and Projections of Future Changes
3.1 Introduction ..............................................................................................................................................82
3.2 What Are The Physical Mechanisms Of Observed Changes In Extremes? .................82
3.2.1 Detection and Attribution: Evaluating Human Influences on Climate Extremes Over
North America ....................................................................................................................................82
3.2.1.1 Detection and Attribution: Human-Induced Changes in Average Climate That
Affect Climate Extremes .................................................................................................................83
3.2.1.2 Changes in Modes of Climate-system Behavior Affecting
Climate Extremes ..............................................................................................................................85
3.2.2 Changes in Temperature Extremes ............................................................................................ 87
3.2.3 Changes in Precipitation Extremes .............................................................................................89
3.2.3.1 Heavy Precipitation ............................................................................................................89
3.2.3.2 Runoff and Drought ...........................................................................................................90
3.2.4 Tropical Cyclones .............................................................................................................................. 92
3.2.4.1 Criteria and Mechanisms For tropical cyclone development .................................92
3.2.4.2 Attribution Preamble ..........................................................................................................94
3.2.4.3 Attribution of North Atlantic Changes ......................................................................... 95
3.2.5 Extratropical Storms ....................................................................................................................... 97
3.2.6 Convective Storms ............................................................................................................................98
3.3 Projected Future Changes in Extremes, Their Causes, Mechanisms,
and Uncertainties ................................................................................................................................... 99
3.3.1 Temperature ......................................................................................................................................99
3.3.2 Frost ....................................................................................................................................................101
3.3.3 Growing Season Length ................................................................................................................101
3.3.4 Snow Cover and Sea Ice ...............................................................................................................102
3.3.5 Precipitation .....................................................................................................................................102
3.3.6 Flooding and Dry Days .................................................................................................................103
3.3.7 Drought..............................................................................................................................................104
3.3.8 Snowfall .............................................................................................................................................105
3.3.9 Tropical Cyclones (Tropical Storms and Hurricanes) ...........................................................105
3.3.9.1 Introduction .........................................................................................................................105
3.3.9.2 Tropical Cyclone Intensity ...............................................................................................107
3.3.9.3 Tropical Cyclone Frequency and Area of Genesis .................................................... 110
3.3.9.4 Tropical Cyclone Precipitation........................................................................................ 113
3.3.9.5 Tropical Cyclone Size, Duration, Track, Storm Surge, and Regions
of Occurrence .................................................................................................................................... 114
3.3.9.6 Reconciliation of Future Projections and Past Variations ....................................... 114
3.3.10 Extratropical Storm ........................................................................................................... 115
3.3.11 Convective Storms .............................................................................................................. 116
4 ........................................................................................................................................................................ 117
Measures To Improve Our Understanding of Weather and Climate Extremes