Three Lectures on Tropical Cyclones

Three Lectures on Tropical Cyclones

Kerry EmanuelMassachusetts Institute of Technology

Spring School on Fluid Mechanics of Environmental HazardsSpring School on Fluid Mechanics of Environmental Hazards

Lecture 1:Lecture 1:Observed CharacteristicsObserved Characteristics

What is a Hurricane?What is a Hurricane?

Formal definition: A tropical cyclone with 1-min average winds at 10 m altitude in excess of 32 m/s (64 knots or 74 MPH) occurring over the North Atlantic or eastern North Pacific

The word The word HurricaneHurricane is derived from the is derived from the Mayan word Mayan word HuracanHuracan and the Taino and and the Taino and

Carib word Carib word HunrakenHunraken, a terrible God of Evil, , a terrible God of Evil, and brought to the West by Spanish and brought to the West by Spanish

explorersexplorers

Illustration from Travels in the West Indies, Theodor DeBry

Early historical encounters: The Mongol invasions of Early historical encounters: The Mongol invasions of Japan in 1274 and 1281Japan in 1274 and 1281

Scene from the 13th century Mongol invasion scrolls, based on a narrative written by the Japanese warrior Takezaki Suenaga.

The View from Space

Airborne Radar: Horizontal Map

360 km(220 mi)

120 km

20 km(12 mi)

(75 mi)

Airborne Radar: Vertical Slice

Azimuthal wind

Temperature perturbation at constant altitude

Radial windRadial wind

Vertical velocityVertical velocity

Angular Angular momentum momentum per unit massper unit mass

2sinM rV r

Tracks of all tropical cyclones, 1985-2005Tracks of all tropical cyclones, 1985-2005

Source: Wikipedia

Annual Cycle of Tropical CyclonesAnnual Cycle of Tropical Cyclones

1950 1960 1970 1980 1990 20000

20

40

60

80

100

120

Year

An

nu

al G

lob

al S

torm

Co

un

t

Global Tropical Cyclones, 1949-2006

1950 1960 1970 1980 1990 20000

5

10

15

20

25

30

Year

An

nu

al S

torm

Co

un

t

North Atlantic Tropical Cyclones, 1949-2006

Better Intensity Metric:Better Intensity Metric:

The Power Dissipation IndexThe Power Dissipation Index

0

3maxPDI V dt

A measure of the total frictional dissipation of A measure of the total frictional dissipation of kinetic energy in the hurricane boundary layer kinetic energy in the hurricane boundary layer

over the lifetime of the stormover the lifetime of the storm

Atlantic Storm Maximum Power DissipationAtlantic Storm Maximum Power Dissipation(Smoothed with a 1-3-4-3-1 filter)

Pow

er D

issi

patio

n In

dex

(PD

I)

Years included: 1870-2006

Data Source: NOAA/TPC

Atlantic Sea Surface Temperatures and Atlantic Sea Surface Temperatures and Storm Max Power DissiaptionStorm Max Power Dissiaption

(Smoothed with a 1-3-4-3-1 filter)

Scal

ed T

empe

ratu

re

Pow

er D

issi

patio

n In

dex

(PD

I)

Years included: 1870-2006

Data Sources: NOAA/TPC, UKMO/HADSST1

Socio-Economic Socio-Economic Consequences of HurricanesConsequences of Hurricanes

Windstorms Account for Bulk of Windstorms Account for Bulk of Insured Losses WorldwideInsured Losses Worldwide

Source: Roger Pielke, Jr.

Total U.S. Hurricane Damage by Decade, in 10Total U.S. Hurricane Damage by Decade, in 101010 2004 U.S. Dollars2004 U.S. Dollars

Population of Florida, 1790-2004

Source: Roger Pielke, Jr.

Total Adjusted Damage by Decade, in 1010 2004 U.S. Dollars

Total Number of Landfall Events, by Category, 1870-2004

U.S. Hurricane Damage, 1900-2004,Adjusted for Inflation, Wealth, and Population

Infamous Tropical CyclonesInfamous Tropical Cyclones

Galveston, 1900Galveston, 1900

East Pakistan, 1970East Pakistan, 1970

Hurricane Katrina, 2005Hurricane Katrina, 2005