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Extreme Events and Climate Variability
X. William Proenza, Director
National Weather Service Southern Region
Fort Worth, Texas
Issues:
Scientists are telling us that global warming
means more extreme weather.
Every year we seem to experience weather
extremes.
What is the origin of extreme events?
A Major Issue for All Countries Is Global
Warming and Its Regional Impacts
-0 .6
-0 .3
0 .0
0 .3
0 .6
0 .9L a n d a n d O cea n
An
omal
y (°
C)
a1880 1900 1920 1940 1960 1980 2000
1880 1900 1920 1940 1960 1980 2000 -1 .2
-0 .9
-0 .6
-0 .3
0 .0
0 .3
0 .6
0 .9
1 .2L a n d
Ano
mal
y (°
C)
c
-0 .4
-0 .1
0 .2
0 .5
0 .8
An
omal
y (°
C)
O cea n
b1880 1900 1920 1940 1960 1980 2000
S ea so n a l C lim a te Im p a c ts D ep en d o n th eS im u lta n e o u s In flu en ces o f:
E x trem e E v en ts a re M o stly R e la te d to C ircu la tio n C h a n g es , i.e . to Va r ia b ility
N a tu ra l C lim ate Va r ia b ility E l N in o /L a N in a P a c ific D e ca d a l O sc illa tio n
A rc tic O sc illa tio n (w e a k im p a c t in T ro p ics )
C lim a te C h a n g e
A tm o sp h e ric N o ise
(P D O )
The El Nino/Southern Oscillation (ENSO) is a major factor in global climate variability.
T h e P a c if ic D e ca d a l O sc illa tio n (P D O )
ty p ic a l w in te r tim e S e a S u r fa c e Tem p e ra tu re (c o lo rs ) ,S ea L ev e l P ressu re (co n to u rs) a n d su rfa ce w in d stress (a r ro w s) a n o m a ly p a ttern s d u rin g w a rm a n d c o o l p h a ses o f P D O
w a rm p h a se c o o l p h a se
L a N ina (J uly 1998-J une 1999)~
Departure from N ormal (mm)E l N ino (J uly 1997-J une 1998)~
Rainfall Changes A ssoc iated w ith EN SO are theL arges t Sourc e of Variability in the T ropic s
E N S O A ls o Impac ts H ur ric ane A c tivity
Soc ietal Impac ts from 1997/98 E l N ino
1. Crop/S toc k Damage 2. E nergy Savings 3. Famine 4. F ires 5. F isheries Dis ruption 6. Health R isks 7. Human Fata lit ies
8. P es ts Inc reased 9. P roper ty Damage10. Tourism Dec reased11. Transportation P roblems12. Soc ial Dis ruptions13. W ildlife Fata lit ies14. Water R ationing
1
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1011
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11
12
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5 1 144
1
11
1434
6
8
9
9 9
101213
5
1
14
69
9
11
789
91
4
78
91113
52
Colombia Gets Less Rain During El Nino
Major Weather-Related Natural Disasters
(1999 La Nina)
60 N50 N
40 N
30 N
20 N
10 N
E Q
10 S
20 S30 S
40 S
50 S
60 S0 60 E 12 0E 18 0 12 0W 60 W 0
SS
S
S S
S
S
F
F
FF
FF
F
F
FF
FF
FFF F
FF
F
F
F
F
F
F
F
FFF
HH
HH
D
D
S Storm s, Hail, TornadoesF Floods, LandslidesH Hurricanes, TyphoonsD Drought
Flood 55,360 $1.3BStorm s 16,863 $17.0BDroughts 404 - Cold Waves 409 $1.3B
VictimsInsured Losses
Regional 1999 Floods Possibly Linked to La Nina
Date Event
April 9-16 Mudslides & heavy rains Columbia:
Cauca, Argelia
May 5-15 High water in Amazonas, Peru
August 15-22 Flooding in eastern Venezuela
Aug 30-Sept 11 Flooding in Columbia: Antioquia,
Cordoba, Choco
Sept 12-29 Persistent rains, floods, mudslides in
Columbia, Honduras, Nicaragua,
Guatamala
Dec 12-19 Major flooding and mudslides in
Venezuela (50,000+ victims)
Impacts of December 1999 Floods
in Venezuela
Extended Pacific Jet Stream& Amplified Storm Track
LLow Pressure
PolarJet
StreamWarm
Cold
Dry
DryWet
Pers istent
E l N in o~
H
Variable Pacific Jet Stream
BlockingHigh
Pressure
PolarJet
Stream
Cold
Dry
Dry
Wet
Warm
Wet
Variab le
L a N in a~
Typical Winter Weather Anomalies
And Atmospheric Circulation Changes
During El Nino & La Nina
L ocation s F or M a jo r Sto rm s (D a ys P e r W in te r S ea s on )
E xten s iv e Sto rm sD ec 9 7-M a r 9 8
M a ss iveIce Sto rm
Ja n 98
Stro ng “N orthe aste r”
Sto rm sJa n-F eb 9 8
To rnad o O utb re akF eb 9 8
F re qu en t Sto rm sN ov 9 7-M a r 9 8
Examples of C limate Control Over Weather Patterns.The Basis of Linking Climate and Weather
LA N ina 1998-1999~Above AverageSto rm s, H u rricane
Force W indsN ov 98 - Feb 99
A ctive H urricaneSeason
A ug-N ov 98
TornadoesJan 1999
N o M ajo r “N ortheaste rs”
Be low N orm alSto rm iness
D ec 98 -Feb 99
M a jor Ice Sto rmJan 99
M a jorSnow Sto rm
Jan 99
Extensive IceSto rm
D ec 98D rought
Spring 1999
Dim inishedHurricane
Threat
Jet Stream Shifts Associated with Clim ate Variability Produce Regional Changes In Extrem e Weather Events
T h e P a c if ic D e c a d a l O sc illa tio n (P D O )
ty p ic a l w in te r tim e S e a S u r fa c e Tem p e ra tu re (c o lo rs ) ,S ea L ev e l P ressu re (co n to u rs) a n d su rfa ce w in d stress (a rro w s) a no m a ly p a ttern s d urin g w arm a nd c oo l p h a ses o f P D O
w a rm p h a se c oo l p ha se
R e fe re n c e : N a th a n M a n tu a U n iv e rs ity o f W a sh in g to n
Tota l Trend Pacific Decadel O scilla tion
Arctic O scilla tion G lobal Warm ing
Contributions to Surface Temperature Trend from 1950-1999
S U M M A RY
E x tre m es resu lt fro m :
- m a jo r c lim a te a n o m a lie s (e .g . e sp e c ia lly E l N in o a n d L a N in a in T ro p ics )
- u n u su a l a tm o sp h er ic c irc u la tio n p a tte rn s (m o s tly re la te d to c lim a te v a ria b il ity )
- fa c to rs a c tin g to g e th e r fo r a ir te m p e ra tu re (e .g . E N S O , P D O , A O , g lo b a l w a rm in g )
T h e im p a c ts o f th e w a rm in g tre n d o n c irc u la tio n c h an g e s , i.e . a lso e x trem e s , is s t ill a re se a rc h issu e .