The Monsoon Circulation, Typhoon Activity, and Island
Rainfall in the Western North Pacific During the Past 50 Years:
Recurring Patterns and Extreme Events
Mark A. Lander
Water and Environmental Research Institute of the Western Pacific
Central Guam
mountains after a
major brushfire.
U
Pohnpei locator maps showing world setting and
Pohnpei Island with Municipalities.
Climate of Micronesia
Climate Change?
Who ya gonna believe? Me, or your own eyes? *
My own rules of thumb: Warwick Rhode Island 1960s, 1970s
First touch of frost: Last week of September
First hard freeze: Last week of October
First day max temp < freezing: Last week of November
These events now occur 2 or 3 weeks later !!
* Groucho Marx
Commonly cited recent climate anomalies
Climate change during my lifetime
Global Warming
Global Cooling
Climate Variability in USAPI
during the past 50 years
• Very large year-to-year changes
Annual Rainfall on Guam 50 inches to 150 inches
• Tropical Cyclones
WNP Basin annual number: 20 to 40!
• ENSO
• Monsoon flow pattern
Weather makers in USAPI
•
•
•
•
•
Tropical Cyclones
Monsoon trough
TUTT/TUTT Cells
ENSO
Mesoscale Convective Systems
If you’re going to change the climate of
Micronesia you have to change the climate of
these !
Climate of Pacific Islands
1500 years BP to now
(MWP through LIA to current)
Problems:
•
No direct measurements, none that go
back more than 100 years (50, at best in
many locations)!
• Proxy records conflicting, and yield some
almost inexplicable local climate and
climate changes (e.g., Washington Island).
Question for Group
• Can one use very recent global temperature
behavior as proxy for larger and longer
transitions: e.g., MWP to LIA?
-- Investigate positions of ITCZ and rainfall
on Washington Island before, during and after the
“Time Magazine Ice Age”
-- 1988 very cold La Nina-related cold water
What did it do to ITCZ?
2004
2000
1996
1992
1988
1984
1980
1976
1972
1968
1964
1960
1956
1952
1948
1944
1940
1936
1932
1928
1924
1920
1916
1912
1908
1904
1900
1896
1892
1888
1884
1880
1876
1988 had very cold equatorial waters. Check position of ITCZ
10000
40
Southern Oscillation Index
30
1988
20
10
0
-10
-20
-30
-40
9000
-50
MONSOON
Summer Monsoon
of the western North
Pacific
Normal surface flow pattern
(black = westerly)
VS 1997
(dashed-line filled = westerly).
Summer Monsoon
Palau
Surface wind flow, August 1997
Strongest Westerly Wind Burst
ever Observed ! (December 1996)
Normal Monsoon
40 N
30 N
20 N
Saipan
Guam
10 N
Pohnpei
Majuro
EQ
100 E
120 E
140 E
160 E
180
Reverse Oriented Monsoon Trough
40 N
30 N
20 N
Saipan
Guam
3
10 N
2
1
Pohnpei
Majuro
EQ
100 E
120 E
140 E
160 E
180
Next Trough Develops
40 N
30 N
20 N
Saipan
Guam
10 N
Pohnpei
Majuro
EQ
100 E
120 E
140 E
160 E
180
Permian Surface winds and rainfall
Cold Tongue
The MJO
C
EQ
C
1
2
Put the only heat source of the entire
planet over the Maritime Continenent:
Easterly winds would extend
across the whole Pacific, Atlantic
and to East Africa. Westerlies
would extend across the Indian Ocean.
SHEAR LINE
G UAM
W
NW M O NSO O N
T C CRAIG
T C ERICA
T C ESET A
GMS IR 00 UTC 22 OCT
Ketsana
Parma
TD??
Reverse-oriented
Monsoon Trough
TD TD
W
Super Typhoon Paka (December 1997)
When low latitude
winds go westerly,
clouds and rain
are found in max
west wind band and
in associated TCs.
Majuro
W.I.
Question for Group:
• How much was this flow pattern changed
by past 1500-year climate changes and how
much can it be changed by anticipated
global warming?
– Location of STR, monsoon trough, TUTT, typhoon
tracks
– ENSO effects
– Large-scale features similar even in Permian!!
Question for Group:
• Washington Island bone dry?
– There would almost have to be a cold tongue (i.e., not
major El Nino like all the time).
– Christmas Island also dry?
• Then ITCZ must either be most of the time in the Southern
Hemisphere, or ITCZ is pushed to the north of W.I. for much
of the year. (check on 1988 – a year with an extensive cold
tongue).
– Meteorological “Equator” currently at 7 North!!
– Palau now dry only because of El Nino (+1) and during
typical September when the monsoon trough moves
well to the north.
ENSO
Micronesia Rainfall in a
Warmer World
1998 HNL conference:
Reduction in mean annual
rainfall from shift in ENSO
* More El Nino Like most of
the time
* More Large El Nino’s
Southern Oscillation Index
Running Sum
40
20
0
1983
-20
Catastrophic flooding
In the Marquesas
Eastern Micronesia
Deadly Typhoon
-40
1992
July 1976
-60
Micronesia-wide
Severe Drought
-80
1998
-100
2006
2002
1998
1994
1990
1986
1982
1978
1974
1970
1966
1962
1958
1954
1950
1946
1942
1938
1934
1930
1926
1922
1918
1914
1910
1906
1902
1898
1894
1890
1886
1882
1878
1874
1870
1866
-120
ENSO Time Series (SOI)
50
DARK BLUE = RUNNING SUM OF SOI 1866-2002
0
-50
-100
RED = Running Sum of time series:
0.4*(month-1) + 0.3*(month-2) + 0.1*(month-3) + RANDOM NUMBER
2002
1998
1994
1990
1986
1982
1978
1974
1970
1966
1962
1958
1954
1950
1946
1942
1938
1934
1930
1926
1922
1918
1914
1910
1906
1902
1898
1894
1890
1886
1882
1878
1874
1870
1866
-150
Pacific Interannual and
Interdecadal Variability
• There is ONLY ENSO.
Time series is autoregressive (several months)
with stochastic forcing. Spectral Peak at ~ 2.6
years.
• Pacific Decadal Oscillation is reddened ENSO.
Time series and fields are similar, but with
longer memory because of mid-latitude mixedlayer deepening.
PDO is reddened ENSO
Question for Group:
• Has ENSO been affected by climate
changes in the past 1500 years?
Frequency, strength, character
• ENSO affects almost everything in USAPI:
Tropical cyclone distribution, rainfall, sea level, monsoon trough
position, and extreme events of weather elements.
ENSO
1998 Climate workshop East-West Center
Consider ENSO in a warmer world:
More frequent strong El Nino’s like 1982-83
and 1997-98?
or
Climate more El Nino-like all the time?
Question: Is this the model for the past 1500 years?
(MWP and LIA ??)
RAINFALL
Micronesia Rainfall by Hour
NOTE: POST-EL NINO YEARS IN RED
2001
1999
1997
1995
1993
1991
1989
1987
1985
1983
1981
1979
1977
1975
1973
1971
1969
1967
120
1965
160
1963
1992
1961
200
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
19
77
19
75
19
73
19
71
19
69
19
67
19
65
19
63
19
61
20
19
59
40
19
57
19
55
2000
1998
80
1959
NOTE: POST-EL NINO YEARS IN RED
1996
1994
1992
100
1957
KOROR ANNUAL RAIN
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
1966
1964
1962
1960
1958
1956
1954
1952
1950
120
1955
ANNUAL RAIN (INCHES)
NOTE: RED INDICATES POST EL NINO YEARS
1953
19
53
19
55
19
57
19
59
19
61
19
63
19
65
19
67
19
69
19
71
19
73
19
75
19
77
19
79
19
81
19
83
19
85
19
87
19
89
19
91
19
93
19
95
19
97
19
99
20
01
GUAM ANNUAL RAIN
MAJURO ANNUAL RAIN
160
140
200
180
160
NORMAL
NORMAL
140
120
60
100
80
60
40
0
20
0
POHNPEI ANNUAL RAIN
NOTE: POST-EL NINO YEARS IN RED
250
180
140
200
100
150
80
60
100
40
20
50
0
0
Guam Rainfall VS Water Table
40
20.00
Integrated Guam Rainfall Anomaly (Red)
VS
Observed A20 Wellhead (Blue)
15.00
20
10.00
0
5.00
0.00
-20
-5.00
-40
-10.00
-60
1982
-15.00
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2001
1999
1997
1995
1993
1991
1989
1987
1985
1983
1981
1979
1977
1975
1973
1971
1969
1967
1965
1963
1961
1959
1957
1955
1953
LONG-TERM SURPLUSES AND
DEFICITS (Pohnpei)
180
130
80
30
-20
JANUARY OF
POST-EL NINO YEAR
-70
-120
19
2
19 6
2
19 8
3
19 0
3
19 2
3
19 4
3
19 6
3
19 8
4
19 0
4
19 2
4
19 4
4
19 6
4
19 8
5
19 0
5
19 2
5
19 4
5
19 6
5
19 8
6
19 0
6
19 2
6
19 4
6
19 6
6
19 8
7
19 0
7
19 2
7
19 4
7
19 6
7
19 8
8
19 0
8
19 2
8
19 4
8
19 6
8
19 8
9
19 0
9
19 2
9
19 4
9
19 6
9
20 8
0
20 0
02
DRY
-----WET
Pohnpei Rainfall
8000
6000
-4000
-6000
40
30
4000
20
2000
10
0
0
-2000
-10
-20
Manoa Rainfall 1921-2007 Running Accumulation
Extreme Value Analysis
15.0
Saipan Int. Airport
with
consideration of typhoons
10.0
I
N
C
H
E
S
8.0
6.0
5.0
4.0
Pongsona
on Guam
100
50
20
3.0
10
2.0
P
E
R 1.0
5
Pohnpei
wet day
Oct 29, 2003
0.8
H
O 0.6
0.5
U
0.4
R
0.3
0.2
0.1
5
10
20 30 40 50 60
IN MINUTES
2
DURATION
3 4 5 6 8 1012 18 24
IN HOURS
IDF chart of selected return
periods at the SIA (blue dots
connected by blue dashed
lines). Because the cause of
the extreme events is
typhoons, this curve may be
considered applicable for all of
Saipan. The intensity-duration
values measured during
Typhoon Pongsona on Guam
(red dots connected by red
dotted line) are shown. Also,
the highest Intensity-duration
values measured by a newly
installed rain gauge network
on Pohnpei have been plotted
(green dots connected by green
dotted line). Without typhoons,
the return-periods at all
durations would be much
lower.
HEAVY RAINFALL IN A
TYPHOON
Max = 175 mm/hr
Questions for Group:
• How have past 1500-year climate changes
affected rainfall in USAPI?
• Can USAPI extreme rainfall events be
affected by global climate changes such as
MWP, LIA and anticipated AGW?
• Do typhoons produce the highest rain rates
at all intervals: 15 minute to 24 hour?
Questions for Group:
• Is the overall rainfall in the tropics heavier in a
warmer world? *
– * I have outstanding bet with Bob Livezy regarding Singapore
rainfall over the past 50 years.
• Or, are only the values of extreme rainfall
elevated in a warmer environment?
– e.g., Trenberth’s claim of Katrina 7% more rain because of AGW
– Every cloud affected? Or just typhoons? (The Katrina Effect)
TYPHOONS
WMO
International
Workshop on
Tropical
Cyclone
Landfall
Processes.
Macao, China.
(21 -25 March
2005)
Tinian
Rota
Guam
SUNDAY MORNING, 8 December 2002
M. Lander
Slide 9
16
35
Western North Pacific Tropical Cyclone
Variability
JTWC
35
Running sum of annual anomalies
25
25
15
15
5
5
Active
-5
-5
Quiet
TY
-15
Quiet
-15
TS + TY
Active
-25
-25
1960
1970
1980
1990
2000
Tropical Cyclone Locations
1970-79
1980-89
145 E
145 E
18 N
18 N
15 N
15 N
12 N
12 N
1970-99
1990-99
145 E
145 E
18 N
18 N
15 N
15 N
More?
12 N
12 N
140 E
150 E
145 E
80
80
70
70
60
70
50
Anatahan
40
80
Saipan
90
15 N
15 N
Tinian
100
Rota
100
Guam
40
90
80
70
60
50
40
50
10 N
10 N
30
40
20
30
20
140 E
145 E
150 E
Contours (at intervals of
10) show the number of
tropical storms and
typhoons per 100-years
expected to pass within 75
nautical miles from any
map location. Analysis is
based on the years 194597. Chart adapted from
Guard, et al. (1999). Note
that on this fine scale,
Guam appears to have a
slightly higher risk of a
tropical storm or a typhoon
than Saipan (60 per 100years, versus 50 per 100years).
PEAC Typhoon Risk Assessment
INCREASED Threat for Marshalls and Guam
NEUTRAL for CHUUK (End of El Nino Year)
YAP
Guam
30N
20N
"El Nino Box"
10N
EQ
100E
120E
1997
140E
1998
160E
180
Majuro
CHUUK
Western North Pacific Tropical Cyclone Distribution*
* Tropical cyclones per 5 x 5 square per year
2007 Tropical Cyclone Distribution
30N
20N
"El Nino Box"
Guam
10N
EQ
100E
120E
1997
140E
2007
160E
180
2007 Tranquility
Guam/CNMI
For all of June, July, August and September, the weather on Guam
has been rather tranquil. Winds have been very light (easterly for the
most part, with a few periods of light westerly wind flow), only one
tropical cyclone (Man-Yi) adversely affected the island (it generated
near-gale winds for one day in early July), and there have been no
extreme island-wide heavy rainfall events. In association with La Niña,
monsoon southwest winds remained mostly to the west of Guam, and
tropical cyclone development was also pushed to the west and north of
Guam. In an environment of light wind, rainfall was produced onisland by short-lived (6-12 hr) mesoscale convective systems, and by
isolated (mostly daytime) thunderstorms that affected only parts of the
island on any given day. Daytime thunderstorms have produced
isolated heavy rainfall totals near 2 or 3 inches in a few hours at some
locations, however, over the course of a month, rainfall amounts in this
weather pattern tend to average near to slightly below normal. …..
(PEAC 4th QTR 2007 Newsletter)
Questions for Group:
• How have past 1500-year climate changes
affected typhoon climate in USAPI?
• More typhoons in a warmer world?
• More very intense typhoons (overall) or as
a higher proportion of all typhoons in a
warmer world? (vice versa for a colder
world? LIA ??)
– Note 2007 Tranquility
• Track changes?
Final Questions for Group:
• How have past 1500-year climate changes
affected typhoon climate in USAPI?
• Can we investigate this by studying changes
to rainfall, typhoons, and extreme events
during observed large departures from
average climate during the past 50 to 100
years? Extrapolate to MWP and LIA?
END
Sunset on Guam Post TY Pongsona
Smoke from fuel fire
Sand from overwash
Photo Courtesy of Roger Edson