Transcript Powerpoint

° The Unexpectedly Cold U.S. of 2008
--- Warm Boundary Forced Signals:
GHG, La Nina, Extratropical SST
--- A Hundred-year cold event?
° Strong Sudden-Stratospheric Warming Ev
--- What impact on troposphere?
° November-January 2009
NOAA CSI Meeting
___ La Nina & Npac SST effect
March 4 2009
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US SFCT Annual Anomalies:Observed
Trend: +0.51°C
C
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3
+0.6°C
100 samples of CMIP runs having ENSO-neutral conditions
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+0.1°C
68 samples of CMIP runs having cold tongue SST anomalies < 2008 OBS6
+0.33°C
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Based on Additional Runs: All US Warming Due to NPacific SST forcing
2008 US SFCT Annual Anomalies
-0.16°C
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OBS 2008
-0.75°C
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OBS 2008 -GHG Signal
-1.19°C
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OBS 2008 -GHG Signal-Natural SST Signal
US SFCT Annual Anomalies:Observed
1917:
Coldest Year Since 1895
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2008 US SFCT Annual Anomalies:150 AMIP Runs
Coldest AMIP Run
C
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-1.2°C
-1.1°C
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-1.2°C
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-1.19°C
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The 2009 Major Stratospheric
Sudden WarmingAn example of close dynamical
troposphere-stratosphere
coupling
Judith Perlwitz and Klaus Weickmann at
NOAA ESRL
Craig Long at NOAA-CPC
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What
Happened?
• Zonal Wind at 10hPa
dropped by 94m/s within 17
days (01/11 to 01/28) from
record high values to record
low values)
• 50 hPa Temperatures over
the pole increased by 40K
within 12 days (01/16 to
01/27)
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The Tropospheric
Cause
• Deceleration of
stratospheric winds
were caused by
propagation of
tropospheric wave
activity into the
stratosphere
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L
H
January 14,
2009
L
H
H
Record Cold in
the Northern
Plains/Upper
Mississippi
Valley
H
L
L
RWD L
H
MJO
Tropical
Forcing
H
“Large
amplitude” RWD
excited by MJO
forced strong
PNA pattern
H
L
L
H
Upward energy
propagation
initiated a
sudden
stratospheric
warming (SSW)
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SSW effects on the
troposphere
SSW caused change in
direction of zonal wind anomalies
over the North Atlantic
1000hPa GPH 1/05 - 1/26/2009
1000 hPa GPH 1/31-2/20/09
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Northern Hemisphere Annular Mode
• Positive phase during most of December
(0.65) and January (0.8), negative phase
during first 2 1/2 weeks in January (?)
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Was the SSW the
cause for snowfall
and cold weather
in London starting
02/02/2009?
• Times online:
• “A change in wind direction in the
stratosphere funnelled cold air from the East
across the country”
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The Perspective
•
•
•
Strong similarities between
observed SSW and
composite.
SSW causes positive NAM
anomalies at the surface up
to 60 days.
This year’s impact may have
last not as long due to La
Nina (?).
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Did the SSW affect
US climate during
February?
• Not really.
Temperature Anomaly
February 2009
FMA (Temperature Anomaly (C)
During negative Annular Mode Phase
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Summary
• The 2009 SSW event was extreme.
• Caused by strong upward fluxes of wave activity from
the troposphere.
• Impact of SSW on troposphere might be limited due
to La Nina
• CPC under lead of Craig Long is monitoring the SSW
for possible tropospheric impacts.
• http://www.cpc.ncep.noaa.gov/products/stratosphere/
strat-trop/
• So far, SSW has impacted weather in Europe, but no
significant impact on US climate.
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Observed November- January 2009 Anomalies
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Observed November- January 2009 200Z Anomalies
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Observed November- January 2009 Anomalies
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Simulated November- January 2009 Anomalies
GOGA, 150-member multi-model
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Simulated November- January 2009 Anomalies
Tropical SSTs, 150-member multi-model
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Simulated NDJ 2009
150-member multi-model
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DJF 2008-09 Temperature
Forecast
Observations
All Stns Non-EC %-covg
8.4
9.7
42.7
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DJF 2008-09 Temperature
Observations
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Monthly Temperature
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DJF 2008-09 Precipitation
Forecast
Observations
All Non-EC % Cov
7.5
26.1
28.9
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DJF 2008-09 Precipitation
Observations
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Monthly Precipitation
Feb
Jan
Dec
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What are the Official Forecasts for US winter climate
0.5 month Lead DJF
0.5 month Lead JFM
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What are the Official Forecast for US winter climate?
0.5 month Lead DJF
0.5 month Lead JFM
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