Past and future changes of wind
storms – latest achievements
and current activities at HZG
Matthias Zahn
Frauke Feser
Martina Schubert-Frisius
Hans von Storch
with thanks to M.Barcikowska,L.Cavicchia,F.Chen
October 8, 2014
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Recently investigated phenomena
polar lows (NA)
polar lows (NP)
c
Dundee
from Fu et al., 2004
typhoons
c
NOAA
medicanes
c
NOAA/MSAT
How do the occurrence frequencies of these
phenomena change over time?
Further HZG work: North-Atlantic storminess by Frauke Feser at 11:00
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Research tools: numerical models
low-res global-domain
Simulation
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Detection
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high-res RCM-domain
different atmosphere models
dynamical downscaling decades
of global data to RCM domain
spectral nudging
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automated storm detection
methods applied
based on scale separation
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Detection of a Jan 1998 polar low
18 Jan 1998, 6:00, Zahn et al., 2008, Tellus
&
&
A
#3*#*+3. ( //
Simulation grid
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5 )-
5 )-
6 &
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digital filter: 200 600km spatial scales
are retained
polar low (PL) signal
becomes more
distinct
used for detection
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Past and future polar low frequency
Zahn and von Storch,
2010, Nature
Number of PLs per winter in the past
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no change in NCEP driven
past over North Atlantic
strong decrease under
IPCC-GHG warming
atmosphere projected to
become more stable
Left: average PLs per IPCC scenario.
Right: area and time-averaged ice free
SST − T500hPa over northern North Atlantic.
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Future PL frequency, North Pacific
from Chen et al., 2014, Clim.Dyn.
number of polar lows per winter in the future
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A1B - C20 SST − T500hPa > 39K frequency
change, red/blue: less/more stable
IPCC scenarios B1, A1B and A2
downscaled to 50km over North Pacific
significant decrease
decrease linked to GHG increase
linked to a more stable atmosphere
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Medicanes, Mediterranean Sea
Cavicchia et al., 2013, Clim.Dyn., 2014, JClim
6
5
4
3
2
past and future annual cycle
1
0
1950
1960
1970
1980
1990
2000
2010
number of medicanes per season
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NCEP(left)/IPCC(right) downscaled
to 10km (double nesting)
rare phenomenon
negligible change over past
decrease with future warming
40 E
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A2-C20 SST − T350hPa > 57K
frequency change, blue: more
stable
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Past and future typhoon frequency
Barcikowska,PhD thesis/ in preparation
black/red: all/most intense typhoons in CLM
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NCEP downscaled to
50km with CLM
slight overall increase
stronger increase of most
intense typhoons
BUT: inhomogeneity likely
detected typhoons in transient A1B scenario
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IPCC A1B downscaled to
50km with CLM
different detection
configurations
decrease with warming
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Current activity: global downscaling
low-res global-domain
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apply a global ECHAM6
dynamical downscaling to global
domain
spectral nudging
enables direct storm studies
linkages between different ocean
basins possible
high potential driving further
models down the chain
high-res global-domain
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Simulating 2004 tropical cyclones
named TCs of the 2004 season from IBTrACS
60˚
50˚
30˚
60˚
90˚
120˚
150˚
180˚
210˚
240˚
270˚
300˚
330˚
0˚
IBTrACS-tracks with counterpart: 55
IBTrACS-tracks without counterpart: 15
40˚
NCEP
China
25˚
25˚
Taiwan
30˚
20˚
10˚
20˚
0˚
20˚
-10˚
-20˚
Phillipines
-30˚
15˚
120˚
-40˚
2004 named IBTRACS WMO tracks,
red/black: without/with detected counterpart in EH6
990
1000
15˚
130˚
1010
1020
hPa
1030
-50˚
EH6
China
25˚
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can improve TC representation
70 tropical cyclones named
55 corresponding tracks detected
next step: discriminate these from
non-TC detections
then apply to ≈ 7 decades
25˚
Taiwan
20˚
20˚
Phillipines
15˚
120˚
990
1000
130˚
1010
1020
15˚
hPa
1030
NOCK-TEN in NCEP-SP and
EH6-MSLP, 24 Oct 2004, 0:00
black crosses: observed,
green cross: detected
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Summary
At HZG, different types of storms:
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were reconstructed using RCMs
are currently simulated using global
downscaling
Storm activity changes:
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no significant past change of activity
decreased activity in a warmed future
decrease linked to more stable atmosphere
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Thank you very much
for your attention
http://coast.hzg.de/staff/zahn/
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