AOGS 11th Annual Meeting, 28 Jul to 01 Aug, 2014, Royton Hotel Sapporo, Japan
Wind storm research at the HZG long-term changes over the Pacific
Dr. Matthias Zahn
Dr. Frauke Feser
Prof. Hans von Storch
with thanks to M.Barcikowska,L.Cavicchia,F.Chen
matthias.zahn@hzg.de
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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?
Also at HZG: Extra-tropical Storms at centennial time scale: Lan Xia at 2.15pm
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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
scale separation methods based
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Simulation of Typhoon Songda
CSFR
CCLM-NN
CCLM-SN
from Barcikowska (2013)
Figure 4.4 Horizontal surface wind speed fields [m s-1] for TC Songda, on 1st September
2004, 00:00. From left: CFSR reanalysis, CCLM-NN, CCLM-SN. For CCLM the first
simulation (simulation no 10 and 20) of each ensemble is shaded, the other simulation are
shown as contour lines: 10 [m s-1] as solid lines, 18 [m s-1] as dotted lines.
Spectral nudging inhibits model variability
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Detection of a Jan 1998 PL case
Zahn et al., 2008, Tellus
&
&
A
#3*#*+3. ( //
Simulation grid
5 )-
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5 )-
6 &
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digital filter: 200 600km spatial scales
are retained
PL signal becomes
more distinct
used for detection
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Past and future PL frequency
Zahn and von Storch,
2010, Nature
Number of PLs per winter in the past
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no change in past
strong decrease under
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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Past PL frequency, North Pacific
Number of detected Polar Lows
from Chen and v.Storch, 2013, Advances in Meteorology
1
250
0.8
200
0.6
150
0.4
100
0.2
50
1948/
1949
1958/
1959
1968/
1969
1978/
1979
PLS
1988/
1989
locations of genesis
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1998/
1999
2008/
2009
0
1948/
1949
1958/
1959
1968/
1969
Detected Polar Low
PDO
1978/
1979
PLS
1988/
1989
1998/
1999
2008/
2009
PNA
ENSO
NCEP downscaled to 50km over North Pacific
upward, but no significant change
link to NP circulation indices:
CPNA = 0.45, CPDO = 0.39, CENSO = 0.22
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Future PL frequency, North Pacific
from Chen et al., 2014, Clim.Dyn.
locations of genesis
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A1B - C20 frequency change of vdT > 39K ,
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
NCEP
°
°10
W
°
°
5 W
0
°
5 E
°
10 E
°
15 E
from Cavicchia et al., 2013, Clim.Dyn.
°
20 E
°
25 E
°
30 E
°
35 E
°
40 E
6
50 N
5
°
45 N
4
°
40 N
3
°
35 N
2
°
30 N
1
°
0
25 N
1950
locations of medicane genesis
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1960
1970
1980
1990
2000
2010
number of medicanes per season
downscaled to 10km (double nesting)
rare phenomenon
negligible change
40 E
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Past typhoon frequency
Barcikowska, in preparation
a)
b)
c)
d)
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
Fig. 3. Trends for yearly occurrences of intense TC estimated with a linear regression
using a least squares fit derived for every 5◦ x 5◦ grid box; for the period 1978-2001, for a)
CCLM-NCEP, b) CCLM-ERA, c) JMA, d) JTWC.
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North: more activity
South: less activity
25
10 / 14
Future typhoon frequency
M. Barcikowska, pers. comm.
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 (M. Schubert-Frisius)
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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Summary
At HZG, different types of storms:
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were reconstructed using RCMs
will be 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
ご清聴ありがとうございました
http://coast.hzg.de/staff/zahn/
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