analysis of four decadal simulations of the skagerrak mesoscale circulation using two ocean models...
TRANSCRIPT
Analysis of four decadal simulations of the Skagerrak mesoscale circulation using
two ocean models
Lars Petter Røed1 and Jon Albretsen2
Presented at OPNet, Geilo, Norway, May 27, 20101Also affiliated with Department of Geosciences, University of Oslo, Norway2 Now at Institute of Marine Research, Flødevigen, Arendal, Norway
Norwegian Meteorological Institute met.no
LPR #2 OPNet, Geilo, Norway, May 27, 2010
Outline
• Background and motivation• Models and configuration• Results• Conclusions
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LPR #3 OPNet, Geilo, Norway, May 27, 2010
The story ....
• Switching ocean forecast model– MIPOM -> ROMS
• Comparison of model results vs. observation
• Heat flux parameterization– Calibrating canonical model version
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LPR #4 OPNet, Geilo, Norway, May 27, 2010
The research learning loop
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LPR #5 OPNet, Geilo, Norway, May 27, 2010
Key questions:
• Is the new model better, or at least as good as the old model?
• If it's not, is it easy to fix?• Method:
– Comparison model vs. observations– Requires (long) simulations
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LPR #6 OPNet, Geilo, Norway, May 27, 2010
Area of interest:
Onsdag 2007-03-28 12UTC
Note mesoscale patterns in SST
Satellite image12 h composite Mar 28, 2007
+48 h forecast valid May 9, 2010 00UTC
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LPR #7 OPNet, Geilo, Norway, May 27, 2010
Grids employed
1.5 km4 km
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LPR #8 OPNet, Geilo, Norway, May 27, 2010
Item MIPOM ROMSResolution 4 km 1.5 km 4 km 1.5 km
# of vertical levels 26 21 32 32
Long (internal) time step
150 s 60 s 120 s 90 s
Ratio of internal to external time step
30 40 30 30
Horizontal dissipation Smagorinsky No explicit diffusion
Vertical mixingMellor-Yamada
2.5 levelGLS mixing scheme
Horizontal advection scheme
2nd order centered 3rd order upwind
Surface fluxes MI-IMStandard ROMS bulk
fluxes (analytic)
Model facts
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LPR #9 OPNet, Geilo, Norway, May 27, 2010
Model facts ...
• Simulation period:– 1981–2007 (+ 1980 spin-up)
• Four simulations– 2 x MIPOM : 4 km and 1.5 km– 2 x ROMS : 4 km and 1.5 km
• Atmospheric forcing: – ERA40 + ECMWF operational analysis
2002-2007
• Tidal forcing:– 8 major tidal components– Forced at open boundaries
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LPR #10 OPNet, Geilo, Norway, May 27, 2010
Model facts ...
• Other forcing at open boundaries:– 4 km:
• SODA reanalysis + climatology 2005-2007
– 1.5 km:• Nested into 4 km
• Rivers:– Climatology
• Baltic outflow– S=12 psu
• No data-assimilation!
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LPR #11 OPNet, Geilo, Norway, May 27, 2010
Observations for validation
• IMR, Norway – Current
measurements (one location, 160 day period)
– Monthly data from the Hirtshals – Torungen section (12 stations, all years)
• ICES database– Irregular data in time
and space (approx. 250.000 measurements of S and T in Skagerrak)
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LPR #12 OPNet, Geilo, Norway, May 27, 2010
Observed surface velocities:
• Courtesy: Rio05, CLS Space Oceanography Division, AVISO
• Speed
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LPR #13 OPNet, Geilo, Norway, May 27, 2010
Currents off western Norway (50 m)
ROMS 4kmMIPOM 4km
Shetland
1981-2007 average (m/s)
Norway
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LPR #14 OPNet, Geilo, Norway, May 27, 2010
Comparison with earlier results
LaCasce et al. (2007) concluded:The ROMS velocities are more energetic and compare more favorably with in situ observations, as do the ROMS-derived means
MIPOM ROMS
2004-2006 average speed at 50 m
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LPR #15 OPNet, Geilo, Norway, May 27, 2010
Surface currents Skagerrak
ROMS 4kmMIPOM 4km
1981-2007 average (m/s)
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LPR #16 OPNet, Geilo, Norway, May 27, 2010
Surface currents Skagerrak
ROMS 4km
1981-2007 average (m/s)
ROMs 1.5km
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LPR #17 OPNet, Geilo, Norway, May 27, 2010
Temperature bias (mod – ICES obs)
1981-2007 average; upper 20 m
ROMS 4kmMIPOM 4km
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LPR #18 OPNet, Geilo, Norway, May 27, 2010
Temperature bias (mod – ICES obs)
1981-2007 average; 50-600 m
ROMS 4kmMIPOM 4km
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LPR #19 OPNet, Geilo, Norway, May 27, 2010
Temperature bias: 0-20m
Red shading: Model too warm (ci: 0.5ºC)
ROMS v2 MIPOM ROMS v1
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LPR #20 OPNet, Geilo, Norway, May 27, 2010
Salinity bias (mod – ICES obs)
1981-2007 average; upper 20 m
ROMS 4kmMIPOM 4km
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LPR #21 OPNet, Geilo, Norway, May 27, 2010
1981-2007 average; 50-600 m
Salinity bias (mod – ICES obs)
MIPOM 4km ROMS 4km
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LPR #22 OPNet, Geilo, Norway, May 27, 2010
2005average
1983average
ROMS 4kmMIPOM 4km
T-S diagram
Blue: ICES data from SkagerrakRed: Model
ROMS 4kmMIPOM 4km
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LPR #23 OPNet, Geilo, Norway, May 27, 2010
Temperature bias (mod – IMR obs)
1981-2007 average
ROMS 4km
0
100
600
MIPOM 4km
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LPR #24 OPNet, Geilo, Norway, May 27, 2010
Temperature bias (mod – IMR obs)
1981-2007 average
ROMS 1.5km
0
100
600
MIPOM 1.5km
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LPR #25 OPNet, Geilo, Norway, May 27, 2010
Salinity bias (mod – IMR obs)
1981-2007 average
ROMS 4km
0
100
600
MIPOM 4km
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LPR #26 OPNet, Geilo, Norway, May 27, 2010
Salinity bias (mod – IMR obs)
1981-2007 average
ROMS 1.5km
0
100
600
MIPOM 1.5km
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LPR #27 OPNet, Geilo, Norway, May 27, 2010
10,0
11,0
0,07
0,03
2,6
2,0
1,50,3
0,60,1
1,90,2
ROMS 4km
12,7
10,1
0,04
0,03
2,5
2,0
1,40,3
0,50,2
1,40,2
MIPOM 4km
Volume fluxes
1981-2007 average (Sv)
More intense cyclonic circulation in Skagerrak!Net flux through Faroe-Shet is negative!
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LPR #28 OPNet, Geilo, Norway, May 27, 2010
234
310
1,7
1,4
89
7749
10
217
47
7,1
253
353
3,6
1,4
104
8460
11
266
72
8,8
7,7 9,7
1981-2007 average (TW)
Heat transport
MIPOM 4km ROMS 4km
50% more heat advected in the cyclonic circulation in Skagerrak
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LPR #29 OPNet, Geilo, Norway, May 27, 2010
458
363
1,3
0,9
90
7351
10
19
6
50 5,5
359
397
2,8
0,9
94
7454
10
215
67 6,4
1981-2007 average (t/s)
Salinity transport
MIPOM 4km ROMS 4km
30% more salt advected in the cyclonic circulation in Skagerrak (re-circulation?)
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LPR #30 OPNet, Geilo, Norway, May 27, 2010
Scatterdiagram – currents: Any skill?
0 m/s 1
1 m/s13 m
50 m
Norwegian Meteorological Institute met.no
LPR #31 OPNet, Geilo, Norway, May 27, 2010
Validation of currents - speed
4km
1.5km
MIPOM ROMS
Speed PDFs: 160 days (27.10.1992-4.4.1993), 13m depth
58.37N,8.51EMeasured total depth: 120mEquilibrium depth: 4km: 233m 1.5km: 163m
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LPR #32 OPNet, Geilo, Norway, May 27, 2010
Validation of currents - speed
4km
1.5km
MIPOM ROMS
Speed PDFs: 160 days (27.10.1992-4.4.1993), 75m depth
58.37N,8.51EMeasured total depth: 120mEquilibrium depth: 4km: 233m 1.5km: 163m
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LPR #33 OPNet, Geilo, Norway, May 27, 2010
ConMan: Speed at S1 at 100 m
West Norway
Measurement period 2.5 years
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LPR #34 OPNet, Geilo, Norway, May 27, 2010
ConMan: Speed at S2 at 100 m
West Norway
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LPR #35 OPNet, Geilo, Norway, May 27, 2010
Validation of currents - direction
4km
1.5km
MIPOM ROMS
Direction PDFs: 160 days (27.10.1992-4.4.1993), 13m depth
58.37N,8.51EMeasured total depth: 120mEquilibrium depth: 4km: 233m 1.5km: 163m
Currents from the NE parallel to the:- coast: 238 deg- local isobaths: 225 deg
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LPR #36 OPNet, Geilo, Norway, May 27, 2010
Validation of currents - direction
4km
1.5km
MIPOM ROMS
Direction PDFs: 160 days (27.10.1992-4.4.1993), 75m depth
58.37N,8.51EMeasured total depth: 120mEquilibrium depth: 4km: 233m 1.5km: 163m
Currents from the NE parallel to the:- coast: 238 deg- local isobaths: 225 deg
Norwegian Meteorological Institute met.no
LPR #37 OPNet, Geilo, Norway, May 27, 2010
Validation of currents
160 days (27.10.1992-4.4.1993)
58.37N,8.51EMeasured total depth: 120mEquilibrium depth: 4km: 233m
1.5km: 163m
Mean Standard deviation
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LPR #38 OPNet, Geilo, Norway, May 27, 2010
ROMS 4kmMIPOM 4km
above 100 m
below 100 m
Obs
Model
0,12
0,35
0
0
Temperature probability distribution
Fre
qu
en
cy
1981-2007 average
MIPOM 4km ROMS 4km
-5 20
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LPR #39 OPNet, Geilo, Norway, May 27, 2010
ROMS 1.5kmMIPOM 1.5km
above 100 m
below 100 m
Obs
Model
0,12
0,35
0
0
Temperature probability distribution
Fre
qu
en
cy
1981-2007 average
MIPOM 1.5km ROMS 1.5km
-5 20
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LPR #40 OPNet, Geilo, Norway, May 27, 2010
ROMS 4kmMIPOM 4km
above 100 m
below 100 m
Obs
Model
0,2
0,7
0
0
Salinity probability distribution
Fre
qu
en
cy
1981-2007 average
MIPOM 4km ROMS 4km
24 36
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LPR #41 OPNet, Geilo, Norway, May 27, 2010
ROMS 1.5kmMIPOM 1.5km
above 100 m
below 100 m
Obs
Model
0,2
0,7
0
0
Salinity probability distribution
Fre
qu
en
cy
1981-2007 average
MIPOM 1.5km ROMS 1.5km
24 36
Norwegian Meteorological Institute met.no
LPR #42 OPNet, Geilo, Norway, May 27, 2010
20,00
22,00
24,00
26,00
28,00
30,00
32,00
34,00
19
80
19
85
19
90
19
95
20
00
20
05
Sal
init
y
Observed MIPOM ROMS
SSS off southern Norway
Norwegian Meteorological Institute met.no
LPR #43 OPNet, Geilo, Norway, May 27, 2010
0,00
5,00
10,00
15,00
20,00
19
80
19
85
19
90
19
95
20
00
20
05
Te
mp
era
ture
(C
)
Observed MIPOM ROMS
SST off southern Norway
Norwegian Meteorological Institute met.no
LPR #44 OPNet, Geilo, Norway, May 27, 2010
Mean kinetic energy
1981-2007 average (J/m2)
MIPOM 4km ROMS 4km8220
7062
13008 13360
7173
10655
20055 17547
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LPR #45 OPNet, Geilo, Norway, May 27, 2010
Mean kinetic energy
1981-2007 average (J/m2)
MIPOM 1.5km ROMS 1.5km
12012 1539818558
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LPR #46 OPNet, Geilo, Norway, May 27, 2010
Eddy kinetic energy
1981-2007 average (J/m2)
MIPOM 4km ROMS 4km
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LPR #47 OPNet, Geilo, Norway, May 27, 2010
Eddy kinetic energy
1981-2007 average (J/m2)
MIPOM 1.5km ROMS 1.5km
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LPR #48 OPNet, Geilo, Norway, May 27, 2010
Horizontal shear conversion
1981-2007 average (W/m2)
MIPOM 4km ROMS 4km
Regions with negative (red colours) convert energy into eddy kinetic energy
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LPR #49 OPNet, Geilo, Norway, May 27, 2010
Horizontal shear conversion
1981-2007 average (W/m2)
MIPOM 1.5km ROMS 1.5km
Regions with negative (red colours) convert energy into eddy kinetic energy
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LPR #50 OPNet, Geilo, Norway, May 27, 2010
Vertical shear conversion
1981-2007 average (W/m2)
MIPOM 4km ROMS 4km
Regions with negative (red colours) convert energy into eddy kinetic energy
Norwegian Meteorological Institute met.no
LPR #51 OPNet, Geilo, Norway, May 27, 2010
Vertical shear conversion
1981-2007 average (W/m2)
MIPOM 1.5km ROMS 1.5km
Regions with negative (red colours) convert energy into eddy kinetic energy
Norwegian Meteorological Institute met.no
LPR #52 OPNet, Geilo, Norway, May 27, 2010
Baroclinic conversion (sum of all sub-terms)
MIPOM 4km ROMS 4km
Regions with negative (blue colours) convert energy into eddy kinetic energy
Dominant terms
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LPR #53 OPNet, Geilo, Norway, May 27, 2010
Baroclinic conversion (sum of all sub-terms)
MIPOM 1.5km ROMS 1.5km
Regions with negative (blue colours) convert energy into eddy kinetic energy
Dominant terms
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LPR #54 OPNet, Geilo, Norway, May 27, 2010
Baroclinic conversion (sub-term no. 1)
MIPOM 4km ROMS 4km
Regions with negative (blue colours) convert energy into eddy kinetic energy
Norwegian Meteorological Institute met.no
LPR #55 OPNet, Geilo, Norway, May 27, 2010
Baroclinic conversion (sub-term no. 1)
MIPOM 1.5km ROMS 1.5km
Regions with negative (blue colours) convert energy into eddy kinetic energy
Norwegian Meteorological Institute met.no
LPR #56 OPNet, Geilo, Norway, May 27, 2010
Baroclinic conversion (sub-term no. 3)
MIPOM 4km ROMS 4km
Regions with negative (blue colours) convert energy into eddy kinetic energy
Norwegian Meteorological Institute met.no
LPR #57 OPNet, Geilo, Norway, May 27, 2010
Baroclinic conversion (sub-term no. 3)
MIPOM 1.5km ROMS 1.5km
Regions with negative (blue colours) convert energy into eddy kinetic energy
Norwegian Meteorological Institute met.no
LPR #58 OPNet, Geilo, Norway, May 27, 2010
Conclusions
• Overall new model (ROMS) performs better than the old model (MIPOM) – Better current frequency distributions– Slightly better skill
• Surface flux parameterization important – Large impact on the heat content– Modified ROMS version superior in both
temperature and salinity distributions
LaCasce et al. (2007) concluded:The ROMS velocities are more energetic and compare more favorably with in situ observations, as do the ROMS-derived means
Norwegian Meteorological Institute met.no
LPR #59 OPNet, Geilo, Norway, May 27, 2010
Final Remarks
• Increased resolution (4km -> 1.5km):• Better score on validation of currents due
to better resolved topography• Validation score in S and T slightly
worsened
• MKE patterns• Comparable, but there are differences
• EKE patterns• Not comparable
• Baroclinic energy conversion:• Due to the pulsating salinity front• Very clearly seen along the Norwegian
Coastal Current
Norwegian Meteorological Institute met.no
LPR #60 OPNet, Geilo, Norway, May 27, 2010
J. Albretsen and
L. P. Røed
JonsMod 2008
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LPR #61 OPNet, Geilo, Norway, May 27, 2010
Norwegian Meteorological Institute met.no
LPR #62 OPNet, Geilo, Norway, May 27, 2010
Temperature bias (mod – ICES obs)
1981-2007 average; 50-600 m
ROMS 4kmMIPOM 4km