2008 ROMS/TOMS European WorkshopSaint Martin d'Heres Campus
Grenoble, France
(1) University of Lisbon, CGUL, IDL(2) University of Hamburg, Center for Marine and Atmospheric Research (ZMAW)
Sensitivity of Iberian upwelling to climate change: a numerical simulation with ROMS forced by RACMO A2 scenario
José Alves (1) Pedro M A Miranda (1) Nuno Serra (2)
Summary
Detailed study during the year 2000 (U, V, W, SST, SSH)
ECMWF – ERA 401960-2000
RACMO1961-19902071-2100
ROMS
Longitude W
Latit
ude
N
-30 -25 -20 -15 -10
32
34
36
38
40
42
44
46
48
50
-6000
-5000
-4000
-3000
-2000
-1000
0
1000
2000
3000
Cape CarvoeiroLatitude: 39.35 N Longitude: 9.4 W
ROMS domain
ROMS RUTGERS version 3.0
Model parametersResolution : horizontal 1/12 (approx =7 km) Mercator projection vertical 30 – sigma layers (theta_s =5.0 ; theta_b=0.4)
Grid: 97 x 153 x 30
Time step DT=900 s (NDTFAST=100 s)
Mellor Yamada 2.5 closure
Mix_Geo_UV and Mix_Geo_TS (mixing on geopotential) constant z
Initial ConditonsLevitus world ocean database
Boundary conditionsRadiation and Nudging
Surface forcing
ATMOSPHERIC DATA (BULK_FLUXES)
ECMWF – ERA 40 ( 6 hour) (1960-2000), 1 degreeRACMO (KNMI) (24 hour) (1961-1990) and (2071-2100), 0.5 degree
Downward shortwave radiation (swrad)× Downward longwave radiation (lwrad) 2m air temperature (Tair) 10 m wind (Uwind, Vwind) pressure (Pair) relative humidity (Qair)
Forcing (ERA 40) at Cape Carvoeiro Year 2000Surface temperature Relative humidity
Surface pressure
Cape Carvoeiro
T (C) Q (%) P (hPa)
mean 16.41 80.31 1018.9
max 23.21 100 1037.2
min 7.90 44.88 985.94
24°C
8°C
Shortwave radiationSurface wind
Year 2000Cape Carvoeiro
Uwind (m/s)
Vwind(m/s)
Swrad(W/m2)
mean 1.31 -2.70 155.48
max 12.64 19.18 648.62
min -10.13 -14.40 0
Forcing (ERA 40) Cape Carvoeiro Year 2000
Results: Summer 2000 at Cape Carvoeiro
1 July 31 August
ROMS
1 July
1 July 1 July
31 August
31 August 31 August
1 2 3
Sea surface height at cape Cape Carvoeiro 2000
1 July 31 August
ROMS
Spatial variability (full year)
Longitude (W)La
titude
(N)
-14 -13 -12 -11 -10 -9 -836
37
38
39
40
41
42
43
44
10
11
12
13
14
15
16
17
18
19
20
Cape Finisterre
Cape Carvoeiro
Cape São Vicente
Most of the events are verified simultaneously along the coast.
Validation near Cape Carvoeiro
Satellite AVHRR (1/4 AVHRR daily OI SST) vs ROMS
AVHRR, NOAA
ROMS
Nearest points
SST during the July and August 2000
Results Summer 2000 episodes
variable Upwelling Episodes
SSTsea surface temperature
decrease T < - 4 K
Uzonal current westward U < 0.3 m/s
Vmeridional current southward V < 0.4 m/s
Wvertical component
upward W < 0.15 mm/s
SSHsea surface height
lower values H < 0.06 m
Upwelling near Iberia is episodicEpisode duration ~1-2 weeksExtension < 50 kmIntensity < 4 K
40 year simulation forced by ERA-40
ECMWFSurface wind( m/s)
1960-1969 1970-1979 1980-1989 1990-1999
U mean (m/s) 1.05 0.97 0.63 0.56
V mean (m/s) -1.14 -1.34 -1.15 -1.22
Wind turned to more NortherlyImplying more frequent (simulated) upwelling
Decade 1960-1969 1970-1979 1980-1989 1990-1999
Mean angle() 317.35 324.10 331.28 335.34
Climate change impacts on upwelling
The upwelling episodes were identified through the analyses of sea surface temperature time series. The threshold considered to identify an upwelling event was a decrease in SST of at least 2C in less than 1 week, followed by an increase of the same magnitude in a similar time period.
Number of events
RACMO model surface winds at Cape Carvoeiro
From 2001-2100, it is observed an increase in the wind intensity, although the mean direction has not changed.
Surface wind (m/s)
1961-1970 1971-1980 1981-1990 Mean1961-1990
U 2.35 1.79 2.04 2.06
V -1.30 -1.07 -1.09 -1.15
Surface wind (m/s)
2071-2080 2081-2090 2091-2100 Mean2071-2100
U 2.87 2.79 2.48 2.71
V -1.34 -1.59 -1.44 -1.46
1961-1970 1971-1980 1981-1990 Mean
Mean angle () 298.95 300.87 298.12 299.17
2071-2080 2081-2090 2091-2100 Mean
Mean angle () 295.03 299.68 300.14 298.31
(1961-1990) (2071-2100)
Atmospheric forcing variables
Increase in the mean temperature of 2.2 C / slight increase in the variabilitySlight decrease in the pressure mean value / increase in the variabilty
110
12
14
16
18
20
22
24T
empe
ratu
re (
ºC)
1
1000
1005
1010
1015
1020
1025
Pre
ssão
(m
bar)
1
1000
1005
1010
1015
1020
1025
Pre
ssão
(m
bar)
110
12
14
16
18
20
22
24
Tem
pera
tura
(ºC
)
TEMPERATURE
SURFACE PRESSURE
50%
mean 1961-1990 2070-2100
U (m/s) -0.0096 -0.0137
SST (C) 16.224 17.9394
ROMS forced with RACMO
ROMS forced with RACMO data(Regional Atmospheric Climate MOdel)
1961-1970 1971-1980 1981-1990 TOTAL
2<T<3 23 30 31 84
3<T<4 7 5 5 17
4<T<5 4 1 1 6
TOTAL 34 36 37 107
2071-2080 2081-2090 2091-2100 TOTAL
2<T<3 25 24 32 81
3<T<4 17 3 10 30
4<T<5 1 3 4 8
TOTAL 43 30 46 119
RACMO control has no relevant decadal tendencies (unlike ERA-40)
10% more
Sligtly increase in the westward horizontal displacement
f
i
t
t
dtUx )0,min(
Increased interanual variability
Number of days with westward current Horizontal displacement
CONTROL A2CONTROL
A2
Increase in the number of events of short duration (1 week)and long duration (4 weeks), decrease in the number of events of medium duration (3 and 4 weeks) , more interdecadal variability
CONTROL
A2
Upwelling duration
Slight increase in the events intensity
CAT I > 4 °C || 3 °C< CATII <4 °C|| 2 °C< CATIII < 3 °C
Upwelling intensity
ConclusionsROMS forced by ERA-40
Increase in the decadal number of upwelling events from 1960 to 2000 due to change in the mean wind direction.
ROMS forced by RACMO control run (1961-1990) Number of upwelling events almost constantRACMO fields do not include observed climate trends
ROMS A2 scenario (2071-2100)10% increase in the number of upwelling events (vs Control run)due to an increase in the wind intensity
A2 2071-2100 simulated upwellingIncreased event duration variability (More long and short events)Slight increase in mean event intensityIncreased interdecadal variability
Future work
Add Tagus estuary to the computational domain in order to study the circulation within the Tagus estuary – grid nesting
Use atmospheric data with a higher spatial resolution
Apply boundary conditions from a global ocean model
Look at other upwelling diagnostics
Mean 1961-1990 2070-2100
eastward horizontal displacement (m)
4.2793e+05 3.9527e+05
westward horizontal displacement (m)
-7.2722e+05 -8.2122e+05
N of days with U>0 167.56 155.40
N of days with U<0 192.69 204.85
ROMS forced with RACMO
Initial conditionsLevitus 1 January
Surface salinity Surface temperature
Longitude (W)
Latit
ude
(N)
-14 -13 -12 -11 -10 -9 -836
37
38
39
40
41
42
43
44
35
35.2
35.4
35.6
35.8
36
36.2
36.4
36.6
36.8
37
Longitude (W)
Latit
ude
(N)
-14 -13 -12 -11 -10 -9 -836
37
38
39
40
41
42
43
44
10
11
12
13
14
15
16
17
18
19
20
ROMS forced with ECMWF ERA 40 data
mean 1961-1990
eastwarddisplacement (m)
6.9122e+05
westward displacement (m)
-9.5504e+05
N of days with U>0 140.30
N of days with U<0 220.70
Climate change impacts on Iberian upwelling
ROMS forced with ERA 40
2K
ROMS forced with RACMO Control vs ERA-40
ERA 40 Vs RACMO
ERA 40 reanalysis data
RACMO data from a climate model
• Quando o modelo ROMS foi forçado com dados do ECMWF-ERA40, no período 1960-2000, verificou-se um aumento do número de episódios de upwelling, enquanto que quando se utilizou o forçamento do modelo RACMO, para o mesmo período, se verificou que o número de episódios de upwelling se manteve praticamente constante.
• Nas projecções para o final do século XXI [2071-2100] (modelo RACMO) verificou-se um aumento do vento junto ao Cabo Carvoeiro e um consequente aumento do número de episódios de upwelling, cerca de 10 % em relação ao verificado no período 1961-1990.
• No Cabo Carvoeiro a maioria dos episódios de upwelling eram e vão continuar a ser de longa duração (4 semanas ou mais) e de baixa intensidade (2<T<3), embora se tenha verificado um ligeiro aumento na intensidade dos episódios.
• O número de dias de upwelling por ano praticamente não sofre alteração.
Sea surface temperatureSST at layers 30-20-10
1961-1990 2070-2100
mean eastward horizontal displacement (m)
1.7830e+04 1.6470e+04
mean westward horizontal displacement (m)
-3.0321e+04 -3.4218e+04
mean U>0 (days) 167.56 155.40
mean U<0 (days) 192.69 204.85
1961-1990 2070-2100
mean U (m/s) -0.0096 -0.0137
mean SST (C) 16.224 17.9394
SST Vertical sections
Cape São Vicente (lat= ???N/lon=??? W)
Cape Carvoeiro (lat= 39.35 N/lon=9.40 W )
Cape Vilano (lat= ???N/ lon=???W )
July and August 2000
SST; SSH; currents U and V
30 year temporal seriesHorizontal displacement (m)Number of days with U>0 and U<0
30 Year temporal seriesU and SST
Currents (U, V and W)
Sea surface heightSSH
Lower values close to the coast during upwelling episodes due to …
STATIONS
Map with stations locations
FLOATS
Map with float trajectories
Validate SST with satellite data
Conclusions
Problems
Sea surface temperature values too low during the winter months
Ver figura em Inglês
1961-1990 2071-2100