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