CLIMA EN ESPAÑA: PASADO, PRESENTE Y FUTURO

Contribución a un Informe de Evaluación del Cambio Climático Regional

11-12-13 Febrero 2009

Presentación: Salat & Pascual

Posible efecto de la diferencia de calentamiento entre el mar y el aire a las

precipitaciones en la cuenca mediterránea

Possible effect of air-sea differential warming trends on the Mediterranean basin precipitation

seasonality

Jordi SALAT y Josep PASCUALInstitut de Ciències del Mar de Barcelona (CSIC)

P. Marítim, 37-49. E-08003 Barcelona.

¿VOLVERÁN LAS LLUVIAS DE PRIMAVERA?

¿Where is the water?

Oceans: 1370 106 km3

Continents: 35 106 km3

Atmosphere: 0,01 106 km3

Global water cycle

On land:

Rivers, lakes, etc: 0,15 106 km3

Continental ice: 29 106 km3

Groundwater: 5,85 106 km3

Water exchanges (hm3/s)?

-3,512,2Atmosphere

2,2-1,3Continent

13,5--Ocean

AtmosphereContinentOceanFrom↓ To→

Percents on global water cycle:

Precipitation on land: 3,5/15,7=22%Rivers: 1,3/15,7= 8%

Global water cycle

Turnover times:

Continental* water:35/0,069 ≈ 500 a

Marine water:1350/0,041 ≈ 33000 a (66x)

Precipitation on land from evaporation on

continents:2,2 hm3/s=0,069 106 km3/a (63%)

ocean:1,3 hm3/s=0,041 106 km3/a (37%)

*including permanent ice caps and ground water

Global water cycle

37 % of precipitation on the continents is originated in the ocean through evaporation

Global water cycle

However, Most research programs on the Global Water Cycle do not properly treat the ocean’s role.

Small components of the terrestrial water cycle receive great attention, yet elements of the much larger oceanic water cycle are ignored!

So that,

We know rather little about oceanic freshwater fluxes because Water Cycle research has focused on land and atmospheric processes, and neglected the much larger oceanic component.

Evaporation over the ocean

On what depends?

1. Sea surface temperature must be higher than air temperature

and2. Evaporation will

+ Increase with sea sea surface temperature+ Increase with wind— Decrease with relative humidity of the air

Recall:37 % of precipitation on the continents is

originated in the ocean through evaporation

If the Earth is retaining heat, warming the air is faster than the ocean.

Because:Specific heat of the ocean is 1100 times higher than the atmosphere.

Thus:1. Air may allow more water vapour2. Evaporation may increase3. Water cycle is accelerating

Global warming

But…The ocean retains heat for longer

As warming the air is going faster than the ocean, the occurrence of sea surface warmer than the air will be less frequent.

Hence:Evaporation over the ocean will decrease

andPrecipitation on the continent originated from the sea could decrease.

Global warming

This is the point!

As warming the air is going faster than the ocean, the occurrence of sea surface warmer than the air will be less frequent.

Hence:Evaporation over the ocean will decrease

andPrecipitation on the continent originated from the sea could decrease.

The Mediterranan

View centered on 55°N 0°

The Mediterranean

The Mediterranean isn’t the sea between the lands …

but the sea between mountains

Dry south

Dominant cold & dry northerly winds

The Mediterranean

Surrounded by mountainsSmall river basins*

Part of the southern side is very dry (desertic) Frequent strong and dry winds in northern side

Evaporation exceeds precipitation over the basin

1. It imports sea water from the ocean, and

2. exports fresh water to other basins

*excluding the Nile river and Black sea basins

The Mediterranean

Mediterranean without

Black Sea

Black Sea Global Mediterranean

Vol. Eq. Height Vol. Eq. Height Vol. Eq. Height (km3/a) (mm) (km3/a) (mm) (km3/a) (mm)

Rivers 514 200 400 950 914 306 Precipitation 884 350 181 430 1065 356

Net Input 1930 760 -189 -450 1741 582 Evaporation 3328 1310 392 930 3720 1244

The Mediterranean

Water balance

Net export of water out of the basin through the atmosphere:1,74 103 km3/a (must equal net input)

The Mediterranean

Is a big desalination plant producing~ 5500 m3/s

for the neighbours

That’s solidarity!

But... may this change with “Global Warming” ?

Local scale: Observationssince 1974 at L’Estartit

air

Seasurface

Sea at 80 m

Monthly temperature series

Summary of trends

 °C/a Annual Winter Spring Summer Fall

Air Temp. 0,054 0,045 0,082 0,062 0,053

Sea surface Temp. 0,036 0,020

0,011 min.

0,043

0,060 max.

0,034

0,049 max.

0,034

0,025 min.

Sea Temp @ 80 m 0,023 0,016 0,019 0,015 0,040

Mean Temp (0-80 m)

0,032 0,019 0,032 0,040 0,040

Air Temp. - SST 0,031 0,024 0,053 0,024 0,021

Annual Cycle

12

14

16

18

20

22

24

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Annual cycle

period of T@20m>17°C

1st.day = -0,77·(year-1974)+176,3 last.day = 0,67·(year-1974)+297,8

120

160

200

240

280

320

360

1974 1978 1982 1986 1990 1994 1998 2002 2006

Juli

an d

ay “Summer period” length

Annual cycle

12

13

14

15

16

17

1974 1978 1982 1986 1990 1994 1998 2002 2006

AIR

SST

Air and sea surface temperature series (April-May)

period of Tair>Tsup

1st.day = -1,42·(year-1974)+132,2 last.day = 0,75·(year-1974)+222,8

0

40

80

120

160

200

240

280

320

360

1974 1978 1982 1986 1990 1994 1998 2002 2006

Julia

n d

ay

“Dry period” length

 

trend of annual

increasetotal

increase series length

T>17@ 20 ("summer") days/year sign days yearsstart period 0,77 ++ 26,18 34end period 0,67 22,78 34

length period 1,44 48,96 34T.air> SST ("dry")

start period 1,42 ++ 49,70 35end period 0,75 ns 26,25 35

length period 2,17 75,95 35

Summary of trends

Trends in local precipitation

% of annual precipitation

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006

Winter: 7,38% Spring: -9,84% Summer: -7,79% Fall: 10,25%

Conclusions

1. A warming trend has been observed in the air and in all the sampled levels at sea (0-80 m)

2. The maximum trend has been observed in spring 3. Warming trend is higher in the air than at sea4. The sea stratified period (summer) has been extended for

49 days in 34 years (24 days anticipated)5. The period with air warmer than sea surface has been

extended for 75 days in 35 years (41 days anticipated)6. This evolution is unfavourable to evaporation during

spring.7. These changes may cause a reduction of spring rainfall,

which accounted for ~30% of the total annual in the Mediterranean basin.

8. The marine component of the Water Cycle is quite relevant but still not well understood.

MUCHAS GRACIAS

THANK YOU