Upload
leo-powell
View
212
Download
0
Tags:
Embed Size (px)
Citation preview
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