AGENZIA REGIONALE PER LA PROTEZIONE DELLAMBIENTE DELLA SARDEGNA ARPAS Andrea Motroni...

AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA

ARPAS

Andrea Motroni

[email protected]

Climate, climate change and desertification in Sardinia

ENVIRONMENTAL PROTECTION AGENCY OF SARDINIA

AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA - ARPAS

Agenda

• Climate characteristics

• Trends in climate

• Evidence of climate change?

• Climate and desertification

14TH European Seminar on Geography of Water - Cagliari, June 26th - July 7th, 2011


The climate of Sardinia is generally classified as “Mediterranean”

Mediterranean climates are located between regions with a

tropical-desert climate and those with a marine-coast climate.

They generally lie between 30 and 40 degrees latitude.

These regions have hot-dry summers and mild-wet winters.



•The Mediterranean Basin can be considered as a transitional area

between tropical zones, where seasons are determined by rainfall

occurrence, and temperate zones, where seasons are determined by

variations in temperature values.

•Consequence: there are great interseasonal variations in

precipitation amounts and in temperature values without the extreme

values typical of the two climatic areas (Chritchfield, 1983; Martyn,

1992)


AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA - ARPASGeneral circulation



•Mediterranean basin is characterized by the highest frequency

and concentration of cyclogenesis events.

•The majority of cyclones are formed in the gulf of Genoa,

probably because of Alps position and the high temperature

gradient between central-northern Europe and the

Mediterranean sea.

• In the transition periods of March-April and September-October

occur the most intense cyclogenetic rain events.

•Mediterranean climate is influenced by the presence of relevant

orographic systems along the Med. Basin -> major cyclones

activity



The great seasonal differences are due to

northward migration of the upper limit of high

pressure cells typical of subtropical areas.

In Summer, high pressure cells reach the

Mediterranean area causing atmospheric

stability which can lead to typical arid

subtropical conditions in June, July, August

with high maximum temperature values.

In the Winter season, the cells leave the Mediterranean sea and lay in north Africa

region. Humid air fluxes and cold Polar fronts characterize autumn, winter and partly

spring seasons in this area



Climate in Sardinia

Except for general synoptic situations (atmospheric pressure)

- Complex orography

- Distance from the sea

- Wind

Can we talk about climate microregions in Sardinia?



Temperature


Temperature in Sardinia• Two transition periods before winter and summer

– September-November– March-April

• Depends on orography and altitude:– Thermal inversion in the valley areas– Eastern coast areas protected from cold north-western dominant winds

• Winter temperature values are mainly determined by the stabilizing effect of the sea (the inner areas of the island show a “continental” behaviour)

• Summer temperature values are influenced by stabilizing effect of anticyclonic cells and a north-south gradient can be seen (maximum temperature also west-east)

• Maximum and minimum temperature values show the same behaviour, but minimum temperature values show less variability



July

Mean maximum temperature 1961-90


AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA - ARPASMean minimum temperature 1961-90

January


AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA - ARPASClimatic mean temperature 1961-90



Precipitation



Precipitation behaviour (where)

• 4 rain microregions:

– Gennargentu and Ogliastra

– Gallura and Limbara

– Campeda

– Sulcis-Iglesiente

• 3 dry regions

– Nurra

– Campidano

– Central-north Sardinia

(1961-90)



Precipitation behaviour (how much)

• Minimum rain values:

– < 400 mm in the south west

• Maximum rain values

– 1200 mm (Gennargentu)

• Regional mean

- 600 mm

(1961-90)



Precipitation behaviour (how)

• Frequency of rainy events– The areas where we have more than

80 days of rain/year are also the areas where it rains the most...

...except for the central-east coast

(1961-90)


AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA - ARPASMean annual rainfall 1961-90

…where we have 50 days/year but rain>than average



Rainfall regimes on daily basis 1961-90



The north-west and south-west regimes are mainly frontal regimes (higher frequency, not very intense rain events)

The central-eastern regime is associated to south-eastern winds which impact the coastal orography in correspondence of cyclones that move along the coast of north Africa leading to convective rain events (less frequent, heavy rain)



Wind



Frequency of instantaneous wind

Fonni

MacomerAlghero

010

2030

0102030

0

10

20

30

0102030

0102030

0102030

01020304050

La Maddalena

0

10

20

30

Capo Frasca

Asinara

0

10

20

30

Decimomannu

0102030

Capo Carbonara

0102030

Carloforte

Perdasdefogu

Capo Bellavista

STAZIONE %

ASINARA 14.5

LA MADDALENA 11.0

ALGHERO 32.7

MACOMER 53.4CAPO FRASCA 24.3

FONNI 39.8

CAPO BELLAVISTA 25.3

PERDASDEFOGU 23.1CARLOFORTE 50.3

DECIMOMANNU 49.8

CAPO CARBONARA 3.9

Calm or variable wind

Percent of hours with wind blowing from different directions

Calm or variable wind (<1.5 m/s)



Monthly means of instaneous wind speed

ALGHERO

0

2

4

6

8

10

1 2 3 4 5 6 7 8 9 10 11 12

mese

1961-1990

LA MADDALENA

0

2

4

6

8

10

1 2 3 4 5 6 7 8 9 10 11 12

mese

1961-1990

CAPO FRASCA

0

2

4

6

8

10

1 2 3 4 5 6 7 8 9 10 11 12

mese

1961-1990

CAPO BELLAVISTA

0

2

4

6

8

10

1 2 3 4 5 6 7 8 9 10 11 12

mese

1961-1990



Monthly means of maximum wind speed

ALGHERO

0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12

mese

1961-1990

LA MADDALENA

0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12mese

1961-1990

CAPO FRASCA

0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12

mese

1961-1990

CAPO BELLAVISTA

0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12mese

1961-1990

AGENZIA REGIONALE PER LA PROTEZIONE DELL’AMBIENTE DELLA SARDEGNA - ARPASBreeze winds in Sardinia


Trends and extreme events



Anomaly Index of mean temperature



Total Amount Precipitation Index

t

j

N

j

jjt

tt

t

P

NSPI

1

)(1

Pjt Total amount of P

j Mean (1961-1990)

j Standard Dev.

(1961-1990)



Precipitation classes – Quality of rain

-3,0

-2,0

-1,0

0,0

1,0

2,0

3,0

4,0

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

idx

anno

1 - 5mm rain events

idx

m.mob.

-3,0

-2,0

-1,0

0,0

1,0

2,0

3,0

4,0

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

idx

anno

5 - 20 mm rain events

idx

m.mob.

-3,0

-2,0

-1,0

0,0

1,0

2,0

3,0

4,0

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

idx

anno

>50 mm rain events

idx

m.mob.

+7.9 +4.4

Precipitazioni fra 20 e 50mm (cumulato)

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

anno

idxm.mob.

20-50 mm rain events



Mean annual rainfall amounts (1951-2000)Mean annual cumulative reference

evapotranspiration (1951-2000)

Aridity trends



4,6% semi-arid

29,8% dry sub-humid

7,5% humid

58,1% sub-humid

1951-00

Aridity Index = P/ETo



•81-90 and 91-00 decades critical for mean temperature raising and rainfall deficit

•91-00 the worst due to more frequent extreme events

•51-60 slightly dry but with average temperature

•But...•1997-2003•2004•2009-2010

Aridity indexAridity indexFAO-UNEP (P/ETo)FAO-UNEP (P/ETo)

14TH European Seminar on Geography of Water Cagliari, June 26th - July 7th, 2011



1996-2005

° driest period/50 ys but…

° carefulness in climate data managing


Standardized Precipitation Index a 24 mesi

y = -0.004x + 1.1424

-3

-2

-1

0

1

2

3

4

52 54 56 58 60 62 64 66 68 70 72 74 75 77 79 81 83 85 87 89 91 93 95 97 98

anno

SP

I a 2

4 m

esi

Precipitation trends SPI 1951-00

year



Sardinia - Number of events with SPI<-1

05

101520253035404550556065707580

1953

1955

1957

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

Year

Nu

mb

er

of

ev

en

ts

Extreme drought events



Mean 1951-00 rainfall totalMean 1951-00 rainfall total



UNCCD(1):“Land degradation in arid, semi-arid and dry/sub-humid areas, resulting from various factors, including climatic variations and human impacts” (UNEP, 1994)

Definition of “desertification”

(1): United Nations Convention to Combat Desertification



…, i.e. desertification is a complex phenomenon strictly

dependent on climate



Extreme climatic events: drought/floods

Pressures on the territory: overgrazing, uncontrolled urbanization/country areas abandonment…

Excessive exploitation of water resourcesWater contamination

Fires and deforestation

Causes of desertification in Sardinia

Soil salinisation



Parent material

Soil texture

Rock fragment

Soil depth

Drainage

Slope gradient

Rainfall

Aridity index

Aspect

Fire risk

Erosion protection

Drought resistance

Plant cover

Land use intensity

Policy

VQIVegetation

Quality Index

SQISoil Quality

Index

CQIClimate

Quality Index

MQIManagement Quality Index

ESAs



Sensitive areas to desertificationESAS

Sardinia



Final remarks

- there are some signicative trends in changing temperature and rainfall values - they can be controversial both in sign (-/+) and in consistency – time and spatial scale problem

climate variability VS. climate change

- desertification is a more human induced process than climate-driven

further investigation on data and monitoring (for example) with bio-indicators are needed




Thank you

[email protected]

AGENZIA REGIONALE PER LA PROTEZIONE DELLAMBIENTE DELLA SARDEGNA ARPAS Andrea Motroni...

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