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CLIMATE
The meteo-climatic conditions of
Sardinia are influenced not only by its geography and
environment, but also and especially by atmospheric
circulation, with air masses of diverse
characteristics and origins entering, and occasionally
remaining over, the island. Particularly during the
cold part of the year, Sardinia is struck by
depressions and troughs running from west to east,
which often decrease further because of the relatively
high temperature of the surface waters and the
island’s particular geo-morphological structure. Also
in winter, air masses often converge on the island
from different directions, whereas, in summer, local
air masses diverge, with very little cloud and
precipitation; circulation at this time is very
slight, with local breezes predominating. The main
“fixed” meteorological and climatic factors affecting
Sardinia are: geographical position, geo-morphological
structure and vegetation. Much more variable elements
are: radiation, from both the sun (direct or diffuse)
and the environment; the temperature of the atmosphere
and the water; the physical characteristics of the air
masses entering and remaining over the island; the
physical conditions and associated difficulties, which
occur over time, particularly in winter; evaporation
of the surface waters and humidity in the atmosphere;
cloudiness; precipitation; atmospheric circulation. It
is worth noting that evaporation from the
Mediterranean is increasing constantly and is not
offset by rainfall and river efflux; sea water is
replenished, above all, by the current from the
straits of Gibraltar, flowing in west to east from the
Atlantic Ocean.
A part of these ocean currents arrives,
split up in several arms, at the Sardinian coasts,
where the current leads from north to south during the
winter months. In summer, there are ocean currents
from south to north along the south-west coast and
along the north-east coast. Finally, along the north
coast and south coast the currents flow from the west
to the east with increasing speed, especially in the
Straits of Bonifacio. In the major inlets along the
whole coastline particular eddies come into being
detaching themselves from the main currents.
Solar radiation
The extent of the global solar
radiation (direct and diffuse) which reaches
Sardinia’s surface has been measured using the data
registered by the three main meteorological stations
(Alghero, Olbia, Cagliari), which belong to radiation
measuring net of the meteorological service of the air
force. This net has got bimetal pyranographs
(i.e. instruments for the measuring of solar
radiation), model Robitzsch at its disposal and
calculates the interrelation between radiation and the
amount of clouds which has been observed by another 18
meteorological stations throughout the island over a
period of 10 years (1961 – 1970).
For each weather station, it calculates
the average monthly values of the global radiation on
the surface and registers them in special maps in
which the corresponding isolines
are marked.
Temperature of the superficial sea
water and of the atmosphere
In order to calculate the water
temperature, scientists take into consideration the
values that ships have been systematically measuring
in the western Mediterranean Sea and in the Tyrrhenian
Sea; proceeding thus, they have worked out the average
water temperatures of the months, seasons and the
whole year in the period between 1967 and 1969.
As regards the atmospheric temperature
they have examined the annual average values of the
daily temperatures, analysing the weather maps
–referring to the four decades between 1926 and 1965 –
of several Sardinian villages situated between the
sea-level and a height of 1000 metres. From the
analysis meteorologists have concluded that the
isotermal line of 16° C passes at a height of 200 /
300 metres for the most part of the island. In the
interior of this isotermal zone temperature goes down
to 15 ° C at a height of 500 metres, to 11° C/ 12°C at
a height of 1000 metres and to 7,5 ° C on the highest
peaks (e.g. of the Gennargentu). In the plains (e.g.
the rivers Tirso and Flumendosa) and on the lower
plateaus - where the sea breezes are less perceptible-
the temperatures rise to about 19 ° C. During
cloudless and windless nights and when the radiation
of the soil is very intense, the average temperature
falls to 16 ° C / 17 ° C in these areas.
Atmospheric humidity, clouds and
precipitation
The examination of the average values
of the atmospheric humidity - which was
uninterruptedly measured at 6 a.m. and at 1 p.m. in
the years between 1926 and 1965 - reveals the
following main characteristics:
a)
in
Sardinia’s coastal areas (breadth 15 – 20 km) there
are the highest annual average values (70 – 75 %)
b)
in the
interior of the island the values are about 50%;
In winter, the highest values vary
between 80% and 100%, whereas in summer, the lowest
values are about 50%.
The amount of clouds has been estimated
with the help of observation data (every three hours)
in the periods of time
mentioned above. These are the results: in the
majority of the examined Sardinian villages there
aren’t nearly any clouds in a third of the year
(0-3/10 cloudy sky). As regards precipitation in
Sardinia, the values of the hydrographical service of
the coast guard and the air force were taken into
consideration; especially several maps of the annual
isolines of precipitation were analysed.
Concerning the four decades between
1926 and 1960, the close and direct interrelation
between precipitation and orientation and structure of
the mountains becomes very evident.
The annual average value for the whole
island is about 780 mm/ year; this corresponds to 75%
of the average value of all the other Italian regions.
The spacial-temporal distribution is quite irregular;
the rainiest period is at 58 % in the period of autumn
and winter and the least rainy period of time is in
spring. Rainless periods are usually in winter; they
last between 10 and 30 days (known as winter
droughts).
Frost is quite rare; generally snow
falls only in altitudes above 500 metres. Here, we may
have snowfall between 50 and 100 times a year, whereas
it may snow in low areas only at 0 - 8 days a year.
Pluviometric (precipitation measuring)
station Dorgali, Casa Cantoniera Noce Secca,
Calagonone Casa Mula.
Sardinia’s milde climate – about 30
days of rainfall throughout the whole year –
guarantees that the target area (Cala Gonone) is
always passable for tourists. It also favours short
trips to the interior, as well as the presence of
foreign tourists during the off-season, on week-ends
and short holidays.
Many thanks to the agency for natural
and cultural tourism “Zente”. |
