Walker - 1967 - A geography of Italy

CLIM A TE
and at Bologna 2-5°i and temperatures may fall to — 7°C for short spells. Coastal
stations on the Adriatic enjoy somewhat milder winters (Trieste 5'3°C, Venice
3-8»C).
The distribution o f temperature within the Alps lends itself less to generalization;
apart from altitude, much depends on aspect, the orientation o f relief in
relation to cold northedy airstreams, the incidence o f the föhn, and the proximity
of lakes, which tend to mitigate the winters (Salö Jan. 4°C and only 27 frosts).
In the deeper valleys temperature inversion is a common occurrence and the
floor is frequently blanketed in fog while the upper slopes are bathed in sunshine.
Sondrio (295m), for example, has an average o f 85 frosty days, and at Bormio
(Jan. — i ‘4°C) temperatures o f — 15° are not tmusual. The climate above about
looom may be classed as Alpine and up to 150 frosty days may be expected.
In the peninsula and islands temperatures reflect the proximity o f the sea as
well as latitude and altitude (Bari 8-4°C, Foggia 6-3°C). The Tyrrhenian shores,
which are less exposed to chilling Polar continental influences and benefit
thermally from the effects o f a deeper sea, are milder than those o f the Adriatic
(Leghorn Jan. 8-o°C; Ancona 4-8°C). On the Calabrian and Sicilian coastlands
severe frosts are rare but temperatures may fall to zero three or four times a year.
Much of the Apennine zone may be classed as Sub-Alpine in temperature and
prolonged frosts are normal; in the intermontane basins temperature inversion
is frequently experienced. Aquila (785m) has a January mean o f 2-i°C and
Capracotta (1421m) o f o-i°C.
Throughout the whole country to a lesser or greater degree maritime influences
are recognizable in the warmth o f the autumn compared with spring,
and in the length o f both intermediate seasons. It should be noted that Italy, in
spite of its enviable climatic reputation, is no more immune than its northern
neighbours from freak weather; the severe winter o f 1956 was particularly
disastrous even in the south o f the country.
HUMIDITY AND PRECIPITATION. It will be apparent from the brief remarks
made above on the changing pressure situation from season to season that the
vast majority o f the rainfall experienced over Italy is o f cyclonic origin, and that
the distribution will be largely determined by the height and orientation o f relief
while the periodicity will depend on the frequency o f depressions along the
various tracks at each season. T he heaviest rainfall occurs in the Alps and the
Pre-Alps, the Ligurian Apennines, and western-most massifs o f the Abruzzi and
Campanian Apennines, and the mountains o f Calabria and north-east Sicily.
The rest o f Sicily, Sardinia and Apulia are particularly dry (see fig. 10).
As regards regime the fundamental distinction is between the North (Liguria
excepted), which receives more than half of its rainfall in the summer half-year
(April-September), and the peninsula and islands which receive the majority
in the winter half-year. On these two major themes there are numerous variations.
In the northern zone winter (Dec., Jan., Feb.), and summer are generally
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