Geoscience Reference
In-Depth Information
G
T
V
C
T
L
Madrid
L
L
Le
S
V
Le
L
V
0
km
200
0
miles
200
CIERZO (C) winter : 6 months
SOLANO (S) summer
TRAMONTANA (T) winter
VENDAVAL (V) winter : 6 months
GALERNA (G) all year esp. winter
LEBECHE (Le) spring and summer
LEVANTE (L) all year : N and W limit
Figure 10.28
Areas affected by the major regional winds in Spain as a function of season.
Source: From Tout and Kemp (1985). By permission of the Royal Meteorological Society.
moving across the eastern Mediterranean,
preceded by a warm southerly
khamsin
and
followed by a northerly airstream, brought up
to 70mm of rain in only four hours to an area of
the southern Negev Desert. Although April is
normally a dry month in the eastern Mediter-
ranean, Cyprus having an average of only three
days with 1mm of rainfall or more, high rainfalls
can occur, as in April 1971 when four depressions
affected the region. Two of these were Saharan
depressions moving eastward beneath the zone
of diffluence on the cold side of a westerly jet
and the other two were intensified in the lee of
Cyprus. The rather rapid collapse of the Eurasian
high pressure cell in April, together with the
discontinuous northward and eastward exten-
sion of the Azores anticyclone, encourages the
northward displacement of depressions. Even if
higher latitude air does penetrate south to the
Mediterranean, the sea surface there is relatively
cool and the air is more stable than during the
winter.
By mid-June, the Mediterranean basin is
dominated by the expanded Azores anticyclone to
the west, while to the south the mean pressure
field shows a low pressure trough extending across
the Sahara from southern Asia (see
Figure 10.26
).
The winds are predominantly northerly (e.g. the
etesians
of the Aegean) and represent an eastward
continuation of the northeasterly trades. Locally,
sea breezes reinforce these winds, but on the
Levant coast they cause surface southwesterlies.
Land and sea breezes, involving air up to 1500m
deep, largely condition the day-to-day weather of
