"كتيّب الجزيرة العربية. المجلد I. ١٩١٧" [‎١‎٤‎٧] (٧٤٨/١٥٦)

PHYSICAL CHARACTER
147
I drain the eastern scarp are the Kharid (said to be perennial),
which loses itself somewhere in the sands east of Janf, and Wadis
I Bana and Tiban, which lead south-eastwards towards the coast
: of the Gulf of Aden.
II
Climate
The climate of Yemen naturally varies very greatly, both in
temperature and rainfall, according to altitude and district. The
coast is extremely damp and, though the sea-breezes lower the
temperature, the excessive humidity makes the heat very trying.
Heavy winds are prevalent from the sea, from north-west in summer
and south-west in winter, both uncomfortably damp. Winds
from the east usually bring sandstorms, but rain seldom reaches
the coast. The Tihamah is fiercely hot by day and fairly cool at
night, but it is comparatively free from the enervating dampness
of the coast-line; its rainfall is scanty and irregular. The maritime
ranges and intramontane plains have a feverish climate with close,
muggy nights, especially in the rainy season among the foot-hills ;
but as one approaches the higher elevation the air becomes more
healthy and bracing. The principal rainfall occurs in spring ; but,
on the higher ground, in summer as well, and then chiefly as
thunderstorms.
On the maritime ridge, at 5,000 ft, and over, winter fogs are
prevalent; mists come up from the ravines in the early after
noon, and lie thick till next morning and sometimes all next
day; they are not, however, without their advantages, as they
favour the growth and development of the coffee plant. This zone,
with its regular rainfall, due chiefly to the influence of the SW.
monsoon, may be considered as the most favoured district of Arabia;
broadly speaking, however, the district has two rainfalls, one in
early spring and another in late summer with the NE. monsoon.
The plateau has a much drier climate, of which that of San'a
may be taken as fairly typical. Here it may be described as cool
and pleasant all the year round : the nights are cold in winter but
the days warm, and in summer the heat, though considerable, is not
oppressive owing to the dryness of the air; a difference of more
than 20° may be sometimes observed between the wet- and dry-bulb
thermometer readings in May. The eastern plateau has much smaller
and less certain rainfall than the west, the bulk of which may be
expected in summer; the periods of fall, however, are often short,
and local famines are not uncommon. The eastern scarp is hot and
has a scanty rainfall, which decreases eastward. Here the season of
such precipitation as there is extends from November to February.
K 2