'Handbook of Yemen' [‎8v] (21/190)

(5) The Plateau zone, being all that lies beyond the Main
Ridge, is, as has been said above, of table-land character
at first, and following the general trend, slopes up to the
southward till it reaches its culmination (9,000 feet) south
of Tbb. At San'a its level is about 7,500 feet. In the
western part it is not unfertile, though less productive
than the fourth and third zones, and it is interspersed with
more frequent barren areas. . As it declines in the eastern
part, it becomes predominantly a dusty steppe with occa
sional oases in low-lying basins which immediately precede
the Great Desert. The edge of the latter, like that of the
Northern Nefud of Arabia, rises high above the level
of the steppe, and springs and wells are found near the
border-line of the two tracts.
This eastern zone does not send, like the corresponding
zones of Asir and Hejaz, any large drainage channels into
Central Arabia, its waters, mainly carried by the adi
Kharid, being unable to pass the great obstruction of the
Red Desert. But from the extreme north (Nejran) a con
siderable wddi flows north by east to an unknown
destination.
The characteristics of the landscape in these five zones
will be dealt with later in greater detail under the different
districts.
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 sea-breezes
lower the temperature, excessive humidity makes the heat
very trying. Heavy winds are prevalent from the sea,
from the north-west in summer and the south-west in
winter, both being uncomfortably damp. Winds from
the east usually bring sandstorms. Rain seldom falls on
the coast. The inner Tihamah is fiercely hot by day and