"كتيّب بلاد الرافدين. المجلد I. ١٩١٨" [‎٣‎٨] (٥٦٨/٤٧)

38
CLIMATE
t
Schlafli, who resided there in 1862-3 and made careful meteoro
logical observations, notes that calms are comparatively rare. Even
though very light airs prevail in the early morning, the wind rises
steadily in the forenoon, and by the early afternoon is blowing
freshly, to drop again at sunset, and this diurnal variation in the
strength of the wind is a normal condition in all the months of
the year except during periods of cold and rainy weather in
winter. Southerly winds are frequent in the winter, but they fall to
a very small number in the summer months.
At Babylon, some seventy miles S. of Baghdad, where observations
were taken three times daily for more than five years, hardly any
calms were recorded. Southerly winds were frequent in the winter
months and in April and May, but were always greatly inferior
to the north-westerly winds, which in the summer months reached
the proportion of 85-5 per cent
At Basra the proportions do not differ greatly from those of the
stations higher up the river, but southerly winds have a rather
greater prevalence in the summer months than farther northwards.
The general character of the air circulation over Mesopotamia
is well indicated by these observations. Throughout the year
a prevailing current from the north-west sweeps over the country
from the hilly country in the north to the shores of the Persian
Gulf. This air has for the most part descended from altitudes
of 4,000 feet or more on the plateaux of Asia Minor and Kurdistan,
and therefore reaches the northern part of upper Mesopotamia
as a dry wind. This is clearly indicated by the low value of the
relative humidity of Urfeh. Passing southwards and entering suc
cessively warmer regions, the air of Mesopotamia is everywhere dry,
except in the delta, where the climatic conditions agree closely with
those in the Persian Gulf. The frequent occurrence of easterly winds
in the northern part of upper Mesopotamia during the winter and
spring is probably connected with the occurrence of depressions in
the Levant, many of which pass over northern Syria or Palestine
into Mesopotamia. Data bearing on the velocity of the wind are
very scanty.
There is probably a well-marked diurnal variation in both the
diiection and the force of the wind in all parts of the country,
but the wind directions at the three hours of observation have been
published for Babylon only. Here the north-westerly wind of the
morning becomes more northerly and even passes to the east of
north by the afternoon, especially in the summer months. Except
in the cold weather or during the passage of depressions, the increase
of wind velocity during the day is usual and is especially marked