"تقرير عسكري عن العراق. المنطقة ٢ (أعلى الفرات)" [و‎‎١‎٨] (١٤٠/٤٠)

During these months agriculture can only be carried on
by the aid of irrigation. The Balikh and Khabur which
never become quite dry maintain a settled population on their
banks. During these rainless months the desert grazing
becomes scorched and dry, thus being quickly exhausted and
keeping the Badawin herdsmen continually on the move,
and compelling them to pasture near the river.
Snow is rarely known to fall, but in the winter of 1919-20
snow fell for three days at Anah, on the 11th, 12th and 13th
February.
Winds .-—The general direction of winds throughout the
year is from the north-west. During the winter months the
direction is rather unsettled, and frequent breezes spring up
from the south. Throughout the summer the wind blows
practically uninterrupedly from the north-west owing to the
centre of high pressure in the Eastern Mediterranean seeking
to balance the low pressure in the Persian Gulf.
The influence of southern hot winds from the Persian Gulf
which usually alternate with the north-west winds throughout
the summer, and which are particularly noticeable in August and
September, when they ripen the date crop, is felt as far north
as Albu Kamal, which is the northern limit of date cultivation.
The prevailing wind passes over the plateau of Anatolia and
descends on the plains as a dry current of air, rapidly heating
up as it descends from the level of the mountains.
Calms are of unusual occurrence and it is the rule for the
wind to attain its maximum velocity during the day. In the
evening the wind diminishes to a gentle breeze, which gradually
gathers speed after dawn the following morning.
During the summer months sand storms of considerable
intensity are frequently met with, and the burning sand, driving
along with it a cloud of dust, provides a most unpleasant
experience. Visibility may be limited to a few hundred feet
for hours together, rendering flying or visual signalling
impossible.
A further obstacle to visual signalling is provided by the
desert mirage which distorts the landscape into unrecognisable
shapes. The laying of land lines is easy, and the atmosphere
permits of the successful use of wireless telegraphy.
Temperature .—The most noteworthy point with regard to
the temperature is the wide range.
The thermometer varies from below freezing to above
120° in the shade, according to the season of the year. The
hottest months are usually August and September, while the
greatest degree of cold is experienced in December and January.
The temperature varies considerably throughout the area, that