THE DESERT CLIMATE 19 



(46° F.) in an average year, might devastate the 

 flora. 



The daily range of temperature is scarcely less 

 striking than the yearly, and is characteristic of all 

 desert areas except those in close proximity to the 

 sea. Cannon quotes figures which show that the 

 extreme daily range of temperature recorded during 

 three years at In Salah and Wargla in the Algerian 

 Sahara is about 36-40° F. (20-22° C.) in the winter 

 months and about 50-52° F. (28-29° C.) in the 

 summer months. The average range of temperature 

 on a single day in Baghdad, Mesopotamia, is 21° F. 

 (11-7° C.) in January and December, and 31° F. 

 (17-2° C.) in August and September. But though 

 the daily fluctuation of temperature is generally 

 highest during the hot months it appears that the 

 greatest range which has ever been recorded in a 

 single day was observed in December at Bir Milgha 

 in Southern Tripoli by Rohlfs : he recorded a range 

 of 68° F. (37-8° C), from 31° F. to 99° F. (- 0-5° C. 

 to 37-2° C), within twenty-four hours. 



Many other instances of extremely rapid change 

 of temperature are on record : Paulsen observed the 

 shade temperature to be 37°, 68°, and 82° F. (3°, 20°, 

 and 28° C), at 6 a.m., 9 a.m., and 1 p.m. in sand 

 desert in Transcaspia. He also records the following 

 figures at Tachta, on the Murgab River, on the 

 23rd of June : 



6 a.m. Shade temperature 78° F. (25-5° C). Sun temperature 



93° F. (34-0° C.) 

 8 a.m. Shade temperature 85° F. (29-5° C). 



