The lowest mean minima throughout the Sudan occur in the win- 

 ter Mean dedly minima are lowest in the extreme north (7.8 C. to 

 23 8°C at Wadi Haifa) and in the west and highest in the Red Sea 

 area (19 20C. to 28.8°C. at Port Sudan). At Juba they range from 

 19 8°C to 22.0°C.; at Wau from 17.6°C. to 22. ^°C.; and at Wad 

 Medani from U.3°C. to 2^.3°C. The seasonal variation decreases 

 from north to south and is very small south of Malakal. Numerous 

 other temperature data may be found in Ireland's (19^8) original 

 summary. 



Rainfall in the Sudan (Figures 324 and 325) is characterized 

 by a remarkably regular decrease in mean annual total from UOO mm. 

 in the south (1500 mm. in eastern Bquatoria mountains J to ^5 nm. 

 or less in the northern deserts. Figure 325 shows the annual 

 rainfall distribution expressed as monthly percentages oi the 

 total, accept coast ally, diagrams represent means over four 

 degree squares. Inland increase in rainy season length from 

 north to south and the anomalous Red Sea area regime are clear- 

 ly shown, as is the notable latitudinal uniformity and the equa- 

 torial double maximum in the extreme south. See Ireland (1948; 

 for further details. 



Climaticaay the Sudan may be divided into three regions: 



1. North of about latitude 19 N. 



2. South of atout latitude 19^. ^ „ ^ ^ „..,, 



3. Red Sea coast and eastern slopes of Red Sea mils. 



North of about latitude 19°N. the desert receives little, 

 infrequent rain or none at all. Strong winter winds with sand, 

 storir^ and occasional frontal rain occur with an influx of coxd 

 air behind a vigorous Mediterranean depression. The desert 

 SLSe characteristically experiences wide diurnal and annual 

 temperature variations. 



South of about latitude 19°N. the typical tropical conti- 

 nental Sim^te is dominated by the annual movement of the boundary 

 be?wSn d^northerlies and moist southerlies, a boundary reaching 

 its nortSn limit in midsummer and its southern limit mmid- 

 iJnter ?he southerlies bring rain that extends five hundred 

 Sles ;r so south from the actual boundary. The raany season 



- 834- 



