The re sults pre sented here de rive mainly from long-term mea sure - ments in the “deep” and “shal low” ur ban can yons shown in Fig. 5.2 and de scribed in Ta ble 5.1. How ever, re sults from short-term mea - sure ments in the com pact neigh bour hood of Seffarine (in the an - cient Me dina) and in the dis persed, new sub urb of Adarissa are also pre sented. The mea sure ment cam paigns are de scribed in Sec tion 5.1.
Sea sonal ur ban–ru ral air tem per a ture vari a tions
The av er age tem per a ture vari a tions for the sum mer and win ter pe ri - ods de fined in Sec tion 5.1 are shown in Figs. 6.1a and 6.2 along side the ru ral tem per a tures (Fez air port). The deep street can yon at the Seffarine (SEF) site had lower max i mum tem per a tures than both the shal low can yon at the Adarissa (ADA) site and the ru ral site, both dur ing the sum mer and win ter. Con versely, day time tem per a tures in the shal low can yon were sim i lar to those of the ru ral site, be ing a few °C warmer in the sum mer pe riod and about 1°C cooler in the win ter pe riod. Dur ing the night, both can yons dis played typ i cal heat is lands, whose in ten sity was greater in the deep can yon.
Intra–ur ban air tem per a ture vari a tions
In Figs. 6.1 and 6.2, it can be seen that the af ter noon dif fer ence be - tween the can yons was es pe cially pro nounced dur ing sum mer. Dur - ing the warm sea son, the dif fer ence in mean max i mum day time tem per a tures be tween the two can yons was 6°C, al though the dif fer - ence was even greater on hot, sunny days (Fig. 6.1b). Dur ing the win ter pe riod, the max i mum dif fer ence be tween the can yons was only 3°C.
From the short-term, in stan ta neous mea sure ments at five lo ca - tions in each neigh bour hood (see Pa per I), it was found that the
max i mum air tem per a ture tended to de crease with in creas ing H/W ra tio. Con se quently, in the com pact neigh bour hood in the Me dina, a dif fer ence as great as 10°C was found be tween dense res i den tial ar - eas and the more open ba zaar area, only 100–150 m away. In the sub ur ban, dis persed neigh bour hood, where all streets have a sim i lar H/W ra tio, the tem per a ture differences were insignificant.
The short-term mea sure ments did not re flect any sig nif i cant in flu - ence from street ori en ta tion on air tem per a ture in ei ther neigh bour - hood.
Sur face tem per a tures
While the sur face tem per a tures of the façades of the deep can yon at the SEF site were sta ble, due to al most com plete shade and low SVF, the shal low can yon at the ADA site showed ex ten sive vari a tion in sur face tem per a tures de pend ing on ori en ta tion, sur face col our and height above ground. Dur ing the sum mer pe riod, the max i mum and min i mum sur face tem per a tures of the deep can yon façades
Fig. 6.1 Av er age tem per a tures for the can yons in Fez: (a) for the whole sum mer pe riod and (b) for the 15 warm est days of the sum mer. (For site keys, see Ta ble 5.1.).
Fig. 6.2
Av er age tem per a tures for the can yons in Fez dur ing the win ter pe riod. (For site keys, see Ta ble 5.1.).
were 28°C and 24°C re spec tively, and the street showed sim i lar tem - per a tures. In the shal low can yon, on the other hand, the tem per a - tures of the light-col oured façades var ied be tween 21 and 40°C, whereas the dark-grey street sur face was the warm est with tem per a - tures reach ing 50°C. Dur ing the win ter, the ten dency was sim i lar, al - though tem per a ture fluc tu a tions were smaller. Façade tem per a tures var ied be tween 11 and 14°C in the deep can yon and be tween 7 and 23°C in the shal low can yon. How ever, lower por tions of façades in the shal low can yon dis played lower max i mum and higher min i mum sur face tem per a tures due to veg e ta tion pro vid ing so lar shad ing by day and pre vent ing ra di a tive cool ing by night (see Fig. 5.2). Hu mid ity
Rel a tive hu mid ity was highly sta ble in the deep can yon at the SEF site but showed large di ur nal vari a tion in the shal low can yon at the ADA site, both in sum mer and win ter (Fig. 6.3). Al though rel a tive hu - mid ity was higher dur ing the win ter pe riod, the hu mid ity in the air – ex pressed as vapour pres sure – was lower (Fig. 6.3). Both in sum - mer and win ter, the deep can yon dis played higher vapour pres sure than the shal low can yon, a dif fer ence that was par tic u larly pro - nounced on sum mer af ter noons.
Wind speed
The wind speed, which was mea sured in stan ta neously on three oc - ca sions per day, var ied greatly from day to day and ac cord ing to the time of the day. Wind speeds were lower and more sta ble in the deep can yon. The av er age wind speed in the deep can yon was 0.4 m/s dur ing both the sum mer and win ter mea sure ment pe ri ods. The
Chapter 6 Re sults
Fig. 6.3 Av er age rel a tive hu mid ity (RH) and vapour pres sure (VP) in the can yons in Fez dur ing (a) the sum mer pe riod and (b) the win ter pe riod. (For site keys, see Ta ble 5.1.).
shal low can yon had an av er age wind speed of 0.7 m/s in sum mer and 0.8 m/s in win ter.