THE DISTRIBUTION OF TEMPERATURE IN THE SUGAR
extremity of the sugar belt. At Eshowe the mean summer "temperature is 71.1°, and the mean winter temperature 63.9°. At Port Shepstone the corr- sponding temperatures are 72.0° and 64.0°; while 100 road miles further south, at Port St. John's, with its mean annual temperature of 67.9°, the su- mer and winter temperatures are 70.8° and 64.9°.
The mean temperature, and the mean summer and winter temperatures, show a regular and orderly in- crease from Port Shepstone along the coastal regions to Mkuzi, where the mean summer temperature has increased by 6.0° and the mean winter by 3.5°, with an increase in mean annual temperature of 4.7°.
Along the sugar belt, the hottest month is Feb- ruary, 75.8°, January taking second place with 75.4°.
The coolest month is July, 62.0°, with June 62.6°.
The mean summer temperature for the entire sugar belt is 73.9°, the mean winter 65.5".
In the large inland valleys, on the other hand, the hottest month is January, and the coolest month June, the temperature gradient being steeper than Experiment Station,
South African Sugar Association, Mount Edgecombe.
March, 1949.
for the other localities. Nearer the coast this te- perature gradient tends to "flatten out."
The mean annual temperature of all stations from Pongola to Stanger, excluding Eshowe on the plateau, is 70.8°. For all stations south of Stanger the mean is 68.7°, 2.1° lower.
The highest mean annual temperature for any station was 73.4° at Mkuzi in 1947, and the lowest 65.8° at Eshowe in 1935.
The highest mean monthly temperature for any single year was 83.5° for January, 1944, at Mkuzi, and the lowest 56.9° for July, 1942, at Eshowe, thus constituting an absolute range of 26.6° in the mean monthly temperature.
The years 1935, 1936, 1939 and 1943 were cool years throughout the sugar belt. It is of passing interest to note that these were, in genera], years of higher rainfall. Further, 1941, with its record high mean temperature of 70.5°, had the lowest mean annual rainfall on the records, namely, only 26.18 inches.
TABLE 2.—TEMPERATURI Station. S. Lat.
Port Shepstone (182/794A) . ... 30° 45' Umbogintwini (211/661) 29° 58' Durban Bluff ( 2 4 1 / 8 2 A ) 29° 52' Durban Airport (241/49) 29° 51' Mount Edgecombe (241/72) ... 29° 40' Verulam (241/68) 29° 37'
Stanger (271/500) 29°19' Eshowe (303/833) 28° 53'
Empangeni (304/736) 28° 46' Nkwaleni (304/43) 28° 42' Cape St. Lucia (339/720) 28° 31' Mkuzi (375/37) 27° 37' Magut (374/275) 27° 33' Pongola (410/203) 27° 23'
] RECORDING STATIONS IN THE E. Long.
30° 27' 30° 56' 31° 03' 31° 03' 31° 04' 31° 04' 31° 17' 31° 27' 31° 55' 31° 33' 32° 24' 32° 02' 31° 37' 31° 38'
Height above sea-level.
50 feet 210 feet 220 feet 20 feet 340 feet 400 feet 400 feet 1,740 feet 450 feet 580 feet 360 feet 450 feet 1,080 feet 900 feet
Distance from sea.
Nil 1 mile
Nil i mile 4 miles 6 miles 7 miles 17 miles 10 miles 19 miles
Nil 35 miles 82 miles 85 miles
SUGAR BELT.
General terrain represented.
Sea coast dunes.
Depressions in sea coast hills Sea coast dunes.
Sea coast plains.
Low coastal hills.
Semi-inland hills.
Semi-inland hills.
Inland plateau.
Low inland hills.
Large inland valleys.
Sea coast dunes.
Large inland valleys.
Inland hills and plains.
Large inland valleys.
TABLE 3—GEOGRAPHICAL DISTRIBUTION OF MEAN TEMPERATURES WITHIN THE SUGAR BELT.
temperature,
Mean M e a n Mean t e m p e r a t u r e , t e m p e r a t u r e , a n n u a l
N o v . - A p r i l . M a y - O c t o b e r . Difference. t e m p e r a t u r e
oF . ° F . o F . °F.
Inland plateau (Eshowe)
Sea coast (Port Shepstone, Durban Bluff, Cape St. Lucia) Coastal regions (Umbogintwini, Durban Airport, Mount
Edgecombe, Verulam, Stanger, Empangeni) Inland valleys (Nkwaleni, Mkuzi, Pongola)
71.1 72.9 73.6 76.0
63.9 65.3
7.2 7.6
67.5 69.1 94
Jan. Feb. March Api
90
T A B L E 1.—MONTHLY MEANS OF RECORDED METEOROLOGICAL DATA AT THE EXPERIMENT STATION, MOUNT EDGECOMBE.
Rainfall in inches Number of rain days Daily rate of fall, inches Highest single fall, inches Date
Total from January 1st Evaporation from water surface, ins.
Daily rate, inches Excess daily rate over rainfall Per cent, relative humidity, 8.30 a.m.
Per cent, relative humidity, 1 p.m Hours of sunshine
Per cent, available daylight Per cent, of skv covered by cloud at
8.30a.m. '
Mean true barometer at 340 ft. in ins.
Absolute maximum Absolute minimum
Mean earth temperature (°I'\) at 1 ft.
Mean earth temperature (°F.) at 2 ft.
Mean earth temperature (°F.) at 4 ft.
Mean solar maximum temp. (°F.) ...
Absolute maximum
Mean grass minimum temp. (°F.) ...
Absolute minimum
Mean screen maximum temp. (°F.)...
Absolute maximum Absolute minimum
Mean screen minimum, temp. (°F.) ...
Absolute maximum Absolute minimum
years.
2 3 23 23 23 2 3 23 13 13
—
21 2 0 21 2 121 21 21 21 14 14 14 8 8 13 13 21 21 21 21 21 21
Period.
1926/48 1926/48 1926/48 1926/48 1926/48 1926/48 1936/48 1936/48 1928/48
-_
1929/48 1928/48 1928/48 1928/48 1928/48 1928/48 1928/48 1935/48 1935/48 1935/48 1935/42 1935/42 1935/47 1935/47 1928/48 1928/48 1928/48 1928/48 1928/48 1928/48
Jan.
3.82 13.7
0.123 2.56 14/35 3.82 5. 70 0.184 0.061 74.7 66.2 189.1 44.3 60.8 29.64 29.98 29.08 79.0 79.6 77.3 137.6 160.0 61.0 44.0 81.2 104.0 66.0 67.0 75.5 56.0
Feb.
4.74 12.1
0.168 3.87 21/32 8.56 4.78 0.169 0.001 76.8 67.5 184.4 48.7 55.9 29.66 30.06 29.12 79.6 79.8 78.7 137.7 160.0 62.6 51.0 81.8 95.0 65.5 67.4 77.0 57.0
Mar.
5.15 12.2
0.166 4.29 16/27 13.71 4.39 0.142 - 0 . 0 2 4 78.7 68.2 198,6 54.1 50.1 29.70 30.14 29.27 78.3 79.2 78.7 132.0 154.0 62.0 46.5 80.2 99.5 65.0 65.7 75.0 54.0
April.
2.59 8 . 4 0.086 4.30 22/43 16.30 3.37 0.112 0.026 78.2 66.0 211.5 62.3 38.9 29.75 30.25 29.21 75.1 76.6 77.1 126.7 149.0 58.2 42.0 78.3 101.0 64.0 62.0 72.0 49.0
May.
2.25 5 . 4 0.073 5.77 5/40 18.55 2.72 0.088 0.015 73.2 59.8 224.0 70.6 31.5 29.81 30.30 29.21 69.8 72.2 74.0 121.8 142.0 51.7 37.5 75.9 94.0 57.0 56.9 69.5 44.0
June.
1 .90 4 . 4 0.063 10.41 12/35 20.45 2.2S 0.076 0.013 68.6 54.8 213.9 69.7 26.5 29.89 30.37 29.30 64.4 67.3 69.9 116.5 133.0 47.2 35.0 72.7 90.0 57.0 52.6 58.0 42.5
July.
1.32 4 . 4 0.043 3.24 9/29 21.77 2.46 0.079 0.036 68.9 54.5 220.7 68.4 27.3 29.91 30.45 29.35 62.9 65.1 67.2 1J7.0 134.0 45.4 32.5 72.1 92.0 56.5 51.7 68.5 41.0
Aug.
1.19 5 . 2 0.038 2.11 5/30 22.96 2.91 0.094 0.056 71.9 58.6 220.7 64.5 33.9 29.89 30.39 29.12 65.0 66.1 67.1 119.5 140.0 48.8 35.0 73.3 100.0 55.0 53.9 67.0 41.5
Sept.
1.95 8 . 1 0.065 2.06 15/29 24.91 3.61 0.120 0.055 70.3 60.4 192.5 54.8 47.7 29.81 30.34 29.13 68.0 68.6 68.6 123.6 147.0 52.1 37.0 74.5 106.5 58.5 57.0 68.0 42.0
Oct.
3.27 14.2
0.105 2.76 9/48 28.18 4.11 0.133 0.028 71.8 65.1 171.6 43.1 59.6 29.75 30.30 29.19 70.9 71.1 70.5 127.4 154.0 57.0 37.0 76.1 102.5 61.0 60.8 71.5 47.0
Nov.
4.22 14.0
0.141 2.60 10/36 32.40 4.79 0.160 0.019 71.6 66.3 167.1 41.1 63.0 29.69 30.14 29.20 73.5 73.5 73.3 130.4 149.5 58.9 42.0 78.1 96.5 58.5 63.3 73.0 50.0
Dec.
4.13 14.3 0.133
2.83 6/34 36.53 5.45 0.176 0.043 71.5 65.8 182.0 42.7 60.4 29.65 30.12 29.14 76.6 76.4 75.0 135.2 167.0 59.8 45.5 80.3 113.5 66.0 65.6 75.5 53.5
Means.
36.53 9 . 7 0.100 10.41 12/6/35 36.53 46.57 0.128 0.028 73.0 62.8 2376.2 54.2 46.3 29.76 30.45 29.08 71.9 73.0 73.1 127.1 167.0 55 4 32.5 77.0 113.5 55.0 60.3 77.0 41.0
96
97 TABLE 4 . - M E A N MONTHLY TEMPERATURES (°F.) FROM 14 RECORDING STATIONS IN THE SUGAR BELT.
Locality.
Port Shepstone Umbogintwini Durban Bluff . Durban Airport Mt. Edgecombe Verulam Stanger Eshowe Empangeni ...
Nkwaleni Cap'e St. Lucia Mkuzi Magut Pongola
Recorder.
Lightkeeper African Explosives ..
Lightkeeper Met. Office Experiment Station C. C. Foss, Esq.
Government Forester Government Forester Government School..
Lightkeeper I. Lamb, Esq Cotton Experiment
Station Supt. Settlement
No. of 17 17
17 7 15 17 16 8 17 6 9 8
1931/ 47 1933/39 1940/47 1931/47 1931/37 1931/45 1931/47 1931/46 1931/38 1931/47 1942/47 1931/39 1940/47
Jan. Feb. Mar.
74.0 74.8 73.4 73.5 74.5 73.1 75.4 75.0 74.1 74.3 74.9 73.2 74.5 75.1 73.9 75.2 77.0 75.1 72.7 73.0 71.6 76.3 77.2 75.6 75.7 75.6 74.3 76.1 77.0 75.2 80.7 79.3 76.8 77.0 76.4 74.6 77.5 77.2 75.9 75.4 75.8 74.2
April.
69.5 70.5 70.8 71.0 70.5 70.3 72.4 69.2 72.6 71.6 72.9 74.7 71.2 72.9 71.4
May.
66.0 66.5 67.5 66.2 66.5 66.0 69.0 65.4 68.3 66.7 68.8 68.9 65.9 66.6 67.0
June.
62.4 62.9 64.5 62.3 62.6 61.8 65.2 61.4 63.4 62.2 64.3 62.4 59.9 61.5 62.6
July.
61.2 61.9 63. 1 61.3 61.9 60.7 64.4 60.5 62.7 61.9 63.5 62.1 60.5 62.6 62.0
Aug.
62.7 63.8 64.0 63.5 63.9 63.2 66.7 63.4 65.2 64.7 66.0 66.0 64.6 65.8 64.6
Sept.
64.8 65.8 64.7 66.2 66.0 66.0 88.1 65.1 67.6 66.9 68.1 71.2 68.4 69.9 67.1
Oct.
67.0 68.2 67.8 68.6 68.6 68.8 71.1 67.4 71.0 71.6 69.6 74.2 72.5 72.4 69.9
Nov.
69.8 70.5 69.1 71.4 70.9 71.6 72.5 69.4 73.2 72.4 72.3 77.8 74.1 75.1 72.2
Dec.
71.8 72.4 71.8 73.5 72.9 73.0 74.6 70.9 75.1 74.4 74.7 78.6 75.8 77.2 74.1
Average 68.0 68.7 68.7 69.1 68.9 68.8 70.9 67.5 70.7 69.8 70.7 72.7 70.1 71.2 69.7
The PRESIDENT reminded the meeting that know- ledge of climatic conditions was essential to the proper understanding of cane growth and that a considerable amount of data was published in the
"Annual Summary of Laboratory Reports. Mr. Beater had made many useful contributions to knowledge of climatic conditions in the sugar belt, and this paper dealt with a subject which had not been covered very fully previously.
Dr. DODDS said that the paper filled a definite vacancy in our records, for although he had published rainfall records from the different districts for many years warmth and freedom from frost was just as important for sugarcane growth as was moisture.
The paper now published had required a great deal
of work in its compilation.
Mr. RAULT wished to know to what extent sucrose per cent, cane figures could be correlated with the records of climatic conditions. At Esperanza, for instance, cane had a very high sucrose content, and he wondered if this could be associated with tem- peratures, or might it be due to high altitude ?
Mr. BEATER replied that he had not as yet attempted to correlate temperature with sucrose percentages, but, in a general way, he would expect a high temperature to induce more rapid growth of cane and thus, if anything, tend to lower the sucrose content. He thought this point raised could be followed up in the future.
99