The Botany of Iceland - 01.12.1930, Page 178
168
H. M0LHOLM HANSEN
maximum and minimum will take place at the different depths.
Thus the temperature minimum in the lower strata will only occur
simultaneously with the tem]>erature maximum at the surface, and
reversely.
The dailv and annual mean temperature of the surface of the
earth is higher than that of the air, just as the daily and annual
amplitude is higher for the surface than for the air.
Table 33.
The annual Rise of Temperature
in Soils with or without Vegetation or Snow Covering at Pawlovvsk
(Russia.) The figures give the mean values of a period of 5 years,
1891-95. After H.Wild 1897 p. 7.
November December January February March April May June August September October v V ears
Snow covering cm 3 16' 31 46 49 19 » » » » » »: (27)
Clouds 8.3 -1-2.0 8.5 -1-6.4 8.3 4-10.2 7.4 -HlO.O 6.5 -4-4 5 5 0 5.9 9.1 6.1 13.4 6.6 15.9 6.6 13.8 7.0 8.7 7.6 ' 7.0
Air temperature C° 2.0 4.0 2.8
Natural external surface . H-2.5 -4-6.8 -í-10.3 4-10.3 -4-6.1 2.0 12.3 17.4 19.4 15.7 9.2 3.5 3.6
Sandv' surface 0 0 cm .... -f-2 6 -4-6.6 -4-10.4 -4- 9.6 4-3.5 4.3 12.3 16.7 18.9 15.5 9.0 3.6 4.0
40 » . ... 0 9 -4-2.6 -4- 6.1 -4- 6.4 -t-2.4 1.8 8.3 13.3 16.7 15.2 9.8 5.-1 4*il
-i- 80 » .. .. 3.3 0.7 -4- 1 9 -4- 2.7 -4-1.2 0.2 4.9 10,1 14.1 13.9 10.3 6.9 4.9
-f-l(j() » .... 5.7 3.8 2.2 1.2 0.8 0.8 2.4 6.2 10.0 11.3 10.3 8.2 5.2
Vegetation orsnovvcovered
surface 0.0 cm -í-0.8 -^2.4 -t- 2.4 4- 1.4 -4-0.7 2.6 9.8 14.7 17.0 14 2 9 0 4.2 5.3
H- 40 » 3.4 1.7 0.9 0.8 0.7 1.4 7.7 11.6 14.6 14.7 11.1 7.3 6.3
-5- 80 > . ... 4.9 3.0 2.0 1.7 1.5 1.7 6.1 9.7 12.6 13.5 11.2 8.3 6.4
-M60 » .... 6.6 4 7 3.5 3.0 2.6 2.4 4.5 7.5 10.0 11.6 11.0 9.1 6.4
29.2
23.1
16.7
10-
19.1
11.0
12.0
9.2
The facts described above apply to bare homogeneous sandy soil,
as invesligated hy H. Wild at Pawlowsk, cf. table 33. If, on the
other hand, the surface is clothed with a natural vegelation or
covered wjth snow, a case likewise investigated by H. Wild in the
same locality and shown in table 33, the facts will be otherwise.
A bare sandy surface has a mean annual temperature of 4.0° with
an annual amplitude of 29.2, a natural surface has a mean annual
temperature of 3.6° and an annual amplitude of 29.2. The surtace
under snow and vegetation, on the other hand, has a mean annual