656 
to the right, which will be explained later. The dying 
down and continued shifting to the right takes place 
in similar fashion. 
LOCAL CIRCULATIONS 
sought in the different behavior of land and water under 
the influence of an equal external heat supply. Water, 
as compared to soil, has a larger thermal capacity and 
LOCAL MEAN TIME 
JUNE 3 JUNE 4 JUNE 5 | 
S 0600 1200 1800 400 0600 1200 1g800 2400 0600 1200 1800 
E aes 
N = a 
WwW ee f A A 
= 
wo 10S 
ath dl iad HINA 
Z=0 
=~ 
RAYS ANNAN ES WN ESS SASS SSSUSSSSSSUONSSSSESSSSSOMNNSSSSENSNANN SANT ASAIN ANSI 0 
L G SIGHS Cc (L 
& 1420 
re 0400 “leas ae 2220 
a 1 f 1 
2 20° \ | 11930 2245 tate 0130 ' al 
y ' } | ’ 0030! : ia 
bs ° H \ 3 I ~ ral 
a 15°; SO ' it } Ha 
Ww I } ny U 1 0 4 { fu 
2 10°F ' env u ' fg 1 I 
= yee gs 0 : 0 
Ti 1 He eet haat ! ' tt | (i 
F 100 1 wa — : 7 
t ip eye Ua i tt 
! ' Deh Cis 1 Ud 1 gy U 
= H 1 ty vt ot 
ag 1 vou Tt i) I 
= {}(0) Ta 
> J uf 
|= 1 4 
a ng 
= 60 
= 
ae) 
Ww 
2 40 a SS SS SS o S Ey — 
E 
a 
=) 
w 
= 20 
Fia. 1.—Registrations of wind speed and direction, temperature, and relative humidity during the characteristic land- and 
sea-breeze days from June 3 to June 5, 1932, at Danzig (LZ = land breeze, S = sea breeze, G = gradient wind, C = calm). 
(After Koschmieder [54).) 
As an example of the tropical form of the land and 
sea breezes the diagram of velocity isopleths by van 
Bemmelen of the land and sea breezes at Batavia is 
reproduced in Fig. 3. It is also an example of the vertical 
velocity distribution during the course of a day. 
Explanation of the Land and Sea Breezes. The cause 
of the land and sea breezes must undoubtedly be 
1300 
1400 
SEA 
Fig. 2.—Hourly variation of relative wind velocity on a 
land- and sea-breeze day at Hoek van Holland as recorded on 
July 31, 1938. (After Bleeker and Schmidt [67].) 
its specific heat per unit volume reaches a value 40 
per cent larger than that of soil. Although water should 
have a smaller temperature variation for the first reason, 
the amplitude of these periodic variations would be 
1.414 that of the land for the second reason. This dif- 
ference is equalized through the much smaller heat 
conductivity of water, and measurements reveal that 
the surfaces of water and sandy or rocky ground have 
temperature variations of comparable order. The depth 
to which radiation penetrates can also not be considered 
responsible for large temperature differences since the 
infrared radiation is immediately absorbed in the upper 
water layers. 
However, if we direct our attention to the turbulent 
mixing of the water by wind and waves, which effects 
a contmuous downward transport of surface heat 
through large masses of water, we recognize that this 
mixing is the cause of the relatively small temperature 
variations. It is now clear that the complete absorption 
of radiant heat in the surface layers of the ground and 
the weaker influence of this form of energy on the 
deeper layers result in an entirely different thermal 
behavior of land and of water. Thus the temperature 
conditions of the ground are determined almost ex- 
clusively by its physical properties, whereas those of 
