Jökull - 01.12.1959, Blaðsíða 5

ablation/c.m.1/h r. in m.m.
I 1
isp FIG. 2,-x-v. ABLATION - CALCULATED
measured near top of dirt cone
FOOT
DATE-IAUG 2 AUG 5 AUG 6 AUG
7AUG 8AUG IIAUG
22AUG
profiles revealed divergence at lieights generally
above one metre. The inaccuracy of the instru-
ments and the percentage error in height me-
asurement increases as the undulating surface
is ajiproaclied. Hence the air layer 20 to 100 cm
height was considered in calculating the tur-
bulent transfer of heat ancl water vapour.
The flux of water vapour and of heat respect-
ively, may be written:
E
P
(5)
Substituting for K (4) in expression (5) and (6)
and integrating between two levels zi and
(20 and 100 cm respectively) to avoid the bound-
ary condition at the surface yields
p V2 k2 (q2 — q1)
loei e------log e ——
ö z0 6 zi
H
P
v2 k2 (T2 - Ti)
, Z2 Z2
log e------log e -
6 z0 ° Zl
EI
0T
P Cp ki-i (-g^—
r)
Separating the constants and using vapour pres-
(6) sures in place of specific humidity
where
E = B v2 (e2 — ei)
C|3 = specific heat of air at constant
pressure
r = dry adiabatic lapse rate =
0.986 X 10~4° C cm-1 which is
so srnall in comparison with
the observed gradients it has
been ignored in evaluating H.
and 3^~= vertical gradient of specific
humidity and of temperature
respectively
where B
k2 M _____________________
RT log e Z“ log e - ~
° z0 ° Zl
ei and e2 = are vapour pressures at heights
zi and z2
M = molecular weight of water
R = universal gas constant
T = Temperature in °A
H = C v2 (T2 - Ti)
3