Jökull


Jökull - 01.12.1959, Page 5

Jökull - 01.12.1959, Page 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

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