De meteorologiske Elementers 
daglige Periode i Sommermaanederne 
i det europæiske Nordhav. 
IG der, saavidt mig bekjendt, ikke foreligger nogen Be- 
stemmelser af de meteorologiske Elementers daglige 
Perioder paa den Havstrækning, som den norske Nord- 
haysexpedition gjennemsejlede i Sommermaanederne 1876, 
1877 og 1878, har jeg anseet det for at være af Interesse 
at se, hvilke Resultater vore timevise meteorologiske Iagt- 
tagelser vilde give i denne Henseende. 
Vistnok er Antallet af Dage, da Expeditionen var i 
Søen, ikke betydeligt, paa samme Tid som den gjennem- 
sejlede Strækning er forholdsvis lang, og Iagttagelserne saa- 
ledes falde noget sparsomt fordelte paa det hele Felt, men 
som et første Forsøg til Oplysning om en vigtig Gren af 
Havets Meteorologi tror jeg, at de vundne Resultater kunne 
have nogen Værdi. Expeditioner af den Art, som Nord- 
havsexpeditionen, kan man kun sjelden gjøre Regning paa 
1 et Farvand som vort Nordhay. 
Den Sammenstilling af lagttagelserne 1 Grupper, hvis 
Middelværdier ere benyttede til Beregningen af de daglige 
Perioder, er fremgaaet af en Række Forsog. Det blev 
først forsogt at beregne hver Maaneds Iagttagelser for sig, 
men dette viste sig upraktiskt, da enkelte Maaneder kom 
til at optræde med altfor faa Iagttagelser til at de uperi- 
odiske Variationer kunde blive nogenlunde ophævede 1 Mid- 
deltallene. I Regelen er derfor den hele Observationsrække 
benyttet for hver Sommer. Hvor de geografiske Hensyn 
syntes at tale derfor, eller Observationerne selv antydede 
det Hensigtsmæssige deri, udskiltes større Grupper inden 
den enkelte Sommer. Naaledes udsondredes lagttagelserne 
af de fleste Elementer fra 1877 i 2 Grupper, den ene om- 
fattende dem, der vare gjorte 1 den varme Haystrom uden- 
for Norges Kyst, og den anden dem, der vare gjorte inden- 
for den grønlandske Polarstrøm og under Opholdet ved 
Den norske Nordhavsexpedition, H. Mohn: Meteorologi. 
Diurnal Period of the 
Meteorological Elements during the 
Summer Months in the European 
Tract of the Northern Ocean. 
AS to the best of my knowledge, no determinations have 
hitherto appeared of the diurnal periods of the meteo- 
rological elements throughout the tract of ocean investigated 
by the Norwegian North-Atlantic-Expedition in the summer 
months of 1876, 1877, and 1878, it will, I presume, be not 
without interest, to show what results the hourly meteoro- 
logical observations taken on the Expedition would give in 
this respect. 
True, the number of days during which the Expedi- 
tion was at sea 18 not considerable; moreover, the distance 
run being comparatively long, the observations are somewhat 
sparingly distributed over the whole tract; but, as a first 
attempt to elucidate an important branch of marine me- 
teorology, some value may, I think, be attached to the 
results. Expeditions of the character of the Norwegian 
North-Atlantic Expedition, will rarely be despatched to a 
tract of ocean such as our Northern Seas. 
The arrangement of the observations in groups, of 
which the mean values served for computing the diurnal 
periods, is based on a series of experiments. At first. the 
observations of each month were computed by themselves; 
this method, however, had to be relinquished, the observa- 
tions in some months being too few to admit of the non- 
periodic variations being anything like satisfactorily eliminated 
in the mean values. As a rule, therefore, I worked with 
When 
geographical eonsiderations were in favour, or the observa- 
tions per se indicated the desirability of so doing, more or 
less comprehensive groups were excluded from the whole 
series for any one of the three summers. 
the observations of most of the 
the whole series of observations for each summer. 
Thus, for instance, 
elements for 1877 
disposed in 2 groups, the one comprising those taken in 
the warm ocean current off the coast of Norway, and the 
were 
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