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100
Lufttrykket b har jeg taget efter Kartet PI. XXXI,
Luftens Temperatur t efter et Kart over É$rsisothermerne,
som jeg har publiceret paa et. andet StedIdet jeg efter
Observationerne fra vor Nordhavs-Expedition2 sætter don
relative Fugtighed til 88 Procent, bliver, naar E er don til
Temperaturen t svarende Maximumspændkraft3, 0.3779 e
— 0.3779 X 0.88 E — { E, og man faar
o — 0.047366. ^17, V log 0.047366 8.67547.
Frictionscoeffienten le sætter jeg for dot aabne Hav
mod moderat Sogang lig 0.0000351.
For den Del af Havet, der er belagt med Is, stiller
Forholdet sig anderledes, idet. Hav-Isens ujevne Overflade
gjor en større Modstand mod Luftens Bevægelse end selv
det storkost oprørte Hav.
Scoresby siger herom"’:
"Naar Vinden blæser sterkt henover en
sammenhængende Pakis eller ot Isflak, bliver dons Kraft meget
formindsket paa nogle faa Miles Vej. Saaledes kan en Storm ofte
blæse Here Timer paa den ene Side af et Flak. førend
den merkes paa den anden, eller, medens der blæser en
Storm i aabent Vande, ville Skibe i Besæt inden
Synsvidde føie kun dons halve Styrke".
Paa det aabne Hav er Forholdet r: G omtrent ligt
7. For den isdækkede Del af Nordhavet sætter jog det
til 5. Dette svarer, som dot vil sees af de nys citerede
Steder, til en Frictionscooffioient af 0.00008, eller den, som
er fundet for Nordamerika. Isgrændseii sw.tt.er jog mellem
Isothennerne for 0° og 1° paa Kartet PI. XVI, saavel
i Østhavet som i Grønlandshavet.
Efter disse Formler og Constanter er Vindens
Retning og Hastighed beregnet for et stort Antal Punkter,
jevnt fordelte over Nordhavet. Resultaterne afsattes i et
Kart, paa hvilket der blev optrukket Pile i Vindens
Retning og Linier for ligestor Vindhastighed. Over det aabne
Hav er Vindens Afbøjningsvinkel omkring 75°, over Isen
or den omkring 60°. Paa det förste Stod danner Vinden
en Vinkel af 15" mod Isobaren, paa det andet 30°.
Kartet. Pl. XXXI, viser det resulterende Vindsystem. Pilene
flyv«; i Vindens Retning. Antallet af Fjer paa Pilene
angiver Hastigheden i Meter pr. Secuncl. Ingen Fjer, mon
en Spids paa Pilen, betegner en Hastighed af mindre end
O.;") Motor. Ved Stationerne paa Island, Færøerne og
Fyr-Stationer paa Norgos Kyst er, ved tykkere Pile med Spids,
angivet Retningen af don i Aarets Lob hyppigste Vind.
1 Zeitschrift der iisterreichischen Gosellschaft für Meteorologie,
ISS4, Aprilheft.
- Den norske Nordhavs-Expedition. H. Mohn. Meteorologi,
S. 1-21, f flg.
s Broch. Tension de la vapeur (Veau. Travaux etc.
1 Zeitschrift der iisterreichischen (resollschaft fiir Meteorologie,
I s77. S. fili og 58. Sprungs Meteorologie, S. 121 og 12:5.
An Account of the Arctic Regions, 1, S 206 og 207.
The pressure, b, 1 took from the map, Pl. XXXI, the
temperature of the air, t, from a map ol’ the isotherms for
the year, that ’I have published elsewhere.1 Now putting,
in accordance with the observations from the North-Atlantic
Expedition,-’ the relative humidity at 88 per cent, then,
assuming E as the maximum-tension corresponding to the
temperature 0.3779 c = 0.3779 X 0.8H E = \ E.
and we have —
b l E
o — 0.047366. ‡i log 0.047366 = 8.6 <54/.
For the open sea, when moderately agitated, I put
the friction-coefficient, k, at 0.000035.1
As regards the part of the ocean covered with ice.
the case is different, the rough surface of sea-ice exerting a
greater resistance to the motion of the air than does even
the most agitated sea.
Scoresby remarks on this subject1"’: —
•’When the wind blows forcibly across a solid pack
or field of ice, its power is much diminished ere it traverses
many miles: Insomuch, that a storm will frequently blow
for several hours on one side of a field, before it be
perceptible on the other; and, while a storm prevails in open
water, ships beset within sight, will not experience
one-half’ of its severity."
Out at sea. the ratio v:G is about equal to 7.
For the ice-covered part’of the North Ocean, f put it at
5. This corresponds, as will appear from the passages in
the works cited above, to a friction-coefficient of 0.00008,
or that found for North America. The ice-limit I put
between the isotherms for 0° and 1°, as given on the
map, Pl. XVI, both in the Barents Sea and in the
Greenland Sea.
From those formula’ and constants, the direction and
velocity of the wind has been computed for a. great
number of points, uniformly distributed over the North Ocean.
The results I sot down in a map. on which arrows were
drawn in the direction of the wind, and lines for equal
velocity of the wind. Over the open sea, the wind’s angle
of deviation is about 75°, over the ice it is about 60°. Over
the open sea, the wind forms with the isobar an angle of
15", over the ice an angle of 30". The map, Pl. XXXI,
exhibits the resulting wind-system. The arrows fly in the
direction of the wind. The number of feathers on an
arrow indicate the velocity in metres per second. No feather
at all, but merely a point, denotes a velocity ol’ less than
0.5 metre. At the Stations on Iceland, the Færoes, and
some Lighthouse-Stations along the coast of Norway, thicker
1 Zeitschrift der iisterreichischen Gcsellschaft. fiir Meteorologie,
1884, Aprilheft.
2 The Norwegian North-Atlantic Expedition. 11. Mohn.
Meteorology, ]). 121, and following.
3 Broch. Tension dc la vapeuv d’eau. Travaux etc.
1 Zeitschrift der österreichischen Gesellschaft. fiir Meteorologie.
1877, |>p. ö.’J and .’>s. Sprungs Meteorologie, pp. 121 and 12:5.
" An Account of the Arctic Regions. Vol. 1, pp. 20(5 and 207.
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