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Ill
For hver af disse Dage udtoges af Karterne
Baro-meterhojden for en Række Punkter paa Havet, nemlig:
For each of these days, 1 took from the charts the
height of the barometer for a series of points 011 the
sea, viz.: —
Nord. Bredde [Lat. .V) lit)" 0.’»° 60°
Længde f. (ir. (Long, from Gr.) :50° \V 30° W 20° W
Nord. Bredde (Lat. N) <55° 70° 7">0
Længde f. Gr. (Long, from Gr.) 0° 0n 0°
70°
20° W
Af disse Tal beregnedes Maanedsmiddel for den
Aarrække, hvori hver Maaned forekommer. (Januar til August
3 Aar. September til November 4 Aar, December 3 Aar).
For de tilsvarende Tidsrum beregnedes Maanedsmiddel
af Barometerstanden for Stationerne Stykkisholin, Akureyri,
Berufjord, Thorshavn, Mandal, Skudesnes, Bergen, Florø,
Aalesund, Christiansund, Brønø, Bodo, Tromsø, Alten og
Vardø. Disse Media for Epoken 1873—70 eller 1873—75
eller 1874—7G subtraheredes fra de normale Maanedsmedia
efter den 24-eller I G-aarige Række. De fundne Ditte ren tser
tjene til at reducere don kortvarige Række efter Karterne
til Kyststationernes normale Værdier.
For Kyststationerne toges for Karternes Epoke
Maanedsmiddel af Barometerhøjden Tvi. 8 Morgen. Disse Medier
subtraheredes fra de normale Maanedsmedia. Differentsen
tjener til at reducere Karternes’ Observationer fra Kl. 8
a.111. til Dagsmediot.
Begge de saaledes udledede Correctioner for liver
Kyststation sloges sammen.
Til Reduction af Barometerstanden paa en Hav-Station
til den normale Barometerhøjde anvendtes i Regelen de
tilsvarende Correctioner for Hero Kyststationer, og disse
gaves ved Beregningen af det endelige Resultat en Vægt,
der var omvendt proportional med Afstanden mellem
Hav-Stationen og den respective Kyst-Station.
Det var ikke muligt, for alle de ovennævnte
Hav-Stationer, at erholde af de synoptiske Karter fuldstændige
Observationsrækker. I saadanne Tilfælder har jeg
com-pletteret Rækkerne, dels ved at construere Karter for de
enkelte Maaneder og udfylde Hullerne derefter, dels ved
at construere Curver for hver Hav-Station, der viste
Lufttrykkets normale aarlige Variation fra Maaned til Maaned,
og paa den Maade interpolere de manglende Værdier.
Disse Curver have ogsaa været særdeles nyttige for de
coniplette Hav-Stationers Vedkommende til at controllere
de udledede Normalværdier, idet deres almindelige Character
maatte variere successivt langs Forbindelseslinierne mellem
Kyststationerne paa begge Sider af Havet, og henimod
Kysterne nærme sig til Kyststationernes.
Hav-Stationernes Barometerhojder vare allerede
reducerede til Havfladen. Land-Stationernes bleve reducerede til
Havfladen, idet Hensyn toges til Lufttemperaturen.
Endelig reduceredes samtlige Barometerhøjder til
absolut Lufttryk eller til den normale Tyngde (ved 45°
Bredde og Havfladen) efter Formelen:
(«0°
ton W
70°
10° E
(in0 70°
10° W 10° W 10° W’
10° E -20° E 40° E
(i0°
70°
:.0° E.
From these figures was computed the monthly mean
for the series of years in which each month occurs.
(January to August 3 years, September to November 4 years,
December 3 years).
For the corresponding periods was computed the mean
monthly height of the barometer for the Stations
Stykkis-holm, Akureyri, Berufjord, Thorshavn, Mandal, Skudesnes,
Bergen, Floro, Aalesund, Christiansund, Brønø, Bodø,
Tromsø, Alten, and Vardø. These means for the interval
1873—1876 01-1873—1875 or 1874- 1876 were subtracted
from the normal monthly means deduced from the
twenty-’ four or the sixteen-years series. The differences thus found
serve for reducing the short series of the charts to the
normal values of the Coastal Stations.
For the Coastal Stations, were taken the monthly means
of the height of the barometer at 8 a. in. for the period
of the charts. These means were subtracted from the
normal monthly means. The difference serves for reducing
the observations in the charts from 8 a. m. to the daily mean.
Both the corrections thus deduced for every Coastal
Station were added together.
For reducing the height of the barometer at a
Sea-Station to the normal height, the corresponding
corrections for several Coastal Stations were as a rule applied,
and these were given, when computing the final result, a
weight inversely proportional to the distance between the
Sea-Station and the respective Coast-Station.
It was not possible to obtain for all the
above-mentioned Sea-Stations complete series of observations
from the Synoptical Charts. In such cases I completed
the series myself, partly by constructing maps for the
different months and then filling up the blanks, and partly
by drawing curves for each Sea-Station that exhibited the
normal annual variation from month to month of the
atmospheric pressure, and thus interpolating the missing values.
These curves have also proved exceedingly useful as regards
the complete Sea-Stations, viz., in controlling the computed
normal values, since their general character could not but
vary successively along the lines of connexion between the
Coastal Stations on both sides of the sea, and, in the vicinity
of the coasts, approach that of the Coastal Stations.
The height of the barometer for the Sea-Stations had
been already reduced to the sea-level. When reducing it
for the Land-Stations to the sea-level, regard was had to
the temperature of the air.
Finally, every height of the barometer was reduced to
absolute atmospheric pressure, or to the normal gravity
(45th parallel of latitude and sea-level), according to the
formula: —
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