. Compendium of meteorology. Meteorology. ATMOSPHERIC TIDES AND OSCILLATIONS 513 Figure 2 (full line) shows the mean lunar daily vari- ation of Greenwich pressure obtained [28] from these A'^ days, by a method of rearrangement of solar hourly values according to lunar time. Happily, this method avoided a pitfall, then unsuspected but afterwards dis- closed by Bartels [12], associated with the use of selected barometrically "quiet" days [41], The total range of pressure in Fig. 2 is less than in., and the change from one lunar hour to the next averages about in. This exc
. Compendium of meteorology. Meteorology. ATMOSPHERIC TIDES AND OSCILLATIONS 513 Figure 2 (full line) shows the mean lunar daily vari- ation of Greenwich pressure obtained [28] from these A'^ days, by a method of rearrangement of solar hourly values according to lunar time. Happily, this method avoided a pitfall, then unsuspected but afterwards dis- closed by Bartels [12], associated with the use of selected barometrically "quiet" days [41], The total range of pressure in Fig. 2 is less than in., and the change from one lunar hour to the next averages about in. This exceeds the average random error in Fig. 2, namely, in., and the systematic nature of the lunar daily variation is clearly manifest. Apart from its meteorological and dynamical interest, this determination has great statistical interest as a remarkable illustration of the "law of combination of random errors"âan example confirmed by many later air-tide determinations, most notably by that of the tidal variation of air temperature at Batavia [36]. (See p. 519.) >- a: on AA'=-jg^lNCH OF MERCURY ^A > o ^A + y\^/\ "^'-'â °IA or UJ ^^ \ / ^\ /\ \ ^ / ^ \ f \ ( \ I. U- \ \o o \\ // \a 0^. \ \ 5" // 10" \\l5" 20"y\// 25^ \ -i \\ ' / / ' A /a/ \\ // \ S \\ / / s 2 \ \ // \\ r^ / \/ ' S \ "^ ^1 2 UJ \ ^ â ^ UJ < V yT-J _l o 1- , h- < Ul cc <S) (Tcon rA' c c/1 in â z bj^ LlJ z < S< Q- < q: oir q: H -Jl- \~ Fig. 2.âThe average lunar daily variation (full line) of barometric pressure at Greenwich, computed from 6457 days' hourly data, 1854-1917; the broken line shows the lunar semi- diurnal component of the variation. Harmonic Analysis and the Harmonic Dial: Units. In Fig. 2 the broken curve represents the lunar semi- diurnal harmonic (or Fourier) component obtained by harmonic analysis of the calculated variation (full line). This component curve represents the type of variation due to the moon,
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectmeteorology
