LUNAR AND SOLAR SEMIDIURNAL VARIATIONS OF BAROMETRIC PRESSURE AT COPENHAGEN 1884-1949 (66 YEARS)

Sixty‐six years of bihourly barometric data for Copenhagen (55°·7N) are used to determine the lunar atmospheric tide there, L2 (p), and also the harmonic components Sn of the solar daily barometric variation S (p), for n = 1, 2, 3, 4, For L2 (p) seasonal means are given as well as the annual mean; for S2 (p) monthly, seasonal and annual mean values are given. The determinations are made for groups of days with different upper limits of range, 6·0 microbars (μb) and 8·7 ph, as well as for all days. It is shown that it is advantageous to exclude the days of larger range from the determination of L2 (p). Days of larger range are most frequent in winter. At that season, for days of smaller range, the mean pressure is higher than in summer. The 66‐year mean annual value of L2 (p) is 10·3 sin (2r + 87°·3) μb, with probable error 2·5 μb; for S2 (p) it is 225 sin (2t + 130°·8), with probable error 2·8 μb; here r and t denote respectively lunar and solar mean local time. Thus, in amplitude, S2 is 21·9 times L2, and in phase S2 exceeds L2 by 43°·5; L2 and S2 at Copenhagen vary seasonally in different ways; in both cases these variations are similar to those observed elsewhere in northern Europe. The corresponding amplitudes for Oslo (59°·9N), found by Haurwitz and Cowley (1967), are somewhat smaller, as might be expected. Copyright © 1969 Royal Meteorological Society