Abstract
Abstract. Simultaneous co-located microbarometer and vertical-pendulum seismometer measurements at St. Petersburg (59.9° N, 29.8° E) with total duration of 4 months are used to study atmospheric oscillations at steady frequencies at periods shorter than 8 h. The temporal behavior of the phase shift between oscillations detected simultaneously by both instruments is analyzed for oscillations of periods up to as short as ~0.5 h. Some of oscillations last up to several days. For the 42–90 min and 2.5–5 h period ranges, the temporal behavior of the power spectra are considered and correlated with the atmospheric angular momentum of zonal wind, tropical cyclones and large earthquakes. Signatures of sequences of subharmonics of the solar tide are revealed with periods up to day/30. There are indications of effects of the 5-day planetary waves and tropical cyclones on wave activity in the ~1–5 h period range. A weak increase of wave activity is observed when large earthquakes occur.
Highlights
The investigation is concerned with atmospheric waves at steady frequencies in the ∼0.5–8 h period range
The coherence spectra in the ∼0.5–12 h period range were obtained from these functions using the Parzen window
The frequencies for half of these oscillations are displaced from the frequencies of the Sm subharmonics with m from 2 to ∼45 no more than by 2 μHz
Summary
The investigation is concerned with atmospheric waves at steady frequencies in the ∼0.5–8 h period range. These waves include subharmonics of the solar tide and atmospheric normal modes. The study is based on simultaneous co-located microbarometer and seismometer measurements of pressure and gravity, respectively, both at the surface. Observed gravity perturbations with time scales more than 0.5 h are mainly caused by atmospheric motions since these result in a continuous redistribution of air masses and the gravity varies due to the Newtonian attraction by these masses (e.g., Farrell, 1972; Spratt, 1982; Muller and Zurn, 1983; Merriam, 1992; Crossley et al, 1995; Zurn and Widmer, 1995; Boy et al, 1998). Seismometer measurements are not exhaustively used for studying the above-mentioned short-period global waves. The purpose of this paper is to attract attention to these measurements as a promising method for wave investigations
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