Wavelet filter analysis of local atmospheric pressure effects on gravity variations |
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Authors: | X-G Hu L-T Liu J Hinderer H-P Sun |
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Institution: | (1) Institute of Geodesy and Geophysics, Chinese Academy of Sciences, 174 Xudong Road Wuhan, 430077, China;(2) Graduate School of Chinese Academy of Sciences, Beijing, China;(3) Institut de Physique du Globe de Strasbourg (UMR 7516 CNRS-ULP), 5 rue Descartes, 67084 Strasbourg, France |
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Abstract: | An efficient method is proposed for the analysis of atmospheric pressure effects on gravity variations. It processes gravity
and pressure signals using an orthogonal filter bank derived from high-degree Daubechies wavelets. The method introduces the
atmospheric pressure admittance, which is both time- and frequency-dependent, and thus provides more information about when
and how the frequency components in the pressure signal influence gravity variations. We demonstrate the efficiency of the
wavelet method by applying it to observations from the Wuhan (China) superconducting gravimeter station. The analysis of gravity
and pressure signals in 14 sub-bands with different bandwidths covering a frequency range from 0.176 to 720 cpd (cycles per
day) reveals that local atmospheric pressure fluctuations start to induce obvious effects on gravity variations in the seismic
band 0.52–1.04 mHz (periods 16 to 32 min) and highly correlate with gravity variation in the long-period seismic mode band
0.26–0.52 mHz (periods 32–64 min). The harmonics of solar-heating-induced atmospheric tides play a leading role in interfering
with the variation of gravity residuals in the frequency band 0.704–11.25 cpd (periods 128 min to 1.42 day). Local atmospheric
pressure effects on gravity variation are very strong in the frequency band 0.176–0.704 cpd (periods 1.42–5.69 day). Accurately
filtering quarter-diurnal tides into a narrow band further demonstrates the efficiency of the wavelet method. After removing
secular gravity changes and long-period atmospheric pressure variations, we show that there are obvious variations of local
pressure admittance on time scales of hours to days. We also reveal seasonal variability of pressure admittances in the band
0.176–0.352 cpd (periods 2.84–5.69 day) after removing the effects of solar-heating atmospheric tides. |
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Keywords: | Wavelet filter Atmospheric pressure admittance Superconducting gravity Gravity variation |
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