Diurnal pressure variations in the Garhwal Himalaya: atmospheric fluctuations associated with the solid Earth tide
Khandelwal, D. D. ; Kumar, Naresh ; Chauhan, Vishal
Air pressure measurements conducted over 5 years at the Garhwal Himalaya (1836 m amsl) in India show (expected) seasonal variations, along with marked diurnal and semi-diurnal fluctuations. Measurements were carried out at 15-min intervals at two sites within ~1 km of each other. Mean monthly air pressure is lowest during summer (June/July) and highest during winter (October-January), with an annual variation of ~10 hPa. The diurnal variation is ~2 hPa, with two minima and two maxima. The pressure minima are usually observed in the evening, between 1600 and 1700 Indian Standard Time (ist) (1030 and 1130 utc) and during the early hours, between 0400 and 0500 ist. The maximum values are observed in the morning, between 1000 and 1100 ist, and at night, between 2200 and 2300 ist. These daily variations are attributed to diurnal and semidiurnal tidal effects, which are well correlated with gravitational variations of ~0.8?gal observed at the same location using a superconducting gravimeter.</p>
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