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| Titel |
The lunar semidiurnal air pressure tide in in-situ data and ECMWF reanalyses |
| VerfasserIn |
Michael Schindelegger, Henryk Dobslaw |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123351
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| Publikation (Nr.) |
 EGU/EGU2016-2585.pdf |
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| Zusammenfassung |
| A gridded empirical model of the lunar semidiurnal air pressure tide L2 is deduced through
multiquadric interpolation of more than 2000 globally distributed tidal estimates from land
barometers and moored buoys. The resulting climatology serves as an independent
standard to validate the barometric L2 oscillations that are present in ECMWF’s
(European Centre for Medium-Range Weather Forecasts) global atmospheric reanalyses
despite the omission of gravitational forcing mechanisms in the involved forecast
routines. Inconsistencies between numerical and empirical L2 solutions are found
to be small even though the reanalysis models typically underestimate equatorial
peak pressures by 10–20% and produce slightly deficient tidal phases in latitudes
south of 30∘N. Through using a time-invariant reference surface over both land and
water and assimilating marine pressure data without accounting for vertical sensor
movements due to the M2 ocean tide, ECMWF-based tidal solutions are also prone to
strong local artifacts. Additionally, the dependency of the lunar tidal oscillation in
atmospheric analysis systems on the meteorological input data is demonstrated based on a
recent ECMWF twentieth-century reanalysis (ERA-20C) which draws its all of its
observational constraints from in-situ registrations of pressure and surface winds. The L2
signature prior to 1950 is particularly indicative of distinct observing system changes,
such as the paucity of marine data during both World Wars or the opening of the
Panama Canal in 1914 and the associated adjustment of commercial shipping routes. |
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