Gravitational atmospheric tides as a probe of Titan's interior: application to Dragonfly

AbstractBayesian interpolation has previously been proposed as a strategy to construct maps of radio occultation (RO) data, but that proposition did not consider the diurnal dimension of RO data. In this work, the basis functions of Bayesian interpolation are extended into the domain of the diurnal cycle, thus enabling monthly mapping of radio occultation data in synoptic time and analysis of the atmospheric tides. The basis functions are spherical harmonics multiplied by sinusoids in the diurnal cycle up to arbitrary spherical harmonic degree and diurnal cycle harmonic. Bayesian interpolation requires a regularizer to impose smoothness on the fits it produces, thereby preventing the overfitting of data. In this work, a formulation for the regularizer is proposed and the most probable values of the parameters of the regularizer determined. Special care is required when obvious gaps in the sampling of the diurnal cycle are known to occur in order to prevent the false detection of statistically significant high-degree harmonics of the diurnal cycle in the atmosphere. Finally, this work probes the ability of Bayesian interpolation to generate a valid uncertainty analysis of the fit. The postfit residuals of Bayesian interpolation are dominated not by measurement noise but by unresolved variability in the atmosphere, which is statistically nonuniform across the globe, thus violating the central assumption of Bayesian interpolation. The problem is ameliorated by constructing maps of RO data using Bayesian interpolation that partially resolve the temporal variability of the atmosphere, constructing maps for approximately every 3 days of RO data.

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NLC and the background atmosphere above ALOMAR

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5701-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 5701-5717 ◽

Cited By ~ 41

Author(s):

J. Fiedler ◽

G. Baumgarten ◽

U. Berger ◽

P. Hoffmann ◽

N. Kaifler ◽

...

Keyword(s):

Diurnal Cycle ◽

Middle Atmosphere ◽

Thermal State ◽

Atmospheric Tides ◽

Data Set ◽

Ice Particles ◽

Cloud Water Content ◽

Radar Measurements ◽

Mf Radar

Abstract. Noctilucent clouds (NLC) have been measured by the Rayleigh/Mie/Raman-lidar at the ALOMAR research facility in Northern Norway (69° N, 16° E). From 1997 to 2010 NLC were detected during more than 1850 h on 440 different days. Colocated MF-radar measurements and calculations with the Leibniz-Institute Middle Atmosphere (LIMA-) model are used to characterize the background atmosphere. Temperatures as well as horizontal winds at 83 km altitude show distinct differences during NLC observations compared to when NLC are absent. The seasonally averaged temperature is lower and the winds are stronger westward when NLC are detected. The wind separation is a robust feature as it shows up in measurements as well as in model results and it is consistent with the current understanding that lower temperatures support the existence of ice particles. For the whole 14-year data set there is no statistically significant relation between NLC occurrence and solar Lyman-α radiation. On the other hand NLC occurrence and temperatures at 83 km show a significant anti-correlation, which suggests that the thermal state plays a major role for the existence of ice particles and dominates the pure Lyman-α influence on water vapor during certain years. We find the seasonal mean NLC altitudes to be correlated to both Lyman-α radiation and temperature. NLC above ALOMAR are strongly influenced by atmospheric tides. The cloud water content varies by a factor of 2.8 over the diurnal cycle. Diurnal and semidiurnal amplitudes and phases show some pronounced year-to-year variations. In general, amplitudes as well as phases vary in a different manner. Amplitudes change by a factor of more than 3 and phases vary by up to 7 h. Such variability could impact long-term NLC observations which do not cover the full diurnal cycle.

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Atmospheric Tides and Oscillations

Compendium of Meteorology ◽

10.1007/978-1-940033-70-9_43 ◽

1951 ◽

pp. 510-530 ◽

Cited By ~ 34

Author(s):

Sydney Chapman

Keyword(s):

Atmospheric Tides

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Lunisolar Atmospheric Tides. II

Australian Journal of Physics ◽

10.1071/ph890439 ◽

1989 ◽

Vol 42 (4) ◽

pp. 439 ◽

Cited By ~ 2

Author(s):

R Brahde

Keyword(s):

Phase Shift ◽

Atmospheric Pressure ◽

Mean Amplitude ◽

Atmospheric Tides ◽

The Moon ◽

Celestial Equator

In an earlier paper (Brahde 1988) it was shown that series of measurements of the atmospheric pressure in Oslo contained information about a one�day oscillation with mean amplitude 0�17 mb. The data consisted of measurements every second hour during the years 1957-67, 1969 and 1977. In the present paper the intervening years plus 1978 and 1979 have been included, increasing the basis from 13 to 23 years. In addition the phase shift occurring when the Moon crosses the celestial equator has been defined precisely, thus making it possible to include all the data.

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The diurnal and semidiurnal tides over Ascension Island (8° S, 14° W) and their interaction with the stratospheric QBO: studies with meteor radar, eCMAM and WACCM

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-4785-2013 ◽

2013 ◽

Vol 13 (2) ◽

pp. 4785-4837 ◽

Cited By ~ 5

Author(s):

R. N. Davis ◽

J. Du ◽

A. K. Smith ◽

W. E. Ward ◽

N. J. Mitchell

Keyword(s):

Seasonal Variation ◽

Climate Model ◽

Middle Atmosphere ◽

Atmospheric Tides ◽

Meteor Radar ◽

Vertical Wavelength ◽

Atlantic Region ◽

Meridional Component ◽

Ascension Island ◽

Good For

Abstract. Horizontal winds in the mesosphere have been measured over Ascension Island (8° S, 14° W) in the tropical mid-Atlantic region throughout the years 2002–2011. The observations were made by a VHF meteor radar. The results reveal the presence of atmospheric tides of large amplitude. The results are analysed to characterise the seasonal and interannual variability of the diurnal and semidiurnal tides. Monthly-mean diurnal tidal amplitudes are found to reach values as large as 48 m s−1 in the meridional component and 41 m s−1 in the zonal. A semiannual seasonal variation is found in diurnal-tidal amplitudes with amplitude maxima at the equinoxes and amplitude minima at the solstices. Diurnal tidal meridional vertical wavelengths are generally in the range 24–30 km. The diurnal zonal vertical wavelengths are similar to the meridional, except for the winter months when the zonal vertical wavelengths are much longer, occasionally exceeding 100 km. Semidiurnal amplitudes are observed to be significantly smaller than diurnal amplitudes. Semidiurnal vertical wavelengths range from 20 to more than 100 km. Our observations of tidal amplitudes and phases are compared with the predictions of the extended Canadian Middle Atmosphere Model (eCMAM) and the Whole Atmosphere Community Climate Model (WACCM). Both eCMAM and WACCM reproduce the trend for greater diurnal amplitudes in the meridional component than the zonal. However, in winter eCMAM tends to over-estimate meridional amplitudes, while WACCM under-estimates zonal and meridional amplitudes. Semidiurnal amplitude predictions are generally good for both models. Vertical wavelength predictions are also generally good for both models, however eCMAM predicts shorter zonal vertical wavelengths than observed for the diurnal tide in winter, while WACCM predicts longer zonal semidiurnal vertical wavelengths than observed for most months. It is found that larger-than-average diurnal and semidiurnal tidal amplitudes occur when the stratospheric QBO at 10 hPa is eastwards, and smaller-than-average amplitudes occur when it is westwards. However, the precise mechanism for this modulation of tidal amplitudes by the stratospheric QBO remains unclear.

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Atmospheric tides and the rotation of Venus I. Tidal theory and the balance of torques

Icarus ◽

10.1016/0019-1035(80)90156-6 ◽

1980 ◽

Vol 41 (1) ◽

pp. 1-17 ◽

Cited By ~ 50

Author(s):

Anthony R. Dobrovolskis ◽

Andrew P. Ingersoll

Keyword(s):

Atmospheric Tides ◽

Tidal Theory

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Global Response of the Ionosphere to Atmospheric Tides Forced from Below: Recent Progress Based on Satellite Measurements

Space Science Reviews ◽

10.1007/s11214-011-9837-1 ◽

2011 ◽

Vol 168 (1-4) ◽

pp. 175-209 ◽

Cited By ~ 27

Author(s):

Dora Pancheva ◽

Plamen Mukhtarov

Keyword(s):

Recent Progress ◽

Atmospheric Tides ◽

Satellite Measurements ◽

Global Response

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On the water barometer erected in the hall of the Royal Society

Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London ◽

10.1098/rspl.1830.0079 ◽

1837 ◽

Vol 3 ◽

pp. 134-136

Keyword(s):

Royal Society ◽

Present Situation ◽

Atmospheric Tides ◽

Steam Boiler ◽

Periodic Oscillations ◽

French Academy ◽

Different Temperatures ◽

History Of ◽

Additional Support ◽

Academy Of Sciences

The author having long considered that a good series of observations with a water barometer would be of great value as throwing light upon the theory of atmospheric tides, of the horary and other periodic oscillations of the barometer, and of the tension of vapourat different temperatures, was desirous of learning whether any such series of observations had ever been made. But he could meet with none having any pretensions to accuracy ; for neither those of Otto Guericke, in whose hands the water barometer was merely a philosophical toy, nor the cursory notices of the experiments of Mariotte upon this subject contained in the History of the French Academy of Sciences, can be considered as having any such claim. The difficulties which opposed the construction of a perfect instrument of this kind long appeared to be insurmountable; but the author at length proposed a plan for this purpose, which, having been approved of by the late Meteorological Committee of the Royal Society, was ordered by the President and Council to be carried into execution. The author then enters fully into the details of the methods he employed for constructing the whole of the apparatus, and for placing in its present situation in the centre of the winding staircase conducting to the apartments of the Royal Society. The tube was very skilfully made by Messrs. Pellattand Co. at the Falcon Glass-house. It was 40 feet long, and one inch in diameter at its lower end; and so nearly cylindrical, throughout its whole extent, as to diminish only by two tenths of an inch at its upper end. A second tube of the same dimensions was also made as a provision in reserve against any accident happening to the first. These tubes were both securely lodged in a square case by means of proper supports. A small thermometer with a platina scale, was introduced into the upper end of the tube. An external collar of glass was united to that end by heating it. This was done with a view of giving it additional support, and of preventing it from slipping. This end of the tube was then drawn out into a fine tube ready for sealing with the blowpipe; and a small stopcock was fitted on to it. The cistern of the barometer was formed by a small copper steam boiler, 18 inches long, 11 wide, and 10 deep, capable of being closed by a cock, and having at the bottom a small receptacle for holding the lower end of the tube, so as to allow of the water in the cistern being withdrawn, without dis turbing that contained in the tube.

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