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Joseph Harrington - One of the best experts on this subject based on the ideXlab platform.

  • the 1998 november 14 occultation of gsc 0622 00345 by saturn ii stratospheric thermal profile power spectrum and gravity waves
    The Astrophysical Journal, 2010
    Co-Authors: Joseph Harrington, R G French, Katia I Matcheva
    Abstract:

    On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345. The occultation latitude was 55.{sup 0}5 S. This paper analyzes the 2.3 {mu}m light curve derived by Harrington and French. A fixed-baseline isothermal fit to the light curve has a temperature of 140 {+-} 3 K, assuming a mean molecular mass of 2.35 AMU. The thermal profile obtained by numerical inversion is valid between 1 and 60 {mu}bar. The vertical temperature gradient is > 0.2 K km{sup -1} more stable than the Adiabatic Lapse Rate, but it still shows the alternating-rounded-spiked features seen in many temperature gradient profiles from other atmospheric occultations and usually attributed to breaking gravity (buoyancy) waves. We conduct a wavelet analysis of the thermal profile, and show that, even with our low level of noise, scintillation due to turbulence in Earth's atmosphere can produce large temperature swings in light-curve inversions. Spurious periodic features in the 'reliable' region of a wavelet amplitude spectrum can exceed 0.3 K in our data. We also show that gravity-wave model fits to noisy isothermal light curves can lead to convincing wave 'detections'. We provide new significance tests for localized wavelet amplitudes, wave model fits, and global power spectramore » of inverted occultation light curves by assessing the effects of pre- and post-occultation noise on these parameters. Based on these tests, we detect several significant ridges and isolated peaks in wavelet amplitude, to which we fit a gravity wave model. We also strongly detect the global power spectrum of thermal fluctuations in Saturn's atmosphere, which resembles the 'universal' (modified Desaubies) curve associated with satuRated spectra of propagating gravity waves on Earth and Jupiter.« less

Katia I Matcheva - One of the best experts on this subject based on the ideXlab platform.

  • the 1998 november 14 occultation of gsc 0622 00345 by saturn ii stratospheric thermal profile power spectrum and gravity waves
    The Astrophysical Journal, 2010
    Co-Authors: Joseph Harrington, R G French, Katia I Matcheva
    Abstract:

    On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345. The occultation latitude was 55.{sup 0}5 S. This paper analyzes the 2.3 {mu}m light curve derived by Harrington and French. A fixed-baseline isothermal fit to the light curve has a temperature of 140 {+-} 3 K, assuming a mean molecular mass of 2.35 AMU. The thermal profile obtained by numerical inversion is valid between 1 and 60 {mu}bar. The vertical temperature gradient is > 0.2 K km{sup -1} more stable than the Adiabatic Lapse Rate, but it still shows the alternating-rounded-spiked features seen in many temperature gradient profiles from other atmospheric occultations and usually attributed to breaking gravity (buoyancy) waves. We conduct a wavelet analysis of the thermal profile, and show that, even with our low level of noise, scintillation due to turbulence in Earth's atmosphere can produce large temperature swings in light-curve inversions. Spurious periodic features in the 'reliable' region of a wavelet amplitude spectrum can exceed 0.3 K in our data. We also show that gravity-wave model fits to noisy isothermal light curves can lead to convincing wave 'detections'. We provide new significance tests for localized wavelet amplitudes, wave model fits, and global power spectramore » of inverted occultation light curves by assessing the effects of pre- and post-occultation noise on these parameters. Based on these tests, we detect several significant ridges and isolated peaks in wavelet amplitude, to which we fit a gravity wave model. We also strongly detect the global power spectrum of thermal fluctuations in Saturn's atmosphere, which resembles the 'universal' (modified Desaubies) curve associated with satuRated spectra of propagating gravity waves on Earth and Jupiter.« less

R G French - One of the best experts on this subject based on the ideXlab platform.

  • the 1998 november 14 occultation of gsc 0622 00345 by saturn ii stratospheric thermal profile power spectrum and gravity waves
    The Astrophysical Journal, 2010
    Co-Authors: Joseph Harrington, R G French, Katia I Matcheva
    Abstract:

    On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345. The occultation latitude was 55.{sup 0}5 S. This paper analyzes the 2.3 {mu}m light curve derived by Harrington and French. A fixed-baseline isothermal fit to the light curve has a temperature of 140 {+-} 3 K, assuming a mean molecular mass of 2.35 AMU. The thermal profile obtained by numerical inversion is valid between 1 and 60 {mu}bar. The vertical temperature gradient is > 0.2 K km{sup -1} more stable than the Adiabatic Lapse Rate, but it still shows the alternating-rounded-spiked features seen in many temperature gradient profiles from other atmospheric occultations and usually attributed to breaking gravity (buoyancy) waves. We conduct a wavelet analysis of the thermal profile, and show that, even with our low level of noise, scintillation due to turbulence in Earth's atmosphere can produce large temperature swings in light-curve inversions. Spurious periodic features in the 'reliable' region of a wavelet amplitude spectrum can exceed 0.3 K in our data. We also show that gravity-wave model fits to noisy isothermal light curves can lead to convincing wave 'detections'. We provide new significance tests for localized wavelet amplitudes, wave model fits, and global power spectramore » of inverted occultation light curves by assessing the effects of pre- and post-occultation noise on these parameters. Based on these tests, we detect several significant ridges and isolated peaks in wavelet amplitude, to which we fit a gravity wave model. We also strongly detect the global power spectrum of thermal fluctuations in Saturn's atmosphere, which resembles the 'universal' (modified Desaubies) curve associated with satuRated spectra of propagating gravity waves on Earth and Jupiter.« less

J E Ramirez - One of the best experts on this subject based on the ideXlab platform.

  • Adiabatic Lapse Rate of nonideal gases the role of molecular interactions and vibrations
    Physical Review E, 2020
    Co-Authors: Bogar Diaz, J E Ramirez
    Abstract:

    We report a formula for the dry Adiabatic Lapse Rate that depends on the compressibility factor and the Adiabatic curves. Then, to take into account the nonideal behavior of the gases, we consider molecules that can move, rotate, and vibRate and the information of molecular interactions through the virial coefficients. We deduce the compressibility factor in its virial expansion form and the Adiabatic curves within the virial expansion up to any order. With this information and to illustRate the mentioned formula, we write the Lapse Rate for the ideal gas, and the virial expansion up to the second and third coefficient cases. To figure out the role of the virial coefficients and vibrations, under different atmospheric conditions, we calculate the Lapse Rate for Earth, Mars, Venus, Titan, and the exoplanet Gl 581d. Furthermore, for each one we consider three models in the virial expansion: van der Waals, square-well, and hard-sphere. Also, when possible, we compare our results to the experimental data. Finally, we remark that for Venus and Titan, which are under extreme conditions of pressure or temperature, our calculations are in good agreement with the observed values, in some instances.

  • effects of the second virial coefficient on the Adiabatic Lapse Rate of dry atmospheres
    European Physical Journal Plus, 2019
    Co-Authors: Emilio Alvarez Navarro, Bogar Diaz, J E Ramirez, Miguel Angel Garciaariza
    Abstract:

    We study the effect of the second virial coefficient on the Adiabatic Lapse Rate of a dry atmosphere. To this end, we compute the corresponding Adiabatic curves, the internal energy, and the heat capacity, among other thermodynamic parameters. We apply these results to Earth, Mars, Venus, Titan, and the exoplanet G1 851d, considering three physically relevant virial coefficients in each case: the hard-sphere, van der Waals, and the square-well potential. These examples illustRate under which atmospheric conditions the effect of the second virial coefficient is relevant. Taking the latter into account yields corrections towards the experimental values of the Lapse Rates of Venus and Titan in some instances.

W E Ward - One of the best experts on this subject based on the ideXlab platform.

  • mesospheric temperature inversions with overlying nearly Adiabatic Lapse Rate an indication of a well mixed turbulent layer
    Geophysical Research Letters, 1995
    Co-Authors: James A. Whiteway, Allan I Carswell, W E Ward
    Abstract:

    The Rayleigh lidar technique was applied to study the thermal structure of the middle atmosphere. Observations were carried out on a routine basis for one year (130 clear nights) at the main campus of York University near Toronto (44°N,80°W). Mesospheric temperature inversions were generally found to occur below a height of 70 km during winter and above during summer. The most interesting aspect of our observations was that the inversions were often associated with an overlying nearly Adiabatic Lapse Rate which extended for several kilometres. We interpret this as being an indication (or signature) of a well-mixed turbulent layer. A one-dimensional numerical model was applied to demonstRate that a well-defined turbulent layer within the mesosphere can bring about a thermal structure quite similar to that which was commonly observed—an inversion with overlying nearly Adiabatic Lapse.