Vladimir Gubenko

A Method for Determination of Internal Gravity Wave Parameters from a Vertical Temperature or Density Profile Measurement in the Earth's Atmosphere

A method for determination of internal gravity wave (IGW) parameters from a single vertical temperature or density profile measurement in the Earth’s atmosphere has been developed. This method may be used for the analysis of profiles measured by any techniques in which the accuracy is enough to measure small (∼1%) amplitudes of the temperature or density fluctuations in the atmosphere. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied then analyzed fluctuations can be considered as wave-induced. The method is based upon the analysis of relative amplitude thresholds of the temperature or density wave field and upon linear IGW saturation theory in which amplitude thresholds are restricted by dynamical instability processes in the atmosphere. In order to approbate the method we have used data of simultaneous radiosonde measurements of the temperature and wind velocity in the Earth’s stratosphere where the saturated IGW propagation has been detected. It is shown that the application of the method to radio occultation temperature data gives the possibility to identify IGWs in the Earth’s lower stratosphere and to determine values of key wave parameters.

Detection of layering in the upper cloud layer of Venus northern polar atmosphere observed from radio occultation data

[1] Observations of radio wave scintillations represent an important tool for measuring of small-scale irregularities in the atmosphere of Venus. Prominent features of enhanced scintillation located in the 60-km region were observed in Mariners 5 and 10, Venera 9, and Pioneer Venus occultations. It is possible that the enhanced scintillations are due to the random turbulence in the upper region which is caused by trapped small-scale gravity waves. However, other interpretations are possible. Thin stable layers, which are commonly observed in the Earth stratosphere under cloud-free conditions, could also contribute to scattering in the Venus stratosphere. If scintillations observed in different occultations are correlated, then these scintillations may be attributed to the persistent layers. Cross correlations of 32-cm radio wave amplitude fluctuations have been determined for seven radio occultation measurements of Venus’s northern polar atmosphere using Venera 15 and 16. Significant cross correlations were found between 59.0 and 61.5 km in four different radio occultations. Layering is revealed in the upper layer of the Venus clouds at altitudes of 59.0–61.5 km, which is specified by enhanced turbulence of the atmosphere. It is found that the lifetime of the small-scale layered irregularities is 2 d or more and that their horizontal extension in the meridional direction can exceed 180 km. A possible cause of emergence of the layered structures inside the upper layer of polar clouds of Venus is discussed.

Characteristics of internal waves in the Martian atmosphere obtained on the basis of an analysis of vertical temperature profiles of the Mars Global Surveyor mission

An original method of determining the characteristics of an internal gravity wave (IGW) was developed using the data of an analysis of individual vertical temperature profile in the planet’s atmosphere. The method is based on an analysis of relative wave amplitude determined from the vertical temperature profile, as well as on the proposition of the IGW linear theory, according to which the wave amplitude is limited by the processes of dynamic (shear) instability in the atmosphere. It is supposed that, when the amplitude of the internal wave reaches the shear instability threshold as the wave propagates upward, a dissipation of wave energy occurs such that the IGW amplitude is maintained at the atmospheric instability threshold. The application of the developed method to vertical temperature profiles obtained from radio occultation measurements of the MGS (Mars Global Surveyor) mission made it possible to identify IGWs in the Martian atmosphere and determine the values of key wave parameters such as intrinsic frequency, amplitudes of the vertical and horizontal disturbances of wind velocity, vertical and horizontal wavelength, intrinsic vertical and horizontal phase (and group) velocities, kinetic, potential, and total energy of IGWs per unit mass, vertical fluxes of wave energy and horizontal momentum. Identified in the Martian atmosphere IGWs, with a vertical wavelength of 4.5–8.2 km, are waves with low intrinsic frequencies close to inertial frequency. Their kinetic energy, as a rule, is greater than potential energy by an order of magnitude. The propagation of these waves causes a significant modulation of the stability of atmospheric stratification that leads to shear instability and the occurrence of thin layers of intermittent turbulence in the Martian atmosphere.

New Applications and Advances of the GPS Radio Occultation Technology as Recovered by Analysis of the FORMOSAT-3/COSMIC and CHAMP Data-Base

Comparative analysis of phase and amplitude variations of GPS radio-holograms allows one to separate the influence of the layered and irregular structures. A possibility exists to measure important parameters of internal waves: the intrinsic phase speed, the horizontal wind perturbations, and, under some assumptions, the intrinsic frequency as function of height in the atmosphere. A new technique was applied to measurements provided during CHAllenging Minisatellite Payload (CHAMP) and the Formosa Satellite-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) radio occultation (RO) missions. As an example of this approach, we establish the atmospheric origin of amplitude and phase variations in the RO signal at altitudes 10–26 km. We observed for the first time in the RO practice examples of internal wave breaking at altitudes between 38 km and 45 km. We obtained geographical distributions and seasonal dependence of atmospheric wave activity with global coverage within the years 2001–2003.