Determination of parameters of the spectrum of internal waves in the stratosphere from space-based observations of strong stellar scintillation |
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| Authors: | A S Gurvich V V Vorob’ev O V Fedorova |
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| Institution: | (1) Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Pyzhevskii per. 3, Moscow, 119017, Russia |
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| Abstract: | Observation of stars from a spacecraft through the Earth’s atmosphere is a constituent part of remote sensing of the atmosphere. Recorded scintillation signals contain data on the structure of air-density irregularities induced by turbulence and internal waves. Currently, parameters of the structure in the stratosphere are determined using the procedures based on the weak-scintillation theory. However, during stellar occultation by the Earth’s atmosphere, scintillation becomes stronger as the line of sight plunges into denser air layers. This paper considers the problem of remote sensing of stratospheric irregularities under strong-scintillation conditions. The scintillation spectra are calculated in the phase-screen approximation under the assumption that the spectrum of the phase added by the screen corresponds to observations through the stratosphere. It is assumed that stratospheric irregularities of air density are generated by an ensemble of saturated internal waves whose three-dimensional spectrum contains two characteristic wave numbers corresponding to the outer and inner scales. In the calculation, no restrictions are imposed on the observed scintillation amplitude. It is shown that the effect of the scintillation amplitude on the observed scintillation spectra appears most prominent for large wave numbers corresponding to irregularities whose sizes are smaller than the inner scale. For these wave numbers, deviations from the weak-scintillation theory become appreciable if the rms relative fluctuation of light intensity exceeds 0.3. In contrast, for small wave numbers corresponding to scales exceeding the outer scale, the weak-scintillation theory remains valid to rms values as large as 2. Analysis of calculated spectra has shown that the parameters of the three-dimensional spectra of stratospheric irregularities can be retrieved under the conditions of relatively strong scintillation characterized by an rms value below 1.5–1.6. |
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