Global distribution of C_T² at altitudes 30–50 km from space‐borne observations of stellar scintillation

Abstract

Locally isotropic turbulence in the stratosphere consists of isolated sporadic patches with random values of temperature structure characteristic CT2. Stellar scintillations measured aboard GOMOS/ENVISAT through the Earth atmosphere provided the first global distribution of the effective characteristic CT,eff2 averaged along sounding ray. For zonal mean, the largest values are achieved in winter polar regions. This observed intense turbulence is probably related to the polar night jet. Relatively weak turbulence is observed at low latitudes. Turbulence intensity map is shown for altitude 42 km in the latitude band ±35°, where the maxima follow the sub‐solar latitude, with enhancements located mainly over continents. Turbulence enhancements are not related with orography. Despite a noticeable correlation with typical regions of deep convection, the overall distribution of CT,eff2 displays a more complicated structure. Analyzed data suggest that the main turbulence sources, at altitudes ∼40 km, are instabilities of stratospheric circulation and gravity wave breaking.

Variable anisotropy of small-scale stratospheric irregularities retrieved from stellar scintillation measurements by GOMOS/Envisat

“…Stellar scintillations in occultation experiments are widely used for probing the atmospheric irregularities of planets and their satellites (Hubbard et al, 1988;Raynaud et al, 2004) and the Earth atmosphere (Gurvich and Kan, 2003a, b;Gurvich et al, 2007;Sofieva et al, 2007aSofieva et al, , b, 2009). The phase screen approximation (Gurvich, 1984;Hubbard et al, 1978) and the theory of weak scintillations (Tatarskii, 1961(Tatarskii, , 1971 provide the basis for analyses of scintillation measurements and reconstructing the parameters of atmospheric irregularities.…”

Using stellar scintillation for studies of turbulence in the Earth’s atmosphere

“…The value of σ 2 I,iso can be estimated using the simplified spectral analysis, as described in [58,105]. This technique uses the fact that scintillation spectra at scales from l W to the scale corresponding to the Nyquist frequency are defined mainly by the turbulent component and they are nearly flat.…”

“…Within the Rytov smooth perturbation approximation [47], there is a fairly simple connection between the (three-dimensional) spectrum of refractive index fluctuations and the two-dimensional scintillation spectrum in the observation plane. So far, these relations have been used to retrieve the parameters of the spatial spectrum of refractive index fluctuations from satellite and in situ scintillation measurements [19][20][21][56][57][58]. The Rytov method is valid when the monochromatic scintillation variance σ 2 I = (I − I ) 2 / I 2 is small, σ 2 I 1 (weak fluctuations).…”

“…GOMOS is equipped with two fast photometers, which record the stellar flux synchronously in the blue (473-527 nm, λ B ≈ 500 nm) and red (646-698 nm, λ R ≈ 672 nm) wavelength ranges with a sampling frequency of 1 kHz in the limb-viewing geometry. The algorithm for the reconstruction of GW and turbulence spectra parameters has been developed further [20], adapted to the GOMOS measurements and applied to a large GOMOS dataset [58,105,106]. Several studies have been dedicated to bichromatic scintillations [107][108][109] and double star occultations [110].…”

Technical note: Scintillations of the double star α Cru observed by GOMOS/Envisat

“…1 in Kyrölä et al, 2004). The scintillation measurements are used for the correction of scintillations in the spectrometer data to achieve a better accuracy of trace gases retrievals (Dalaudier et al, 2001;Sofieva et al, 2009b), for temperature profiling with a high vertical resolution (Dalaudier et al, 2006), and for studying small-scale processes in the stratosphere (Gurvich et al, , 2007Sofieva et al, 2007a, b;2009a).…”