Abstract
Abstract. Approaches for estimations of effective turbulent diffusion and energetic parameters from characteristics of anisotropic and isotropic spectra of perturbations of atmospheric refractivity, density and temperature are developed. The approaches are applied to the data obtained with the GOMOS instrument for measurements of stellar scintillations on-board the Envisat satellite to estimate turbulent Thorpe scales, LT, diffusivities, K, and energy dissipation rates, ϵ, in the stratosphere. At low latitudes, effective values are LT ~ 1–1.1 m, ϵ ~ (1.8–2.4) × 10−5 W kg−1, and K ~ (1.2–1.6) × 10−2 m2 s−1 at altitudes of 30–45 km in September–November 2004, depending on different assumed values of parameters of anisotropic and isotropic spectra. Respective standard deviations of individual values, including all kinds of variability, are δLT ~ 0.6–0.7 m, δϵ ~ (2.3–3.5) × 10−2 W kg−1, and δK ~ (1.7–2.6) × 10−2 m2 s−1. These values correspond to high-resolution balloon measurements of turbulent characteristics in the stratosphere, and to previous satellite stellar scintillation measurements. Distributions of turbulent characteristics at altitudes of 30–45 km in low latitudes have maxima at longitudes corresponding to regions of increased gravity wave dissipation over locations of stronger convection. Correlations between parameters of anisotropic and isotropic spectra are evaluated.
Highlights
Internal gravity waves (IGWs) with energy propagating upwards are important for dynamical processes and mixing in the middle atmosphere (Fritts and Alexander, 2003)
We developed approaches to use these spectral parameters for estimating turbulent kinetic energy dissipation rates and turbulent diffusivities produced by smallscale isotropic turbulence
We developed approaches for estimations of effective turbulent diffusion and energetic parameters from characteristics of anisotropic and isotropic spectra of perturbations of atmospheric refractivity, density and temperature
Summary
Internal gravity waves (IGWs) with energy propagating upwards are important for dynamical processes and mixing in the middle atmosphere (Fritts and Alexander, 2003). Gavrilov: Turbulent diffusivities and energy dissipation rates in the stratosphere global temperature measurements with the satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). Relative intensity fluctuations can be as strong as several hundred percent (see Sofieva et al, 2010) These scintillations are due to air temperature and density irregularities produced by IGWs, turbulence and different instabilities, which produce perturbations of atmospheric refractivity. GOMOS contains two photometers recording stellar light at a sampling frequency of 1 kHz synchronously in 473–527 nm and 646–698 nm spectral bands during star sets behind the Earth’s limb These measurements were used to estimate parameters of anisotropic and isotropic spectra of temperature perturbations produced by IGWs and small-scale turbulence in the stratosphere (Gurvich and Kan, 2003a; Sofieva et al, 2007, 2009, 2010). We estimated the mentioned turbulent characteristics at altitudes of 30–45 km in September– November 2004 at latitudes 20◦ S–20◦ N and in January 2005 at middle latitudes 34–36◦ N and compared them with available satellite, balloon and high-resolution radiosonde data
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