High-resolution temperature profiles retrieved from bichromatic stellar scintillation measurements by GOMOS/Envisat

In this paper, we describe the inversion algorithm for retrievals of high vertical resolution temperature profiles (HRTPs) using bichromatic stellar scintillation measurements in the occultation geometry. This retrieval algorithm has been improved with respect to nominal ESA processing and applied to the measurements by Global Ozone Monitoring by Occultation of Stars (GOMOS) operated on board Envisat in 2002–2012. The retrieval method exploits the chromatic refraction in the Earth's atmosphere. The bichromatic scintillations allow the determination of the refractive angle, which is proportional to the time delay between the photometer signals. The paper discusses the basic principle and detailed inversion algorithm for reconstruction of high-resolution density, pressure and temperature profiles in the stratosphere from scintillation measurements. The HRTPs are retrieved with a very good vertical resolution of ∼200 m and high precision (random uncertainty) of ∼1–3 K for altitudes of 15–32 km and with a global coverage. The best accuracy is achieved for in-orbital-plane occultations, and the precision weakly depends on star brightness. The whole GOMOS dataset has been processed with the improved HRTP inversion algorithm using the FMI's scientific processor; and the dataset (HRTP FSP v1) is in open access. The validation of small-scale fluctuations in the retrieved HRTPs is performed via comparison of vertical wavenumber spectra of temperature fluctuations in HRTPs and in collocated radiosonde data. We found that the spectral features of temperature fluctuations are very similar in HRTPs and collocated radiosonde temperature profiles. HRTPs can be assimilated into atmospheric models, used in studies of stratospheric clouds and used for the analysis of internal gravity waves' activity. As an example of geophysical applications, gravity wave potential energy has been estimated using the HRTP dataset. The obtained spatiotemporal distributions of gravity wave energy are in good agreement with the previous analyses using other measurements.

Indigenous use of stellar scintillation to predict weather and seasonal change

Indigenous peoples across the world observe the motions and positions of stars to develop seasonal calendars. Changing properties of stars, such as their brightness and colour, are also used for predicting weather. Combining archival studies with ethnographic fieldwork in Australia’s Torres Strait, we explore the various ways Indigenous peoples utilise stellar scintillation (twinkling) as an indicator for predicting weather and seasonal change, and examine the Indigenous and Western scientific underpinnings of this knowledge. By observing subtle changes in the ways the stars twinkle, Meriam people gauge changing trade winds, approaching wet weather and temperature changes. We then examine how the Northern Dene of Arctic North America utilise stellar scintillation to forecast weather.

High-resolution temperature profiles (HRTP) retrieved from bi-chromatic stellar scintillation measurements by GOMOS/Envisat

In this paper, we describe the inversion algorithm for retrievals of high vertical resolution temperature profiles using bi-chromatic stellar scintillation measurements in the occultation geometry. This retrieval algorithm has been improved with respect to nominal ESA processing and applied to the measurements by Global Ozone Monitoring by Occultation of Stars (GOMOS) operated on board Envisat in 2002–2012. The retrieval method exploits the chromatic refraction in the Earth's atmosphere. The bi-chromatic scintillations allow the determination of the refractive angle, which is proportional to the time delay between the photometer signals. The paper discusses the basic principle and detailed inversion algorithm for reconstruction of high resolution density, pressure and temperature profiles (HRTP) in the stratosphere from scintillation measurements. The HRTP profiles are retrieved with very good vertical resolution of ~200 m and high accuracy of ~1–3 K for altitudes of 15–32 km and with a global coverage. The best accuracy is achieved in in-orbital-plane occultations, and the accuracy weakly depends on star brightness. The whole GOMOS dataset has been processed with the improved HRTP inversion algorithm using the FMI's Scientific Processor; and the dataset (HRTP FSP v1) is in open access. The validation of small-scale fluctuations in the retrieved HRTP profiles is performed via comparison of vertical wavenumber spectra of temperature fluctuations in HRTP and in collocated radiosonde data. We found that the spectral features of temperature fluctuations are very similar in HRTP and collocated radiosonde temperature profiles. HRTP can be assimilated into atmospheric models, used in studies of stratospheric clouds and in analysis of internal gravity waves activity. As an example of geophysical applications, gravity wave potential energy has been estimated using the HRTP dataset. The obtained spatio-temporal distributions of gravity wave energy are in good agreement with the previous analyses using other measurements.

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

In this paper, we consider possibilities for studying the anisotropy of small-scale air density irregularities using satellite observations of bi-chromatic stellar scintillations during tangential occultations. Estimation of the anisotropy coefficient (the ratio of the characteristic horizontal to vertical scales) and other atmospheric parameters is based on the comparison of simulated/theoretical and experimental auto-spectra and coherency spectra of scintillation. Our analyses exploit a 3-D model of the spectrum of atmospheric inhomogeneities, which consists of anisotropic and isotropic components. For the anisotropic component, a spectral model with variable anisotropy is used. Using stellar scintillation measurements by GOMOS (Global Ozone Monitoring by Occultation of Stars) fast photometers, estimates of the anisotropy coefficient are obtained for atmospheric irregularities with vertical scales of 8–55 m at altitudes of 43–30 km. It is shown that the anisotropy increases from about 10 to 50 with increasing vertical scales.

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

In this paper, we consider possibilities for studying the anisotropy of small-scale air density irregularities using satellite observations of bi-chromatic stellar scintillations during tangential occultations. Estimation of the anisotropy coefficient (the ratio of the characteristic horizontal to vertical scales) and other atmospheric parameters is based on the comparison of simulated/theoretical and experimental auto-spectra and coherency spectra of scintillation. Our analyses exploit a 3-D model of the spectrum of atmospheric inhomogeneities, which consists of anisotropic and isotropic components. For the anisotropic component, a spectral model with variable anisotropy is used. Using stellar scintillation measurements by GOMOS (Global Ozone Monitoring by Occultation of Stars) fast photometers, estimates of the anisotropy coefficient are obtained for atmospheric irregularities with vertical scales of 8–55 m at altitudes of 43–30 km. It is shown that the anisotropy increases from about 10 to 50 with increasing vertical scales.

Estimates of turbulent diffusivities and energy dissipation rates from satellite measurements of spectra of stratospheric refractivity perturbations

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.

Turbulent diffusivities and energy dissipation rates in the stratosphere from GOMOS satellite stellar scintillation measurements

Parameters of anisotropic and isotropic spectra of refractivity, density and temperature perturbations obtained from GOMOS satellite measurements of stellar scintillations are used to estimate turbulent Thorpe scales, LT, diffusivities, K, and energy dissipation rates, ε, in the stratosphere. At low latitudes, average values for altitudes 30–45 km in September–November 2004 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 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)×10−5 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 30–45 km in low latitudes have maxima at longitudes 30–100° W, 0–60° E and 90–180° E, which correspond to continent locations. Correlations between parameters of anisotropic and isotropic spectra are studied.