scholarly journals Anisotropy of small-scale stratospheric irregularities retrieved from scintillations of a double star α-Cru observed by GOMOS/ENVISAT

2012 ◽  
Vol 5 (11) ◽  
pp. 2713-2722 ◽  
Author(s):  
V. Kan ◽  
V. F. Sofieva ◽  
F. Dalaudier
Keyword(s):  
Double Star ◽  
Satellite Observations ◽  
Spectral Model ◽  
Small Scale ◽  
Anisotropy Coefficient ◽  
Air Density ◽  
Ozone Monitoring ◽  
Vertical Scales

Abstract. In this paper, we discuss estimating anisotropy of air density irregularities (ratio of characteristic horizontal and vertical scales) from satellite observations of bi-chromatic scintillations of a double star whose components are not resolved by the detector. The analysis is based on fitting experimental auto- and cross-spectra of scintillations by those computed using the 3-D spectral model of atmospheric irregularities consisting of anisotropic and isotropic components. Application of the developed method to the scintillation measurements of the double star α-Cru by GOMOS (Global Ozone Monitoring by Occultation of Stars) fast photometers results in estimates of anisotropy coefficient of ~15–20 at altitudes 30–38 km, as well as other parameters of atmospheric irregularities. The obtained estimates of the anisotropy coefficient correspond to small-scale irregularities, close to the buoyancy scale.

scholarly journals Anisotropy of small-scale stratospheric irregularities retrieved from scintillations of a double star α-Cru observed by GOMOS/ENVISAT

2012 ◽  
Vol 5 (4) ◽  
pp. 4881-4904
Author(s):  
V. Kan ◽  
V. F. Sofieva ◽  
F. Dalaudier
Keyword(s):  
Double Star ◽  
Satellite Observations ◽  
Spectral Model ◽  
Small Scale ◽  
Anisotropy Coefficient ◽  
Air Density ◽  
Ozone Monitoring ◽  
Vertical Scales

Abstract. In this paper, we discuss estimating anisotropy of air density irregularities (ratio of characteristic horizontal and vertical scales) from satellite observations of bi-chromatic scintillations of a double star whose components are not resolved by the detector. The analysis is based on fitting experimental auto- and cross-spectra of scintillations by those computed using the 3-D spectral model of atmospheric irregularities consisting of anisotropic and isotropic components. Application of the developed method to the scintillation measurements of the double star α-Cru by GOMOS (Global Ozone Monitoring by Occultation of Stars) fast photometers results in estimates of anisotropy coefficient of ~15–20 at altitudes 30–38 km, as well as other parameters of atmospheric irregularities. The obtained estimates of the anisotropy coefficient correspond to small-scale irregularities, close to the buoyancy scale.

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

2014 ◽  
Vol 7 (6) ◽  
pp. 1861-1872 ◽  
Author(s):  
V. Kan ◽  
V. F. Sofieva ◽  
F. Dalaudier
Keyword(s):  
Satellite Observations ◽  
Small Scale ◽  
Anisotropy Coefficient ◽  
Atmospheric Parameters ◽  
Air Density ◽  
Ozone Monitoring ◽  
D Model ◽  
Vertical Scales ◽  
Stellar Scintillation ◽  
Variable Anisotropy

Abstract. 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.

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

2014 ◽  
Vol 7 (2) ◽  
pp. 1275-1304
Author(s):  
V. Kan ◽  
V. F. Sofieva ◽  
F. Dalaudier
Keyword(s):  
Satellite Observations ◽  
Small Scale ◽  
Anisotropy Coefficient ◽  
Atmospheric Parameters ◽  
Air Density ◽  
Ozone Monitoring ◽  
D Model ◽  
Vertical Scales ◽  
Stellar Scintillation ◽  
Variable Anisotropy

Abstract. 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.

Internal Wave Generation by a Combination of Tidal and Steady Currents

2021 ◽  
Author(s):  
Xiaolin Bai ◽  
Kevin Lamb ◽  
José da Silva
Keyword(s):  
Internal Wave ◽  
Wave Generation ◽  
Satellite Observations ◽  
Internal Tides ◽  
Small Scale ◽  
Western Boundary ◽  
Boundary Current ◽  
Reanalysis Dataset ◽  
Amazon Shelf ◽  
Internal Wave Generation

<p>In the presence of topography, two main contributors for internal wave energy are tide-topography interaction transferring energy from the barotropic tide to internal tides, and lee wave generation when geostrophic currents or eddying abyssal flows interact with topography. In the past few decades, many studies considered the respective contribution of the oscillating flows or steady background flows, but few investigations have considered both.  </p><p>In this talk, we consider the joint effects of tidal and steady currents to investigate internal wave generation and propagation on the Amazon shelf, a hotspot for internal solitary wave (ISW) generation. The Amazon Shelf is off the mouth of the Amazon River in the southwest tropical Atlantic Ocean, affected by strong tidal constituents over complex bottom bathymetry and a strong western boundary current, the North Brazilian Current (NBC). Both satellite observations and numerical modelling are used in this study. Satellite observations provide a clear visualization of the wave characteristics, such as temporal and spatial distributions, propagating direction and its relation to background currents. Based on parameters from satellite observations and reanalysis dataset, we set up a model to numerically investigate the dynamics of the ISW generation. We demonstrate that the small-scale topography contributes to a rich generation of along-shelf propagating ISW, which significantly contribute to the ocean mixing and potentially cause sediment resuspension. Moreover, the ISW-induced currents also contribute to the sea surface wave breaking as observed by satellite measurements. In addition, statistics based on a decade of satellite images and numerical investigations on seasonal variations of the ISWs and the NBC improve our understanding of the generation and evolution of these nonlinear internal waves in the presence of background currents.</p>

scholarly journals Estimating European volatile organic compound emissions using satellite observations of formaldehyde from the Ozone Monitoring Instrument

2010 ◽  
Vol 10 (23) ◽  
pp. 11501-11517 ◽  
Author(s):  
G. Curci ◽  
P. I. Palmer ◽  
T. P. Kurosu ◽  
K. Chance ◽  
G. Visconti
Keyword(s):  
Satellite Observations ◽  
Atmospheric Composition ◽  
Ozone Monitoring Instrument ◽  
Top Down ◽  
Bottom Up ◽  
Voc Emissions ◽  
The Balkans ◽  
Monitoring Instrument ◽  
Volatile Organic ◽  
Ozone Monitoring

Abstract. Emission of non-methane Volatile Organic Compounds (VOCs) to the atmosphere stems from biogenic and human activities, and their estimation is difficult because of the many and not fully understood processes involved. In order to narrow down the uncertainty related to VOC emissions, which negatively reflects on our ability to simulate the atmospheric composition, we exploit satellite observations of formaldehyde (HCHO), an ubiquitous oxidation product of most VOCs, focusing on Europe. HCHO column observations from the Ozone Monitoring Instrument (OMI) reveal a marked seasonal cycle with a summer maximum and winter minimum. In summer, the oxidation of methane and other long-lived VOCs supply a slowly varying background HCHO column, while HCHO variability is dominated by most reactive VOC, primarily biogenic isoprene followed in importance by biogenic terpenes and anthropogenic VOCs. The chemistry-transport model CHIMERE qualitatively reproduces the temporal and spatial features of the observed HCHO column, but display regional biases which are attributed mainly to incorrect biogenic VOC emissions, calculated with the Model of Emissions of Gases and Aerosol from Nature (MEGAN) algorithm. These "bottom-up" or a-priori emissions are corrected through a Bayesian inversion of the OMI HCHO observations. Resulting "top-down" or a-posteriori isoprene emissions are lower than "bottom-up" by 40% over the Balkans and by 20% over Southern Germany, and higher by 20% over Iberian Peninsula, Greece and Italy. We conclude that OMI satellite observations of HCHO can provide a quantitative "top-down" constraint on the European "bottom-up" VOC inventories.

scholarly journals Features of formation of small-scale wave disturbances during a sudden magnetospheric compression

2017 ◽  
Vol 3 (2) ◽  
pp. 34-42
Author(s):  
Алексей Моисеев ◽  
Aleksey Moiseev ◽  
Дмитрий Баишев ◽  
Dmitry Baishev ◽  
Владимир Мишин ◽  
...  
Keyword(s):  
Wave Front ◽  
Geomagnetic Field ◽  
Compression Wave ◽  
Interplanetary Medium ◽  
Interplanetary Shock ◽  
Satellite Observations ◽  
Small Scale ◽  
Plasma Parameters ◽  
Wave Disturbances ◽  
Periodic Changes

Quasi-periodic changes of the geomagnetic field and plasma parameters in the range of Pc 5 pulsations, which occurred immediately after the interaction of interplanetary shock (IPS) with Earth’s magnetosphere in the event of April 24, 2009 at 00:53 UT are examined using ground and satellite observations. The pulsations were localized at latitudes 66–74° in the noon (11 MLT) and evening (20 MLT) sectors. The analysis of hodographs of the geomagnetic field changes both from satellite and ground observations has shown the presence of vortical disturbances. In this event, both the IPS front in the interplanetary medium and the compression wave front in the magnetosphere had a slope in the ZGSM=0 plane; the inclination angle was 14° in the interplanetary medium and 34° in the magnetosphere.

Determination of upper-atmosphere air density and scale height from satellite observations

1959 ◽  
Vol 252 (1268) ◽  
pp. 16-27 ◽  
Keyword(s):  
Satellite Orbit ◽  
Major Axis ◽  
Scale Height ◽  
Rate Of Change ◽  
Satellite Observations ◽  
Upper Atmosphere ◽  
Semi Major Axis ◽  
Air Density ◽  
Standard Deviations

A solution is obtained for the rate of change of semi-major axis and perigee distance of a satellite orbit with time due to the resistance of the atmosphere. The logarithm of air density is assumed to vary quadratically with height, and the oblateness of the atmosphere is taken into account. The calculation of perigee air density in terms of the rate of change of satellite period is dealt with; and the method is applied to data at present available on six different satellites. The variation of air density with height is obtained as ln ρ = -28·59(±0·15) - ( h - 200 )/46(±5) + 0·028(±0·013) ( h - 200) 2 /(46) 2 for h in the range of approximately 170 to 700 km, where ρ is in grams/cm 3 , h is in kilometres and standard deviations are given in brackets.

scholarly journals Retrieval and satellite intercomparison of O<sub>3</sub> measurements from ground-based FTIR Spectrometer at Equatorial Station: Addis Ababa, Ethiopia

2013 ◽  
Vol 6 (2) ◽  
pp. 495-509 ◽  
Author(s):  
S. Takele Kenea ◽  
G. Mengistu Tsidu ◽  
T. Blumenstock ◽  
F. Hase ◽  
T. von Clarmann ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Addis Ababa ◽  
Michelson Interferometer ◽  
Ftir Spectra ◽  
Satellite Observations ◽  
Ozone Monitoring Instrument ◽  
Equatorial Station ◽  
Ozone Monitoring ◽  
Relative Differences ◽  
Good Agreement

Abstract. Since May 2009, high-resolution Fourier Transform Infrared (FTIR) solar absorption spectra have been recorded at Addis Ababa (9.01° N latitude, 38.76° E longitude, 2443 m altitude above sea level), Ethiopia. The vertical profiles and total column amounts of ozone (O3) are deduced from the spectra by using the retrieval code PROFFIT (V9.5) and regularly determined instrumental line shape (ILS). A detailed error analysis of the O3 retrieval is performed. Averaging kernels of the target gas shows that the major contribution to the retrieved information comes from the measurement. The degrees of freedom for signals is found to be 2.1 on average for the retrieval of O3 from the observed FTIR spectra. The ozone Volume Mixing Ratio (VMR) profiles and column amounts retrieved from FTIR spectra are compared with the coincident satellite observations of Microwave Limb Sounding (MLS), Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), Tropospheric Emission Spectrometer (TES), Ozone Monitoring Instrument (OMI), Atmospheric Infrared Sounding (AIRS) and Global Ozone Monitoring Experiment (GOME-2) instruments. The mean relative differences in ozone profiles of FTIR from MLS and MIPAS are generally lower than 15% within the altitude range of 27 to 36 km, whereas difference from TES is lower than 1%. Comparisons of measurements of column amounts from the satellite and the ground-based FTIR show very good agreement as exhibited by relative differences within +0.2% to +2.8% for FTIR versus MLS and GOME-2; and −0.9 to −9.0% for FTIR versus OMI, TES and AIRS. The corresponding standard deviations are within 2.0 to 2.8% for FTIR versus MLS and GOME-2 comparisons whereas that of FTIR versus OMI, TES and AIRS are within 3.5 to 7.3%. Thus, the retrieved O3 VMR and column amounts from a tropical site, Addis Ababa, is found to exhibit very good agreement with all coincident satellite observations over an approximate 3-yr period.

scholarly journals Adjoint inversion of Chinese non-methane volatile organic compound emissions using space-based observations of formaldehyde and glyoxal

2018 ◽  
Vol 18 (20) ◽  
pp. 15017-15046 ◽  
Author(s):  
Hansen Cao ◽  
Tzung-May Fu ◽  
Lin Zhang ◽  
Daven K. Henze ◽  
Christopher Chan Miller ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Organic Compound ◽  
A Priori ◽  
Satellite Observations ◽  
Anthropogenic Sources ◽  
Anthropogenic Emissions ◽  
Top Down ◽  
Volatile Organic ◽  
Annual Total ◽  
Ozone Monitoring

Abstract. We used the GEOS-Chem model and its adjoint to quantify Chinese non-methane volatile organic compound (NMVOC) emissions for the year 2007, using the tropospheric column concentrations of formaldehyde and glyoxal observed by the Global Ozone Monitoring Experiment 2A (GOME-2A) instrument and the Ozone Monitoring Instrument (OMI) as quantitative constraints. We conducted a series of inversion experiments using different combinations of satellite observations to explore their impacts on the top-down emission estimates. Our top-down estimates for Chinese annual total NMVOC emissions were 30.7 to 49.5 (average 41.9) Tg yr−1, including 16.4 to 23.6 (average 20.2) Tg yr−1 from anthropogenic sources, 12.2 to 22.8 (average 19.2) Tg yr−1 from biogenic sources, and 2.08 to 3.13 (average 2.48) Tg yr−1 from biomass burning. In comparison, the a priori estimate for Chinese annual total NMVOC emissions was 38.3 Tg yr−1, including 18.8 Tg yr−1 from anthropogenic sources, 17.3 Tg yr−1 from biogenic sources, and 2.27 Tg yr−1 from biomass burning. The simultaneous use of glyoxal and formaldehyde observations helped distinguish the NMVOC species from different sources and was essential in constraining anthropogenic emissions. Our four inversion experiments consistently showed that the Chinese anthropogenic emissions of NMVOC precursors of glyoxal were larger than the a priori estimates. Our top-down estimates for Chinese annual emission of anthropogenic aromatics (benzene, toluene, and xylene) ranged from 5.5 to 7.9 Tg yr−1, 2 % to 46 % larger than the estimate of the a priori emission inventory (5.4 Tg yr−1). Three out of our four inversion experiments indicated that the seasonal variation in Chinese NMVOC emissions was significantly stronger than indicated in the a priori inventory. Model simulations driven by the average of our top-down NMVOC emission estimates (which had a stronger seasonal variation than the a priori) showed that surface afternoon ozone concentrations over eastern China increased by 1–8 ppb in June and decreased by 1–10 ppb in December relative to the simulations using the a priori emissions and were in better agreement with measurements. We concluded that the satellite observations of formaldehyde and glyoxal together provided quantitative constraints on the emissions and source types of NMVOCs over China and improved our understanding on regional chemistry.

scholarly journals Features of formation of small-scale wave disturbances during a sudden magnetospheric compression

2017 ◽  
Vol 3 (2) ◽  
pp. 36-44
Author(s):  
Алексей Моисеев ◽  
Aleksey Moiseev ◽  
Дмитрий Баишев ◽  
Dmitry Baishev ◽  
Владимир Мишин ◽  
...  
Keyword(s):  
Wave Front ◽  
Geomagnetic Field ◽  
Compression Wave ◽  
Interplanetary Medium ◽  
Front Propagation ◽  
Interplanetary Shock ◽  
Satellite Observations ◽  
Small Scale ◽  
Plasma Parameters ◽  
Wave Disturbances

Quasi-periodic changes of the geomagnetic field and plasma parameters in the range of Pc 5 pulsations, which occurred immediately after the interaction of interplanetary shock (IPS) with Earth’s magnetosphere in the event of April 24, 2009 at 00:53 UT are examined using ground and satellite observations. The pulsations were localized at latitudes 66–74° in the noon (11 MLT) and evening (20 MLT) sectors. The analysis of hodographs of the geomagnetic field changes both from satellite and ground observations has shown the presence of vortical disturbances. In this event, both the IPS front in the interplanetary medium and the compression wave front in the magnetosphere had a slope in the ZGSM=0 plane; the inclination angle was 14° in the interplanetary medium and 34° in the magnetosphere. The location of the vortical disturbances in the magnetosphere at different radial distances, i.e. X~5.5 Re in the noon sector and X ~–6.3 ÷–7.3 Re in the evening sector, is in agreement with the front inclination. As inferred from satellite observations, the maximum intensity of wave disturbances in both the sectors was registered in the toroidal component of the magnetic field. This suggests the resonant mechanism of excitation of these disturbances. The analysis of distribution of velocities of plasma flow and compression wave front propagation in the magnetosphere’s equatorial plane has revealed that the vortical disturbances occurred in regions where these velocities were noticeably different in magnitude.

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