scholarly journals Evidence of meso-scale structure in the high-latitude thermosphere

2001 ◽  
Vol 19 (1) ◽  
pp. 37-46 ◽  
Author(s):  
A. L. Aruliah ◽  
E. Griffin
Keyword(s):  
Atmospheric Composition ◽  
Neutral Atmosphere ◽  
Neutral Winds ◽  
Neutral Gas ◽  
Composition And Structure ◽  
Direct Measurements ◽  
Fabry Perot ◽  
Instruments And Techniques ◽  
Eiscat Radar ◽  
Made In

Abstract. There is a widely held assumption that the thermospheric neutral gas is slow to respond to magnetospheric forcing owing to its large inertia and therefore, may be treated as a steady state background medium for the more dynamic ionosphere. This is shown to be over simplistic. The data presented here compare direct measurements of the thermospheric neutral winds made in Northern Scandinavia by Fabry-Perot Interferometers (FPIs) with direct measurements of the ionosphere made by the EISCAT radar and with model simulations. These comparisons will show that the neutral atmosphere is capable of responding to ionospheric changes on mesoscale levels, i.e., spatial and temporal scale sizes of less than a few hundred kilometres and tens of minutes, respectively.Key words. Atmospheric composition and structure (air-glow and aurora; instruments and techniques) – Ionosphere (ionosphere-atmosphere interactions)

scholarly journals Mesospheric temperatures from observations of the hydroxyl (6–2) emission above Davis, Antarctica: A comparison of rotational and Doppler measurements

2001 ◽  
Vol 19 (3) ◽  
pp. 359-365 ◽  
Author(s):  
J. L. Innis ◽  
F. A. Phillips ◽  
G. B. Burns ◽  
P. A. Greet ◽  
W. J. R. French ◽  
...  
Keyword(s):  
The Other ◽  
Atmospheric Composition ◽  
Austral Winter ◽  
Data Set ◽  
Composition And Structure ◽  
Fabry Perot ◽  
Instruments And Techniques ◽  
The Mean ◽  
Observational Errors ◽  
Line Widths

Abstract. We present observations of the hydroxyl (6–2) airglow lines from ~ 87 km altitude obtained at Davis station, Antarctica, in the austral winter of 1999. Nine nights of observations were made of the P-branch near λ840 nm with a Czerny-Turner scanning spectrometer (CTS); at the same time, high-resolution Fabry-Perot Spectrometer (FPS) spectra were collected of the Q1(1) doublet at λ834 nm. Rotational temperatures were determined from the CTS observations, while Doppler temperatures were derived from the line-widths of the FPS Q1(1) spectra. Absolute temperatures determined by these methods are uncertain by ~ 2 and ~ 20 K, respectively. For the comparison we set the value of the reflective finesse of the FPS at λ834 nm so the mean FPS temperature from one night of simultaneous data was equal to that from the CTS, and then looked at the measured variations in each data set for the other eight nights. Both instruments show the upper mesosphere temperature to vary in a similar manner to within the observational errors of the measurements, implying an equivalence of the rotational and Doppler temperatures. We believe that this is the first published simultaneous, same-site, comparison of rotational and Doppler temperatures from the OH emission. Key words. Atmospheric composition and structure (airglow and aurora; pressure density and temperature; instruments and techniques)

scholarly journals On the fast movements of the thermosphere: an interpretation

2000 ◽  
Vol 18 (12) ◽  
pp. 1651-1656
Author(s):  
J. Lilensten ◽  
P. O. Amblard
Keyword(s):  
Rotation Velocity ◽  
Atmospheric Composition ◽  
Neutral Wind ◽  
Typical Size ◽  
F Region ◽  
Optical Experiment ◽  
Atmospheric Composition And Structure ◽  
Composition And Structure ◽  
Eiscat Radar

Abstract. We examine the oscillations of the meridional neutral wind in the F region as seen by the EISCAT radar. We propose an interpretation in term of eddies (tourbillons) of typical size of a few tens to a few hundreds of kilometers. The observed rotation velocity is a few hundreds of meters per second. We suggest that the tourbillons are a common feature of thermospheric movements. We propose an optical experiment to check the validity of this assumption.Key words: Atmospheric composition and structure (thermosphere · composition and chemistry) · Ionosphere (ionosphere · atmosphere interactions)

scholarly journals Doppler temperatures from O(<sup>1</sup>D) airglow in the daytime thermosphere as observed by the Wind Imaging Interferometer (WINDII) on the UARS satellite

2002 ◽  
Vol 20 (2) ◽  
pp. 203-212 ◽  
Author(s):  
C. Lathuillère ◽  
W. A. Gault ◽  
B. Lamballais ◽  
Y. J. Rochon ◽  
B. H. Solheim
Keyword(s):  
Atmospheric Composition ◽  
Large Set ◽  
Temperature Variations ◽  
Data Processing Software ◽  
Imaging Interferometer ◽  
Composition And Structure ◽  
Instruments And Techniques ◽  
The Mean ◽  
First Time ◽  
Good Agreement

Abstract. From 1992 to 1997, the WINDII interferometer on board the UARS satellite acquired a large set of thermospheric data from the O(1D) and O(1S) airglows. We report here for the first time on daytime O(1D) Doppler temperatures obtained with version 5.11 of the WINDII data processing software. Using a statistical analysis of the temperatures independently measured by the two WINDII fields of view, we estimate that the temperature variations larger than 40 K can be considered as geophysical. Comparisons of WINDII temperatures measured during magnetically quiet days with temperatures obtained by the MSIS-90 and DTM-94 thermospheric models show a 100 K bias. We demonstrate, however, that the modeled temperature variations represent very well the mean temperature variation observed by WINDII over 4 years. We also show that the observed latitudinal/local time variation is in very good agreement with the two empirical models. Finally, the temperature variations during a magnetically disturbed day are found to be qualitatively well represented in form by the models, but largely underestimated. The presence of non-thermal atoms and instrument related issues are discussed as possible explanations for the 100 K bias between the WINDII Doppler temperatures and the empirical models.Key words. Atmospheric composition and structure (air-glow and aurora; pressure, density and temperature; instruments and techniques)

scholarly journals The red-sky enigma over Svalbard in December 2002

2005 ◽  
Vol 23 (5) ◽  
pp. 1593-1602
Author(s):  
F. Sigernes ◽  
N. Lloyd ◽  
D. A. Lorentzen ◽  
R. Neuber ◽  
U.-P. Hoppe ◽  
...  
Keyword(s):  
Scattered Light ◽  
Atmospheric Composition ◽  
The Sun ◽  
Polar Stratospheric Clouds ◽  
Atmospheric Sciences ◽  
Composition And Structure ◽  
History Of Geophysics ◽  
History Of ◽  
Instruments And Techniques ◽  
Stratospheric Clouds

Abstract. On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral measurements from the Auroral Station in Adventdalen confirm that the light was scattered sunlight. Even though the Sun was between 11.8 and 14.6deg below the horizon during the event, the measured intensities of scattered light on the southern horizon from the scanning photometers coincided with the rise and setting of the Sun. Calculations of actual heights, including refraction and atmospheric screening, indicate that the event most likely was scattered solar light from a target below the horizon. This is also confirmed by the OSIRIS instrument on board the Odin satellite. The deduced height profile indicates that the scattering target is located 18–23km up in the stratosphere at a latitude close to 73–75° N, southeast of Longyearbyen. The temperatures in this region were found to be low enough for Polar Stratospheric Clouds (PSC) to be formed. The target was also identified as PSC by the LIDAR systems at the Koldewey Station in Ny-Ålesund (79° N, 12° E). The event was most likely caused by solar illuminated type II Polar Stratospheric Clouds that scattered light towards Svalbard. Two types of scenarios are presented to explain how light is scattered. Keywords. Atmospheric composition and structure (Transmissions and scattering of radiation; Middle atmospherecomposition and chemistry; Instruments and techniques) – History of geophysics (Atmospheric Sciences; The red-sky phenomena)

scholarly journals High resolution 2-D maps of OI 630.0 nm thermospheric dayglow from equatorial latitudes

1998 ◽  
Vol 16 (8) ◽  
pp. 997-1006
Author(s):  
D. Pallam Raju ◽  
R. Sridharan
Keyword(s):  
High Resolution ◽  
Gravity Waves ◽  
Large Scale ◽  
Equatorial Electrojet ◽  
Equatorial Ionosphere ◽  
Atmospheric Composition ◽  
Scale Feature ◽  
Equatorial Ionization Anomaly ◽  
Composition And Structure ◽  
Instruments And Techniques

Abstract. The first-ever high resolution 2-D maps of OI 630.0 nm dayglow obtained from equatorial latitudes clearly reveal the movement as a large-scale feature of the equatorial ionization anomaly (EIA). These also show the presence of wave-like features classified as gravity waves presumably originating at the crest of the EIA, similar to the equatorial electrojet acting as a source of these waves. These results are presented and discussed.Key words. Atmospheric composition and structure (Airglow and aurora) · Ionosphere (Equatorial ionosphere; Instruments and techniques).

scholarly journals Seasonal variations of O<sub>2</sub> atmospheric and OH(6−2) airglowand temperature at mid-latitudes from SATI observations

2004 ◽  
Vol 22 (3) ◽  
pp. 819-828 ◽  
Author(s):  
M. J. López-González ◽  
E. Rodríguez ◽  
R. H. Wiens ◽  
G. G. Shepherd ◽  
S. Sargoytchev ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Key Words ◽  
Sierra Nevada ◽  
Seasonal Variations ◽  
Annual Variation ◽  
Emission Rate ◽  
Atmospheric Composition ◽  
Emission Rates ◽  
Composition And Structure ◽  
Instruments And Techniques

Abstract. More than 3 years of airglow observations with a Spectral Airglow Temperature Imager (SATI) installed at the Sierra Nevada Observatory (37.06°N, 3.38°W) at 2900m height have been analyzed. Values of the column emission rate and vertically averaged temperature of the O2 atmospheric (0–1) band and of the OH Meinel (6–2) band from 1998 to 2002 have been presented. From these observations a clear seasonal variation of both emission rates and rotational temperatures is inferred at this latitude. It is found that the annual variation of the temperatures is larger than the semi-annual variation, while for the emission rates the amplitudes are comparable. Key words. Atmospheric composition and structure (airglow and aurora; pressure density and temperature; instruments and techniques)

scholarly journals Validation of GOME total ozone by means of the Norwegian ozone monitoring network

1999 ◽  
Vol 17 (3) ◽  
pp. 430-436 ◽  
Author(s):  
G. Hansen ◽  
A. Dahlback ◽  
F. Tønnessen ◽  
T. Svenøe
Keyword(s):  
Total Ozone ◽  
Middle Atmosphere ◽  
Monitoring Network ◽  
High Arctic ◽  
Atmospheric Composition ◽  
Pixel Size ◽  
Composition And Structure ◽  
Instruments And Techniques ◽  
Ozone Monitoring ◽  
Good Agreement

Abstract. The Global Ozone Monitoring Experiment (GOME) onboard the ERS-2 satellite has been in operation since July 1995. The Norwegian ground-based total ozone network has played an important role both in the main validation during the commissioning phase and in the validation of upgraded versions of the analysis algorithms of the instrument. The ground-based network consists of various spectrometer types (Dobson, Brewer, UV filter instruments). The validation of the second algorithm version used until January 1998 reveals a very good agreement between GOME and ground-based data at solar zenith angles <60° and deviations of GOME total ozone data from ground-based data of up to ±60 DU (~20%) at zenith angles >60°. The deviations strongly depend on the season of the year, being negative in summer and positive in winter/spring, The deviations furthermore show a considerable scattering (up to ±25 DU in monthly average values of 5° SZA intervals), even in close spatial and temporal coincidence with ground-based measurements, especially in the high Arctic. The deviations are also dependent on the viewing geometry/ground pixel size with an additional negative offset for the large pixels used in the backswath mode and at solar zenith angles >85°, compared to forward-swath pixels.Key words. Atmospheric composition and structure (middle atmosphere · composition and chemistry; instruments and techniques)

scholarly journals An efficient algorithm for the large-scale smoothing of scattered data retrieved from remote sounding experiments

2003 ◽  
Vol 21 (7) ◽  
pp. 1645-1652 ◽  
Author(s):  
D. Fussen
Keyword(s):  
Large Scale ◽  
Noisy Data ◽  
Scattered Data ◽  
Atmospheric Composition ◽  
Structure Evolution ◽  
Test Cases ◽  
Composition And Structure ◽  
Remote Sounding ◽  
Instruments And Techniques ◽  
Regularization Operator

Abstract. We present a new algorithm for smoothing/interpolation of two-dimensional fields applicable to noisy data observed at scattered sites. The technique is based on a special statistics allowing one to simultaneously minimize the fit residual and the correlation between residuals of adjacent points. The principle of the method is first explained in the 1-D case and then extended to the 2-D case by adjunction of a regularization operator. The method is compared with different algorithms (Loess-Renka, Biharmonic Spline and kriging) in three test cases related to remote sounding of the Earth’s atmosphere by space-borne experiments.Key words. Atmospheric composition and structure (evolution of the atmosphere; instruments and techniques; general or miscellaneous)

scholarly journals Space-borne clear air lidar measurements in the presence of broken cloud

2003 ◽  
Vol 21 (3) ◽  
pp. 639-647 ◽  
Author(s):  
I. Astin ◽  
C. Kiemle
Keyword(s):  
General Circulation ◽  
Ground Level ◽  
Atmospheric Dynamics ◽  
Atmospheric Composition ◽  
Lidar Data ◽  
Meteorology And Atmospheric Dynamics ◽  
Composition And Structure ◽  
Lidar Measurements ◽  
Instruments And Techniques ◽  
Along Track

Abstract. A number of proposed lidar systems, such as ESA’s AEOLUS (formerly ADM) and DIAL missions (e.g. WALES) are to make use of lidar returns in clear air. However, on average, two-thirds of the globe is covered in cloud. Hence, there is a strong likelihood that data from these instruments may be contaminated by cloud. Similarly, optically thick cloud may not be penetrated by a lidar pulse, resulting in unobservable regions that are overshadowed by the cloud. To address this, it is suggested, for example, in AEOLUS, that a number of consecutive short sections of lidar data (between 1 and 3.5 km in length) be tested for cloud contamination or for overshadowing and only those that are unaffected by cloud be used to derive atmospheric profiles. The prob-ability of obtaining profiles to near ground level using this technique is investigated both analytically and using UV air-borne lidar data recorded during the CLARE’98 campaign. These data were measured in the presence of broken cloud on a number of flights over southern England over a four-day period and were chosen because the lidar used has the same wavelength, footprint and could match the along-track spacing of the proposed AEOLUS lidar.Key words. Atmospheric composition and structure (aerosols and particles) Meteorology and atmospheric dynamics (instruments and techniques; general circulation)

scholarly journals Measurement errors in cirrus cloud microphysical properties

1998 ◽  
Vol 16 (2) ◽  
pp. 266-276 ◽  
Author(s):  
H. Larsen ◽  
J.-F. Gayet ◽  
G. Febvre ◽  
H. Chepfer ◽  
G. Brogniez
Keyword(s):  
Measurement Errors ◽  
Cloud Microphysics ◽  
Radiative Properties ◽  
Atmospheric Composition ◽  
Cirrus Cloud ◽  
Radiative Processes ◽  
Microphysical Properties ◽  
Composition And Structure ◽  
Instruments And Techniques ◽  
Limited Accuracy

Abstract. The limited accuracy of current cloud microphysics sensors used in cirrus cloud studies imposes limitations on the use of the data to examine the cloud's broadband radiative behaviour, an important element of the global energy balance. We review the limitations of the instruments, PMS probes, most widely used for measuring the microphysical structure of cirrus clouds and show the effect of these limitations on descriptions of the cloud radiative properties. The analysis is applied to measurements made as part of the European Cloud and Radiation Experiment (EUCREX) to determine mid-latitude cirrus microphysical and radiative properties.Key words. Atmospheric composition and structure (cloud physics and chemistry) · Meteorology and atmospheric dynamics · Radiative processes · Instruments and techniques

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