scholarly journals Observations on Stratospheric-Mesospheric-Thermospheric temperatures using Indian MST radar and co-located LIDAR during Leonid Meteor Shower (LMS)

2002 ◽  
Vol 20 (11) ◽  
pp. 1869-1876
Author(s):  
R. Selvamurugan ◽  
C. V. Devasia ◽  
A. R. Jain ◽  
C. Raghava Reddi ◽  
P. B. Rao ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Fold Increase ◽  
Meteor Shower ◽  
Atmospheric Composition ◽  
Temperature History ◽  
Good Time ◽  
Maximum Height ◽  
Mst Radar ◽  
Leonid Meteor Shower ◽  
Meteor Trails

Abstract. The temporal and height statistics of the occurrence of meteor trails during the Leonid meteor shower revealed the capability of the Indian MST radar to record large numbers of meteor trails. The distribution of radio meteor trails due to a Leonid meteor shower in space and time provided a unique opportunity to construct the height profiles of lower thermospheric temperatures and winds, with good time and height resolution. There was a four-fold increase in the meteor trails observed during the LMS compared to a typical non-shower day. The temperatures were found to be in excellent continuity with the temperature profiles below the radio meteor region derived from the co-located Nd-Yag LIDAR and the maximum height of the temperature profile was extended from the LIDAR to ~110 km. There are, how-ever, some significant differences between the observed profiles and the CIRA-86 model profiles. The first results on the meteor statistics and neutral temperature are presented and discussed below.  Key words. Atmospheric composition and structure (pres-sure, density, and temperature) History of geophysics (at-mospheric sciences) Meteorology and atmospheric dynamics (middle atmosphere dynamics)

A technique for reconstructing the spatial characteristics of a long-lived meteor trails on all-sky cameras

2020 ◽  
Author(s):  
Tatiana Syrenova ◽  
Roman Vasilyev ◽  
Alexander Beletsky ◽  
Alexander Mikhalev ◽  
Eselevich Maxim
Keyword(s):  
Basic Research ◽  
Solar Observatory ◽  
Meteor Shower ◽  
Meteor Showers ◽  
Main Attention ◽  
Optical Instruments ◽  
Meteor Trail ◽  
Leonid Meteor Shower ◽  
Meteor Trails ◽  
Python Programming

<p>Over the years, reports of meteor trails lasting up to one hour have periodically appeared in the literature. These observations are usually associated with particularly strong meteor showers, such as Leonids. In [Kelley et al. 2000] some interesting observations of such trails related to the 1998 Leonid meteor shower event are presented [2]. In publications devoted to the study of this phenomenon in the optical range, the main attention is paid to processes that cause a prolonged luminescence of meteor showers [Kelley et al., 2000]. Meanwhile, this phenomenon is of great interest for diagnosing the Earth upper atmosphere state and the ionosphere. The bulk of the work in this direction is based on radar observations of ionization traces, the duration of which in some cases reaches several minutes [Kashcheev et al., 1967].</p><p>This paper reports on long-lived meteor trails (LMT), which was recorded simultaneously using two optical instruments recording night sky emissions. The first all-sky camera is located at the Geophysical Observatory of the ISTP SB RAS, near the Tory (51.80 N, 103.10 E) and is designed to record the spatial picture of the 630 nm emission intensity [http: // atmos. iszf.irk.ru/ru/data/keo]. The second all-sky camera is located in the Sayan Solar Observatory of the ISTP SB RAS, near the Mondy (51.60 N, 100.90 E). A meteor trail lasting 35-40 minutes was recorded on November 18, 2017 after a meteoroid explosion on 22.23.19 UT with two cameras from different directions. Further, an algorithm was developed with the Python programming language the geographical coordinates of this event were calculated, as well as the height of the highlight</p><p>. The meteoroid explosion height and the ellipsoidal trail was being 65-70 km. Then the meteor track bow spread horizontally in a southward for 30-40 minutes at an average velocity of 58 m/s. This technique can be used to determine the main characteristics of various phenomena in the atmosphere, such as waves, SAR-arcs, meteor tracks and others.</p><p>This work was supported by a grant from the Russian Foundation for Basic Research N19-35-90093.</p>

scholarly journals Rarefied gas flows through meshes and implications for atmospheric measurements

2001 ◽  
Vol 19 (5) ◽  
pp. 563-569 ◽  
Author(s):  
J. Gumbel
Keyword(s):  
Middle Atmosphere ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Atmospheric Composition ◽  
Gas Flows ◽  
Atmospheric Measurements ◽  
Rarefied Gas Flows ◽  
Flow Disturbances ◽  
Composition And Structure ◽  
Compression Effects

Abstract. Meshes are commonly used as part of instruments for in situ atmospheric measurements. This study analyses the aerodynamic effect of meshes by means of wind tunnel experiments and numerical simulations. Based on the Direct Simulation Monte Carlo method, a simple mesh parameterisation is described and applied to a number of representative flow conditions. For open meshes freely exposed to the flow, substantial compression effects are found both upstream and downstream of the mesh. Meshes attached to close instrument structures, on the other hand, cause only minor flow disturbances. In an accompanying paper, the approach developed here is applied to the quantitative analysis of rocket-borne density measurements in the middle atmosphere.Key words. Atmospheric composition and structure (instruments and techniques; middle atmosphere – composition and chemistry)

scholarly journals Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

2018 ◽  
Vol 36 (1) ◽  
pp. 253-264 ◽  
Author(s):  
Gabriel Augusto Giongo ◽  
José Valentin Bageston ◽  
Paulo Prado Batista ◽  
Cristiano Max Wrasse ◽  
Gabriela Dornelles Bittencourt ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Near Infrared ◽  
Middle Atmosphere ◽  
Convective Cloud ◽  
Atmospheric Composition ◽  
Secondary Wave ◽  
King George Island ◽  
Composition And Structure ◽  
Waves And Tides ◽  
Energy And Momentum

Abstract. The main goals of this work are to characterize and investigate the potential wave sources of four mesospheric fronts identified in the hydroxyl near-infrared (OH-NIR) airglow images, obtained with an all-sky airglow imager installed at Comandante Ferraz Antarctic Station (EACF, as per its Portuguese acronym) located on King George Island in the Antarctic Peninsula. We identified and analyzed four mesospheric fronts in 2011 over King George Island. In addition, we investigate the atmospheric background environment between 80 and 100 km altitude and discuss the ducts and propagation conditions for these waves. For that, we used wind data obtained from a meteor radar operated at EACF and temperature data obtained from the TIMED/SABER satellite. The vertical wavenumber squared, m2, was calculated for each of the four waves. Even though no clearly defined duct (indicated by positive values of m2 sandwiched between layers above and below with m2  < 0) was found in any of the events, favorable propagation conditions for horizontal propagation of the fronts were found in three cases. In the fourth case, the wave front did not find any duct support and it appeared to dissipate near the zenith, transferring energy and momentum to the medium and, consequently, accelerating the wind in the wave propagation direction (near to south) above the OH peak (88–92 km). The likely wave sources for these four cases were investigated by using meteorological satellite images and in two cases we could find that strong instabilities were potential sources, i.e., a cyclonic activity and a large convective cloud cell. In the other two cases it was not possible to associate troposphere sources as potential candidates for the generation of such wave fronts observed in the mesosphere and secondary wave sources were attributed to these cases. Keywords. Atmospheric composition and structure (airglow and aurora) – meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

scholarly journals Stratospheric ozone depletion during the 1995–1996 Arctic winter: 3-D simulations on the potential role of different PSC types

2001 ◽  
Vol 19 (9) ◽  
pp. 1163-1181 ◽  
Author(s):  
J. Hendricks ◽  
F. Baier ◽  
G. Günther ◽  
B. C. Krüger ◽  
A. Ebel
Keyword(s):  
Ozone Depletion ◽  
Middle Atmosphere ◽  
Spatial Scales ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Particle Growth ◽  
Atmospheric Composition ◽  
Formation Mechanisms ◽  
Three Dimensional Model ◽  
Type Ia

Abstract. The sensitivity of modelled ozone depletion in the winter Arctic stratosphere to different assumptions of prevalent PSC types and PSC formation mechanisms is investigated. Three-dimensional simulations of the winter 1995/96 are performed with the COlogne Model of the Middle Atmosphere (COMMA) by applying different PSC microphysical schemes. Model runs are carried out considering either liquid or solid PSC particles or a combined microphysical scheme. These simulations are then compared to a model run which only takes into account binary sulfate aerosols. The results obtained with the three-dimensional model agree with trajectory-box simulations performed in previous studies. The simulations suggest that conditions appropriate for type Ia PSC existence (T < TNAT ) occur over longer periods and cover larger areas when compared to conditions of potential type Ib PSC existence. Significant differences in chlorine activation and ozone depletion occur between the simulations including only either liquid or solid PSC particles. The largest differences, occurring over large spatial scales and during prolonged time periods, are modelled first, when the stratospheric temperatures stay below TNAT , but above the threshold of effective liquid particle growth and second, in the case of the stratospheric temperatures remaining below this threshold, but not falling below the ice frost point. It can be generally concluded from the present study that differences in PSC microphysical schemes can cause significant fluctuations in ozone depletion modelled for the winter Arctic stratosphere.Key words. Atmospheric composition and structure (aerosols and particles; cloud physics and chemistry; middle atmosphere composition and chemistry)

scholarly journals Surface ultraviolet radiation over east Siberia: seasonal variations

2002 ◽  
Vol 20 (4) ◽  
pp. 559-564
Author(s):  
A. V. Mikhalev ◽  
M. A. Chernigovskaya ◽  
A. Yu. Shalin ◽  
E. S. Kazimirovsky
Keyword(s):  
Ultraviolet Radiation ◽  
Uv Radiation ◽  
Middle Atmosphere ◽  
Ground Level ◽  
Atmospheric Composition ◽  
Time Interval ◽  
East Siberia ◽  
Solar Ultraviolet Radiation ◽  
Composition And Structure ◽  
Asymmetric Behaviour

Abstract. The results of spectral measurements of the daily near-noon surface direct solar ultraviolet radiation in the wavelength range of 295–345 nm obtained in Irkutsk (East Siberia) for the time interval of 1998–2000 are presented. For the period under consideration, the seasonal UV radiation variations are analysed that are associated with the total ozone dynamics, the transition of cyclonic and anticyclonic (Siberian anticyclone) periods, the presence of snow cover, and other factors. The analysis reveals an asymmetric behaviour of the seasonal course in ground-level UV radiation around the time of the summer solstice, with seasonal variation dependence on the wavelength. We have determined the irregular variations of surface UV radiation that is typical for the region, with their properties dependent on the season and on the spectral range analysed. The similarity of the above noted features from year to year was revealed.Key words. Atmospheric composition and structure (Transmission and scattering of radiation; instruments and techniques) – Meteorology and atmospheric dynamics (middle atmosphere dynamics)

scholarly journals Mountain wave motions determined by the Esrange MST radar

1999 ◽  
Vol 17 (7) ◽  
pp. 957-970 ◽  
Author(s):  
A. Réchou ◽  
V. Barabash ◽  
P. Chilson ◽  
S. Kirkwood ◽  
T. Savitskaya ◽  
...  
Keyword(s):  
Imaging System ◽  
Weather Conditions ◽  
Radar Data ◽  
Visual Observation ◽  
Optical Measurements ◽  
Atmospheric Composition ◽  
Leeward Side ◽  
Mesoscale Meteorology ◽  
Mst Radar ◽  
Lee Waves

Abstract. A European campaign of ground-based radar, lidar and optical measurements was carried out during the winter of 1996/1997 (28 December-2 February) to study lee waves in the northern part of Scandinavia. The participants operated ozone lidars, backscatter lidars and MST radars at ALOMAR/Andoya and Esrange/Kiruna, and an ALIS imaging system in Kiruna. The Andoya site was generally windward of the Scandinavian mountains, the Kiruna site on the leeward side. The goal of the experiment was to examine the influence of lee waves on the formation of Polar Stratospheric Clouds (PSCs). This paper studies the radar data from MST-radar ESRAD located at Esrange [68.°N, 21.°E], i.e. in the lee of the mountains. We present three cases where strong lee waves were observed: in one case they propagated upwards to the lower stratosphere and in the other two cases they were trapped or absorbed in the troposphere. We examine the local waves and the direction and strength of the local wind using the radar, the synoptic meteorological situation using weather maps (European Meteorological Bulletin) and the synoptic stratospheric temperatures using ECMWF data. We observed that waves propagate up to the stratosphere during frontal passages. When anticyclonic ridges are present, the propagation to the stratosphere is very weak. This is due to trapping of the waves at or below the tropopause. We also show that the radar data alone can be used to characterise the different weather conditions for the three cases studied (through the variation of the height of the tropopause). The synoptic stratospheric temperatures in the three cases were similar, and were above the expected threshold for PSC formation. Lidar and visual observation of PSCs and nacreous clouds, respectively, showed that these were present only in the case when the lee waves propagated up to the lower stratosphere.Key words. Atmospheric composition and structure (aerosols and particles) · Electromagnetic (wave propa- gation) · Meteorology and atmospheric dynamics (mesoscale meteorology)

The Leonid meteor shower of 1898

1898 ◽  
Vol 19 ◽  
pp. 156
Author(s):  
Edwin F. Sawyer
Keyword(s):  
Meteor Shower ◽  
Leonid Meteor Shower

scholarly journals On the influence of neutral turbulence on ambipolar diffusivities deduced from meteor trail expansion

2002 ◽  
Vol 20 (11) ◽  
pp. 1857-1862 ◽  
Author(s):  
C. M. Hall
Keyword(s):  
Middle Atmosphere ◽  
Atmospheric Dynamics ◽  
Meteorology And Atmospheric Dynamics ◽  
Middle Atmosphere Dynamics ◽  
Radar Echoes ◽  
Meteor Trail ◽  
Meteor Trails

Abstract. By measuring fading times of radar echoes from underdense meteor trails, it is possible to deduce the ambipolar diffusivities of the ions responsible for these radar echoes. It could be anticipated that these diffusivities increase monotonically with height akin to neutral viscosity. In practice, this is not always the case. Here, we investigate the capability of neutral turbulence to affect the meteor trail diffusion rate.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence)

scholarly journals MST radar and polarization lidar observations of tropical cirrus

2001 ◽  
Vol 19 (8) ◽  
pp. 873-882 ◽  
Author(s):  
Y. Bhavani Kumar ◽  
V. S. Siva Kumar ◽  
A. R. Jain ◽  
P. B. Rao
Keyword(s):  
Doppler Radar ◽  
Tropical Meteorology ◽  
Vertical Shear ◽  
Atmospheric Composition ◽  
Tropical Region ◽  
Convective Activity ◽  
Mst Radar ◽  
Source Mechanisms ◽  
Linear Depolarization Ratio ◽  
Favorable Period

Abstract. Significant gaps in our understanding of global cirrus effects on the climate system involve the role of frequently occurring tropical cirrus. Much of the cirrus in the atmosphere is largely due to frequent cumulus and convective activity in the tropics. In the Indian sub-tropical region, the deep convective activity is very prominent from April to December, which is a favorable period for the formation of deep cumulus clouds. The fibrous anvils of these clouds, laden with ice crystals, are one of the source mechanisms for much of the cirrus in the atmosphere. In the present study, several passages of tropical cirrus were investigated by simultaneously operating MST radar and a co-located polarization lidar at the National MST Radar Facility (NMRF), Gadanki (13.45° N, 79.18° E), India to understand its structure, the background wind field and the microphysics at the cloud boundaries. The lidar system used is capable of measuring the degree of depolarization in the laser backscatter. It has identified several different cirrus structures with a peak linear depolarization ratio (LDR) in the range of 0.1 to 0.32. Simultaneous observations of tropical cirrus by the VHF Doppler radar indicated a clear enhancement of reflectivity detected in the vicinity of the cloud boundaries, as revealed by the lidar and are strongly dependent on observed cloud LDR. An inter-comparison of radar reflectivity observed for vertical and oblique beams reveals that the radar-enhanced reflectivity at the cloud boundaries is also accompanied by significant aspect sensitivity. These observations indicate the presence of anisotropic turbulence at the cloud boundaries. Radar velocity measurements show that boundaries of cirrus are associated with enhanced horizontal winds, significant vertical shear in the horizontal winds and reduced vertical velocity. Therefore, these measurements indicate that a circulation at the cloud boundaries suggest an entrainment taking place close to these levels. The analysis of simultaneous lidar and MST Radar observations can thus yield valuable information on the structure and dynamics of the cirrus, specifically near the boundaries of such clouds.Key words. Atmospheric composition and structure (cloud physics and chemistry; instruments and technique) - Meteorology and atmospheric dynamics (tropical meteorology)

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