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Browsing by Author "Sivakumar, V"

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LIDAR for atmosphere research over Africa

Author: Sivakumar, V ; Moema, D ; Bollig, C ; Sharma, Ameeth ; Mbatha, N ; Malinga, S ; Mengistu, G ; Bencherif, H ; Keckhut, P Date: Nov 2008 This paper describes the LIDAR for atmosphere research over Africa and current initiatives being undertaken in South Africa. A mobile LIDAR system is being developed at the Council for Scientific and Industrial Research (CSIR) National Laser ... Read more
Lidar observation of middle atmospheric gravity wave activity over a southern sub-tropical station, Reunion Island (21°S; 55°E)

Author: Sivakumar, V ; Bencherif, H ; Faduilhe, D Date: Jul 2006 The prevailing convective activity over tropics and subtropical regions acts as an important source for the generation of GW. Reunion Island (21°S, 55°E) is located in sub-tropics where a large number of convective phenomena occur. Hence, the ... Read more
Lidar observations of sodium layer over low latitude, Gadanki (13.5° N, 79.2° E): seasonal and nocturnal variations

Author: Prasanth, PV ; Sivakumar, V ; Sridharan, S ; Kumar, YB ; Bencherif, H ; Rao, DN Date: Oct 2009 In this paper, researchers present seasonal and nocturnal variations of mesospheric sodium (Na) layer parameters observed over Gadanki (13.5° N, 79.2° E), based on 166 nights during the period from January 2005 to December 2006, for the first ... Read more
Mean ozone and water vapour height profiles for Southern hemisphere region using radiosonde or ozonesonde and haloe satelite data

Author: Sivakumar, V ; Gizaw Mengistu, DT ; Botai, OJ Date: 2009 The aim of this work is to construct a model (mean) profile for ozone and water vapor in Southern hemisphere latitude using 14 years (1993-2006) of Halogen Occultation Experiment (HALOE) satellite data and about 10 years (1998-2007) of the ... Read more
Multi-scale organization of water vapor over low and mid-tropical Africa

Author: Botai, OJ ; Sivakumar, V ; Combrinck, CL ; Rautenbach, CJD Date: 2009 In this study, data from the Southern Hemisphere ADditional OZonesondes (SHADOZ) are used to compute the spatially averaged water vapour (WVg) over low and mid-tropical Africa. Based on the SHADOZ stations, reanalysis data from the National ... Read more
NOMAD and the usage of Megha-Tropique data-products

Author: Sivakumar, V Date: Jul 2006 The objective of the proposal ( NOMAD ) were: Middle atmospheric temperature structure and dynamics using Lidars over the Indian Ocean Region ( Reunion-21°S, Durban-30°S, Gadanki-13°N, in addition to NDSC sites: OHP-46°N, Lauder-45°S, ... Read more
On the use of a regression model for trend estimates from ground-based atmospheric observations in the Southern hemisphere

Author: Bencherif, H ; Begue, NM ; Diab, CR ; Sivakumar, V ; Keckhut, P Date: Sep 2010 The present reports on the use of a multi-regression model adapted at Reunion University for temperature and ozone trend estimates. Depending on the location of the observing site, the studied geophysical signal is broken down in form of a ... Read more
Rayleigh LIDAR and satellite (HALOE, SABER, CHAMP and COSMIC) measurements of stratosphere-mesosphere temperature over a southern sub-tropical site, Reunion (20.8° S; 55.5° E): climatology and comparison study

Author: Sivakumar, V ; Vishnu Prasanth, P ; Kishore, P ; Bencherif, H ; Keckhut, P Date: 2011 For the first time, climatology of the middle atmosphere thermal structure is presented, based on 14 years of LIDAR and satellite (HALOE, SABER, CHAMP and COSMIC) temperature measurements. The data is collected over a southern sub-tropical ... Read more
Rayleigh LiDAR investigation of stratospheric sudden warming over a low latitude station, Gadanki (13.5ºN; 79.2ºE) – a statistical study

Author: Charyulu, DV ; Sivakumar, V ; Bencherif, H ; Narayano Rao, D Date: Aug 2007 In this paper, the authors report the statistical characteristics of Stratospheric Sudden Warming (SSW) events observed over a low latitude station, Gadanki; 13.5°N, 79.2°E. The study uses 7 years (1998 to 2004) of quasi-continuous nighttime ... Read more
Rayleigh lidar investigation of sudden stratospheric warming observed over northern and southern hemisphere stations

Author: Sivakumar, V ; Bencherif, H ; Acharyulu, DV ; Hauchecorne, A ; Rao, DN ; Sharma, S ; Rao, PB Date: Jul 2006 First observation of the Stratospheric Sudden Warming (SSW) was made by Scherhag in 1952, using radiosonde measurements over Berlin. Schoeberl (1978) provided a review on theory and observations of stratospheric warming using results reported ... Read more
Rayleigh lidar observations of double stratopause structure over three different northern hemisphere stations

Author: Sivakumar, V ; Bencherif, H ; Hauchecorne, A ; Keckhut, P ; Rao, DN ; Sharma, S ; Chandra, H ; Jayaraman, A ; Rao, PB Date: Sep 2006 Using four years of Rayleigh lidar data collected from three different northern hemisphere stations (Gadanki 13.5° N, 79.2° E ; Mt. Abu 24.5° N, 72.7° E and Observatoire de Haute Provence: OHP; 44° N, 6° E), the characteristics of double ... Read more
Retrieval of atmospheric boundary layer height by CSIR NLC mobile LIDAR, Pretoria (25.5° S; 28.2° E), South Africa

Author: Sivakumar, V ; Sharma, Ameeth ; Bollig, C Date: Jul 2011 In this paper, the authors present the preliminary methods for detection of the boundary layer based on backscattered signals from a mobile LIDAR (LIght Detection And Ranging) developed at Council for Scientific and Industrial Research (CSIR) ... Read more
Retrieval of relative humidity from CSIR-NLC mobile LIDAR backscatter measurements

Author: Tesfaye, M ; Sivakumar, V ; Botai, J ; Moema, D ; Sharma, Ameeth ; Bollig, C ; Hannes Rautenbach, CJ deW ; Mengistu, G Date: Sep 2009 The CSIR-NLC mobile LIDAR has been operated at the University of Pretoria during October 2008 for a better understanding of the atmosphere's boundary layer evolution and aerosol (solid particles suspended in the air) concentrations. The ... Read more
A review of the mobile LIDAR system developed at the CSIR and a proposed improvement of the system

Author: Shikwambana, L ; Sivakumar, V ; Sharma, Ameeth Date: Jul 2012 LIDAR is an acronym for light detection and ranging, it is analogous to radar (radio detection and ranging), except that it is based on discrete light pulses and measured travel times. We report on the mobile LIDAR system developed at the ... Read more
Solar ultraviolet radiation measurements at South African and Reunion Island Coastal Sites: An indicator of public sun protection

Author: Wright, CY ; Brogniez, C ; Ncongwane, KP ; Sivakumar, V ; Coetzee, G ; Metzger, J-M ; Auriol, F ; Deroo, C ; Sauvage, B Date: Sep 2013 Solar ultraviolet radiation (UVR) has the potential to cause biological harm to humans. Intensity of solar UVR at the Earth’s surface depends on several factors, such as total column ozone and cloud cover, and temporal trends are usually ... Read more
Statistical characteristics of sudden stratospheric warming as observed over the observatoire de Haute Provence (44°N, 6°E) during the 1981-2001 period

Author: Sivakumar, V ; Bencherif, H Date: Apr 2006 During some winters, zonal-mean configuration is dramatically disrupted with polar stratospheric temperatures increasing rapidly with time, leading to a poleward increase of zonal-mean temperature and, on occasion, a reversal of zonal-mean ... Read more
Stratospheric ozone transboundary transport to upper troposphere North Africa

Author: Ture, K ; Tsidu, GM ; Sivakumar, V Date: Sep 2011 Stratosphere-troposphere exchange (STE) influences the chemical composition of both the stratosphere and the troposphere and represents an important aspect of global change [Butchart and Scaife, 2001]. It is also often associated with severe ... Read more
Study of stable atmospheric boundary layer characterization over highveld region of South Africa

Author: Luhunga, P ; Djolov, G ; Sivakumar, V Date: Sep 2011 The aim of the paper is to study the SBL characteristics over the Highveld region of South Africa using automatic observational network data, theoretical models and recently developed mobile LiDAR system at the Council for Scientific and ... Read more
Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar - [Article]

Author: Mbatha, N ; Sivakumar, V ; Malinga, SB ; Bencherif, H ; Pillay, SR Date: 2010 The occurrence of sudden stratospheric warming (SSW) excites disturbances in the mesosphere-lower thermospheric (MLT) wind and temperature. Here, researchers have examined the high frequency (HF) radar wind data from the South African National ... Read more
Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar measurements [Conference paper]

Author: Mbatha, N ; Malinga, S ; Sivakumar, V ; Pillay, S ; Bencherif, H Date: Jul 2009 Neutral atmosphere (including the MLT) and ionosphere are linked by energy and momentum transfer. Thus, this whole region forms a coupled system in which influences that originates at one height or in one region can have profound influence ... Read more

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