Indian Journal of Radio & Space Physics

Total visitors: 11 since 10-01-08

(CODEN : IJRSAK        ISSN : 0367-8393)

VOLUME 36

NUMBER 6

DECEMBER 2007

 

CONTENTS

 

Foreword cum Guest Editorial

        K K Mahajan*

455

 

Near-terminator Martian ionosphere during sunspot cycle 23 from Mars Global Surveyor radio science measurements

        Ashok Kumar*, Neelesh K Lodhi & K K Mahajan

 

459

 

Forty years of whistler research in India

        Birbal Singh*

468

 

On the progress of four decades of beacon satellite studies in India
 – A brief review

        P V S Rama Rao*

 

476

 

Mesospheric backscatter echoes as observed by the Indian MST Radar Facility at Gadanki

        S C Chakravarty* & Jayati Datta

 

491

 

Recent studies on cloud and precipitation phenomena for propagation characteristics over India

        S K Sarkar* & Anil Kumar

 

504

Daytime optical investigation of the equatorial mesopause energetics in the context of equatorial MLTI coupling: Recent results

        Tarun Kumar Pant*, C Vineeth & R Sridharan

 

516

 

A short review on wind profiler observations of lower and middle atmospheric processes over Gadanki

        T Narayana Rao* & D Narayana Rao

 

528

Long-term trends in the upper atmosphere & ionosphere: Models & observations

        K K Mahajan*, Ashok Kumar & Neelesh K Lodhi

545

Trace gases over the Indian region

        Shyam Lal*

558

 

Altitudinal variation surface aerosol with change in site: A comparative study

        S L Jain*, Pavan S Kulkarni, B C Arya, Arun Kumar, Sachin D Ghude &
Pankaj Singh

573

 

Spatial distribution in aerosol mass and size characteristics between Delhi and Hyderabad during land campaign in February 2004

        Prabhat K Gupta, Khem Singh, C K Dixit, Nahar Singh, C Sharma, S Sahai, Arvind K Jha, D P Singh, M K Tiwari & S C Garg

 

578

Seasonal emissions of methane and nitrous oxide from rice-wheat cropping system during 2002 and 2003

        Vandana Gupta*, Pratul Sharma, Vaishali Pradhan, S Bhat, C Sharma, P Johri, Krishan Kumar & Prabhat K Gupta

 

 

584

Annual Index

 

589

Referees of the Year

 

595

___________________

*Authors for correspondence

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 457-465

 

 

Near-terminator Martian ionosphere during sunspot cycle 23 from Mars Global Surveyor radio science measurements

Ashok Kumar, Neelesh K Lodhi & K K Mahajan

Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110 012, India

Received 31 July 2007; accepted 28 September 2007

Radio Science experiment on the Mars Global Surveyor (MGS) has measured a large number of electron density profiles in the near-terminator Martian ionosphere, from December 1998 to March 2005, thus covering rising, maximum and declining phase of sunspot cycle 23. More than a dozen data sets, EDS 1 to EDS 13, are now available at the public website and these sets contain profiles numbering from a few tens in some sets to several hundreds in others. On any one day, several profiles were measured at a constant solar zenith angle (χ) but at different longitudes. However, χ varied considerably during each data set and in this paper about 2000 profiles have been analysed to study the height (hm) and density (Nm) of the primary peak as a function of solar zenith angle. A significant decrease of Nm is seen with increasing χ, but hm starts increasing at χ above 80° only. To examine how close the Martian primary peak is to an ideal Chapman layer, values of exponent, k and sub-solar peak density, No in the equation Nm = No (cos χ)k were obtained by using the largest number of profiles employed ever before. A value of 0.45 for the exponent k deduced is somewhat smaller than the value of 0.5 expected for an ideal Chapman layer. Value of No was found to be 1.75 × 1011 m–3. Anomalous features in the Mars ionosphere seen in the earlier MGS data are found to be present in the latest data also.

Keywords: Martian ionosphere, Mars Global Surveyor (MGS), Chapman layer, Electron density profiles, Solar zenith angle

PACS No.: 96.35.Kx

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 466-473

 

 

Forty years of whistler research in India

Birbal Singh

Department of Electronics and Communication Engineering, Faculty of Engineering & Technology
R B S College, Bichpuri, Agra 283 105 (UP), India

Received 12 July 2007 ; accepted 16 August 2007

An up to date review of whistler research in India has been presented which is an extension of previous reviews by Somayajulu et al. [Indian J Radio Space Phys, 1 (1972) 102], and Singh [Indian J Radio Space Phys, 22 (1993) 139]. In this review efforts have been made to highlight the recent advancements in technology adopted for recording and analysis of whistlers, re-interpretations of some old data, general consensus in propagation mechanism, and effects of ionospheric irregularities on whistler propagation in the low latitude ionosphere. Some new results of existence of ELF emissions in the low latitude ionosphere as determined from the satellite DEMETER data and Trimpi/TLE phenomena in the low latitude ionosphere as observed from phase and amplitude monitoring of VLF transmitter signals have been presented.

Keywords: Whistler propagation, ELF emissions, Ionospheric irregularities, VLF signal

PACS No.: 94.30.Tz

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 474-488

 

 

On the progress of four decades of beacon satellite studies
in India – A brief review

 

P V S Rama Rao

Department of Physics, Andhra University, Visakhapatnam 530 003, India

Email: palurirao@yahoo.com

Received 20 September 2007; accepted 24 October 2007

Forty years of progress of the radio beacon research of the ionosphere carried out in India using the signals from both orbiting as well as geostationary satellites by various researchers has been briefly reviewed. Several features in the typical equatorial and low latitude characteristics on the occurrence and morphological behaviour of the total electron content (TEC) and the ionospheric scintillations are presented. The need for the measurement of absolute TEC, its real time prediction as well as the prediction in the onset of scintillations, their amplitudes and durations, in the context of the possible application of these space weather phenomena in the satellite based communication and navigation systems, with particular reference to the effective implementation of the programmes such as GPS Aided Geo Augmented Navigation (GAGAN) are discussed.

Keywords: Radio beacon, GAGAN, Total electron content (TEC), Scintillations, Ionospheric scintillations, Satellite communication, Satellite navigation

PACS No.: 94.20.Vv, 94.20.Dd

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 489-501

 

 

Mesospheric backscatter echoes as observed by the Indian MST
Radar Facility at Gadanki

 

S C Chakravarty & Jayati Datta

ISRO Headquarters, Antariksh Bhavan, New BEL Road, Bangalore 560 094

Received 14 September 2007; accepted 26 October 2007

The Indian Mesosphere Stratosphere Troposphere (MST) radar facility at Gadanki (13.5şN, 79.2şE) has been utilised to characterise the mesospheric backscattered signals by considering already available results and new analysis of past and recent data sets. Individual days data as well as continuous and long term Common Mode Observation (CMO) data have been used to study (1) the basic features of mesospheric return echoes, (2) scattering layer heights, (3) relation to mesospheric turbulence governed through weather phenomena, (4) spatial and temporal variability, (5) seasonal patterns and, (6) inter-annual changes. While the present results have been found to be consistent, with the earlier results, some new aspects have been brought out. A broad theoretical background is provided relevant to turbulent scattering of radar waves so that the results are interpreted from this perspective. The main results of the mesospheric studies with the Gadanki radar include the very intermittent nature of echoes varying with radar beam directions and time. Temporal variations of the radar returned signals are found to be related to the growth and decay of eddies, generated by atmospheric turbulence. The mean height of mesospheric scattering layer is around 72 km and the life period of the turbulence patches generally lies in the range 10-20 min. In the months of June-July and September-October of 2003, the intensity of radar returned signals were stronger compared to other months and there is an elevation of the mean scattering layer by ~2 km with the decrease in solar activity between 2003 and 2005.

Keywords: MST radar, Mesospheric backscatter, Backscatter echoes

PACS No.: 94.10.Dy

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 502-513

 

 

Recent studies on cloud and precipitation phenomena for propagation characteristics over India

S K Sarkar & Anil Kumar

Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110 012, India

e-mail:sksarkar@mail.nplindia.ernet.in

Received 3 August 2007 ; accepted 21 August 2007

Radio propagation above a frequency of 10 GHz is affected by precipitation in terms of attenuation due to its high dielectric constant. As far as Indian subcontinent is concerned, rain and cloud are the most important ones. Thus, there is still tremendous need to develop a strong database on these parameters. The work carried out on cloud and rain characteristics in relation to radio wave propagation over India in recent years only, from 2000 till today is reviewed in this paper. These results are useful to design as well as for estimation performance of microwave communication and for radar propagation over different locations situated in different geographical regions of India.

Keywords:   Precipitation, Rain, Cloud, Thunderstorm, Microwave communication, Millimeter wave communication,                              Attenuation, Noise temperature, Conventional radar, Doppler radar

PACS No.:  92.60. Nv; 84.40.-x

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 514-525

 

 

Daytime optical investigation of the equatorial mesopause energetics in the context of equatorial MLTI coupling: Recent results

Tarun Kumar Pant, C Vineeth & R Sridharan

Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum 695 022

E Mail: tarun_kumar@vssc.gov.in

Received 21 August 2007; accepted 12 September 2007

First experimental evidences for the mesopause energetic changes in context of (a) counter electrojet (CEJ); (b) solar flare; and (c) solar eclipse in the equatorial mesopause region using a daytime optical photometer are presented. The photometer has been operated in a scanning mode to probe the thermosphere and mesopause regions simultaneously in north-south direction over Trivandrum (8.5oN; 77oE; dip lat. 0.5oN). The striking features observed are (i) enhancement in the wave activity as seen in the mesopause temperature, during the eclipse, (ii) cooling of the mesopause during the equatorial electrojet (EEJ) reversal and (iii) decrease in mesopause temperature during a flare. These observations are discussed to highlight the vertical coupling of the mesopause with thermosphere-ionosphere region, mainly through neutral dynamics.

Keywords: Equatorial mesopause, Mesopause energetics, Equatorial electrojet, Counter electrojet, Mesosphere-lower thermosphere ionosphere (MLTI)

PACS No.: 94.10.Dy

 

 

 

 

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 526-542

 

 

A short review on wind profiler observations of lower and middle atmospheric processes over Gadanki

 

T Narayana Rao & D Narayana Rao

National Atmospheric Research Laboratory, Gadanki 517 112, India

Received 17 August 2007; accepted 30 August 2007

National Atmospheric Research Laboratory (NARL), a unique site having Mesosphere Stratosphere Troposphere (MST) Radar, Lower Atmospheric Wind Profiler (LAWP), Lidars, disdrometer, Optical Rain Gauge, Automatic Weather Station, vertical profiling with GPS soundings, and a dual frequency GPS receiver, has been operating all these instruments to support the scientific research dealing with dynamics of the lower, middle and upper atmosphere, coupling between these regions and precipitating systems. Several interesting results have been obtained making use of the experimental facilities at NARL. It is, indeed, a difficult task to review all of them in a short paper. In this communication, an attempt has been made; however, to review the exciting scientific outcome resulted from Indian MST radar LAWP measurements, confining ourselves to dynamical and microphysical aspects of atmospheric processes in the troposphere and lower stratosphere. A variety of atmospheric phenomena occurring over a wide range of temporal and spatial scales are discussed, starting from microscale turbulence within the radar resolution volume to mesoscale processes, like convection and associated processes, and to synoptic and planetary scale waves with proper referencing, wherever required.

Keywords: Wind profilers, Middle atmospheric dynamics, Radar meteorology, Clear air turbulence, Gravity waves

PACS No.: 92.60.Dj; 92.60.Ek

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 543-555

 

 

Long-term trends in the upper atmosphere and ionosphere:
Models and observations

K K Mahajan, Ashok Kumar & Neelesh K Lodhi

Radio & Atmospheric Sciences Division, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

Received 22 October 2007; accepted 1 November 2007

Theoretical models predict a 10 K cooling in the mesosphere and 50 K cooling in the thermosphere in response to doubling of CO2 and CH4 from present day mixing ratios. In the mesosphere this cooling is expected to bring-in considerable changes in the individual ion concentration, but no significant change in the total ion density. In the thermosphere, atmospheric density would decrease and the heights of the ionospheric E- and F2-layers will drop by about 2 and 20 km, respectively. There would be little change in the critical frequency of these layers but electron density will decrease in the topside and increase in the bottomside ionosphere due to this lowering. Early results from some individual ionosonde stations showed the predicted decrease in the height of the F2-peak, but statistical analysis of ionospheric data from stations spread all over the globe did not indicate any significant trend in this parameter, as well as in the height of the E-layer and density of the F2-layer. The E and F1 layers peak densities, however, showed negative trends. Satellite drag data have provided convincing evidence of decrease in atmospheric density in the thermosphere during the last few decades. Better statistical methods are needed to filter out long-term solar activity and magnetic activity influences for detecting long-term trends in the F2 layer. Measurements of low frequency reflection heights from 1959 to 2003 at the mid-latitude station Kuhlungsborn show a long-term decreasing trend, an observation in agreement with the expected cooling in the mesosphere.

Keywords: Upper atmosphere, Ionosphere, Trace gases, Mesosphere cooling Thermosphere cooling

PACS No.: 94.10.Dy

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 556-570

 

 

Trace gases over the Indian region

 

Shyam Lal

Physical Research Laboratory, Ahmedabad 380 009, Gujarat, India

Received 3 September 2007; accepted 14 September 2007

Some of the main results related to atmospheric ozone, related trace gases and aerosols in India are reviewed in this paper. Variability in tropospheric ozone has been observed, while there are no observed changes in the stratospheric ozone. Surface measurements of these species are being carried out by various research groups. Even though pollution levels are higher, surface ozone rarely exceed 100 ppbv in India. Aerosols show large spatial and temporal variability. There is a need for detailed measurements of these trace gases covering different regions in India and vertical distributions in the troposphere. Satellite measurements of these constituents are needed to understand their long range transport.

Keywords: Trace gases, Ozone, Aerosols, Carbon dioxide, Methane, Nitrous oxide

PACS No.: 92.60.Hp

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 571-575

 

 

Altitudinal variation of surface aerosol with change in site:
A comparative study

 

S L Jain, Pavan S Kulkarni, B C Arya, Arun Kumar, Sachin D Ghude* & Pankaj Singh

Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110 012

*I&OT Division, Indian Institute of Tropical Meteorology, Pashan, Pune 411 008

Email: sljain@mail.nplindia.ernet.in

Received 21 September 2007; accepted 28 September 2007

The study of size distribution of atmospheric aerosols is an important tool in understanding and managing aerosol effects on health, visibility and climate. The measurements of surface aerosols, both mass-size distribution and mass concentration, were carried out in the campaign mode at Leh (34°09˘N, 77°34˘E, 3441 m asl), Hanle (32°47˘N, 78°58˘E, 4517 m asl) and Delhi (28°39˘N, 77°13˘E, 220 m asl) during July 2003 to examine their variation with altitudinal and anthropogenic activity. A 15 channel portable particle size aerosol spectrometer GRIMM was used for carrying out the experiment. The aerosol spectrometer is equipped with class 3-B laser as the light source and uses a light scattering technology for single particle counts in the range > 0.3 µm to > 20.0 µm. During the period of observation at all three sites, the pattern of total mass concentration was found to be influenced by supermicron range mass concentration. The higher values of aerosol mass concentration observed at Delhi as compared with those observed at Leh and Hanle on all the channels show a large amount of anthropogenic activity taking place around Delhi vis-à-vis the other two sites. It is further observed that the mass-size distribution changes with the change in altitude and anthropogenic activity.

Keywords: Surface aerosol, Mass-size distribution, Submicron range, Supermicron range, Mass concentration

PACS No.: 92.60.Mt

 

 

 

 

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 576-581

 

Spatial distribution in aerosol mass and size characteristics between Delhi and Hyderabad during land campaign in February 2004

Prabhat K Gupta, Khem Singh, C K Dixit, Nahar Singh, C Sharma,

S Sahai, Arvind K Jha, D P Singh, M K Tiwari & S C Garg

National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110 012 (India)

E-mail: prabhat@mail.nplindia.ernet.in

Received 14 September 2007 ; accepted 28 September 2007

Mass and size distribution of aerosols was studied using different measurement techniques, along Delhi-Hyderabad land corridor, to understand the spatial variability of aerosols over north central Indian region, from Delhi to Hyderabad and back, in the month of February 2004. Aerosol mass loading of Quartz Crystal Microbalance (QCM) derived up to PM25, PM10, PM2.5, PM1 size fractions, were found to be in the range of 17-56, 16-54, 8-44 and 5-37 µg m-3, respectively. The QCM derived up to PM10, PM2.5 and PM1 with respect to total aerosol mass (PM25) are 90%, 80% and 70%, respectively, which indicate the dominance of finer particles. The PM10 aerosol concentrations measured by High Volume Respirable Dust Sampler (HV-RDS) had an average value of 48 µg m-3 with the range of 27-75 µg m-3. Aerosol average concentrations by HV-RDS were observed to be 54 ħ 5 µg m-3 near urban areas, 48 ħ 2 µg m-3 in forest area and 44 ħ 22 µg m-3 in rural areas along the land corridor.

Keywords:   Particulate matter; High volume sampler; Anderson cascade impactor; Aerosol size distribution; Quartz crystal microbalance

PACS No.: 92.60.Mt

 

Indian Journal of Radio & Space Physics

Vol. 36, December 2007, pp. 582-585

 

Seasonal emissions of methane and nitrous oxide from rice-wheat cropping system during 2002 and 2003

Vandana Gupta, Pratul Sharma, Vaishali Pradhan, S Bhat, C Sharma, P Johri, Krishan Kumar* & Prabhat K Gupta

Analytical Chemistry Section, National Physical Laboratory, New Delhi 110 012, India

*School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 046, India

E-mail: prabhat@mail.nplindia.ernet.in

Received 6 August 2007; accepted 21 September 2007

Methane (CH4) and nitrous oxide (N2O) are important atmospheric greenhouse gases (GHGs) and rice-wheat ecosystem has been identified as one of the important anthropogenic sources of GHGs in agriculture sector. The water management in a given rice-wheat ecosystem plays a crucial role in its GHGs emission. It has been observed that the water regime in irrigated rice fields with sandy loam soils becomes intermittently flooded, due to high water percolation, which has a direct bearing on CH4 emissions. Wheat crop on the other hand does not need water flooding; hence N2O becomes important due to oxic environment. Intermittently flooded water regimes were simulated at NPL experimental fields to estimate the seasonal emissions of CH4 and N2O from rice-wheat cropping system during 2002-2003. The CH4 and N2O flux from wheat ecosystem was in the range of – 0.36-1.06 mg m–2 h–1 and – 0.10-1.22 mg m–2 h–1, respectively. The CH4 and N2O emission from rice cultivation was in the range of – 0.65-1.25 mg m–2 h–1 and – 0.32-0.43 mg m–2 h–1, respectively, from irrigated intermittently flooded (IR-IF) multiple aeration (MA) ecosystem. The CH4 and N2O seasonal integrated flux (Esif) from wheat cultivation are 1.02 + 0.26 and 0.50 + 0.12 gm–2, respectively, and from rice cultivation for IR-IF-MA ecosystem 0.52 + 0.36 and 0.28 + 0.20 gm–2, respectively. The CH4 emissions were significantly low from IR-IF-MA rice ecosystem and were surprisingly higher comparatively, from the wheat crop. It may be because of frequent rainfall events and high soil temperature in wheat cropping season.

Keywords: Greenhouse gases (GHG); Rice-wheat ecosystem; Water management

PACS No.: 92.70.Er