Indian Journal of Radio & Space Physics

 

Total visitors: 756  since 20-02-07

(CODEN : IJRSAK        ISSN : 0367-8393)

VOLUME 36

NUMBER 1

FEBRUARY 2007

 

CONTENTS

 

Guest Editorial: Sea remote sensing – A monitoring technique for sea environment

      Maurizio Migliaccio*

 

7

Long-term variation of cosmic ray anisotropy during high amplitude days

        Rajesh K Mishra* & Rekha Agarwal Mishra

 

9

 

 

Seasonal and magnetic activity variations of nighttime ionospheric F-region vertical plasma drifts at Ibadan

        Oyedemi S Oyekola*

 

 

14

Improvements of Indian standard time at NPL, New Delhi, maintained through GPS network

        P Banerjee*, Arundhati Chatterjee, Manish Verma & A K Suri

 

 

20

Study of aerosol optical depth and precipitable water vapour content at Rajkot, a tropical semi-arid station

        Ritweej Rajeev Ranjan*, Nandita D Ganguly, H P Joshi & K N Iyer

 

 

27

Atmospheric subsidence and the surface temperature variability in the pre-monsoon month over a semi-arid north peninsular Indian station: A case study

        S M Deshpande, J R Kulkarni, R R Joshi*, N Singh, S H Damle & G B Pant

 

 

33

Retrieval of atmospheric temperature and moisture profiles from satellite data over India using the ICI inversion model

        Devendra Singh* & R C Bhatia

 

 

44

Behaviour of methane emission from a paddy field of high carbon content

        N N Purkait, A K Saha, Sanghamitra De & D K Chakrabarty*

 

52

Surface ozone variability between two different Antarctic sites

        Ashok Kumar*, V B Gupta, S L Jain, Sachin D Ghude & Pavan S Kulkarni

 

59

Comparison of emissivity and scattering coefficient of two samples of Aravali rocks and dry soils of Rajasthan at frequencies of X-band

        O P N Calla*, Dinesh Bohra, Sanjib Kumar Agarwalla, Sandip Ghosh, Chetan Bohra & Rajesh Vyas

 

 

65

___________________

*Authors for correspondence

 

 


Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 9-13

 

 

Long-term variation of cosmic ray anisotropy during high amplitude days

Rajesh K Mishra

Computer and IT Section, Tropical Forest Research Institute, Mandla Road,  Jabalpur (M P) 482 021, India

and

Rekha Agarwal Mishra

Department of Physics, Govt. Model Science College (Autonomous),  Jabalpur (M P)  482 001, India

E-mail: rkm_30@yahoo.com or rajeshkmishra20@hotmail.com

Received 28 March 2006; revised 23 October 2006; accepted 16 November 2006

In the present study the occurrence of a large number high amplitude event (HAE) of cosmic ray diurnal anisotropy during 1981-1994 has been examined as a function of solar activity using the hourly neutron monitor data of Deep River station. The diurnal time of maximum for both HAE as well as for all days is found to shift significantly towards an earlier time as compared to the co-rotational/azimuthal direction since the year 1991 onward. It is found that diurnal amplitude significantly deviates and reaches its maximum, and phase remains in the co-rotational direction during the years close to solar activity maximum for HAE. The occurrence of HAE is dominant in the declining phase of solar activity. The amplitude as well as phase of the cosmic ray diurnal anisotropy during HAEs is well correlated with the sunspot numbers.

Keywords: Cosmic ray, Solar cycle, Sunspot numbers, Anisotropy.

PACS Nos.: 96.40.Kk, 96.40. -z, 96.40.Cd, 96.60 Qc

 

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 14-19

 

 

Seasonal and magnetic activity variations of nighttime ionospheric
F-region vertical plasma drifts at Ibadan

Oyedemi S Oyekola

Department of Physics, University of Ibadan, Ibadan, Nigeria

(E-mail: osoyekola@yahoo.com)

Received 27 March 2006; revised 23 June 2006; accepted 30 August 2006

Nighttime F-region vertical electrodynamic drifts at Ibadan (lat. 7.4°N, long. 3.9°E; -6° dip) are obtained from the hourly-recorded ionosonde hF data during 1957-58 International Geophysical Year (IGY) under geomagnetic quiet and disturbed conditions. The present results indicate strong seasonal variations in the drifts, even during quiet geomagnetic conditions. The downward nighttime average electrodynamic drift is found to be nearly 10 m/s. The drifts are consistently downward between ~2100 and 0500 hrs LT sector. The evening reversal time from upward daytime to downward nighttime does not vary much except during the June solstice months when it is found to be least, while it occurs early in December solstice and equinox. An equinoctial maximum in pre-reversal enhancements of the vertical drift is also noted. The present results are found to be completely consistent with some results obtained for some low latitude ionospheric stations, Jicamarca (lat. 11.9°S, long. 76.8°W; 1°N dip), and Trivandrum (lat. 8.36°N, long. 76.6°E; 0.5°N dip) that use different measurement techniques. Possible sources of the quiet-time variability in the electrodynamics can arise from changes in the global wind system and their resultant dynamo conditions, and changes in conductivity due to solar flux variability.

Keywords: Nighttime plasma-drift, Ionospheric variations, Equatorial F-region

PACS No.: 92.20.Ji

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 20-26

 

 

Improvements of Indian standard time at NPL, New Delhi, maintained through GPS network

P Banerjee, Arundhati Chatterjee, Manish Verma & A K Suri

Time and Frequency Section, National Physical Laboratory, New Delhi 110012, India

Received 1 March 2006; accepted 8 November 2006

The National Physical Laboratory (NPL), New Delhi, has been maintaining Universal Coordinated Time (UTC) through GPS network to keep it linked to UTC coordinated by International Bureau of Weights and Measure(BIPM) for more than ten years.  Recent measures of housing of cesium clock in a controlled environment, the procurement of new receivers with prior calibration, maintaining the temperature of antenna at a fixed point and the adjustments of required phase and frequency from time to time, have been taken to improve the quality of UTC(NPLI). In view of this, the status of UTC(NPLI) has been studied analytically and exhaustively. The substantial improvement in the performance of the time scale UTC(NPLI) has been observed. This paper elaborates these observations.

Keywords: Indian standard time, UTC, GPS network, Atomic clock

PACS No.: 84.40.Ua; 06.30.Ft

IPC code : G01S13/04; G01S13/06

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 27-32

 

 

Study of aerosol optical depth and precipitable water vapour content
at Rajkot, a tropical semi-arid station

Ritweej Rajeev Ranjan, Nandita D Ganguly, H P Joshi & K N Iyer

Department of Physics, Saurashtra University, Rajkot 360 005, India

Received 5 December 2005; revised 24 March 2006, accepted 5 July 2006

Aerosol optical depth (AOD) at 1020 nm for the period July 2004 - July 2005 and at six different wavelengths ranging from 380 nm to 1020 nm for March-June 2005 is studied. The measurements are being made at the tropical semi-arid location Rajkot (22°18˘ N, 70°44˘ E, 142 m above sea level) using a hand-held microprocessor-based sun photometer, MICROTOPS-II under the aegis of ISRO’s Geosphere Biosphere Programme (IGBP). Precipitable water vapour is estimated from the measurements of solar intensity at 936 nm and 1020 nm. The AOD shows seasonal variation with high values (0.41) in summer and low values (0.11) in winter. Angstrom wavelength exponent a has been found to be high (0.59) during March, indicating relative dominance of accumulation-mode particles. During summer season, low value (0.25) of Angstrom wavelength exponent a indicates relative dominance of coarse-mode particles. The changes in the column water vapour have been found to be correlated with the changes in AOD. This is supported by the observed increase of AOD with relative humidity at high humidity values.

Keywords: Aerosol, Aerosol optical depth, Water vapour content, Tropical semi-arid station

PACS No.: 92.60.Mt; 92.60.Sz; 92.60.Jq

IPC Code: G 01 W 1/17; G 08 C 23/04

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 33-43

 

Atmospheric subsidence and the surface temperature variability in the pre-monsoon month over a semi-arid north peninsular Indian station: A case study

S M Deshpande, J R Kulkarni, R R Joshi, N Singh, S H Damle & G B Pant

Indian Institute of Tropical Meteorology, Pune 411 008, India

Received 17 January 2006; revised 21 September 2006; accepted 6 December 2006

Variability in maximum temperature in the month of March 2004 over Pune, a station representative of semi-arid region of north peninsular India, has been studied. The vertical wind velocity data measured by UHF wind profiler, installed at Pune (18.31oN, 73.58oE) has been utilized. Hourly averaged vertical wind velocity profiles were obtained four times a day, on a three hourly basis from 0800 to 1700 hrs IST (Indian Standard Time) in March 2004. The vertical velocity is found to have a typical mean and standard deviation of 10 and 15-20 cm/s, respectively. The mean structure of the vertical distribution showed predominately upward motion extending up to 2-3 km and predominately downward motion in the 3-6 km layers. After removing the effects of radiative and advective heating, the anomalies in the maximum temperature over Pune are found to be statistically related with the depth of the atmospheric column over which the subsidence occurs.

Keywords: Wind profiler, Vertical velocity, Subsidence depth, Temperature anomaly

PACS No: 92.70.Cp; 92.60.Gn

 

Indian Journal of Radio Space Physics

Vol. 36, February, 2007, pp. 44-51

 

 

Retrieval of atmospheric temperature and moisture profiles from satellite data over India using the ICI inversion model

Devendra Singh1 and R C Bhatia2

1Department of Science and Technology, Technology Bhavan, New Mehrauli Road, New Delhi 110 016

2India Meteorological Department, Lodhi Road, New Delhi 110 003

Received 27 January 2006; revised 7 November 2006; accepted 8 December 2006

Radiance measurements from satellites offer the opportunity to retrieve atmospheric variables at much higher spatial resolution than is presently afforded by in situ measurements (e.g., radiosondes). However, the accuracy of these retrievals is crucial to their usefulness, and the ill-posed nature of the problem precludes a straight forward solution. In this paper, Inversion Coupled with Image (ICI) model has been investigated to retrieve vertical temperature and moisture profiles of earth’s atmosphere from infrared and microwave brightness temperatures from a polar-orbiting satellite. The analyses were done using the Advanced TIROS Operational Vertical Sounder (ATOVS) data for the January and July 2002 representing winter and summer conditions. The results are compared with NCEP (National Center for Environmental Prediction) reanalysis data 1 × 1 degree latitude and longitude. Emphasis has been given in analyzing the role of the channels combination used in the retrieval process. Different surface types (sea and land) and atmospheric conditions (clear and cloudy sky) were also considered.

Keywords: Atmospheric temperature profile, Atmospheric moisture profile, Inversion model

PACS No: 92.60.Hp

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 52-58

 

 

Behaviour of methane emission from a paddy field of high carbon content

N N Purkait, A K Saha & Sanghamitra De

S K Mitra Centre for Research in Space Environment, Institute of Radiophysics & Electronics, University of Calcutta,
92, Acharya Prafulla Chandra Road, Calcutta 700 009, India

and

D K Chakrabarty

Centre for Environment Survey, Vidya Nagar Society 29/251, Ahmedabad 380 015, India

E-mail: dkchakra@icenet.net

Received 3 May 2006; revised 8 December 2006; accepted 15 December 2006

Behaviour of methane emission from the paddy field of Lakshmikantapur has been studied for two full crop years, 1998-99 and 2003-04. The soil of this place has carbon content greater than 0.7 %. Two types of crops , namely, Kharif and Rabi are grown during a full crop year. Measurements were made from the beginning to the end of the plant life. Simultaneously water level and soil temperature were also measured. It is found that occasionally methane emission takes place by ebullition-yielding high value of concentration. It has diurnal variation with maximum around 1400 hrs LT. There are two peaks of emission in the whole plant life; for Kharif, the second peak is lower than the first peak and for Rabi, it is the other way round. Soil temperature affects methane emission more than water level.

Keywords:  Methane, Paddy field, Days after transplant (DAT), Kharif, Rabi

PACS No.: 89.60. Fe; 92.60. Sz; 92.70.Cp

 

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 59-64

 

Surface ozone variability between two different Antarctic sites

 

Ashok Kumar & V B Gupta

School of Future Studies and Planning, Devi Ahilya University, Indore 452 017

E-mail: ashok_kumarg@yahoo.com

and

S L Jain, Sachin D Ghude & Pavan S Kulkarni

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

Received 8 February 2006; revised 21 November 2006; accepted 21 December 2006

The study deals with the temporal and spatial variability of 365 days hourly mean surface ozone data for Syowa and McMurdo stations in Antarctica. The analyses not only show the seasonal and diurnal variation of surface O3 in Antarctica, but also present statistics of surface O3 variability on temporal scale. Diurnal variations of 3.9% and 0.8% have been observed in surface O3 at Syowa and McMurdo, respectively. Surface O3 during summer season at Syowa and McMurdo stations is observed to be 56% and 64%, respectively. The correlation between the surface O3 concentrations at Syowa and McMurdo stations implies that the 18% of the variation is due to local weather conditions.

Keywords: Surface Ozone, Antarctica, Seasonal and diurnal variation.

PACS No.: 82.50.Bc; 82.50. Hp; 82.50. Nd; 92.60. Hp

 

 

Indian Journal of Radio & Space Physics

Vol. 36, February 2007, pp. 65-71

 

 

Comparison of emissivity and scattering coefficient of two samples of Aravali rocks and dry soils of Rajasthan at frequencies of X-band

 

O P N Calla, Dinesh Bohra, Sanjib Kumar Agarwalla, Sandip Ghosh, Chetan Bohra & Rajesh Vyas

International Centre for Radio Science, A-23, Shastri Nagar, Jodhpur 342 003

Received 11 May 2005; revised 21 July 2006; accepted 17 August 2006

By the action of climate and living organism, soil is formed from weathered rock. It inherits the mineral matter and organic matter from its parent rock and living organisms, respectively. The study of the emission behaviour and scattering behaviour of both soil and rock of a particular place is thus important, as the electrical properties of them may be different. In the present paper, the comparison of emissivity and scattering coefficient values of loamy sand and pure sand type dry soils of Rajasthan and Aravali rock samples has been made. The values are estimated at microwave frequencies.

Keywords: Emissivity, Scattering coefficient, X-band, Soils, Aravali rocks, Microwave frequency

PACS No: 95.75 Rs; 84.40 Xb, 78.20 Ci

IPC Code: G 01 N3 3/24; G 01 N 22/00