July, 2006

July, 2006   ||  Volume 10 No.3

Earth’s Environment and Solar-terrestrial Science
(K. R. Ramanathan Memorial Lecture)

G. Madhavan Nair
Chairman, ISRO


Seasonal variation of SST and mean OLR distribution over Indian Ocean warm pool

Indian Institute of Tropical Meteorology, Dr.Homo Bhaha Road, Pashan, Pune - 411008.
E- mail: panchwag@tropmet.res.in



In order to examine the seasonal variation of SST distribution over Indian Ocean warm pool (IOWP), a recent climatological atlas is consulted. It is seen from SST distribution of (a) annual mean and (b) August monsoon mean that the temperature distribution is more or less similar in both. Examination of the seasonal distribution of SST has revealed that the small scale changes in convection of shorter duration, i.e. diurnal and synoptic basis, appear to be operating independently, irrespective of warm and cold core water masses. The seasonal mean OLR distribution over the domain of 10°N-15°S, and 60°-100°E for the seasons (a)winter, (b)spring, (c)summer monsoon and (d)post monsoon has been studied. The OLR can be used as a proxy for rainfall. It is interesting to note that the eastern equatorial Indian Ocean seems to be highly convective during all the seasons as compared to western equatorial Indian Ocean. It is clearly revealed that there exists always a relationship between the processes that take place in the IOWP and the rainfall distribution over the Indian sub-continent. Attempt has been made to bring out the coherent relationship that exists among the three parameters of SST, rainfall and cloud cover.

Fractal Analysis for Geomagnetic Secular Variations

M.Sridharan and A.M.S.Ramasamy1
IIG Magnetic Observatory, Pondicherry University Campus, Pondicherry - 605 014
1Department of Mathematics, Pondicherry University, Pondichery - 605 014.


Fractal Analysis deals with the science of complexity. Fractal analysis is more economical and most powerful method for analyzing the time series data. Fractal geometry allows the description of natural patterns by simple numbers, to facilitate their comparison and to establish and test models of pattern formation (Kruhl, 1994) The purpose of this paper is to study the geometrical complexity of geomagnetic secular variations estimated by fractal dimension, the disorder of the unpredictable secular variations estimated by Lyapunov exponent and the non linear system represented at each instant of time by a point which traces out a trajectory during this time defined by the state of variables- phase space analysis, for the available data of geomagnetic secular variations at Indian observatories. The result of the analysis confirms the previous results of secular variation anomalies at the Indian observatories. Regional inconsistencies for the declination (D) and vertical (Z) components for the Hyderabad and Sabhawala observatories are brought out in this paper. Analytical technique and the results of the analysis are discussed

Sea surface temperatures as predictors of cyclonic activity over the North Indian Ocean

G.Krishnakumar, Alaka S.Gadgil1 and M.Rajeevan

India Meteorological Department, National Data Centre, Shivaji Nagar, Pune – 411 005
1 Department of Geography, University of Pune

Tropical Cyclone (TC) activities over the North Indian Ocean (Comprising Bay of Bengal (BOB) and Arabian Sea (AS)) constitute one of the major natural disasters for our country. Indian Coasts are very much vulnerable and susceptible to TCs. In order to understand the TC activities, estimations of their frequency and cyclone days (CD), are necessary. In this study, the Sea Surface Temperatures (SST) over the Indian Ocean region (50 ° E – 120° E and 30 ° S – 30 ° N) are used as predictors. The set of regression equations are formulated for the months of May, October and November, as they are the months with maximum frequencies of occurrences of cyclones over North Indian Ocean. The performances of these equations are also discussed.

Azimuthal square array resistivity studies to infer active fault zones in the areas of known seismicity, Kottayam District, Kerala - A case study

N.Ramanujam, K.Nathakiri Murugan and A.Antony Ravindran

Post Graduate Department of Geology and Research Centre,
V.O.Chidambaram College, Tuticorin – 628 008.

The earthquakes in Kerala are restricted between NNW-SSE and NE and SW trending fault and fracture system. Correlation of earthquake events has close proximity to the lineaments. To compare the seismic activities with the fracture patterns, depth wise resistivity structures of fault / fracture and horizontal conductivity zones and their orientation are detected using Square Array resistivity (dc) technique in Edamarugu, Rendatrumukku and Valliapara of Kottayam district, Kerala. The square array sounding requires 65% less surface area than Wenner or Schlumberger technique and records the regional bedrock anisotropy. The heterogeneities obscured due to the variations of bed rock, relief and placement error are overcome by the higher apparent anisotropy measured by square array. The apparent resistivity obtained from the square array technique are plotted as Azimuthal Polar plots, Cartesian Azimuthal graphs and depth sounding curves to scan the depth wise fracture/fault orientation and gliding plane. The conductivity strikes identified from these plots have been categorized as primary, secondary and tertiary conductive and resistive zones. The horizontal permeable zones independent of direction have been identified at various depths. The detection of the fault/fracture zone with low resistivity values has greater significance in seismological studies. Prominent resistivity lows correlated with seismically activated fault zones in the study area are discussed in detail.

Simulation of SST fluctuations and circulation in the Equatorial Indian Ocean

D.W.Ganer, A.A.Deo and P.S.Salvekar

Indian Institute of Tropical Meteorology, Dr.Homi Bhabha Road, Pasha, Pune – 411 008
E-mail : tsd@tropmet.res.in

Inter-annual variability in the equatorial Indian Ocean sometimes exhibits large Sea Surface Temperature (SST) fluctuations. The SST anomaly gradient between eastern and western equatorial Indian Ocean during summer season (June-October) becomes greater than 1°C. This east-west SST anomaly gradient is independent of ENSO and may be a natural oscillation of the Indian Ocean. Such fluctuations are observed in many years during the decade 1990-2000. In the present study a 2½ layer thermodynamic ocean model has been used to simulate inter-annual variability in the circulation and SST anomaly (SSTA) fluctuations in the Indian Ocean. The model simulated SST over the Tropical Indian Ocean is in close agreement with observed SST. The warm SSTA in the western equatorial Indian Ocean and cold SSTA in the eastern equatorial Indian Ocean during the years 1994 and 1997 and, opposite SSTA during the years 1992 and 1996, are well simulated by the model.

Antarctic sea ice variability in recent years and its relationship with Indian Ocean Sea Surface Temperature

Shailendra Rai and A.C.Pandey1

K.Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad,

Allahabad – 211 002.
1Department of Physics, University of Allahabad, Allahabad – 211 001.
E.mail : r_shail77@rediffmail.com, r_shail1977@yahoo.co.in

Antarctic sea ice edge variability is analyzed for 23 years (1982-2004) data of satellite passive microwave observation. Sea ice edge anomaly averaged around Antarctica shows nearly zero trend in the time domain. The positive trend of Ross, Weddell seas and Indian Ocean is reduced and the sea ice accumulation in Pacific Ocean region is increased but the sea ice variability in Bellingshausen/Amundsen seas is unaffected in recent years. Maximum Antarctic Sea ice concentration trend of 0.01 degrees/year is found during summer season for the period 1982-1998 but the same season shows a negative trend for the period 1982-2004. On the regional scale the trend differs from season to season. Ross and Weddell seas show positive trend whereas Bellingshausen/Amundsen sea shows negative trend for all the seasons. The relationship of Antarctic sea ice variability with Indian Ocean SST is studied and found that the most persistent positive relation exists for the southeast Indian Ocean region, off Australia.

Application of Satellite Remote Sensing Data for Assessment of Land Use and Land Cover Changes in Krishna District, Andhra Pradesh

B.Surya Prakasa Rao, K.S.R.Murthy1, G.Vijay Lakshmi and N.Venkateswarlu2

Dept. of Geo- Engineering, College of Engineering, Andhra University,

Visakhapatnam – 530 003
1Department of Earth Sciences, Faculty of Science, Addis Ababa University, Ethiopia
2National Geophysical Research Institute, Hyderabad. – 500 007
E.mail : bosukonda@rediffmail.com

The applicability of temporal remote sensing digital data supported by conventional data in the impact assessment of cyclones and storm surges on an ecologically and economically significant fertile delta area in terms of changes in land use /land cover has been attempted. The changes in land use/land cover classes in the cyclone prone delta area of river Krishna in the state of Andhra Pradesh, India during the period 1990-2000 were mapped and were studied through digital interpretation of IRS-1A and IRS-1C images. Digital image classification using supervised classification technique with maximum likelihood algorithm with the help of principal component analysis has been implemented on multi-dated digital data to study the changes in the study area. Aquaculture and agricultural land show increasing trend, where as, the areas under fallow land, water logged marshy and water bodies have shown a declining trend. Degraded forest, forest plantation, sandy area and mud flats show minor changes. A notable increase is observed in aquaculture and agriculture lands. The aqua area has increased to about 6.57% in total geographical area (TGA) and 51.91% in total aqua farm area. It was observed that fallow land, water bodies and waterlogged areas have been converted into aquaculture and other agriculture uses. The declining trend in forest plantations, degraded forest and plantations and increase of aquaculture farms lead to environmental degradation in this area. It is concluded that the importance of remote sensing data in combination with other relevant data to help in more detailed understanding of the land use / land cover and its changes in different time periods.

Electro lithofacies analysis for depositional history and stratigraphy of Manuguru Coalfield using geophysical well logs

G. Uday Bhaskar

Exploration Division, S.C.CO.Ltd. , Vittalnagar P O, Godavarikhani-505 214
E.mail: uday_bhaskar_g @yahoo.com

The present study is perhaps the first attempt of applying geophysical log method in stratigraphic correlation of Permian Gondwana sequences of India. The concepts of electrofacies analysis and sedimentary environments from the conventional geophysical well logs of partially cored wells formed the basic data to build up the Permian stratigraphic framework and depositional history of Manuguru Coalfield of Pranhita-Godavari Valley, Andhra Pradesh, India. The regionally extensive coal seams located at different stratigraphic levels and easily identified by their finger prints/signatures on the geophysical logs are chosen as the genetic sequential stratigraphic boundaries to map the facies distribution of the enclosing strata and view the basin at different stages of development. The correlated strata are also analysed using standard facies maps and suitably interpreted for geometry and depositional architecture. This type of approach that integrated the geophysical and geological information provides an excellent methodology to unravel the stratigraphic complexities of the valley, and a predictive framework to coal and coal-bed methane exploration programmes.

Geological and Structural Inferences from Satellite Image in Parts of the Eastern Dharwar Craton, India.

B.Veeraiah1, D.Himabindu and G.Ramadass

1 National Geophysical Research Institute, Hyderabad, AP, India –500 007
Center of Exploration Geophysics, Osmania University, Hyderabad, AP, India- 500 007.

The geological interest of the Precambrian Dharwar craton in the Indian peninsular shield stems from its complexity. An IRS-ID LISS-III satellite image covering an area of approximately 18,900 sq. km corresponding to the region in and around Maddur, Narayanpet and Makthal in the eastern Dharwar craton was digitally processed and visually interpreted to present a schematic map of the geology and elucidate the structural fabric of the region. The disposition of the schist belts, shear zones and various faults and other lineaments in the region are delineated. The findings are significant in relation to structural data in the region and form a part of the geo-structural database for ground surveys.