April, 2012

April, 2012   ||  Volume 16 No.2


Comparison of Long Term Rainfall Trends In Urban and Nonurban Regions of Indian Land Mass and Its Probable Implication

S. C. Ganda and S. K. Midya*

Department of Atmospheric Science, University of Calcutta, 51/2 Hazra Road, Kolkata-700019
Email: drskm06@yahoo.co.in and sadhab.ganda@epcos.com,
* Corresponding author

The paper presents a comparison of the rates of rainfall in fourteen Indian meteorological subdivisions, with fourteen major Indian cities located in those subdivisions. These comparisons of the rates have been done for both the monsoon period as well as annual rainfall. The long term trends of monsoon and annual rainfalls in fourteen major Indian cities have been reported earlier. Using WMO procedure the trends of rainfall on the meteorological subdivisions, consisting of fourteen Indian cities are calculated. The Indian cities having population more than 1 million are considered as urban. The meteorological subdivisions are considered as nonurban though a small part of it is occupied by the city.
Quantitative analysis of the rainfall data over the Indian land is done and following important results are obtained.
(i) the rainfall rates in most of the urban areas are higher than the corresponding subdivisional rates since the later part of the last century.
(ii) even with the same economic trend some cities are showing reverse trend of rainfall compared with the corresponding subdivisions.
(iii) subdivisional rainfalls, monsoon as well as the annual, are showing decreasing trend for the same period for more than 70% cases.


Relationship between sea surface temperature and surface air temperature over Arabian Sea, Bay of Bengal and Indian Ocean
A. K. Jaswal, Virendra Singh1 and S. R. Bhambak
India Meteorological Department, Shivajinagar, Pune – 411 005
1India Meteorological Department, Lodhi Road, New Delhi-110 003
Email: jaswal4@gmail.com

Climatology and relationship of Sea Surface Temperature (SST) and Surface Air Temperature (SAT) over the Arabian Sea, Bay of Bengal and Indian Ocean north of 15oS are examined on annual and seasonal time scales using the Voluntary Observing Ships data for a period of 40 years (1961-2000). Seasonally, spatial patterns of climatological SST indicate large northward spread of temperatures greater than 28oC from winter to summer in the Arabian Sea and the Bay of Bengal. During monsoon season, there is appreciable cooling in the western half of the Arabian Sea while the entire Bay of Bengal still remains warm (>28oC). The SST and SAT correlation coefficients are quite high over the Arabian Sea and the Indian Ocean as compared to the Bay of Bengal, providing a good justification for using SST as an indicator of SAT variability over these regions. Relationship between SST and SAT indicates same variance over the Arabian Sea and large parts of the north Indian Ocean. But variance ratios of SST and SAT over the Bay of Bengal are quite high for all seasons, indicating a less energetic atmosphere causing smaller SAT variance as compared to SST variance over the area. The striking feature of the mean SST and SAT difference field is the change from strong winter patterns to weak monsoon patterns for sensible heat exchange over the Arabian Sea and the Bay of Bengal.

Study and Mapping of Ground Water Prospect using Remote Sensing, GIS and Geoelectrical resistivity techniques – a case study of Dhanbad district, Jharkhand, India

V.K.Srivastava, Devendra Nath Giri and Pawan Bharadwaj
Dept. of Applied Geophysics, Indian School of Mines, Dhanbad - 826004, India
E-mail: ismkvinay@gmail.com


Water is an important natural resource, which is available both on surface as well as in recharge zone of weathered layer and in various other suitable water reservoir formations/structures below the surface. As the availability of surface water is erratic and irregular one needs to study and map the underground water reservoirs. Dhanbad district of Jharkhand state is in general part of hard rock terrain, which is mainly covered by Chottanagpur Granite Gneissic Complex and has no perennial river sources for water supply. Therefore, in view of the upcoming industrialization in the region there is need to exploit groundwater resource, which is limited and confined to fractured and weathered zones. Even though the region receives copious rain, the terrain and soil condition allows little storage of water. Hence, the region faces shortage of water in dry seasons. Therefore, it is necessary to explore and study the ground water resources effectively using suitable techniques. Various workers have successfully applied Remote Sensing technique in exploration, evaluation and management of ground water resources in an area as a whole and the results have been published. In this paper also mapping and management strategies for ground water resources have been studied, by analyzing IRS LISS II multi band remote sensing data along with geological as well as geophysical resistivity sounding data carried out at places in GIS environment. Finally, based on the integrated thematic maps, weighted analysis in Arc GIS ground water resource prospect map of the area has been prepared and discussed.
The study has brought out that the high groundwater potential zones are confined along lineaments and in pediment areas. Also alluvial fills, valley fills form potential zones. The other geomorphic units like buried pediplain, peniplains and denundational hills form zones of moderate to good groundwater prospects. Dissected pediments, inselberg complex, undulating upland and buried pediment with intermontane valley are zones of poor prospects. Very poor regions occupy a small part of total study area and are mainly confined to undulating upland and residual hills.  

Alarming Acidic Nature of Rainwater in the Industrial zone of Visakhapatnam and its Implication
1Y.Somu Naidu and 2C.Kavitha
1Department of Geophysics, Andhra University, Visakhapatnam-530 003
2Department of Electronics, GITAM University, Visakhapatnam

Industrialization began in the city of Visakhapatnam from 1950 onwards resulting in transfer of cations and anions to atmosphere. In particular, the commissioning of Steel plant, Chemical factory and Simhadri Thermal Power Corporation (STPC) during the period 1983 to 2003 polluted the ‘industrial atmosphere’ hazardously. The pH of rainwaters showed a steady decline from basic nature to a critical acidic value of 4.0. The alkaline agents like NH4 and Ca failed in vain to neutralize the major acidic agents like NO3 and SO4. The ratio, SO-4 + NO-3 / NH+4 + Ca+, which was <1 during 1980s, reached a range of 2.0 to 5.9 by 2005. The average electrical conductivity also supports, the phenomenon with its ascent from 45µs/cm in 1983 to 156 µs/cm in 2005. Remedial measures need to be taken on priority, to arrest irreversible damage.