• A S Rajawat

      Articles written in Journal of Earth System Science

    • Retrieval of sea surface velocities using sequential Ocean Colour Monitor (OCM) data

      J S Prasad A S Rajawat Yaswant Pradhan O S Chauhan S R Nayak

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      The Indian remote sensing satellite, IRS-P4 (Oceansat-I) launched on May 26th, 1999 carried two sensors on board, i.e., the Ocean Colour Monitor (OCM) and the Multi-frequency Scanning Microwave Radiometer (MSMR) dedicated for oceanographic research. Sequential data of IRS-P4 OCM has been analysed over parts of both east and west coast of India and a methodology to retrieve sea surface current velocities has been applied. The method is based on matching suspended sediment dispersion patterns, in sequential two time lapsed images. The pattern matching is performed on a pair of atmospherically corrected and geo-referenced sequential images by Maximum Cross-Correlation (MCC) technique. The MCC technique involves computing matrices of cross-correlation coefficients and identifying correlation peaks. The movement of the pattern can be calculated knowing the displacement of windows required to match patterns in successive images. The technique provides actual flow during a specified period by integrating both tidal and wind influences. The current velocities retrieved were compared with synchronous data collected along the east coast during the GSI cruise ST-133 of R.V. Samudra Kaustubh in January 2000. The current data were measured using the ocean current meter supplied by the Environmental Measurement and CONtrol (EMCON), Kochi available with the Geological Survey of India, Marine Wing. This current meter can measure direction and magnitude with an accuracy of ±5‡ and 2% respectively. The measurement accuracies with coefficient of determination (R2) of 0.99, for both magnitude (cm.s-1) and direction (deg.) were achieved.

    • Simulation of suspended sediment transport initialized with satellite derived suspended sediment concentrations

      Ratheesh Ramakrishnan A S Rajawat

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      Suspended sediment transport in the Gulf of Kachchh is simulated utilizing the suspended sediment concentration (SSC) derived from Oceansat OCM imagery, as the initial condition in MIKE-21 Mud Transport model. Optimization of the model mud parameters, like settling velocity and critical shear stress for erosion are realized with respect to the sediment size distribution and the bottom bed materials observed in the Gulf. Simulated SSCs are compared with alternate OCM derived SSC. The results are observed to be impetus where the model is able to generate the spatial dynamics of the sediment concentrations. Sediment dynamics like deposition, erosion and dispersion are explained with the simulated tidal currents and OCM derived sediment concentrations. Tidal range is observed as the important physical factor controlling the deposition and resuspension of sediments within the Gulf. From the simulation studies; maximum residual current velocities, tidal fronts and high turbulent zones are found to characterise the islands and shoals within the Gulf, which results in high sediment concentrations in those regions. Remarkable variability in the bathymetry of the Gulf, different bed materials and varying tidal conditions induces several circulation patterns and turbulence creating the unique suspended sediment concentration pattern in the Gulf.

    • Monitoring implementation of desertification combating plan using geomatics – A case study, districts Dhar and Jhabua, Madhya Pradesh

      Dasgupta Arunima P S Dhinwa A S Rajawat

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      The world’s drylands are subject to desertification as a result of extended droughts, climate change, and human activities. Development in drylands depends on addressing degradation of the ecosystem, main-streaming sustainable natural resources management, and building upon the existing adaptive capacities of communities and institutions. In this regard, recent scientific results aimed to promote sustainable development through action plans for combating desertification. In India, under the Integrated Mission for Sustainable Development (IMSD) programme, remote sensing based integrated land and water resource studies were carried out with an objective to generate locale specific action plans for sustainable development of a region. A specific study was carried out, in districts of Jhabua and Dhar, in Madhya Pradesh using Composite Land Development Sites (CLDS) approach for forest and wasteland development and soil and water conservation. Various treatments were suggested and implemented in 1995. The present study was carried out with an objective to monitor the positive impacts of combating plan implementation through visual interpretation and NDVI analysis of temporal images of LISS III data, since 1991 to 2013. The study reveals that there is substantial increase in the area of irrigated agricultural land with increase in number of check dams along with the stream channels.

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