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Ahmadābād, India

Sarangi R.K.,Marine and Earth science Group
Marine Geodesy | Year: 2011

The daily and weekly averaged Indian Remote Sensing satellite IRS-P4 Ocean Color Monitor (OCM) derived chlorophyll images were generated and interpreted in terms of pretsunami, tsunami, and posttsunami periods in the Bay of Bengal and Andaman Sea. There has been observation of increase in chlorophyll concentration up to 5.0 mg/m3 in the tsunami-affected coastal waters. The high chlorophyll concentration lasted for about one week after the tsunami catastrophe. The standard deviation for different transects in the tsunami-affected water were plotted. The high chlorophyll has been observed for selected transects in the aftermath of the tsunami event in coastal regions, and offshore water has also shown increase in chlorophyll concentration (~1.0 mg/m3) in the Bay of Bengal. The analysis indicated that the tsunami waves might have displaced and spread the high chlorophyll coastal water towards offshore. NASA Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua daytime sea surface temperature (SST) daily images were retrieved and displayed during December 21, 2004, to January 6, 2005, and indicated the cooling (0.5-1°C) in the Bay of Bengal around Tamil Nadu and Andhra coast. The National Oceanographic and Atmospheric Prediction-National Center for Environment Prediction (NOAA-NCEP) data for five weeks (December 9, 2004-January 12, 2005) were retrieved to study the SST variability trend in prior to MODIS data and indicated 0.5-1°C cooling of the Bay of Bengal water off Kakinada, Chennai, Cuddalore, and Nagapattinam region on December 26 and 28, 2004. © Taylor & Francis Group, LLC. Source


Sarangi R.K.,Marine and Earth science Group
Indian Journal of Marine Sciences | Year: 2011

Impact of three different cyclones on the Bay of Bengal water and its surface chlorophyll concentration has been studied in three different zones during October-December 2000 using 24 scenes of IRS-P4 Ocean Color Monitor (OCM). The chlorophyll concentration found to be increasing up to 5.0 mg/m 3 with effect of cyclones and hurricanes. The data has been correlated with Sea Surface Temperature (SST) and wind speed from NOAA-Pathfinder-5 and Quickscat scatterometer, respectively. There has been observation of 2-3°C decrease in SST with movement of cyclone. The wind speed has peaked up to 10-15 m/sec in the cyclonic zones. Source


Srivastava P.K.,Indian Institute of Technology Kharagpur | Majumdar T.J.,Marine and Earth science Group | Bhattacharya A.K.,Indian Institute of Technology Kharagpur
Journal of Earth System Science | Year: 2010

In this study, an attempt has been made to estimate land surface temperatures (LST) and spectral emissivities over a hard rock terrain using multi-sensor satellite data. The study area, of about 6000km2, is a part of Singhbhum-Orissa craton situated in the eastern part of India. TIR data from ASTER, MODIS and Landsat ETM+ have been used in the present study. Telatemp Model AG-42D Portable Infrared Thermometer was used for ground measurements to validate the results derived from satellite (MODIS/ASTER) data. LSTs derived using Landsat ETM+ data of two different dates have been compared with the satellite data (ASTER and MODIS) of those two dates. Various techniques, viz., temperature and emissivity separation (TES) algorithm, gray body adjustment approach in TES algorithm, Split-Window algorithms and Single Channel algo- rithm along with NDVI based emissivity approach have been used. LSTs derived from bands 31 and 32 of MODIS data using Split-Window algorithms with higher viewing angle (50°) (LST1 and LST2) are found to have closer agreement with ground temperature measurements (ground LST) over waterbody, Dalma forest and Simlipal forest, than that derived from ASTER data (TES with AST 13). However, over agriculture land, there is some uncertainty and difference between the measured and the estimated LSTs for both validation dates for all the derived LSTs. LST obtained using Single Channel algorithm with NDVI based emissivity method in channel 13 of ASTER data has yielded closer agreement with ground measurements recorded over vegetation and mixed lands of low spectral contrast. LST results obtained with TIR band 6 of Landsat ETM+ using Single Channel algorithm show close agreement over Dalma forest, Simlipal forest and waterbody with LSTs obtained using MODIS and ASTER data for a different date. Comparison of LSTs shows good agreement with ground measurements in thermally homogeneous area. However, results in agriculture area with less homogeneity show difference of LST up to 2°C. The results of the present study indicate that continuous monitoring of LST and emissivity can be undertaken with the aid of multi-sensor satellite data over a thermally homogeneous region. © Indian Academy of Sciences. Source


Singh S.K.,Marine and Earth science Group | Kulkarni A.V.,Marine and Earth science Group | Chaudhary B.S.,Kurukshetra University
Journal of Earth System Science | Year: 2011

Snow is a highly reflecting object found naturally on the Earth and its albedo is highly influenced by the amount and type of contamination. In the present study, two major types of contaminants (soil and coal) have been used to understand their effects on snow reflectance in the Himalayan region. These contaminants were used in two categories quantitatively - addition in large quantity and addition in small quantity. Snow reflectance data were collected between 350 and 2500 nm spectral ranges and binned at 10 nm interval by averaging. The experiment was designed to gather the field information in controlled conditions, and radiometric observations were collected. First derivative, band absorption depth, asymmetry, percentage change in reflectance and albedo in optical region were selected to identify and discriminate the type of contamination. Band absorption depth has shown a subtle increasing pattern for soil contamination, however, it was significant for small amounts of coal contamination. The absorption peak asymmetry was not significant for soil contamination but showed a nature towards left asymmetry for coal. The width of absorption feature at 1025 nm was not significant for both the contaminations. The percentage change in reflectance was quite high for small amount of coal contamination rather than soil contamination, however, a shift of peak was observed in soil-contaminated snow which was not present in coal contamination. The albedo drops exponentially for coal contamination rather than soil contamination. © Indian Academy of Sciences. Source


Solanki H.U.,Marine and Earth science Group | Dwivedi R.M.,Marine and Earth science Group
Indian Journal of Geo-Marine Sciences | Year: 2015

A bio-physical model was developed to estimate zooplankton production in the Arabian Sea using satellite derived chlorophyll concentration (CC) and sea surface temperature (SST). For this, US Joint Global Ocean Flux Study (US JGOFS) 1995 cruises in-situ data has been used. A 3D plot was generated using in-situ measured chlorophyll, temperature and zooplankton bio-mass. Scatter plot indicated linear and exponential relationship between CC - zooplankton biomass, temperature and zooplankton, respectively. A typical range of 24º-26º C water temperature was found preferable for zooplankton production. Based on this study a multiple regression analysis was carried out to derive coefficients for the development of algorithm. Correlation co-efficient (r2) of multiple regression analysis was 0.78. An empirical algorithm was developed using these co-efficient. This algorithm was applied to Oceansat-1 derived chlorophyll concentration and NOAA-AVHRR derived SST to generate zooplankton images showing zooplankton biomass distribution and concentration. Model was validated through synchronous in-situ observations. Zooplankton biomass was measured on board Sagar Kanya and Sagar Sampda in the Arabian Sea. Regression analysis indicated co-relation co-efficient (r2) = 0.74. © 2015, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved. Source

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