Satellite-Based Estimation of Instantaneous Radiative Fluxes Over Continental USA – a Case Study     

Dibyendu Dutta  D. V. Mahalakshmi  Manisha Singh  Prachi Goyal  Soubhik Paul  Jaswant Raj Sharma  Vinay Kumar Dadhwal 《Journal of the Indian Society of Remote Sensing》2015,43(4):841-849

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Nowcasting visibility during wintertime fog over the airport of a metropolis of India: decision tree algorithm and artificial neural network approach     

Dutta  Debashree  Chaudhuri  Sutapa 《Natural Hazards》2015,78(2):1349-1367

Natural Hazards - The endeavor of the present research is to nowcast the spatial visibility during fog over the airport of Kolkata (22.6°N; 88.4°E), India, with artificial neural network...  相似文献   

Groundwater arsenic contamination in Ganga–Meghna–Brahmaputra plain, its health effects and an approach for mitigation     

Dipankar Chakraborti  Mohammad Mahmudur Rahman  Bhaskar Das  Bishwajit Nayak  Arup Pal  Mrinal Kumar Sengupta  Md. Amir Hossain  Sad Ahamed  Manabendranath Sahu  Kshitish Chandra Saha  Subhash Chandra Mukherjee  Shyamapada Pati  Rathindra Nath Dutta  Quazi Quamruzzaman 《Environmental Earth Sciences》2013,70(5):1993-2008

The authors’ survey of the Ganga–Meghna–Brahmaputra (GMB) plain (area 569,749 km²; population >500 million) over the past 20 years and analysis of more than 220,000 hand tube-well water samples revealed groundwater arsenic contamination in the floodplains of the Ganga–Brahmaputra river (Uttar Pradesh, Bihar, Jharkhand, West Bengal, and Assam) in India and the Padma–Meghna–Brahmaputra river in Bangladesh. On average, 50 % of the water samples contain arsenic above the World Health Organization guideline value of 10 μg/L in India and Bangladesh. More than 100 million people in the GMB plain are potentially at risk. The authors’ medical team screened around 155,000 people from the affected villages and registered 16,000 patients with different types of arsenical skin lesions. Arsenic neuropathy and adverse pregnancy outcomes have been recorded. Infants and children drinking arsenic-contaminated water are believed to be at high risk. About 45,000 biological samples analyzed from arsenic-affected villages of the GMB plain revealed an elevated level of arsenic present in patients as well as non-patients, indicating that many are sub-clinically affected. In West Bengal and Bangladesh, there are huge surface water in rivers, wetlands, and flooded river basins. In the arsenic-affected GMB plain, the crisis is not over water scarcity but about managing the available water resources.  相似文献   

Variability of Indian monsoonal rainfall over the past 100 ka and its implication for C3–C4 vegetational change     

Shailesh Agrawal  Prasanta Sanyal  Anindya Sarkar  Manoj Kumar Jaiswal  Koushik Dutta 《Quaternary Research》2012,77(1):159-170

Oxygen and carbon isotope ratios of soil carbonate and carbon isotope ratios of soil organic matter (SOM) separated from three cores, Kalpi, IITK and Firozpur, of the Ganga Plain, India are used to reconstruct past rainfall variations and their effect on ambient vegetation. The δ¹⁸O values of soil carbonate (δ¹⁸O_SC) analyzed from the cores range from ? 8.2 to ? 4.1‰. Using these variations in δ¹⁸O_SC values we are able, for the first time, to show periodic change in rainfall amount between 100 and 18 ka with three peaks of higher monsoon at about 100, 40 and 25 ka. The estimation of rainfall variations using δ¹⁸O value of rainwater-amount effect suggests maximum decrease in rainfall intensity (~ 20%) during the last glacial maximum. The δ¹³C values of soil carbonate (δ¹³C_SC) and SOM (δ¹³C_SOM) range from ? 6.3 to + 1.6‰ and ? 28.9 to ? 19.4‰, respectively, implying varying proportions of C₃ and C₄ vegetations over the Ganga Plain during the last 100 ka. The comparison between monsoonal rainfall and atmospheric CO₂ with vegetation for the time period 84 to 18 ka indicate that relative abundances of C₃ and C₄ vegetations were mainly driven by variations in monsoonal rainfall.  相似文献   

Vegetation Dynamics from Denoised NDVI Using Empirical Mode Decomposition     

Rahul Verma  Subashisa Dutta 《Journal of the Indian Society of Remote Sensing》2013,41(3):555-566

A novel approach to study vegetation dynamics is introduced, using the Empirical Mode Decomposition (EMD) to analyze NDVI time series. The NDVI time series which is nonlinear and nonstationary can be decomposed by EMD into components called intrinsic mode functions (IMFs), based on inherent temporal scales. The highest frequency component which has been found to represent noise is subtracted from the original NDVI series; thus smoothing the noisy signal. The different key features describing vegetation phenology have been extracted by analyzing the noise free signal. The lowest frequency component (last IMF) is the trend in the NDVI series. The trend in the series has been identified finding the Sen’s slope of last IMF, and the non-parametric seasonal Mann–Kendall test has been used to confirm the significance of the observed trend. The method has been applied on per–pixel basis to the SPOT Vegetation NDVI product covering Northeast India and surrounding regions for the time span of 1998–2009. Results show that the method has performed well in identifying the pixel clusters with significant trends. Hotspot regions with severe vegetation degeneration have been identified, and the relationship of the observed trends with the expected causative variables such as land use and land cover, topographic relief, and anthropogenic causes has been explored. The spatial locations of these critical regions closely matches with the findings of the previous studies carried out locally in the region, mainly indicating the shifting cultivation practice to be the main cause for land cover change.  相似文献   

Viewing Angle Effect on the Remote Sensing Monitoring of Wheat and Rice Crops     

Hafizur Rahman  D. A. Quadir  A. Z.M. Zahedul Islam  Sukumar Dutta 《国际地球制图》2013,28(1):74-79

Abstract

Bidirectional reflectance characteristics of a wheat and a rice canopy were studied using radiometric measurements over the two canopies with an Exotech Radiometer Model 100AX. For both rice and wheat, the measurements exhibited significant variations in reflectance amplitude for varying viewing zenith angles and their values decreased from backward to forward scattering direction. Reflectance obtained its maximum value in the backscatter direction for the viewing angle that corresponds approximately to the solar zenith angle at the time of measurements. Canopy background condition (irrigated or non‐irrigated) was an important determining factor of canopy reflectance particularly in the near‐infrared region of the solar spectrum. Furthermore, bidirectional response characteristics of a vegetation canopy were influenced by the amount of vegetation cover.  相似文献   

Orbital evolution measurement of the accreting millisecond X-ray pulsar SAX J1808.4-3658     

Chetana Jain  Anjan Dutta  Biswajit Paul 《Journal of Astrophysics and Astronomy》2007,28(4):197-206

We present results from a pulse timing analysis of the accretion-powered millisecond X-ray pulsar SAX J1808.4-3658 using X-ray data obtained during four outbursts of this source. Extensive observations were made with the proportional counter array of the Rossi X-ray Timing Explorer (RXTE) during the four outbursts that occurred in 1998, 2000, 2002 and 2005. Instead of measuring the arrival times of individual pulses or the pulse arrival time delay measurement that is commonly used to determine the orbital parameters of binary pulsars, we have determined the orbital ephemeris during each observation by optimizing the pulse detection against a range of trial ephemeris values. The source exhibits a significant pulse shape variability during the outbursts. The technique used by us does not depend on the pulse profile evolution, and is therefore, different from the standard pulse timing analysis. Using 27 measurements of orbital ephemerides during the four outbursts spread over more than 7 years and more than 31,000 binary orbits, we have derived an accurate value of the orbital period of 7249.156862(5) s (MJD = 50915) and detected an orbital period derivative of (3.14 ± 0.21) × 10⁻¹² s s⁻¹. We have included a table of the 27 mid-eclipse time measurements of this source that will be valuable for further studies of the orbital evolution of the source, especially with ASTROSAT. We point out that the measured rate of orbital period evolution is considerably faster than the most commonly discussed mechanisms of orbital period evolution like mass transfer, mass loss from the companion star and gravitational wave radiation. The present time scale of orbital period change, 73 Myr is therefore likely to be a transient high value of period evolution and similar measurements during subsequent outbursts of SAX J1808.4-3658 will help us to resolve this.  相似文献   

Changing Pattern of Channel Morphology of Alaknanda River in Srinagar Valley (Garhwal Himalaya), India     

D. D. Chauniyal  Surajit Dutta  Sapna Semwal 《Journal of the Indian Society of Remote Sensing》2018,46(9):1379-1387

The Alaknanda River is the most significant parental river of Ganga and forms an 11.5 km long and 2.5 km wide valley, locally known as the Srinagar Valley. The purpose of the present study is to highlight the recent landform changes in the Alaknanda channel course after the Kedarnath disaster, 2013. The Kedarnath flood completely changed the channel morphology of the Alaknanda river. The river changed its course at Srikot, SSB and Sriyantra Tapu with lower terraces being silted by sands at Ranihat, SSB, Bhaktiyana and Sriyantra Tapu. A new depositional terrace also formed opposite to Sriyantra Tapu. New lateral channel bars, braided channels, back swamp, rapids, pools and river souls were identified in the channel course of the river. Shifting of the channel course at Chauras still remains a serious problem for the Garhwal University Chauras Campus. About 2–5 m silt was deposited on the lower terrace at SSB, and ITI. The Srikot river bed was appended to 4.60 m. Shifting of channel course remains a serious threat to the Srinagar valley. Urbanization, sand and boulders mining, construction of dam, hydrological canal, road and settlements are the prominent example of anthropogenic activities which affect the shifting channel.  相似文献   

Remote Sensing for Martian Studies: Inferences from Syrtis Major     

Vidhya Ganesh Rangarajan  Rishikesh Bharti  Sandeep K. Mondal  C. Pradhan  S. Dutta 《Journal of the Indian Society of Remote Sensing》2018,46(9):1537-1551

Remote sensing techniques have proved to be highly efficient in the exploration of Mars. Availability of several sensors operating across the electromagnetic spectrum on-board orbiters, landers and rovers has helped better understand the surface and atmospheric conditions on the Red planet. This article summarises the application potential of the sensors operating in different wavelength regions for Martian surface studies. Mars unlike Earth allows for utilizing remote sensing techniques in the complete thermal infrared region, owing to narrow absorption regions from a singularly dominant CO₂ atmosphere which facilitate detailed lithological mapping. This work also reviews various methodologies adopted till date to study the lithology, mineralogy and fluvial geomorphology including inferences from Syrtis Major volcanic construct. It is evident from the studies, Syrtis Major has well developed fluvial channels mostly attributed to lava flows. However, spectroscopic studies reveal the presence of hydroxylated and hydrated minerals which indicate that lava might not be the sole factor resulting in channel generation in the construct. Future space missions with high resolution payloads targeting this volcanic construct are indispensable to study these channels in detail.  相似文献   

Analysis of Beams on Pasternak Foundation Using Quintic Displacement Functions     

Dutta  Ashis Kumar  Mandal  Jagat Jyoti  Bandyopadhyay  Debasish 《Geotechnical and Geological Engineering》2021,39(6):4213-4224

Geotechnical and Geological Engineering - Beams supported by elastic foundations one of the complex soil-structure interaction problems and analysis carried out using the concept of “beam on...  相似文献