Identification of Aman Rice Crop in Bangladesh Using Temporal C-Band SAR – A Feasibility Study     

S. Panigrahy  V. Jain  C. Patnaik  J. S. Parihar 《Journal of the Indian Society of Remote Sensing》2012,40(4):599-606

In-season rice area estimation using C-band Synthetic Aperture Radar (SAR) data from RADARSAT-1 is being done in India for more than a decade. Decision rule based models in backscatter domain have been calibrated and validated using extensive field data and a long term backscatter signature bank of rice fields has been developed. Since the rice crop growing environment in India is a diverse one in the world having all the rice cultural types, the rice backscatter is quite exhaustive. This paper highlights the results of classification of rice lands in Bangladesh using the signature bank of India. The results showed that the Aman rice crop of Bangladesh has a typical temporal backscatter of shallow and intermediate rice fields of that of West Bengal state. The mean backscatter of the intermediate/deep water fields in southern Bangladesh was ?19?dB, while that of shallow cultural types mostly in northern Bangladesh was ?17?dB. The signature of the rice crop in Southern Bangladesh matched well with that of Gangetic West Bengal, particularly that of the 24 Parganas, Howrah and Hughli districts. The signature of rice crop in the Sub-Himalayan West Bengal particularly that of Dinajpur and Maldah districts matched well with that of the northern area of Bangladesh. State level rice area estimated using the selected models was found with in 5% deviation from that of the reported acreage.  相似文献   

Differential behaviour of a Lesser Himalayan watershed in extreme rainfall regimes     

Pankaj Chauhan  Nilendu Singh  Devi Datt Chauniyal  Rajeev S Ahluwalia  Mohit Singhal 《Journal of Earth System Science》2017,126(2):22

Climatic extremes including precipitation are bound to intensify in the global warming environment. The present study intends to understand the response of the Tons sub-watershed in Lesser Himalaya, in 3 years with entirely different hydrological conditions (July 2008–June 2011) in terms of discharge, sediment flux and denudation rates. Within an uncertainty limit of ±20%, the mean interannual discharge (5.74 ± 1.44 m ³ s ^?1) (±SE), was found highly variable (CV: 151%; 0.8–38 m ³ s ^?1). In a normal rainfall year (2008–2009; ～1550 mm), the discharge was 5.12 ± 1.75 m ³ s ^?1, whereas in a drought year (2009–2010), it reduced by 30% with the reduction in ～23% rainfall (CV: 85%). In an excessive rainfall year (once-in-a-century event) (2010–2011; ～3050 mm), discharge as well as total solid load was ～200% higher. Monsoon months (July–September) accounted for more than 90% of the annual solid load transport. The ratio of dissolved to suspended solid (C/P ratio) was consistently low (<1) during monsoon months and higher (1–7) during the rest of the dry period. C/P ratio was inversely (R ²=0.49), but significantly (P <0.001) related to the rainfall. The average mechanical erosion rate in the three different rainfall years was 0.24, 0.19 and 1.03 mmyr ^?1, whereas the chemical erosion was estimated at 0.12, 0.11 and 0.46 mmyr ^?1, respectively. Thus, the average denudation rate of the Tons sub-watershed has been estimated at 0.33 mmyr ^?1 (excluding extreme rainfall year: 1.5 mmyr ^?1). Our results have implications to understand the hydrological behaviour of the Lesser Himalayan watersheds and will be valuable for the proposed and several upcoming small hydropower plants in the region in the context of regional ecology and natural resource management.  相似文献   

Monitoring of TDS and conductivity in groundwater in the seismically active region in NW Himalayas, India     

Arvind Kumar  Surinder Singh  Bikramjit Singh Bajwa  Sandeep Mahajan  Rajeev Kalia  Sunil Dhar 《地震学报(英文版)》2010,(3):295-299

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Interferometer phase calibration sources — III. The regions +20 ≤ δ _B1950 ≤ + 35° and +75 ≤ δ _B1950 ≤ + 90°     

P. N. Wilkinson  I. W. A. Browne  A. R. Patnaik  J. M. Wrobel  & B. Sorathia 《Monthly notices of the Royal Astronomical Society》1998,300(3):790-816

We present a catalogue of 540 compact radio sources in the declination ranges +20 ≤ δ _B1950 ≤ + 35° and +75 ≤ δ _B1950 ≤ + 90°, the positions of which have been measured to an rms accuracy of about 55 mas with the Very Large Array (VLA). These sources are primarily intended for use as phase calibration sources for MERLIN. However, they will also be suitable as phase calibrators for the VLA and can be considered as candidate phase calibrators for very long baseline interferometry (VLBI) networks.  相似文献   

Visible-Near Infrared Reflectance Spectroscopy for Rapid Characterization of Salt-Affected Soil in the Indo-Gangetic Plains of Haryana,India   总被引：6，自引：0，他引：6  

Rajeev Srivastava  Madhurama Sethi  R. K. Yadav  D. S. Bundela  Manjeet Singh  S. Chattaraj  S. K. Singh  R. A. Nasre  Sita Ram Bishnoi  Sanjay Dhale  D. S. Mohekar  A. K. Barthwal 《Journal of the Indian Society of Remote Sensing》2017,45(2):307-315

Management of salt-affected soils is a challenging task in the input intensive rice-wheat cropping zone of the Indo-Gangetic plains (IGP). Timely detection of salt-affected areas and assessment of the degree of severity are vital in order to narrow down the potential gap in yield. Conventional laboratory techniques of saturation extract electrical conductivity (EC_e) and sodium adsorption ration (SAR) for soil salinity assessment are time-consuming and labour intensive; the VNIR (visible-near infrared) reflectance spectroscopy technique provides ample information on salinity and its attributes in an efficient and cost-effective way. This study aims to develop robust soil reflectance spectral models for rapid assessment of soil salinity in the salt affected areas of the IGP region of Haryana using VNIR reflectance spectroscopy. The results indicated that the spectral region between 1390 and 2400 nm was highly sensitive to measure changes in salinity. The developed hyperspectral models explained more than 80 % variability in EC_e, and other salinity related attributes (saturated extract Na⁺, Ca²⁺ + Mg²⁺, Cl^? and SAR) in the validation datasets. With the increasing availability of data from hyperspectral sensors in near future, the study will be very useful in real time monitoring of soils in the spatio-temporal context; enabling the farmers of IGP area to deal with salt degradation more effectively and efficiently.  相似文献   

Estimating apparent thermal diffusivity of soil using field temperature time series     

Pathmanathan Rajeev  Jayantha Kodikara 《Geomechanics and Geoengineering》2016,11(1):28-46

Reliable estimates of soil thermal properties such as heat capacity, thermal conductivity, and diffusivity are important in analysis of heat transmission through soils in applications such as shallow geothermal applications, buried electrical conduits, and in general heat/fluid flow analyses. A number of analytical, numerical and experimental methods are available to determine the soil thermal properties. In this paper, the analytical and numerical methods developed on the basis of one-dimensional heat conduction equation are used to estimate the apparent thermal diffusivity of soil. Three of the four analytical methods, Amplitude, Phase, and Arctangent provide explicit equations for the apparent thermal diffusivity. Two methods, Harmonic and Numerical, make use of large number of temperature measurements to implicitly solve for the apparent thermal diffusivity. The temperature time series data monitored at different depths in two field sites in Melbourne, Australia for more than 2 year period were used to estimate the apparent thermal diffusivity of soil down to 2 m depth. The apparent thermal diffusivity was calculated using all five methods and compared with laboratory experimental results. The effectiveness of each method in predicting the thermal diffusivity was compared and observed discrepancies were discussed. Finally, the observed soil temperature data for a 12 month period are used to model the temperature variation in the ground analytically using Harmonic method and the model prediction for the following 12 month was compared independently with the field measurements. The analytical model prediction is found to be in good agreement with the field monitored data.  相似文献   

High resolution climatic record entombed in fossil hominid dental enamel     

Rajeev Patnaik 《Journal of the Geological Society of India》2012,79(5):540

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Changes in the measured image separation of the gravitational lens system PKS 1830-211     

C. Jin  M. A. Garrett  S. Nair  R. W. Porcas  A. R. Patnaik  R. Nan 《Monthly notices of the Royal Astronomical Society》2003,340(4):1309-1316

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2016+112: a gravitationally lensed type II quasar     

L. V. E. Koopmans  &#;  M. A. Garrett  R. D. Blandford  C. R. Lawrence  A. R. Patnaik  R. W. Porcas 《Monthly notices of the Royal Astronomical Society》2002,334(1):39-47

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Assessing the utility of 210Pb geochronology for estimating sediment accumulation rates on river floodplains in Fiji     

James P. Terry  Rajeev Lal  Sitaram Garimella 《Singapore journal of tropical geography》2011,32(1):102-114

Low‐energy gamma ray spectroscopy has been employed to estimate floodplain sedimentation rates using measurements of ²¹⁰Pb in floodplain alluvium. The utility of the technique is assessed through the analysis of excess (unsupported) ²¹⁰Pb profiles in three sediment cores taken from the floodplain of the Labasa River on Vanua Levu in northern Fiji. A low‐energy germanium spectrometer (LEGe) was used for the nondestructive determination of excess ²¹⁰Pb in a region cultivated intensively with sugarcane. Measured average historical (c. 25 years) vertical accretion rates are between 2.2 and 4.4 cm yr^?1. The findings are broadly comparable with published sedimentation rates from analyses of radionuclide profiles elsewhere in the tropical South Pacific Islands, but the rates are higher than those measured previously at the same Labasa River sites using ¹³⁷Cs profiles. Accelerated soil erosion owing to cane burning and land tillage seems to be largely responsible for sediment production, although flood‐related effects such as channel accretion by coarse bedload and the emplacement of large organic debris also influence floodplain sedimentation. However, application of the ²¹⁰Pb technique in Fiji (and perhaps neighbouring island countries) is found to have serious drawbacks compared to the more robust ¹³⁷Cs method, owing principally to the low ²¹⁰Pb concentrations in the sandy alluvial sediment tested.  相似文献