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Intensification of Aila (May 2009) due to a warm core eddy in the north Bay of Bengal 总被引：1，自引：0，他引：1
A very severe cyclonic storm ??Aila?? hit West Bengal on 26 May 2009. The storm intensified when it encountered with a warm core (SST?=?31°C) anti-cyclonic eddy (ACE4) in the north Bay of Bengal. The storm intensity increased by 43% due to this eddy, which is comparable with that (34%) obtained from a best fit line (derived from several numerical experiments over north-west Pacific Ocean). The shallow mixed layer of the large-scale ocean and deep mixed layer inside the eddy appear to be crucial parameters besides translation speed of the storm (Uh), ambient relative humidity and thermal stratification below mixed layer, in the storm intensification. From the eddy size and Uh, the eddy feedback factor is found to be about 0.4 (i.e. 40%), which is close to the above. Since there exists an inverse relationship between Uh and UOHC (upper ocean heat content), slow (fast) moving storms require high (low) UOHC. The warm ACE4 with a high UOHC of 149?kj/cm2 (300% higher than the climatological value) and deep warm layer (D26?=?126?m) opposes the cooling induced by the storm and helps for the intensification of the storm through the supply of large enthalpy (latent?+?sensible) flux. 相似文献
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Concomitant with careless human interference in the delicate environmental balance, the Earth’s surface is witnessing a variety of changes in land use and land cover (LULC). Acquisition of a sound understanding of LULC is an important aspect of maintaining a sustainable, benign, healthy environment. The present work highlights a spatiotemporal study on the LULC features of Alappuzha District, an ecologically fragile area in southern Kerala, a state in South India. The study area faces diverse environmental challenges including decline of landforms, rising sea levels, population expansion and anthropogenic encroachments on the ecological balance. This investigation compiles an audited account of the modifications, in each class of LULC, using geospatial technologies. We interpreted satellite imagery from the Landsat 8 and the Landsat multispectral scanner for the years 1973 and 2017. The LULC aspects were categorized into seven classes: waterbody, waterlogged area, mixed vegetation, built-up land, uncultivated area, paddy field and sandy area. Our findings affirm that the expansiveness of the built-up land area is directly proportional to the growth of the population. Advanced technologies such as remote sensing and geographic information system accentuate alterations in land use patterns over time and the extent to which the changes affect the human population and the natural habitat. We verified the results of our research by assessment of accuracy and ground truth confirmation of the LULC features.
相似文献4.
B. Sridevi T.V. Ramana MurtyY. Sadhuram M.M.M. RaoK. Maneesha S. Sujith KumarP.L. Prasanna 《Estuarine, Coastal and Shelf Science》2010
Internal waves (IW) are identified off Bhimilipatnam, east coast of India, from the time series CTD (hourly interval) and thermistor chain data (2 min interval) collected during 23–25 Feb 2007. The measurements were carried out at 94 m water depth on the continental shelf edge. These data sets are used to describe the characteristics of IW and their impact on acoustic fields. Garrett and Munk (GM) model has been used to predict the characteristics of low frequency (LF) IW with space and time. Active IW are seen in the layers 54 m–94 m with a velocity of 0.548 km h−1 and the wavelengths of the order of 0.03 km–21.8 km. The model could capture the IW features in the thermocline region accurately than at the bottom. This could be due to the limitation of the model which considers linearity. High frequency IW observed at the bottom could be due to the advection of tidal currents over the shallow irregular bottom in the presence of stratification. The study emphasizes linear IW rather than transient non-linear waves induced by tidal interaction with topography. 相似文献
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Maneesha Gupta Anuja Sharma B. Kartikeyan 《Journal of the Indian Society of Remote Sensing》2017,45(2):195-207
The single-frequency Radar Imaging Satellite-1 (RISAT-1) Synthetic Aperture Radar (SAR) (launched in April, 2012) is designed to provide a wide variety of imaging options compared to the prevailing SAR missions. The scale of the calibration task for the RISAT-1 mission is increased with the inclusion of multiple beams and polarizations (single, dual and quad) along with circular/hybrid polarization capabilities, for the first time from space. Significant efforts have been made in the evolution of SAR processor for the provision of radiometrically and geometrically calibrated products to the users. After the commissioning phase, RISAT-1 was put into routine operations in Oct. 2012. Since then extensive beam coverage of Amazon rainforest in various modes was carried out to evaluate the calibration parameters and SAR processor performance. Subsequently, the processor version 1.2.0 was improved to version 1.3.0 and with further modifications to version 1.4.0. This article details the analysis carried out at each processor version, by quality evaluation team, to quantify the parameter behaviour and to give feedback on the processor performance to the SAR processor team. The various radiometric quality parameters evaluated and monitored are shape of the antenna pattern, gamma-naught, backscattering coefficient (sigma-naught), speckle index, radiometric resolution and Noise Equivalent Sigma Zero (NESZ). Data studied for the analysis is in Single Look Complex (SLC) for stripmap mode and multilook (Ground range) for ScanSAR and stripmap mode in dual and circular polarizations. The performance of version 1.4.0 for all the beams (near-to-far) is found to be consistent and meeting the mission specifications for the product. 相似文献
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Impact of atmospheric and physical forcings on biogeochemical cycling of dissolved oxygen and nutrients in the coastal Bay of Bengal 总被引：1，自引：0，他引：1
V. V. S. S. Sarma B. Sridevi K. Maneesha T. Sridevi S. A. Naidu V. R. Prasad V. Venkataramana T. Acharya M. D. Bharati Ch. V. Subbaiah B. S. Kiran N. P. C. Reddy V. V. Sarma Y. Sadhuram T. V. R. Murty 《Journal of Oceanography》2013,69(2):229-243
Time-series observations were conducted off Visakhapatnam, central west coast of Bay of Bengal, from October 2007 to April 2009 to examine the influence of physical and atmospheric processes on water column nutrients biogeochemistry. The thermal structure displayed inversions of 0.5 to 1.0° C during winter and were weaker in summer. The water column was vertically stratified during the entire study period and was stronger during October–November 2007 and August–December 2008 compared to other study periods. High concentrations of chlorophyll-a and nutrients were associated with the extreme atmospheric events. The strong relationship of nutrients with salinity indicates that physical processes, such as circulation, mixing and river discharge, have a significant control on phytoplankton blooms in the coastal Bay of Bengal. Phosphate seems to be a controlling nutrient during winter whereas availability of light and suspended matter limits production in summer. Formation of low oxygen conditions were observed in the bottom waters due to enhanced primary production by extreme atmospheric events; however, re-oxygenation of bottom waters through sinking of oxygen-rich surface waters by a warm core (anticyclonic) eddy led to its near recovery. This study reveals that atmospheric and physical processes have significant impacts on the water column biogeochemistry in the coastal Bay of Bengal. 相似文献
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