Characteristics of spectral aerosol optical depths over India during ICARB     

S. Naseema Beegum  K. Krishna Moorthy  Vijayakumar S. Nair  S. Suresh Babu  S. K. Satheesh  V. Vinoj  R. Ramakrishna Reddy  K. Rama Gopal  K. V. S. Badarinath  K. Niranjan  Santosh Kumar Pandey  M. Behera  A. Jeyaram  P. K. Bhuyan  M. M. Gogoi  Sacchidanand Singh  P. Pant  U. C. Dumka  Yogesh Kant  J. C. Kuniyal  Darshan Singh 《Journal of Earth System Science》2008,117(1):303-313

Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Ångström parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Ångström coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from tshe adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Ångström exponent (α) remained significantly lower (～1) over the Arabian Sea compared to Bay of Bengal (BoB) (～1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of α, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in α over the BoB.  相似文献   

Urban development policy in India with special reference to Himachal Pradesh     

Kant S 《Population geography : a journal of the Association of Population Geographers of India》1993,15(1-2):29-40

This paper addresses the following questions: 1) What have been the government policies, programs, and perceptions dominating the urban development scenario in India? 2) What has been the outcome of these policies and programs of urban development? 3) What should be the strategy of future urban development with reference to the Indian hill state of Himachal Pradesh? The paper critically evaluates the Indian ethos pertaining to the urbanization process, urban development policies pursued in the Five Year Plans, the current thinking on urbanization, and the main issues in urban development. It has been observed that not only is the urbanization level in Himachal Pradesh quite low, but also that the urban development here suffers from a number of serious problems. Acute shortage of building space, limited capacity to mobilize resources from their own sources, overcrowding, and slum dwelling are some such problems. Unfortunately, urbanization has not been visualized as generative of economic growth and employment opportunities both at the state and national government levels. Therefore, the major thrust of Plan policies has been to arrest rural-urban migration. However, recently there has been a desire to manage urban affairs through a new policy seeking production efficiency and cost effectiveness.  相似文献   

Late Pleistocene–Holocene hydrologic changes in the interfluve areas of the central Ganga Plain, India     

Pradeep Srivastava  Indra Bir Singh  Shikha Sharma  Uma Kant Shukla  Ashok Kumar Singhvi   《Geomorphology》2003,54(3-4):279-292

Abandoned channel belts, ponds and point bar deposits of palaeochannels in the interfluve regions of the central Ganga Plain suggest changes in the morphohydrologic conditions during the Latest Pleistocene–Holocene. Stratigraphy of these ponds comprises channel sand at the base overlain by shell-bearing clayey silt. The contact of the two facies marks the phase when channels converted into standing water bodies. Point bar deposits of some palaeochannels are overlain by oxidised aeolian sand, indicating that the channel abandonment possibly occurred due to the desiccation and aridity in the region.Optically stimulated luminescence (OSL) chronometry of the pond sediments suggests that the deposition of the basal channel sand started before 13 ka and continued up to 8 ka. The ponds formed around 8–6 ka when the channel activity ceased. Evidence from the point bar deposits also indicates that the fluvial activity in the region ended sometime during 7–5 ka. This was followed by aeolian aggradation. The present study thus suggests that the hydrologic conditions in the Gangetic plains, i.e. initiation of channels and their abandonment, formation of microgeomorphologic features such as ponds and their eventual siltation, were controlled largely by climatic changes (i.e. monsoon changes) supported by tectonic activity. For the past 2 ka, increasing human and related agricultural activity has substantially accentuated the natural siltation rate of ponds.  相似文献   

Decumbent development: Urban sprawl in the Guwahati Metropolitan Area,India     

Chandra Kant Pawe  Anup Saikia 《Singapore journal of tropical geography》2020,41(2):226-247

Urban sprawl has become a global phenomenon as an outcome of growing population and rapid urbanization. Previous studies have addressed the rising incidence of uncontrollable urban development, particularly in peri-urban areas of cities, leading to chronic urban sprawl. The city of Guwahati, a million city in north east India, has expanded significantly in recent years. In this article, the links between population and growth of built-up areas were examined using geo-spatial techniques and remotely sensed datasets. The results indicate that the sprawl has accentuated in recent years. The intensity of land use remained uneven due to marked variations in the distribution of built-up areas, plausibly an outcome of unplanned urban growth. If current trends are anything to go by, future urban sprawl could pose serious threats to the vulnerable eco-sensitive and peri-urban areas of Guwahati. Secondary cities have unfortunately received scant attention in urban policy research, and Guwahati, epitomizes urban woes in a developing country.  相似文献   

Detection of 2011 Sikkim earthquake-induced landslides using neuro-fuzzy classifier and digital elevation model     

Krishna Kant Singh  Akansha Singh 《Natural Hazards》2016,81(2):1027-1050

  相似文献   

Multi-criteria decision analysis for planning and management of groundwater resources in Balod District,India     

Tarun Kumar  Amar Kant Gautam  D. C. Jhariya 《Environmental Earth Sciences》2016,75(8):649

  相似文献   

Hydrogeochemical Characterization and Groundwater Quality of Jamshedpur Urban Agglomeration in Precambrian Terrain,Eastern India     

Nishi Kant  Prasoon Kumar Singh  Bijendra Kumar 《Journal of the Geological Society of India》2018,91(1):67-75

This paper reports petrography, geochemistry and Rb-Sr age data on the rare metal bearing Neoarchean fertile (Nb-Ta) granite at Allapatna and elucidates its petrogenesis and role in Nb-Ta-Li-Be mineralization. The Allapatna granite (AG) intrudes the Tonalitic-Trondhjemitic - Granodioritic (TTG) Peninsular Gneiss and analysed SiO₂ (72.3-75.6 wt%), K₂O (4.0-5.7wt%), Na2O (3.0-4.4wt%), CaO (0.7-1wt%), MgO (0.13-0.25wt%) and K₂O/Na₂O (>1) indicating evolved nature. The presence of muscovite, biotite and garnet in the mode, peraluminous nature and high initial ⁸⁷Sr/⁸⁶Sr ratio (0.7284±0.0083) attest to their S-type characteristics. Varying Nb/Ta ratio and high Li with moderate abundance of Cs further indicate affinity to Li-Cs-Ta (LCT) type granite-pegmatite system. TheAG showing whole rock Rb-Sr isochron age of 2803± 68 Ma, is the oldest reported fertile granite in India parental to rare metal pegmatites hosting Nb-Ta, Be, and Li resources. Partial melting of a mixed source consisting of both basement TTG rocks and metapelites has generated such type of granitic magma. Fractionation of such granitic magma possibly has given rise to the rare metal (Ta-Nb-Li-Be) bearing pegmatites intruding the nearby schist belt.  相似文献   

Recession of Milam Glacier,Kumaun Himalaya,Observed via Lichenometric Dating of Moraines     

Kapil Bisht  Yogesh Joshi  Shashi Upadhyay  Poonam Metha 《Journal of the Geological Society of India》2018,92(2):173-176

Glaciers being very sensitive to climate change have been identified as one of the best indicators of climate change and evidences have proved that most of the Himalayan glaciers have receded with an increased rate during the recent past under the influence of global warming. Lichenometric study was carried out on the moraines of Milam glacier (located in Pithoragarh district of Uttarakhand) with the help of lichen species Dimelaena oreina having an average annual growth rate of 1.31 mm. The study revealed that Milam glacier has receded 1450 m in last 69.37 years with an average recession rate of 20.90 m/year. Since lichenometric studies are cost effective and ecofriendly in comparison to carbon dating, satellite and remote sensing based studies and also reliable, hence, it should be promoted in Himalaya which is an abode of glaciers.  相似文献   

Variations of trace gases over the Bay of Bengal during the summer monsoon     

I A Girach  Narendra Ojha  Prabha R Nair  Yogesh K Tiwari  K Ravi Kumar 《Journal of Earth System Science》2018,127(1):15

In situ measurements of near-surface ozone (\(\hbox {O}_{3})\), carbon monoxide (CO), and methane (\(\hbox {CH}_{4})\) were carried out over the Bay of Bengal (BoB) as a part of the Continental Tropical Convergence Zone (CTCZ) campaign during the summer monsoon season of 2009. \(\hbox {O}_{3}\), CO and \(\hbox {CH}_{4}\) mixing ratios varied in the ranges of 8–54 ppbv, 50–200 ppbv and 1.57–2.15 ppmv, respectively during 16 July–17 August 2009. The spatial distribution of mean tropospheric \(\hbox {O}_{3}\) from satellite retrievals is found to be similar to that in surface \(\hbox {O}_{3}\) observations, with higher levels over coastal and northern BoB as compared to central BoB. The comparison of in situ measurements with the Monitoring Atmospheric Composition & Climate (MACC) global reanalysis shows that MACC simulations reproduce the observations with small mean biases of 1.6 ppbv, –2.6 ppbv and 0.07 ppmv for \(\hbox {O}_{3}\), CO and \(\hbox {CH}_{4}\), respectively. The analysis of diurnal variation of \(\hbox {O}_{3}\) based on observations and the simulations from Weather Research and Forecasting coupled with Chemistry (WRF-Chem) at a stationary point over the BoB did not show a net photochemical build up during daytime. Satellite retrievals show limitations in capturing \(\hbox {CH}_{4}\) variations as measured by in situ sample analysis highlighting the need of more shipborne in situ measurements of trace gases over this region during monsoon.  相似文献   

Generation of fraction images from AVHRR data using linear mixing model     

Yogesh Kant  KVS Badarinath 《Journal of the Indian Society of Remote Sensing》1998,26(1-2):23-27

The coarse resolution satellite data have been widely used for regional and global studies as they provide high temporal frequency. The information contained in the coarse resolution pixels are mostly mixture of several components. The extraction of information contained in a pixel find its role in Geosphere-Biosphere context. The present study address the utility of constrained least square model applied to coarse spatial resolution data from NOAA-AVHRR for generating fraction images of vegetation, soil and water/shade. The red and near-infrared channels have been used to run the constrained least square model to generate fraction images. The derived fraction images are related to normalised difference vegetation index (NDVI) for model validation. The results suggest that vegetation fraction components are strongly correlated with NDVI values (r²=0.98). The soil fractions (r²=?0.84) and water/shade fractions (4²=?0.97) are negatively correlated with NDVI. The relationship between the fraction images and NDVI show the potential of the model in deriving sub-pixel component information using coarse resolution data.  相似文献