Dynamical downscaling approach for wintertime seasonal-scale simulation over the Western Himalayas     

Pushp R. Tiwari  Sarat C. Kar  Uma C. Mohanty  Sagnik Dey  Palash Sinha  P. V. S. Raju  M. S. Shekhar 《Acta Geophysica》2014,62(4):930-952

The performance of RegCM4 for seasonal-scale simulation of winter circulation and associated precipitation over the Western Himalayas (WH) is examined. The model simulates the circulation features and precipitation in three distinct precipitation years reasonably well. It is found that the RMSE decreases and correlation coefficient increases in the precipitation simulations with the increase of model horizontal resolutions. The ETS and POD for the simulated precipitation also indicate that the performance of model is better at 30 km resolution than at 60 and 90 km resolutions. This improvement comes due to better representation of orography in the high-resolution model in which sharp orography gradient in the domain plays an important role in wintertime precipitation processes. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. Overall, the results suggest that 30 km model produced better skill in simulating the precipitation over the WH and this model is a useful tool for further regional downscaling studies.  相似文献   

Estimation of wave period statistics using numerical coastal wave model     

G. Muraleedharan  Mourani Sinha  A. D. Rao  N. Unnikrishnan Nair  P. G. Kurup 《Natural Hazards》2009,49(2):165-186

We used field and model wave data to investigate that zero crossing and average wave period distribution follow Gamma distribution. Since Gamma CDF is an infinite power series, further mathematical treatment is difficult. Hence its shape parameter is approximated to the nearest integer to arrive at Erlang distribution. An expression is derived from Erlang distribution to estimate various mean wave periods and significant wave period and validated by relative root mean square (RRMS) error criteria. It is shown by mathematical logic that the significant wave period distribution follows Erlang (or Gamma) distribution and is validated. The average of one-third and one-tenth highest wave periods (T _s ) estimated from Erlang distribution are in accordance with the values computed from recorded buoy and numerical coastal wave model wave period data. The predicted T _s values from coastal wave model wave period data underestimates the values from buoy wave period data.  相似文献   

Sea Levels and Coastal Inundation Due to Tropical Cyclones in Indian Coastal Regions of Andhra and Orissa     

S. K. Dube  P. Chittibabu  A. D. Rao  P. C. Sinha  T. S. Murty 《Marine Geodesy》2013,36(2):65-73

Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding.  相似文献   

Modeling of circulation and salinity in Hooghly estuary     

P. C. Sinha  Y. R. Rao  S. K. Dube  A. D. Rao  A. K. Chatterjee 《Marine Geodesy》2013,36(2):197-213

The circulation and salinity distribution in the Hooghly Estuary have been studied by developing a two‐dimensional depth‐averaged numerical model for the lower estuary, where the flow is vertically well mixed. This has been coupled with a one‐dimensional model for the upper estuary, where the flow is assumed to be unidirectional and well mixed over the depth and breadth. The Hooghly River receives high freshwater discharge during the monsoon season (June to September), which has significant effect on the salinity distribution in the estuary. The model‐simulated currents, elevations, and salinities are in good agreement with observations during the dry season. However, during the wet season the computed salinities seem to deviate slightly from the observed values.  相似文献   

Validating the use of object-based image analysis to map commonly recognized landform features in the United States     

Samantha T. Arundel  Gaurav Sinha 《制图学和地理信息科学》2013,40(5):441-455

ABSTRACT

The U.S. Geological Survey (USGS) National Geospatial Program (NGP) seeks to i) create semantically accessible terrain features from the pixel-based 3D Elevation Program (3DEP) data, and ii) enhance the usability of the USGS Geographic Names Information System (GNIS) by associating boundaries with GNIS features whose spatial representation is currently limited to 2D point locations. Geographic object-based image analysis (GEOBIA) was determined to be a promising method to approach both goals. An existing GEOBIA workflow was modified and the resulting segmented objects and terrain categories tested for a strategically chosen physiographic province in the mid-western US, the Ozark Plateaus. The chi-squared test of independence confirmed that there is significant overall spatial association between terrain categories of the GEOBIA and GNIS feature classes. Contingency table analysis also suggests strong category-specific associations between select GNIS and GEOBIA classes. However, 3D visual analysis revealed that GEOBIA objects resembled segmented regions more than they did individual landform objects, with their boundaries often failing to correspond to match what people would likely perceive as landforms. Still, objects derived through GEOBIA can provide initial baseline landscape divisions that can improve the efficiency of more specialized feature extraction methods.  相似文献   

Occurrence of scheelite-powellite in the rocks of Mahakoshal Group, Wyndhamganj area, Sonbhadra district, Uttar Pradesh     

M. A. Khan  Asfar Hakim  S. Syed Ameer Rasool  V. P. Sinha 《Journal of the Geological Society of India》2012,80(4):579-583

Scheelite and Powellite occur as dissemination and fractures filling in the hornfels and tourmaline-garnet granite in the Palaeoproterozoic rocks of Mahakoshal Group, at about 2.5 km north of Wyndhamganj, Sonbhadra district, Uttar Pradesh. This new find opens new vistas for the search of tungsten mineralization along the contact zones of Mahakoshal Group and the younger granite.  相似文献   

Geophysical and geomorphological approach for locating groundwater potential zones in Sukinda chromite mining area   总被引：2，自引：2，他引：0  

Ratnakar Dhakate  D. K. Chowdhary  V. V. S. Gurunadha Rao  R. K. Tiwary  Amlendu Sinha 《Environmental Earth Sciences》2012,66(8):2311-2325

The impact of mining causes deterioration of environment and decline of groundwater level in the adjoining mining areas, which influences groundwater source for domestic and agriculture purposes. This necessitated locating and exploiting of new groundwater source. A fast, cost-effective and economical way of locating and exploration is to study and analyze remote sensing data. Interpreted remote sensing data were used to select sites for carrying out surface geophysical investigations. Various geomorphologic units were demarcated, and the lineaments were identified by interpretation of false color composite satellite imageries. The potential for occurrence of groundwater in the Sukinda Valley was classified as very good, good, moderate and poor by interpreting the images. Sub-surface geophysical investigations, namely vertical electrical soundings, were carried out to delineate and demarcate potential water-bearing zones. Integrated studies of interpretation of geomorphologic, lineaments and geophysical data (aquifer thickness) were used to prepare groundwater potential map. The studies reveal that the groundwater potential of shallow aquifers is due to geomorphologic features, and the potential of deeper aquifers is determined by lineaments and degree of weathering.  相似文献   

Hydrogeochemical processes and quality assessment of groundwater in Dumka and Jamtara districts, Jharkhand, India     

Abhay Kumar Singh  G. C. Mondal  T. B. Singh  S. Singh  B. K. Tewary  A. Sinha 《Environmental Earth Sciences》2012,67(8):2175-2191

The hydrogeochemical study of groundwater in Dumka and Jamtara districts has been carried out to assess the major ion chemistry, hydrogeochemical processes and groundwater quality for domestic and irrigation uses. Thirty groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, anions (F^?, Cl^?, NO₃ ^?, HCO₃ ^?, SO₄ ^2?) and cations (Ca²⁺, Mg²⁺, Na⁺, K⁺). The analytical results show the faintly alkaline nature of water and dominance of Mg²⁺ and Ca²⁺ in cationic and HCO₃ ^? and Cl^? in anionic abundance. The concentrations of alkaline earth metals (Ca²⁺?+?Mg²⁺) exceed the alkali metals (Na⁺?+?K⁺) and HCO₃ ^? dominates over SO₄ ^2??+?Cl^? concentrations in the majority of the groundwater samples. Ca?CMg?CHCO₃ is the dominant hydrogeochemical facies in 60?% of the groundwater samples, while 33?% samples occur as a mixed chemical character of Ca?CMg?CCl hydrogeochemical facies. The water chemistry is largely controlled by rock weathering and ion exchange processes with secondary contribution from anthropogenic sources. The inter-elemental correlations and factor and cluster analysis of hydro-geochemical database suggest combined influence of carbonate and silicate weathering on solute acquisition processes. For quality assessment, analyzed parameter values were compared with Indian and WHO water quality standards. In majority of the samples, the analyzed parameters are well within the desirable limits and water is potable for drinking purposes. Total hardness and concentrations of TDS, Cl^?, NO₃ ^? _, Ca²⁺ and Mg²⁺ exceed the desirable limits at a few sites, however, except NO₃ ^? all these values were below the highest permissible limits. The calculated parameters such as sodium adsorption ratio, percent sodium (%Na) and residual sodium carbonate revealed excellent to good quality of groundwater for agricultural purposes, except at few sites where salinity and magnesium hazard (MH) values exceeds the prescribed limits and demands special management.  相似文献   

The Indus flood of 2010 in Pakistan: a perspective analysis using remote sensing data   总被引：1，自引：1，他引：0  

Kumar Gaurav  R. Sinha  P. K. Panda 《Natural Hazards》2011,59(3):1815-1826

The Indus flood in 2010 was one of the greatest river disasters in recent history, which affected more than 14 million people in Pakistan. Although excessive rainfall between July and September 2010 has been cited as the major causative factor for this disaster, the human interventions in the river system over the years made this disaster a catastrophe. Geomorphic analysis suggests that the Indus River has had a very dynamic regime in the past. However, the river has now been constrained by embankments on both sides, and several barrages have been constructed along the river. As a result, the river has been aggrading rapidly during the last few decades due to its exceptionally high sediment load particularly in reaches upstream of the barrages. This in turn has caused significant increase in cross-valley gradient leading to breaches upstream of the barrages and inundation of large areas. Our flow accumulation analysis using SRTM data not only supports this interpretation but also points out that there are several reaches along the Indus River, which are still vulnerable to such breaches and flooding. Even though the Indus flood in 2010 was characterized by exceptionally high discharges, our experience in working on Himalayan rivers and similar recent events in rivers in Nepal and India suggest that such events can occur at relatively low discharges. It is therefore of utmost importance to identify such areas and plan mitigation measures as soon as possible. We emphasize the role of geomorphology in flood analysis and management and urge the river managers to take urgent steps to incorporate the geomorphic understanding of Himalayan rivers in river management plans.  相似文献   

Peperite occurrence and its implications on origin and temporal development of the Proterozoic Dhala basin,Mohar area,Shivpuri district,Madhya Pradesh     

K. K. Sinha  Pradeep Pandey  C. L. Bhairam  P. S. Parihar 《Journal of the Geological Society of India》2011,77(2):183-189

In the western part of Bundelkhand massif, a caldera with intra-caldera sediments, known as Dhala Formation, occurs as an outlier in and around Mohar village of Shivpuri district, Madhya Pradesh. For the first time, occurrence of peperite is being reported from the basal part of the Dhala sediment. Two types of peperites have been recognized: blocky and fluidal or globular with variable morphology. In peperitic zones, features like soft sediment deformations, presence of sediment into the rhyolite along cracks, vesiculation of the sediments and other evidences suggestive of sediment fluidization are some definite characteristics of interaction of hot magma with wet sediments forming peperite. The occurrence of peperites reflects the contemporaniety of deposition of the Dhala sediments and volcanism, which is well in accordance to the volcanic origin of Dhala structure. Further, the nature of unconformity between the Dhala and overlying Kaimur which is characterized by merely a few centimeter thick pebbly/conglomeratic bed does not appear to represent a large hiatus as expected between the Semri and Kaimur of Vindhyan Supergroup. So, the contemporaniety of the Dhala Formation (at least the lower part) as reflected by occurrence of peperites, coupled with the available age of the rhyolite and the nature of the unconformity between the Dhala and overlying Kaimur provide convincing evidence to correlate the Dhala Formation with the Lower part of the Kaimur and unlikely with the Semri Group or Bijawar as proposed earlier.  相似文献