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61.
Wet and dry spell analysis of Global Climate Model-generated precipitation using power laws and wavelet transforms 总被引:2,自引:2,他引:0
Ashok K. Mishra Mehmet ?zger Vijay P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):517-535
Climate model simulations for the twenty-first century point toward changing characteristics of precipitation. This paper
investigates the impact of climate change on precipitation in the Kansabati River basin in India. A downscaling method, based
on Bayesian Neural Network (BNN), is applied to project precipitation generated from six Global Climate Models (GCMs) using
two scenarios (A2 and B2). Wet and dry spell properties of monthly precipitation series at five meteorologic stations in the
Kansabati basin are examined by plotting successive wet and dry durations (in months) against their number of occurrences
on a double-logarithmic paper. Straight-line relationships on such graphs show that power laws govern the pattern of successive
persistent wet and dry monthly spells. Comparison of power-law behaviors provides useful interpretation about the temporal
precipitation pattern. The impact of low-frequency precipitation variability on the characteristics of wet and dry spells
is also evaluated using continuous wavelet transforms. It is found that inter-annual cycles play an important role in the
formation of wet and dry spells. 相似文献
62.
M. K. Singh 《Journal of the Geological Society of India》2011,77(1):35-41
The paper concerns mainly with properties of packing of the Proterozoic Chandarpur and Khairagarh sandstones of Chhattisgarh
Basin. An attempt has been made to decipher the nature of boundary between Chandarpur Group and overlying Raipur Group on
the basis of grain packing. For the purpose of study based on eight representative thin sections of Chandarpur and Khairagarh
sandstones, measurements of grain size distribution, types of grain contacts, packing density (Pd), packing proximity (Pp)
and linear regression analysis has been carried out. The relation of packing density with packing proximity of Khairagarh
sandstone shows positive correlation coefficient (r) with linear regression equation (y) and no clear trend in packing proximity
(Pp) vs grain size (Is) is observed whereas Chandarpur sandstone shows packing density increases and packing proximity decreases
with linear regression equation (y) and correlation coefficient (r). Chandarpur grain size tends to increase with packing
density (Pd) whereas packing proximity (Pp) increases but Khairagarh sandstone packing density (Pd) decrease with increase
of grain size (Is) and packing proximity (Pp) tends to increase with decrease in grain size. Above study indicates that packing
behaviour of Chandarpur sandstones and Khairagarh sandstones are entirely different. 相似文献
63.
Late Paleocene-middle Eocene Subathu Formation represents the earliest deposits of the western Himalayan foreland basin. A
large part of this formation is comprised of impure limestone and grey shale intercalations. The limestones contain sole marks,
intraformational conglomerates, hummocky cross stratification and wave ripples. The occurrence of sole marks suggests that
they are developed by the unidirectional currents at the initial phase of the storm that resulted erosion and subsequent deposition.
The intraformational limestone conglomearate also suggests erosion of the earlier deposited limestone hardgrounds as a consequence
of storm associated transgression. The hummocky cross stratification formed by the oscillatory flows during the long-shore
littoral drift. The depth of formation of the hummocky cross stratified limestone facies was less than 40 m and most likely
deposited between shore-face to backshore regions of the gulf similar to present day Persian Gulf. The identification of deeper
facies (shelf facies) from Pakistan and coastal facies from India suggest that the gulf was open from the west and closed
from the east. 相似文献
64.
Site response studies in Agartala Urban agglomeration 总被引:1,自引:0,他引:1
A systematic investigation using digital microearthquake recorders with short period SS-1 seismometers, covering 76 sites
in and around Agartala city, has been carried out for site response (SR) studies in the area. In the northern part of the
area, SR varies from 1.15 to 1.85 corresponding to peak frequency 0.76 to 0.93 Hz where soil is mostly semi-consolidated and
stiffer than recent Quaternary deposits (Haora River formation). In the southern part of the area, SR varies from 1.12 to
2.42 corresponding to peak frequency from 0.71 to 0.85 Hz within the Dupitila formation (early Quaternary). It is observed
that estimated SR from H/V increases from edges to middle of the Haora River valley and impedance contrast fallows the similar
trend. This reflects that site response by H/V is influenced by impedance contrast, whereas computed amplification from 1-D
model shows opposite trend. The maximum amplification at fundamental frequency of resonance, 1.04 Hz estimated from H/V by
near to BH-7, is 2.5 times greater than the impedance contrast/ratio derived from 1-D model for same location. Relationship
between resonance frequency and depth was obtained by applying quarter wavelength and Bard (2000) methodologies, which shows linearity, whereas H/V shows its nonlinearity characteristic in soil across the valley part of
Haora River. Shear wave velocities, and subsequently, SPT index and factor of safety (by cyclic stress approach) were estimated
from geotechnical parameters. Vs30 and site response data were used in this study for getting a first hand information about
soil stiffness condition in the area. The estimation of SPT index and factor of safety could be a useful tool for delineating
liquefied and none liquefied zones at various depth levels, especially where water table exists at a very shallow level. The
expected liquefiable zone was observed at depths varying from 6–25 m beneath the soil bearing zones where percentage of fines
is estimated to be more than 35% for the area. This knowledge about subsurface soil characteristics will be useful for the
civil engineers/city planners, which can be taken into account at the time of constructing earthquake-resistant structures
in the area. 相似文献
65.
We present the seismic energy, strain energy, frequency–magnitude relation (b-value) and decay rate of aftershocks (p-value) for the aftershock sequences of the Andaman–Sumatra earthquakes of December 26, 2004 (M
w 9.3) and March 28, 2005 (M
w 8.7). The energy released in aftershocks of 2004 and 2005 earthquake was 0.135 and 0.365% of the energy of the respective
mainshocks, while the strain release in aftershocks was 39 and 71% for the two earthquakes, respectively. The b-value and p-value indicate normal value of about 1. All these parameters are in normal range and indicate normal stress patterns and
mechanical properties of the medium. Only the strain release in aftershocks was considerable. The fourth largest earthquake
in this region since 2004 occurred in September 2007 off the southern coast of Island of Sumatra, generating a relatively
minor tsunami as indicated by sea level gauges. The maximum wave amplitude as registered by the Padang, tide gauge, north
of the earthquake epicenter was about 60 cm. TUNAMI-N2 model was used to investigate ability of the model to capture the minor
tsunami and its effect on the eastern Indian Coast. A close comparison of the observed and simulated tsunami generation, propagation
and wave height at tide gauge locations showed that the model was able to capture the minor tsunami phases. The directivity
map shows that the maximum tsunami energy was in the southwest direction from the strike of the fault. Since the path of the
tsunami for Indian coastlines is oblique, there were no impacts along the Indian coastlines except near the coast of epicentral
region. 相似文献
66.
A first-order seismotectonic model was created for South Africa. This was done using four logical steps: geoscientific data
collection, characterisation, assimilation and zonation. Through the definition of subunits of concentrations of earthquake
foci and large neotectonic and structural domains, seismotectonic structures, systems and domains were created. Relatively
larger controls of seismicity exist between the Great Escarpment and the coast. In the south, this region is characterised
by large aeromagnetic anomalies and large EW trending faults. In the west, it is characterised by the NW–SE trending Wegener
stress anomaly, radial-trending dykes and earthquake clusters. In the east, it is characterised by a large neotectonic domain
where several large historical earthquakes occurred. In the centre of South Africa, several clusters of earthquake activity
are found, often related to mining activity. Further north, seismicity is related to both mining activity and neotectonic
deformation. This work contributes to the development of a seismotectonic model for South Africa by (1) bringing together,
digitally, several data sets in a common GIS platform (geology, geophysics, stress, seismicity, neotectonics, topography,
crustal and mantle structure and anisotropy), (2) understanding the significance of data sets for seismotectonic zonation
and limitations thereof and (3) obtaining a reasonable regional model for use in seismic hazard assessments. 相似文献
67.
Impact of satellite soundings on the simulation of heavy rainfall associated with tropical depressions 总被引:1,自引:1,他引:0
The present study is carried out to examine the impact of temperature and humidity profiles from moderate resolution imaging
spectroradiometer (MODIS) or/and atmospheric infrared sounder (AIRS) on the numerical simulation of heavy rainfall events
over the India. The Pennsylvania State University–National Centre for Atmospheric Research fifth-generation mesoscale model
(MM5) and its three-dimensional variational (3D-Var) assimilation technique is used for the numerical simulations. The heavy
rainfall events occurred during October 26–29, 2005, and October 27–30, 2006, were chosen for the numerical simulations. The
results showed that there were large differences observed in the initial meteorological fields from control experiment (CNT;
without satellite data) and assimilation experiments (MODIS (assimilating MODIS data), AIRS; (assimilating AIRS data); BOTH
(assimilating MODIS and AIRS data together)). The assimilation of satellite data (MODIS, AIRS, and BOTH) improved the predicted
thermal and moisture structure of the atmosphere when compared to CNT. Among the experiments, the predicted track of tropical
depressions from MODIS was closer to the observed track. Assimilation of MODIS data also showed positive impact on the spatial
distribution and intensity of predicted rainfall associated with the depressions. The statistical skill scores obtained for
different experiments showed that assimilation of satellite data (MODIS, AIRS, and BOTH) improved the rainfall prediction
skill when compared to CNT. Root mean square error in quantitative rainfall prediction is less in the experiment which assimilated
MODIS data when compared to other experiments. 相似文献
68.
Snow cover depletion under changed climate with the help of remote sensing and temperature data 总被引:1,自引:1,他引:0
Sanjay K. Jain L. N. Thakural R. D. Singh A. K. Lohani S. K. Mishra 《Natural Hazards》2011,58(3):891-904
Snow cover depletion curve (SDC) is one of the important variables in snow hydrological applications, and these curves are very much required for snowmelt runoff modeling in a snowfed catchment. Remote sensing is an important source of snow cover area which is used for preparation of SDC. Snow cover maps produced by Moderate Resolution Imaging Spectroradiometer (MODIS) satellites are one of the best source of satellite-based snow cover area at a regular interval. Therefore, in this study, snow cover maps have been prepared for the years 2000?C2005 using MODIS data. The study area chosen viz. Beas basin up to Pandoh dam falls in western Himalayan region. For snowmelt runoff modeling, catchment is divided into number of elevation zones and SDC is required for each zone. When sufficient satellite data are not available due to cloud cover or due to some other reasons, then SDC can to be generated using temperature data. Under changed climate conditions also, modified SDC is required. Therefore, to have SDC under such situations, a relationship between snow cover area and cumulative mean temperature has been developed for each zone of the catchment. This procedure of having snow cover maps has two main purposes. First, it could potentially be used to generate snow cover maps when cloud-free satellite data are not available. Second, it can be used to generate snow-covered area in a new climate to see the impact of climate change on snowmelt runoff studies. 相似文献
69.
Quantitative modeling of groundwater in Satluj River basin of Rupnagar district of Punjab using remote sensing and geographic information system 总被引:3,自引:1,他引:2
Chander Kumar Singh Satyanarayan Shashtri Amit Singh Saumitra Mukherjee 《Environmental Earth Sciences》2011,62(4):871-881
Water is a fluctuating resource making it difficult to measure in time and in space. To demonstrate the efficiency of the
geographic information system (GIS) for groundwater studies, information on the parameters controlling groundwater such as
lithology, geomorphology and lineament analysis were analyzed. LISS-III and Landsat satellite image of the area was used to
infer information on the geologic lineaments and geomorphology. To delineate linear features enhancement and direction, filtering
was performed on single bands of Landsat images. Thematic maps for geology, slope, geomorphology and lineament were prepared
and integrated in GIS by assigning the weights and ranking to various parameters controlling the occurrence of groundwater
to generate the groundwater potential map for the study area. The results indicate that the floodplain of river and its adjoining
areas have very good groundwater potential, whereas the steeply sloping area in the northern part having high relief and slope
possesses poor groundwater potential. 相似文献
70.
A study of arsenic,iron and other dissolved ion variations in the groundwater of Bishnupur District,Manipur, India 总被引:1,自引:1,他引:0
Jayalakshmi Devi Oinam AL. Ramanathan Anurag Linda Gurmeet Singh 《Environmental Earth Sciences》2011,62(6):1183-1195
The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent
years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water
standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were
highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon
(1–200 μg L−1) as compared to pre-monsoon (1–108 μg L−1) and monsoon (2–99 μg L−1). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization
(WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative
correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur
area has an arsenic contamination problem, which is expected to increase in the near future. 相似文献