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991.
Doppler weather radar based nowcasting of cyclone Ogni 总被引:3,自引:0,他引:3
Soma Sen Roy V. Lakshmanan S. K. Roy Bhowmik S. B. Thampi 《Journal of Earth System Science》2010,119(2):183-199
In this paper, we describe offline analysis of Indian Doppler Weather Radar (DWR) data from cyclone Ogni using a suite of
radar algorithms as implemented on NEXRAD and the advanced algorithms developed jointly by the National Severe Storms Laboratory
(NSSL) and the University of Oklahoma. We demonstrate the applicability of the various algorithms to Indian radar data, the
improvement in the quality control and evaluate the benefit of nowcasting capabilities in Indian conditions. New information
about the tropical cyclone structure, as derived from application of the algorithms is also discussed in this study. 相似文献
992.
The Gondwana sediments comprising fine-grained shales, carbonaceous shales, sandstones and the coal horizon in borecore RT-4
(approximately 547.00m thick) from Tamra block, Raniganj Coalfield, Damodar Basin, are analyzed palynologically. Based on
the distribution pattern of marker palynotaxa, two assemblage zones are identified. In the Barren Measures Formation, dominance
of enveloping monosaccate (Densipollenites) along with striate bisaccate (Striatopodocarpites, Faunipollenites) pollen taxa, and the FAD’s of Kamthisaccites and Arcuatipollenites observed at 30.75, have equated this strata (30.75–227.80 m thick) with the Raniganj Formation of Late Permian in age. Downwards
in the Barakar Formation, between 423.80–577.70 m depths, an abundance of non-striate (Scheuringipollenites) and striate (Faunipollenites and Striatopodocarpites) bisaccate pollen taxa is observed, that dates late Early Permian in age. 相似文献
993.
The flux rate of cosmic rays incident on the Earth’s upper atmosphere is modulated by the solar wind and the Earth’s magnetic
field. The amount of solar wind is not constant due to changes in solar activity in each solar cycle, and hence the level
of cosmic ray modulation varies with solar activity. In this context, we have investigated the variability and the relationship
of cosmic ray intensity with solar, interplanetary, and geophysical parameters from January 1982 through December 2008. Simultaneous
observations have been made to quantify the exact relationship between the cosmic ray intensity and those parameters during
the solar maxima and minima, respectively. It is found that the stronger the interplanetary magnetic field, solar wind plasma
velocity, and solar wind plasma temperature, the weaker the cosmic ray intensity. Hence, the lowest cosmic ray intensity has
good correlations with simultaneous solar parameters, while the highest cosmic ray intensity does not. Our results show that
higher solar activity is responsible for a higher geomagnetic effect and vice versa. 相似文献
994.
Yu. V. Baryshev I. V. Sokolov A. S. Moskvitin T. A. Fatkhullin N. V. Nabokov B. Kumar 《Astrophysical Bulletin》2010,65(4):311-325
We present an analysis of BV R
c
I
c
observations of the field sized around 4′ × 4′ centered at the host galaxy of the gamma-ray burst GRB021004 with the 6-m
BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We measured the magnitudes and
constructed the color diagrams for 311 galaxies detected in the field (S/N>3). The differential and integral counts of galaxies
up to the limit, corresponding to 28.5 (B), 28.0 (V), 27.0 (R
c
), 26.5 (I
c
) were computed. We compiled the galaxy catalog, consisting of 183 objects, for which the photometric redshifts up to the
limiting magnitudes 26.0 (B), 25.5 (V), 25.0 (R
c
), 24.5 (I
c
) were determined using the HyperZ code. We then examined the radial distribution of galaxies based on the z estimates. We have built the curves expected in the case of a uniform distribution of galaxies in space, and obtained the
estimates for the size and contrast of the possible super-large-scale structures, which are accessible with the observations
of this type. 相似文献
995.
Munendra Singh Amit Kumar Singh Swati Nupur Srivastava Sandeep Singh A. K. Chowdhary 《Environmental Earth Sciences》2010,59(8):1703-1715
In the northern part of the Indian sub-continent, the Gomati River (a tributary of the Ganga River) was selected to study
the dynamics of Arsenic (As) mobilization in fluvial environment of the Ganga Plain. It is a 900-km-long, groundwater-fed,
low-gradient, alluvial river characterized by monsoon-controlled peaked discharge. Thirty-six water samples were collected
from the river and its tributaries at low discharge during winter and summer seasons and were analysed by ICP-MS. Dissolved
As and Fe concentrations were found in the range of 1.29–9.62 and 47.84–431.92 μg/L, respectively. Arsenic concentration in
the Gomati River water has been detected higher than in its tributaries water and characteristically increases in downstream,
attributed to the downstream increasing of Fe2O3 content, sedimentary organic carbon and silt-clay content in the river sediments. Significant correlation of determination
(r
2 = 0.68) was also observed between As and Fe concentrations in the river water. Arsenic concentrations in the river water
are likely to follow the seasonal temperature variation and reach the level of World Health Organization’s permissible limit
(10 μg/L) for drinking water in summer season. The Gomati River longitudinally develops reducing conditions after the monsoon
season that mobilize As into the river water. First, dissolved As enters into pore-water of the river bed sediments by the
reductive dissolution of Fe-oxides/hydroxides due to microbial degradation of sedimentary organic matter. Thereafter, it moves
upward as well as down slope into the river water column. Anthropogenically induced biogeochemical processes and tropical
climatic condition have been considered the responsible factors that favour the release of As in the fluvial environment of
the Ganga Plain. The present study can be considered as an environmental alarm for future as groundwater resources of the
Ganga–Brahmaputra Delta are seriously affecting the human–environment relationship at present. 相似文献
996.
A baseline study of trace metals in a coral reef sedimentary environment,Lakshadweep Archipelago 总被引:3,自引:1,他引:2
Anu Gopinath S. M. Nair N. C. Kumar K. V. Jayalakshmi D. Pamalal 《Environmental Earth Sciences》2010,59(6):1245-1266
Surficial and core samples collected from the sedimentary microenvironments of Lakshadweep Archipelago were analysed for their
trace metal contents. The synoptical relations in spatial distributions with respect to environmental conditions such as pH,
organic carbon and sediment texture were inter-correlated. Some of the metals exhibited good correlations with Fe/Mn, which
reflect their similarity in distribution rather than anthropogenic enrichment. Inter-relating the variations in metal—pH relationships
with metal—organic carbon, in general, those which exhibited positive correlations with pH, displayed negative interactions
with organic carbon content and vice versa. Comparatively, higher values of Fe in the mangrove area of one of the islands
highlight the possibility of precipitation of Fe as iron sulphides, which are common in mangrove ecosystem. Based on the contamination
factors for Pb, Zn and Cd, as well as the geo-accumulation index of Cd, it can be generalised that some of the islands remain
polluted with respect to these elements. An evaluation based on pollution load index shows that none of the islands surveyed
for this study posed a serious threat in trace metal pollution. Bray Curtis similarity index was computed to find out the
similarity among metals/islands, using non-transformed data of metal concentrations. Group linkage clustering technique was
used for drawing dendrograms to show the similarity among them. 相似文献
997.
Yongkang Xue Fernando De Sales W. K.-M. Lau Aaron Boone Jinming Feng Paul Dirmeyer Zhichang Guo Kyu-Myong Kim Akio Kitoh Vadlamani Kumar Isabelle Poccard-Leclercq Natalie Mahowald Wilfran Moufouma-Okia Phillip Pegion David P. Rowell Jae Schemm Siegfried D. Schubert Andrea Sealy Wassila M. Thiaw Augustin Vintzileos Steven F. Williams Man-Li C. Wu 《Climate Dynamics》2010,35(1):3-27
This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models’ (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among models in simulating spatial correlation, intensity, and variance of precipitation compared with observations. Furthermore, the majority of models fail to produce proper intensities of the African Easterly Jet (AEJ) and the tropical easterly jet. AMMA Land Surface Model Intercomparison Project (ALMIP) data are used to analyze the association between simulated surface processes and the WAM and to investigate the WAM mechanism. It has been identified that the spatial distributions of surface sensible heat flux, surface temperature, and moisture convergence are closely associated with the simulated spatial distribution of precipitation; while surface latent heat flux is closely associated with the AEJ and contributes to divergence in AEJ simulation. Common empirical orthogonal functions (CEOF) analysis is applied to characterize the WAM precipitation evolution and has identified a major WAM precipitation mode and two temperature modes (Sahara mode and Sahel mode). Results indicate that the WAMME models produce reasonable temporal evolutions of major CEOF modes but have deficiencies/uncertainties in producing variances explained by major modes. Furthermore, the CEOF analysis shows that WAM precipitation evolution is closely related to the enhanced Sahara mode and the weakened Sahel mode, supporting the evidence revealed in the analysis using ALMIP data. An analysis of variability of CEOF modes suggests that the Sahara mode leads the WAM evolution, and divergence in simulating this mode contributes to discrepancies in the precipitation simulation. 相似文献
998.
S. Abhilash K. Mohankumar S. Shankar Das K. Kishore Kumar 《Meteorology and Atmospheric Physics》2010,109(3-4):73-90
This study examines the time–height variation and structure of a tropical mesoscale convective system (TMCS). Convection experiments using VHF (53 MHz) radar aimed at improving the understanding of the vertical structure of TMCS occurred over Gadanki (13.5°N, 79.2°E), India during 21–22 June 2000 has been selected for the study. The time–height variations of reflectivity and vertical velocity exhibits four distinct patterns and have been used to classify four subjectively identified types of echoes; viz., formative, mature, transition zone and stratiform regions associated with TMCS. Average vertical velocity profiles were distinctive for each region. The mean vertical motion is upward at all levels in the troposphere during the formative phase. The vertical motion in the mature region is downward in the lower troposphere and upward in the middle and upper troposphere. The maximum upward motion is found in the middle troposphere and secondary maxima near the tropopause level. The transition zone is characterized by strong downdraft in the lower troposphere with local pockets of updrafts in the middle and upper troposphere. The magnitude of the mean vertical motion is considerably reduced in the stratiform region and is downward in the lower troposphere and upward in the upper troposphere. Time–height variation of reflectivity has been analyzed separately for each region. The observed diminished echo zone and tropopause break/weakening during the mature phase and two enhanced reflectivity zone in the stratiform region is also observed. A Cloud System Resolving Model (CSRM) simulation of the same event has been carried out. The CSRM simulations were able to capture the structure of the storm and are consistent with the observations. The model output in conjunction with observations has been used to validate the hypothesis. 相似文献
999.
K. H. V. Durga Rao V. Bhanumurthy P. S. Roy 《Journal of the Indian Society of Remote Sensing》2009,37(4):587-600
Hydrological modelling of large river catchments is a challenging task for water resources engineers due to its complexity
in collecting and handling of both spatial and non-spatial data such as rainfall, gauge discharges, and topographic parameters.
In this paper an attempt has been made to use satellite-based rainfall products such as Climatic Prediction Centre (CPC)-National
Oceanic and Atmospheric Administration (NOAA) data for hydrological modelling of larger catchment where the limited field
rainfall data is available. Digital Elevation Models (DEM) such as Global DEM (1 km resolution) and Shuttle Radar Topography
Mission (SRTM) 3-arc second (90 m resolution) DEM have been used to extract topographic parameters of the basin for hydrological
modelling of the study area. Various popular distributed models have been used in this study for computing excess rainfall,
direct runoff from each sub-basin, and flow routing to the main outlet. The Brahmaputra basin, which is very complex both
hydraulically and hydrologically due to its shape, size, and geographical location, has been examined as study area in this
study. A landuse map derived from the satellite remote sensing data in conjunction with DEM and soil textural maps have been
used to derive various basin and channel characteristics such as each sub-basin and channel slope, roughness coefficients,
lag-time. Percentage of residual flows computed between observed flows and simulated flows using Global and SRTM DEMs are
discussed. It is found that the topographic parameters computed using SRTM DEM could improve the model accuracy in computing
flood hydrograph. Need of using better resolution satellite data products and the use of high-density field discharge observations
is discussed. 相似文献
1000.
Provenance studies of anomalously high-flux layers of ice-rafted detritus (IRD) in North Atlantic sediments of the last glacial cycle show evidence for massive iceberg discharges coming from the Hudson Strait region of the Laurentide Ice Sheet (LIS). Although these so-called Heinrich events (H events) are commonly thought to be associated with abrupt drawdown of the LIS interior, uncertainties remain regarding the sector(s) of this multi-domed ice sheet that conveyed ice through Hudson Strait. In Northern Québec and Labrador (NQL), large-scale patterns of glacial lineations indicate massive ice flows towards Ungava Bay and Hudson Strait that could reflect the participation of the Labrador–Québec ice dome in H events. Here we evaluate this hypothesis by constraining the source of NQL glacial deposits, which provide an estimate of the provenance characteristics of IRD originating from this sector. Specifically, we use 40Ar/39Ar ages of detrital hornblende grains in 25 till samples distributed along a latitudinal transect (lat. 58°) extending east and west of Ungava Bay. The data show that tills located west and southwest of the Ungava Bay region are largely dominated by hornblende grains with Archean ages (>2.6 Ga), while tills located east of Ungava Bay are characterized by grains with early Paleoproterozoic ages (2.0–1.8 Ga), although most samples contain a few Archean-age grains. IRD derived from the NQL region should thus be characterized by a large proportion of Archean-age detrital grains, which contrasts significantly with the predominant Paleoproterozoic 40Ar/39Ar ages (1.8–1.6 Ga) typically reported for the dominant age population of hornblende grains in H layers. Comparisons with IRD through the last glacial cycle from a western North Atlantic core off Newfoundland do not show evidence for any prominent ice-rafted event with the provenance characteristics of NQL glacial deposits, thereby suggesting that significant ice-calving event(s) from the Labrador–Québec sector may have been limited throughout that interval. Although these results tend to point towards a relative stability of this ice dome during H events, our study also indicates that further provenance work is required on IRD proximal to the Hudson Strait mouth in order to constrain with a greater confidence the sector(s) of the LIS that fed ice into Hudson Strait during H events. Alternatively, these results and other paleogeographic considerations tend to support models suggesting that part of the Ungava Bay glacial lineations could be associated with a Late-Glacial ice flow across Hudson Strait. 相似文献