Numerical simulation of physical and dynamical characteristics associated with the severe thunderstorm on April 5, 2015 at Kushtia and Jhenaidah     

Samarendra Karmakar  Dewan Abdul Quadir  Mohan Kumar Das 《Natural Hazards》2017,86(3):1127-1146

The paper deals with the study of the physical and dynamical characteristics of a severe thunderstorm, which had occurred on April 5, 2015, at about 2100 UTC in the southwestern Bangladesh with location around 23.3–23.7N and 89.0–89.4E within the upazilas (sub-districts) of Kumarkhali and Shailkupa under the districts of Kushtia and Jhenaidah, respectively. The thunderstorm was associated with numerous hails of large size. More than 5000 birds which used to live in the bird sanctuary at Shailkupa and 22,011 birds in Chhaglapara Bird Sanctuary of Kumarkhali died as they were hit by the hails. Large hails also damaged crops, houses and forests over the thunderstorm hit areas. The evolution of the thunderstorm is studied by the WRF model, which is initialized using the National Centers for Environmental Prediction Final reanalysis data of 0000 UTC of April 5, 2015. The simulated results provide a basis to study the physical and dynamical characteristics of the thunderstorm, which are generally not identified by the meteorological observations which are too sparse. The model has captured a micro-low over Kumarkhali and its neighborhood, which favored the occurrence of the severe thunderstorm. The model simulated rainfall is about 26 mm near the place of occurrence, which matches well with the area where the reflectivity of hydrometeor is maximum. The convective available potential energy is found to be 1600 J kg^?1 at 1730 UTC near the place of occurrence of the thunderstorm; this indicates high atmospheric instability over the thunderstorm location for the formation of the thunderstorm. The vertical velocity, convergence, cloud water mixing ratio and the ice water mixing ratio and their vertical extensions are found to be satisfactory and responsible for the occurrence of large hails associated with the thunderstorm.  相似文献   

Trace gases and PM2.5-bound metal abundance over a tropical urban environment,South India     

M  Abdul Shukkur  V.G  Gopikrishna  N.G  Vishnu  Mohan  Mahesh 《Journal of Atmospheric Chemistry》2021,78(3):193-208

Pre and Post-Monsoon levels of ambient SO₂, NO₂, PM_2.5 and the trace metals Fe, Cu, etc. were measured at industrial and residential regions of the Kochi urban area in South India for a period of two years. The mean PM_2.5, SO₂ and NO₂ concentrations across all sites were 38.98?±?1.38 µg/m³, 2.78?±?0.85 µg/m³ and 11.90?±?4.68 µg/m³ respectively, which is lower than many other Indian cities. There was little difference in any on the measured species between the seasons. A few sites exceeded the NAAQS (define acronym and state standard) and most of the sites exceeded WHO (define acronym and state standard) standard for PM_2.5. The average trace metal concentrations (ng/m³) were found to be Fe (32.58)?>?Zn (31.93)?>?Ni (10.13)?>?Cr (5.48)?>?Pb (5.37)?>?Cu (3.24). The maximum concentration of trace metals except Pb were reported in industrial areas. The enrichment factor, of metals relative to crustal material, indicated anthropogenic dominance over natural sources for the trace metal concentration in Kochi’s atmosphere. This work demonstrates the importance of air quality monitoring in this area.

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Possible evidence of remotely triggered and delayed seismicity due to the 2001 Bhuj earthquake (Mw?=?7.6) in western India     

G. Surve  G. Mohan 《Natural Hazards》2012,64(1):299-310

Remote triggering by large earthquakes at regional distances is a globally observed phenomenon. However, there are no reports of observations of dynamic triggering at regional distances of several source lengths associated with the large Mw?=?7.6 Bhuj earthquake of January 26, 2001, in western India. In the present study, a swarm of over 140 microearthquakes that occurred about 500?km southeast of Bhuj, in the geothermal province of the Western Ghats in the Deccan volcanic province (DVP) of India, immediately after the occurrence of the Bhuj earthquake in 2001 is investigated. The post-Bhuj seismicity (M?<?2.0) occurred in three bursts spread over 2?months with each burst of intense activity lasting for 2?C3?days. All the three bursts of seismicity occurred in the same volume along a 5-km-long NW?CSE trending fault. The temporal coincidence and the sudden rise in seismicity that interrupts the characteristically low background seismicity strongly suggest that the Bhuj earthquake may have remotely triggered this activity. The triggered seismicity began approximately 2.5?h after the onset of the Bhuj mainshock and continued well after the passage of the surface waves, suggesting that the dynamic stresses possibly gave rise to secondary time-dependent mechanisms leading to the triggering. It is proposed that the triggered and delayed seismicity is possibly a consequence of the redistribution in pore fluid pressure due to the Bhuj earthquake. This is the first documented observation of remotely triggered seismicity at regional distances due to the Bhuj earthquake.  相似文献   

Assessment of heavy metal pollution in lake sediments of Katedan Industrial Development Area,Hyderabad, India     

P. K. Govil  J. E. Sorlie  D. Sujatha  A. K. Krishna  N. N. Murthy  K. Rama Mohan 《Environmental Earth Sciences》2012,66(1):121-128

Spatial distribution and temporal trends studies were carried out at Katedan Industrial Development Area (KIDA) near Hyderabad, capital of Andhra Pradesh state, India under Indo-Norwegian Institutional Cooperation Program, to find out the extent of contamination in streams and lake sediments from the discharge of industrial effluents. Stream and lake sediment samples were collected from the five lakes in the study area and connecting water streams. The samples were analyzed by XRF spectrometer for toxic elements. The studies reveal that the stream sediments with in the KIDA and the impounded Noor Mohammed Lake down stream have high concentration of some of the toxic elements like chromium, nickel, lead, arsenic, zinc etc. The geology of the area indicates that the study area consists of residual soil of acidic rocks, which are predominantly of Archaean gneisses and granites having low to medium concentrations of chromium and nickel. The source of these high concentration of elements like lead 2,300 mg/kg, copper 1,500 mg/kg, arsenic 500 mg/kg, chromium 500 mg/kg etc. cannot be derived from the surrounding acidic rocks and may be attributed to the industrial effluents released in the ditches and random dumping of hazardous solid waste. It was observed that the metal concentrations increased in the streams during the dry season (pre-monsoon period). After the monsoon rains, the metal concentrations in the streams were reduced by half which may be due to dilution. The eroded sediments are deposited in the lake where very high concentrations were encountered. Overflowing of the lake will spread the contamination further downstream. The lake sediments will remain as a major source of contamination by desorption to the water phase regardless of what happens to the effluent discharge in the KIDA. However, some samples showed enrichment of lead, arsenic and nickel during post-monsoon, which were collected near the dumpsite due to the leaching of toxic elements from the dump site to the lakes. Some of the toxic elements like nickel and copper have not shown any dilution but have increased after the rains, which could be due to the leaching of arsenic from the dumpsite to the lake along with rainwater. Geochemical maps showing the distribution of heavy/trace elements in streams and lakes are prepared and presented in this paper. Effect of toxic elements on the health of the residents in the surrounding residential areas is also discussed.  相似文献   

Spatial Metrics to Analyse the Impact of Regional Factors on Pattern of Urbanisation in Gurgaon,India     

Sadhana Jain  Divyani Kohli  Ram Mohan Rao  Wietske Bijker 《Journal of the Indian Society of Remote Sensing》2011,39(2):203-212

In recent years, there has been lot of emphasis on the study of urban land use/ land cover changes to discover the growth pattern due to rapid urbanisation. This study presents spatial metrics and gradient analysis approach for quantifying and capturing changes in urban landscape using LISS III imagery of 1999, 2001 and 2004 of Gurgaon, India. A combination of spatial metrics i.e. percentage of landscape, mean patch size, number of patches, landscape shape index and largest patch index, available in Fragstats ver. 3.3, have been used to quantify the patterns of urban growth in different directions in terms of size, shape and complexity of development. The local built-up areas were quantified by the “moving window” technique. A gradient analysis has been carried out through sampling from a reference point to 8 km in 16 directions with a window size of 500 mts. Results of this study demonstrate the potential of spatial metrics and gradient modelling to quantify the impact of regional factors on the growth pattern of Gurgaon city.  相似文献   

Effects of monsoonal rainfall on waste dump stability and respective geo-environmental issues: a case study   总被引：1，自引：1，他引：0  

Mohan Yellishetty  William J. Darlington 《Environmental Earth Sciences》2011,63(6):1169-1177

The stability of mine waste dumps is of critical importance and an issue, the mining industry of Goa, India is continually facing. The State of Goa receives high rainfall of around 3,000 mm annually. This heavy monsoonal rainfall is often believed to be the cause of dump slope instability. In light of several dump collapses encountered in the State and their damaging effects on both mine operations and local geo-environmental conditions, this paper examines their stability considering various geotechnical factors and the downstream environmental effects of a slope failure. The mechanical properties of dump waste material are reported at different compaction levels. The effect of these properties and changes in pore-water pressure are specifically examined using limit equilibrium analysis. An empirical formula is developed relating dump height, material mechanical parameters and pore-water pressure to the factor of safety of the slope. It was found that the level of compaction experienced by the material had a significant effect on the factor of safety.  相似文献   

Velocity of ground water percolation at Indaram, Godavari sub-basin, India     

Mohan L. Gupta  S. R. Sharma 《Journal of the Geological Society of India》2013,81(4):543-548

We present values of velocity of ground water percolation (Vg) over large depth intervals, varying from shallow to deeper depths in Indaram area of Godavari sub-basin. The velocities have been estimated using available measured geothermal data. Sub-surface temperatures were measured in seven boreholes. Terrestrial heat flow values are calculated using temperature data and measured values of thermal conductivity of core samples. The results show that Vg is ～3.4 ×10^?7 cm /sec in the top layers (70–150 m) and decreases to ～0.04×10^?7 cm/sec in the deeper levels around 350 m depth and becomes negligibly small thereafter, thereby, indicating that the overall permeability of the sub-surface layers, due to the occurrence of successions of permeable, semi-permeable layers gets reduced to more or less zero at depths around 350 m. The value of Thermal Peclet Number, which is the ratio of the heat transfer through convection to that through conduction, naturally becomes negligible around this depth in the area. The observed consistency of the magnitude of heat flow through various deep sections is a clear indicator that water percolation is practically reduced to zero at depths around 320–400 m and that conduction is the dominant mechanism of heat transfer below the inferred depth section, while the upper layers are dominated by recharge at various depths by near surface water from streams at Indaram.  相似文献   

Katol meteorite shower, Maharashtra: A preliminary study     

G. Suresh  S. H. Wankhade  Mohamed Shareef  Vivek P. Malviya  Binod Kumar  M. Mohan 《Journal of the Geological Society of India》2013,81(2):151-157

A meteorite shower occurred in Katol (21° 15′ 30″ N; 78° 35′ 00″ E; at an elevation of 415 m above msl), Nagpur district of Maharashtra state, India on May 22, 2012 between 14:00 to 14:30 hrs (Indian Standard Time) with a presently observed strewn field of ～5.0 sq km area. The event was experienced by the hundreds of inhabitants with a loud noise and fire ball between Akola in the west to Nagpur in the east. The Geological Survey of India has so far collected 27 meteorite pieces with a total weight of 3500 gm. The locations, size, shape and surface features of the individual meteorite pieces have been recorded. Based on their physical properties, mineralogy, mineral chemical mapping and REE chemistry, the Katol meteorites have been classified as olivine-rich H5 type differentiated stony meteorite with reconstituted chondrules. The preliminary evidence suggests the presence of pre-solar grains in Katol meteorite.  相似文献   

Hybrid attenuation model for estimation of peak ground accelerations in the Kutch region, India     

A. Joshi  Ashvini Kumar  K. Mohan  B. K. Rastogi 《Natural Hazards》2013,68(2):249-269

The Kutch region of Gujarat in India is the locale of one of the most devastating earthquake of magnitude (M _w) 7.7, which occurred on January 26, 2001. Though, the region is considered as seismically active region, very few strong motion records are available in this region. First part of this paper uses available data of strong motion earthquakes recorded in this region between 2006 and 2008 years to prepare attenuation relation. The developed attenuation relation is further used to prepare synthetic strong motion records of large magnitude earthquakes using semiempirical simulation technique. Semiempirical simulation technique uses attenuation relation to simulate strong ground motion records of any target earthquake. The database of peak ground acceleration obtained from simulated records is used together with database of peak ground acceleration obtained from observed record to develop following hybrid attenuation model of wide applicability in the Kutch region: $$ \begin{aligned} \ln \left( {\text{PGA}} \right) & = - 2.56 + 1.17 \, M_{\text{w}} - \, 0.015R - 0.0001\ln \left( {E + 15} \right) \\ &\quad 3.0 \le M_{\text{w}} \le 8.2;\quad 12 \le R \le 120;\quad {\text{std}} . {\text{ dev}}.(\sigma ): \pm 0.5 \\ \end{aligned} $$ ln ( PGA ) = ? 2.56 + 1.17 M w ? 0.015 R ? 0.0001 ln ( E + 15 ) 3.0 ≤ M w ≤ 8.2 ; 12 ≤ R ≤ 120 ; std . dev . ( σ ) : ± 0.5 In the above equation, PGA is maximum horizontal ground acceleration in gal, M _w is moment magnitude of earthquake, R is hypocentral distance, and E is epicentral distance in km. The standard deviation of residual of error in this relation is 0.5. This relation is compared with other available relations in this region, and it is seen that developed relation gives minimum root mean square error in comparison with observed and calculated peak ground acceleration from same data set. The applicability of developed relation is further checked by testing it with the observed peak ground acceleration from earthquakes of magnitude (M _w), 3.6, 4.0, 4.4, and 7.7, respectively, which are not included in the database used for regression analysis. The comparison demonstrates the efficacy of developed hybrid attenuation model for calculating peak ground acceleration values in the Kutch region.  相似文献   

Neoarchean suprasubduction zone arc magmatism in southern India: Geochemistry,zircon U-Pb geochronology and Hf isotopes of the Sittampundi Anorthosite Complex     

M. Ram Mohan  M. Satyanarayanan  M. Santosh  Paul J. Sylvester  Mike Tubrett  Rebecca Lam 《Gondwana Research》2013,23(2):539-557

The Sittampundi Anorthosite Complex (SAC) in southern India is one of the well exposed Archean layered anorthosite-gabbro-ultramafic rock associations. Here we present high precision geochemical data for the various units of SAC, coupled with zircon U-Pb geochronology and Hf isotopic data for the anorthosite. The zircon ages define two populations, the older yield a concordia age of 2541 ± 13 Ma, which is interpreted as the best estimate of the magmatic crystallization age for the Sittampundi anorthosite. A high-grade metamorphic event at 2461 ± 15 Ma is suggested by the upper intercept age of the younger zircon population. A Neoproterozoic event at 715 ± 180 Ma resulted in Pb loss from some of the metamorphic zircons. The magmatic age of the anorthosite correlates well with the timing of crystallization of the arc-related ~ 2530 Ma magmatic charnockites in the adjacent Salem Block, while the metamorphic age is synchronous with the regional metamorphic event. The geochemical data suggest that the rocks were derived from a depleted mantle source. Sub-arc mantle metasomatism of slab derived fluids and subsequent partial melting produced hydrous, aluminous basalt magma. The magma fractionated at depth to produce a variety of high-alumina basalt compositions, from which the anorthositic complex with its chromite-rich and amphibole-rich layers formed as cumulates within the magma chamber of a supra-subduction zone arc. The coherent initial¹⁷⁶Hf/¹⁷⁷Hf ratios and positive εHf values (1.7 – 4.5) of the magmatic zircons in the anorthosite are consistent with derivation of a rather homogeneous juvenile parent magma from a depleted mantle source. Our study further confirms that the southern part of the Dharwar Craton was an active convergent margin during the Neoarchean with the generation and emplacement of suprasubduction zone arc magmas which played a significant role in continental growth.  相似文献