Assimilation of the multisatellite data into the WRF model for track and intensity simulation of the Indian Ocean tropical cyclones

Weather Research and Forecasting (WRF-ARW) model and its three-dimensional variational data assimilation (3D-Var) system are used to investigate the impact of the Quick Scatterometer (QuikSCAT) near surface winds, Special Sensor Microwave/Imager (SSM/I)-derived Total Precipitable Water (TPW), and Meteosat-7-derived Atmospheric Motion Vectors (AMVs) on the track and intensity prediction of tropical cyclones over the North Indian Ocean. The case of tropical cyclone, Gonu (June 2007; Arabian Sea), is first tested and the results show significant improvements particularly due to the assimilation of QuikSCAT winds. Three other cases, cyclone Mala (April 2006; Bay of Bengal), Orissa super cyclone (October 1999; Bay of Bengal), and Very Severe Cyclonic storm (October 1999; Bay of Bengal), are then examined. The prediction of cyclone tracks improved significantly with the assimilation of QuikSCAT winds. The track improvement resulted from the relocation of the initial cyclonic vortices after the assimilation of QuikSCAT wind vectors. After the assimilation of QuikSCAT winds, the mean (for four cyclone cases) track errors for first, second, and third day forecasts are reduced to 72, 101, and 166?km, respectively, from 190, 250, and 381?km of control (without QuikSCAT winds) runs. The assimilation of QuikSCAT winds also shows positive impact on the intensity (in terms of maximum surface level winds) prediction particularly for those cyclones, which are at their initial stages of the developments at the time of data assimilation. The assimilation of SSM/I TPW has significant influence (negative and positive) on the cyclone track. In three of the four cases, the assimilation of the SSM/I TPW resulted in drying of lower troposphere over cyclonic region. This decrease of moisture in TPW assimilation experiment resulted in reduction of cyclonic intensity. In three of the four cyclones, the assimilation of Meteosat-7 AMVs shows negative impact on the track prediction.     

A novel Seahorse-shaped,small-scale structure from Almora Crystalline Zone,Uttarakhand, India

International Journal of Earth Sciences -     

Water Quality Assessment Using Physicochemical and Bacteriological Parameters of Fateh Sagar Lake,Udaipur, India

In the present study assessment of physicochemical and bacteriological parameters of Lake Fateh Sagar of Udaipur (Rajasthan), India was done. Water samples were collected during different seasons for analysis of physicochemical parameters such as pH, temperature, total alkalinity, total hardness, dissolved oxygen, biological oxygen demand and chemical oxygen demand. In addition, the bacteriological analysis like total bacterial and coliform count was detected. Incidences of Escherichia coli and their antibiotic resistance pattern were analyzed, which is the major microbiological indicator of faecal contamination. The values of some physicochemical and many of the bacteriological parameters were found above the permissible limits for drinking water recommended by World Health Organization. E. coli isolates were identified by morphological, biochemical and molecular characteristics using E. coli specific 16S rRNA gene based primers namely 16E1, 16E2 and 16E3 and universal primers namely 27F and 1492R by PCR. It was found that most of E. coli strains were strongly resistant to kanamycin, ampicillin, cefixime, polymyxin B, penicillin, vancomycin, rifampicin and streptomycin. The study of water quality is of significant value because the drinking water supply of the city is dependent on this lake and present study indicated that the lake water is polluted with reference to these analyzed parameters.     

Finite volume model for reactive transport in fractured porous media with distance- and time-dependent dispersion

Abstract

There are very few studies of fractured porous media that use distance- and time-dependent dispersion models, and, to the best of our knowledge, none which compare these with constant dispersion models. Therefore, in this study, the behaviour of temporal and spatial concentration profiles with distance- and time-dependent dispersion models is investigated. A hybrid finite volume method is used to solve the governing equations for these dispersion models. The developed numerical model is used to study the effects of matrix diffusion coefficient, groundwater velocity and matrix and fracture retardation factor on concentration profiles in the application of constant, distance-dependent and time-dependent dispersion models. In addition, an attempt is made to evaluate the applicability of these dispersion models by using the models to simulate experimental data. It was found that a better fit to the observed data is obtained in the case of distance- and time-dependent dispersion models as compared to the constant dispersion model. Thus, these numerical experiments indicate that distance- and time-dependent dispersion models have better simulation potential than the constant dispersion model.     

Corrigendum to“Characterization of partial melting events in garnet-cordierite gneiss from the Kerala Khondalite Belt,India”[Geosci.Front.11(2020),597-611]

The sample location in our paper(Sorcar et al.,2020)was incorrectly marked in Fig.1,although the GPS location was reported correctly.The corrected sample location of garnet-cordierite gneiss is shown in Fig.1.The sample location falls within the Achankovil Shear Zone(ASZ)and not in the Trivandrum Block as stated in our paper.Thus,the Tonian ultrahigh-temperature(UHT)metamorphic event reported in our paper is applicable to ASZ,and not for the Trivandrum Block.The related discussion on Gondwana correlation in our paper may be viewed and read in that context.     

Internal waves over the shelf in the western Bay of Bengal: a case study

Generation and propagation of internal waves (IWs) in the coastal waters of the extended shelf of the western Bay of Bengal are investigated for late winter by using the Massachusetts Institute of Technology General Circulation Model (MITgcm). The model is forced with astronomical tides and daily winds. Monthly climatological temperature and salinity fields are used as initial conditions. The simulations are compared with time series observations of temperature and currents from acoustic Doppler current profiler (ADCP) and conductivity-temperature-depth (CTD) moored at three locations south of Gopalpur: two at a local depth of 100 m and another at 400-m depth during 19–21 February 2012. The comparison of the spectral estimates for the time series of temperature from the model and observations are in reasonable agreement for the near-tidal frequency waves. The peak of temperature spectra is always found near the shelf break region which steadily lost its intensity over the continental shelf. The calculation of Richardson number reflected the presence of local mixing due to density overturning in the shelf region. To understand further the generation and propagation of internal tides in the region, energy flux and conversion of barotropic-to-baroclinic M₂ tidal energy are examined. The model simulations suggest that the internal tide is generated all along the shelf slope. The energy flux analysis shows that the internal tides propagate to either side of the generation sites.     

Poroelastic Modeling of a Heterogeneous Geologic Medium: A Case Study from Kanto Basin in Japan

Vertical geological heterogeneity, such as clay content and grain size variation, may affect land subsidence caused by groundwater extraction. In order to test this hypothesis, one-dimensional pore-water mass balance and force balance equations of a water-saturated poroelastic medium were solved under different heterogeneous geological conditions. Results showed that clay content and grain size variation in sandstone could affect subsidence rates by up to an order of magnitude due to the changes in stiffness and permeability of the medium, indicating the importance of small-scale heterogeneity in subsidence simulation studies. Predicted values of subsidence were in good agreement with field measurements for two sites in the Kanto groundwater basin in Japan, showing the applicability of the model to other groundwater basins with clay-rich aquifers.     

Dynamic response analysis of tube array in partially filled calandria

An efficient procedure is presented for dynamic response analysis of horizontal tube array in partially filled calandria including hydrodynamic interaction effects. The procedure is general enough to consider the transfer of energy between the fluid-coupled tubes, and effects of moderator sloshing on the magnitude and the distribution of hydrodynamic forces. It has been demonstrated that the conventional added mass approach fails to represent behaviour of the tube array correctly, and it is therefore necessary to consider the flexibility of all the tubes along two directions simultaneously. The procedure presented can simulate the added damping effects due to hydrodynamic interaction. The possible use of a tuned damper tube is suggested for controlling sloshing effects for tube array in a calandria where tube frequencies and sloshing frequencies are closely spaced. The presence of surface damping in the tuned tube further brings down the response, and the suggested procedure can be effectively used to control unwarranted sloshing effects. Copyright © 1999 John Wiley & Sons, Ltd.     

Provenances of possible turbidites and volcanoclastic sediments in the northern part of Narcondam-Barren Basin,Andaman Sea

Turbidity currents are marine avalanches consisting of dilute mixture of sediment and water. These deposits are known as turbidite deposits or turbidites. Seismo-turidites are indicative of submarine landslide caused due to ground shaking associated with great earthquake. Evidence for turbidite and volcanic deposits is observed on subsurface sediments from a gravity core collected at a water depth of 1689 m in the northern part of Narcondam-Barren Basin, Andaman Sea during the present study. To constrain the mode of sediment transport, global bathymetric model (GBM) data was used to generate digital bathymetric model (DBM). The bathymetric model shows two active channels: one in Martaban Canyon, along Sagaing Fault (drainage A), and the second one in the western part (drainage B). The moderately sinuous nature with channel-levee system of drainage B is also identified in high-resolution MBES grid model. Coarse fraction (+230 ASTM) studies of the core reveal the presence of multiple sand layers at different levels. SEM-EDAX and electron probe microanalysis (EPMA) studies confirmed subangular quartz-rich layers at 114–116 and 166–169 cm with transparent nature and subrounded amphibole-rich layer at 151–155 cm. The source of these anomalous sand layers observed in the core is from the outer shelf relict sand. These relict sand brought to the Narcondam-Barren Basin by drainage B, which formed by slumping/sliding material in the outer Ayeyarwady shelf induced by ground shaking/earthquake. Geochemical studies show a low Ca/Fe ratio and high Sr values in GC-01 where there is a high terrigenous percentage which implies a seismo-turbidite deposit. On the other hand, the geochemical studies clearly show that pumice at 25–40 cm is volcanic derivatives during Holocene. Since some of the mega-scale slumps are tsunamigenic, such studies are significant to locate submarine slump/slides.     

Early prediction of onset of south west monsoon from ERS-1 scatterometer winds

Detailed analysis of the surface winds over the Indian Ocean derived from ERS-1 scatterometer data during the years 1993 and 1994 has been used to understand and unambiguously identify the onset phase of south-west monsoon. Five day (pentad) averaged wind vectors for the period April to June during both years have been examined to study the exact reversal of wind direction as well as the increase in wind speed over the Arabian Sea in relation to the onset of monsoon over the Indian west coast (Kerala). The related upper level humidity available from other satellites has also been analysed. The results of our analysis clearly show a consistent dramatic reversal in wind direction over the western Arabian Sea three weeks in advance of the onset of monsoon. The wind speed shows a large increase coinciding with the onset of monsoon. These findings together show the dominant role of sea surface winds in establishing the monsoon circulation. The study confirms that the cross equatorial current phenomenon becomes more important after the onset of monsoon.