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1.
Santanu Kumar Bhowmik 《Journal of Earth System Science》1997,106(3):131-146
A suite of rocks from Borra Carbonate Granulite Complex (BCGC) in the Eastern Ghats granulite belt displays superposed structures
and overprinted mineral assemblages that reveal multiple episodes of tectonothermal reworking of the complex under granulite
facies condition. Five distinct episodes of deformation (D1, D2, D3, D4 and D5) and four phases of metamorphism (M1, M2, M3 and M4) are recorded. The signature of the earliest tectonothermal event, D1 is a gneissic foliation (S1) denned by segregation of peak granulite facies mineral assemblages corresponding to prograde M1 metamorphism. M2 metamorphic overprint represents an episode of near-isobaric cooling of the complex under a static condition. D2 represents an episode of ductile deformation manifested by isoclinal folding (F2) and associated extensional structures, within a broad framework of coaxial bulk deformation. The present study reveals that
D2 took place subsequent to M2 - Subsequent deformation, D3, produced F3 folds and also deformations of boudins formed during D2. M3, which is synchronous with F3, represents a near isothermal decompression of the BCGC. This was followed by a weak structural readjustment (D4), producing E-W cross folds. The latter was not, however, associated with any recognizable petrological reworking. In the
terminal events, deformation (D5) and mineral reactions (M4) were localized along narrow intersecting shear zones. The latter acted as channelways for carbonic and still later hydrous
fluid infiltration. The available thermobarometric data from BCGC and other areas of the Eastern Ghats belt reveal that reworking
during M2 and M3 ensued in a thermally perturbed regime. The high thermal regime might also have persisted during carbonic fluid infiltration
related to terminal reworking (M4). 相似文献
2.
Kevin Stanley L. Kurt Kreuger Priyasree Bhowmik Narjes Shojaati Alexa Elliott 《International journal of geographical information science》2016,30(9):1853-1872
ABSTRACTIn the past decade society has entered a technological period characterized by handheld computing that supports input and processing from numerous sensors. Today’s mobile phones offer the ability to integrate input from sensors monitoring various external and internal sources (e.g., accelerometer, magnetometer, microphone, GPS, wireless Internet, and Bluetooth). Furthermore, these raw inputs can be integrated and processed in ways that can offer novel representations of human behaviour. As a result, new opportunities to examine and better understand human spatial behaviour are available; one such application is the constant monitoring of a group of people over an extended period of time. Such a research setting lends itself to natural experiments that emerge as a result of regular and on-going observations. We report here on the observation of a natural experiment that took place in the context of a month-long monitoring study of 28 participants using mobile phone-based ubiquitous sensor monitoring. The implications for public health and transportation planning are discussed. 相似文献
3.
Summary The study provides a concise and synthesized documentation of the current level of skill of the operational NWP model of India
Meteorological Department based on daily 24 hours forecast run of the model during two normal monsoon years 2001 and 2003
making detailed inter-comparison with daily rainfall analysis from the use of high dense land rain gauge observations. The
study shows that the model, in general, is able to capture three regions of climatologically heavy rainfall domains along
Western Ghats, Northeast India and over east central India, over the domain of monsoon trough. However, the accuracy in prediction
of location and magnitude of rainfall fluctuates considerably. The inter-comparison reveals that performance of the model
rainfall forecast deteriorated in 2003 when rainfall over most parts of the region was significantly under-predicted. These
features are also reflected in the error statistics. The study suggests that there is a need to maximize the data ingest in
the model with a better data assimilation scheme to improve the rainfall forecast skill. 相似文献
4.
Soma Sen Roy Subhendu Brata Saha S. K. Roy Bhowmik P. K. Kundu 《Meteorology and Atmospheric Physics》2014,124(3-4):143-166
Nowcasting in the India Meteorological Department (IMD) is being provided for T + 0 to T + 2 h, using the Warning Decision Support System (WDSS-II) software. Prior to operational nowcasting over the Indian region, the parameters of the nowcast algorithm tool of the software were optimized, and accuracy was evaluated for various weather systems over Delhi. This optimization is demonstrated in this study with reference to three weather systems over Delhi, with each case representing one of three typical types of cloud systems over the region. These are—(a) convective lines associated with winter and early pre-monsoon weather systems, (b) deep convective cells that form in the pre-monsoon (April–June) and post-monsoon season (October–November) and (c) wide convective echoes that form during the monsoon season. The efficacy of the algorithm was assessed on a frame-by-frame basis as well as holistically for entire convective episodes. The important findings of the frame-by-frame study are (1) the inability of the inbuilt growth-decay algorithm to capture the evolution of storm cells, (2) setting of the threshold of detection of storms and tracking storms and (3) number of scales through which storms should be tracked. The holistic capabilities of the nowcast algorithm were tested for entire convective episodes using Model Evaluation Tools software. The results indicate that the advection algorithm tends to move the convective areas faster than observed at all time scales. Hence the multi-scale segmentation approach (over the two-scale approach) increases the smoothening of the output, at the cost of decreased nowcast skill. The inter-event comparison indicates that the low-intensity convective line zones, which are characteristic of winter and early pre-monsoon weather systems, have the most rapid temporal change in the overall area under convection. This leads to larger area errors during nowcasting of these systems. On the other hand, pre-monsoon systems comprised mostly isolated cells that reach great heights and move very fast, but do not have much horizontal area growth. The error in the nowcasting of these systems is mostly in respect of location error, as well as error in forecast of the intensity of the cells. The overall error in nowcasting is least for the monsoon systems over the Delhi region. 相似文献
5.
S D Kotal S K Bhattacharya S K Roy Bhowmik P K Kundu 《Journal of Earth System Science》2014,123(7):1637-1652
An objective NWP-based cyclone prediction system (CPS) was implemented for the operational cyclone forecasting work over the Indian seas. The method comprises of five forecast components, namely (a) Cyclone Genesis Potential Parameter (GPP), (b) Multi-Model Ensemble (MME) technique for cyclone track prediction, (c) cyclone intensity prediction, (d) rapid intensification, and (e) predicting decaying intensity after the landfall. GPP is derived based on dynamical and thermodynamical parameters from the model output of IMD operational Global Forecast System. The MME technique for the cyclone track prediction is based on multiple linear regression technique. The predictor selected for the MME are forecast latitude and longitude positions of cyclone at 12-hr intervals up to 120 hours forecasts from five NWP models namely, IMD-GFS, IMD-WRF, NCEP-GFS, UKMO, and JMA. A statistical cyclone intensity prediction (SCIP) model for predicting 12 hourly cyclone intensity (up to 72 hours) is developed applying multiple linear regression technique. Various dynamical and thermodynamical parameters as predictors are derived from the model outputs of IMD operational Global Forecast System and these parameters are also used for the prediction of rapid intensification. For forecast of inland wind after the landfall of a cyclone, an empirical technique is developed. This paper briefly describes the forecast system CPS and evaluates the performance skill for two recent cyclones Viyaru (non-intensifying) and Phailin (rapid intensifying), converse in nature in terms of track and intensity formed over Bay of Bengal in 2013. The evaluation of performance shows that the GPP analysis at early stages of development of a low pressure system indicated the potential of the system for further intensification. The 12-hourly track forecast by MME, intensity forecast by SCIP model and rapid intensification forecasts are found to be consistent and very useful to the operational forecasters. The error statistics of the decay model shows that the model was able to predict the decaying intensity after landfall with reasonable accuracy. The performance statistics demonstrates the potential of the system for improving operational cyclone forecast service over the Indian seas. 相似文献
6.
Md.?Shahjahan Md.?Farajul?Kabir Kizar?Ahmed?Sumon Lipi?Rani?Bhowmik Harunur?RashidEmail author 《中国海洋湖沼学报》2017,35(1):109-114
Sumithion is widely used to control brittle in paddy fields and tiger bug in fish larval rearing ponds. The objective of this study was to elucidate the toxic effects of sumithion on larval stages of stinging catfish Heteropneustes fossilis. Larvae were exposed to two concentrations (150 and 250 μg/L) of sumithion with one control in three replicates of each. Larvae samples were collected at 20- and 24-h intervals followed by observation under a digital microscope. Exposures of stinging catfish larvae to sumithion produced deformities including irregular head shape, lordosis, yolk sac edema, body arcuation, tissue ulceration, etc. The mortality rates of larvae were significantly increased in response to increase in sumithion concentrations. Furthermore, around 30% of the total adult stinging catfish reared in sumithiontreated aquaculture ponds were found to be deformed permanently. These findings highlight that exposure of stinging catfish to sumithion at the critical and sensitive stages in their life cycle may significantly reduce the number of returning adults. Therefore, the use of sumithion for crop protection needs to be considered carefully and alternatives to sumithion should to be developed for controlling aquatic insects in aqua-ponds during larval rearing. 相似文献
7.
A dynamical statistical method is applied for operational forecasting of the Bay of Bengal tropical cyclone “Nargis” of April–May 2008. The method consists of three forecast components, namely (a) analysis of Genesis Potential Parameter (GPP) and maximum potential intensity, (b) track prediction, and (c) 12 hourly intensity prediction for forecasts up to 72 hours. The results of the study showed that GPP could provide necessary predictive signal at early stages of development on the further intensification of the low pressure system into a tropical cyclone. The landfall forecast position errors by different operational numerical models (NWP) showed landfall position errors ranging from 10 km to 150 km and landfall time error ranges from 6 hours early to 6 hours delay. The dynamical statistical model is capable to provide 12 hourly nearly realistic intensity forecasts up to 60 hours of forecast. 相似文献
8.
Joyjit Dey R Jayangonda Perumal Subham Sarkar Anamitra Bhowmik 《Journal of Earth System Science》2017,126(6):83
In the NW Sub-Himalayan frontal thrust belt in India, seismic interpretation of subsurface geometry of the Kangra and Dehradun re-entrant mismatch with the previously proposed models. These procedures lack direct quantitative measurement on the seismic profile required for subsurface structural architecture. Here we use a predictive angular function for establishing quantitative geometric relationships between fault and fold shapes with ‘Distance–displacement method’ (D–d method). It is a prognostic straightforward mechanism to probe the possible structural network from a seismic profile. Two seismic profiles Kangra-2 and Kangra-4 of Kangra re-entrant, Himachal Pradesh (India), are investigated for the fault-related folds associated with the Balh and Paror anticlines. For Paror anticline, the final cut-off angle \(\beta =35{^{\circ }}\) was obtained by transforming the seismic time profile into depth profile to corroborate the interpreted structures. Also, the estimated shortening along the Jawalamukhi Thrust and Jhor Fault, lying between the Himalayan Frontal Thrust (HFT) and the Main Boundary Thrust (MBT) in the frontal fold-thrust belt, were found to be 6.06 and 0.25 km, respectively. Lastly, the geometric method of fold-fault relationship has been exercised to document the existence of a fault-bend fold above the Himalayan Frontal Thrust (HFT). Measurement of shortening along the fault plane is employed as an ancillary tool to prove the multi-bending geometry of the blind thrust of the Dehradun re-entrant. 相似文献
9.
Sayantan Bhowmik Cesar A. Mantilla Sanjay Srinivasan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(8):1085-1090
Tracking the migration of the CO2 plume is essential in order to better manage the operation of geologic sequestration of CO2. However, the large cost of most monitoring technologies, such as time-lapse seismic, limits their application. We investigated
the application of a probabilistic history matching methodology using routine measurements of injection data, which are affected
by the presence of large-scale heterogeneities, as an inexpensive alternative to track the migration of CO2 plume in an aquifer. The approach is demonstrated first through a synthetic example in which the ability to detect the presence
of flow barriers was tested. In a second example, we applied our method to the In Salah field, one of the largest geological
sequestration projects in the world, where the main direction of high permeability features was inferred. The accuracy and
reproducibility of the results show that our approach for assisted history matching is an economic and viable option for plume
monitoring during geologic CO2 sequestration. 相似文献
10.
In this paper, impact of Indian Doppler Weather Radar (DWR) data, i.e., reflectivity (Z), radial velocity (Vr) data individually and in combination has been examined for simulation of mesoscale features of a land-falling
cyclone with Advance Regional Prediction System (ARPS) Model at 9-km horizontal resolution. The radial velocity and reflectivity
observations from DWR station, Chennai (lat. 13.0°N and long. 80.0°E), are assimilated using the ARPS Data Assimilation System
(ADAS) and cloud analysis scheme of the model. The case selected for this study is the Bay of Bengal tropical cyclone NISHA
of 27–28 November 2008. The study shows that the ARPS model with the assimilation of radial wind and reflectivity observations
of DWR, Chennai, could simulate mesoscale characteristics, such as number of cells, spiral rain band structure, location of
the center and strengthening of the lower tropospheric winds associated with the land-falling cyclone NISHA. The evolution
of 850 hPa wind field super-imposed vorticity reveals that the forecast is improved in terms of the magnitude and direction
of lower tropospheric wind, time, and location of cyclone in the experiment when both radial wind and reflectivity observations
are used. With the assimilation of both radial wind and reflectivity observations, model could reproduce the rainfall pattern
in a more realistic way. The results of this study are found to be very promising toward improving the short-range mesoscale
forecasts. 相似文献