Triggering of earthquakes at Koyna,India and hammer drilling for the pilot borehole     

Madugula  Uma Anuradha  Rekapalli  Rajesh  Sudheer  K.  Jagadeesh  P.  Satyanarayana  H. V. S. 《Natural Hazards》2021,109(1):1191-1199

Natural Hazards - Koyna located near the West Coast of India is an outstanding case of artificial water reservoir-triggered seismicity. It is observed that annually earthquakes get triggered in the...  相似文献   

Wavelet-ANFIS models for forecasting monsoon flows: Case study for the Gandak River (India)   总被引：2，自引：0，他引：2  

Rajeev Ranjan Sahay  Vinit Sehgal 《Water Resources》2014,41(5):574-582

WANFIS, a conjunction model of discreet wavelet transform (DWT) and adaptive neuro-fuzzy inference system (ANFIS) was developed for forecasting the current-day flow in a river when only available data are historical flows. Discreet wavelet transform decomposed the observed flow time series (OFTS) into wavelet components which captured useful information on three resolution levels. A smoothened flow time series (SFTS) was formed by filtering out the noise wavelet components and recombining the effective wavelet components. WANFIS model is essentially an ANFIS model with SFTS hydrograph as the input, while ANFIS and autoregression (AR) models, developed for comparison purpose, use OFTS hydrograph as input. For performance evaluation, the developed models were utilized for predicting daily monsoon flows for the Gandak River in Bihar state of India. During monsoon (June–October), this river carries large flows making the entire North Bihar unsafe for habitation or cultivation. Based on various performance indices, it was concluded that WANFIS models simulate the monsoon flows in the Gandak more reliably than ANFIS and AR models. The best performing WANFIS model, with four previous days’ flows as input, predicted the current-day Gandak flows with 80.7% accuracy while ANFIS and AR models predicted it with only 71.8 and 51.2% accuracies.  相似文献   

Impact of doubled CO2 on the interaction between the global and regional water cycles in four study regions     

Zhao Li  Uma S. Bhatt  Nicole Mölders 《Climate Dynamics》2008,30(2-3):255-275

Results from a suite of 30-year simulations (after spin-up) of the fully coupled Community Climate System Model version 2.0.1 are analyzed to examine the impact of doubling CO₂ on interactions between the global water cycle and the regional water cycles of four similar-size, but hydrologically and thermally different study regions (the Yukon, Ob, St Lawrence, and Colorado river basins and their adjacent land). A heuristic evaluation based on published climatological data shows that the model generally produces acceptable results for the control 1× CO₂ concentration, except for mountainous regions where it performs like other modern climate models. After doubling CO₂, the Northern Hemisphere receives significantly (95% confidence level) more moisture from the Southern Hemisphere during the boreal summer than under 1× CO₂ conditions, and the phase of the annual cycle of net moisture transport to areas north of 60°N shifts to a month later than in the reference simulation. Precipitation and evapotranspiration in the doubled CO₂ simulation increase for the Yukon, Ob, and St Lawrence, but decrease, on average, for the Colorado region compared to the reference simulation. For all regions, interaction between global and regional water cycles increases under doubled CO₂, because the amount of moisture entering and leaving the regions increases in the warmer climate. The degree of change in this interaction depends on region and season, and is related to slight shifts in the position/strength of semi-permanent highs and lows for the Yukon, Ob, and St Lawrence; in the Colorado region, higher temperatures associated with doubling CO₂ and the anticyclone located over the region increase the persistence of dry conditions.  相似文献   

Role of nonlinear localized structures and turbulence in magnetized plasma     

Neha Pathak  Nitin Yadav  R. Uma  R. P. Sharma 《Astrophysics and Space Science》2016,361(9):287

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Deriving Crop Phenology Metrics and Their Trends Using Times Series NOAA-AVHRR NDVI Data     

Vinay Kumar Sehgal  Surabhi Jain  Pramod Kumar Aggarwal  Somnath Jha 《Journal of the Indian Society of Remote Sensing》2011,39(3):373-381

In this study, an attempt has been made to derive the spatial patterns of temporal trends in phenology metrics and productivity of crops grown, at disaggregated level in Indo-Gangetic Plains of India (IGP), which are helpful in understanding the impact of climatic, ecological and socio-economic drivers. The NOAA-AVHRR NDVI PAL dataset from 1981 to 2001 was stacked as per the crop year and subjected to Savitzky-Golay filtering. For crop pixels, maximum and minimum values of normalized difference vegetation index (NDVI), their time of occurrence and total duration of kharif (June-October) and rabi (November–April) crop seasons were derived for each crop year and later subjected to pixel-wise regression with time to derive the rate and direction of change. The maximum NDVI value showed increasing trends across IGP during both kharif and rabi seasons indicating a general increase in productivity of crops. The trends in time of occurrence of peak NDVI during kharif dominated with rice showed that the maximum vegetative growth stage was happening early with time during study period across most of Punjab, North Haryana, Parts of Central and East Uttar Pradesh and some parts of Bihar and West Bengal. Only central parts of Haryana showed a delay in occurrence of maximum vegetative stage with time. During rabi, no significant trends in occurrence of peak NDVI were observed in most of Punjab and Haryana except in South Punjab and North Haryana where early occurrence of peak NDVI with time was observed. Most parts of Central and Eastern Uttar Pradesh, North Bihar and West Bengal showed a delay in occurrence of peak NDVI with time. In general, the rice dominating system was showing an increase in duration with time in Punjab, Haryana, Western Uttar Pradesh, Central Uttar Pradesh and South Bihar whereas in some parts of North Bihar and West Bengal a decrease in the duration with time was also observed. During rabi season, except Punjab, the wheat dominating system was showing a decreasing trend in crop duration with time.  相似文献   

Hydraulic conductivity of shallow sandy aquifers: Effects of sedimentologic and diagenetic differences     

K. O. Uma  E. P. Loehnert 《Environmental Geology》1994,23(3):171-181

The relationship between values of hydraulic conductivity determined from grain-size methods,K _gr, and those from pumping-test methods,K _pt, have been evaluated statistically using data from recent and older sandy materials. It is shown that both methods generally give the same values only in recent sediments that have not been subjected to significant diagenetic alteration and give variable results in older and diagenetically altered sediments. The ratioK _pt/K_gr appears to vary, probably in response to the degree of diagenetic alteration. It is further found that methods incorporating the effects of grain size (d1O or d50) and sorting could give betterK values than those incorporating the effect of grain-size only and, thus, suggest the joint inclusion of both parameters in the grain-size determination of permeability.  相似文献   

Trends and Change-Point in Satellite Derived Phenology Parameters in Major Wheat Growing Regions of North India During the Last Three Decades     

Debasish Chakraborty  Vinay Kumar Sehgal  Rajkumar Dhakar  Deb Kumar Das  Rabi Narayan Sahoo 《Journal of the Indian Society of Remote Sensing》2018,46(1):59-68

The virtual certainty of the anticipated climate change will continue to raise many questions about its aggregated impact of environmental changes on our regional food security in imminent future. Crop responses to these changes are certain, but its exact characteristics are hardly understood at regional scale due to complex overlapping effects of climate change and anthropogenic manipulation of agro-ecosystem. This study derived phenology of wheat in north India from satellite data and analyzed trends of phenology parameters over last three decades. The most striking change-point period in phenology trends were also derived. The phenology was derived from two sources: (1) STAR-Global vegetation Health Products-NDVI, and (2) GIMMS-NDVI. The results revealed significant earliness in start of growing season (SOS) in Punjab and Haryana while delay was found in Uttar Pradesh (UP). End of the wheat season almost always occurred early, to even those place where SOS was delayed. Length of growing season increased in most of Punjab and northern Haryana whereas its decrease dominated in UP. The early sowing practice of the farmers of the Punjab and Haryana may be one of the adaptation strategies to manage the terminal heat stress in reproductive stage of the crop in the region. The change-point occurred in late 1990s (1998–2000) in Punjab and Haryana, while in eastern UP it was in early 1990s (1990–1995). Despite the difference in temporal aggregation and spatial resolution, both the datasets yielded similar trends, confirming both the robustness of the results and applicability of the datasets over the region. The results demands further research for proper attribution of the effects into its causes and may help devising crop adaption practices to climatic stresses.  相似文献   

Remote Sensing-Based Yield Forecasting for Sugarcane (<Emphasis Type="Italic">Saccharum officinarum</Emphasis> L.) Crop in India     

S. K. Dubey  A. S. Gavli  S. K. Yadav  Seema Sehgal  S. S. Ray 《Journal of the Indian Society of Remote Sensing》2018,46(11):1823-1833

Early yield assessment at local, regional and national scales is a major requirement for various users such as agriculture planners, policy makers, crop insurance companies and researchers. This current study explored a remote sensing-based approach of predicting sugarcane yield, at district level, using Vegetation Condition Index (VCI), under the FASAL programme of the Ministry of Agriculture & Farmers’ Welfare. 13-years’ historical database (2003–2015) of NDVI was used to derive the VCI. NDVI products (MOD-13A2) of MODIS instrument on board Terra satellite at 16-day interval from first fortnight of June to second fortnight of October (peak growing period) were used to calculate the VCI. Stepwise regression technique was used to develop empirical models between VCI and historical yield of sugarcane over 52 major sugarcane-growing districts in five states of India. For all the districts, the empirical models were found to be statistically significant. A large number of statistical parameters were computed to evaluate the performance of VCI-based models in predicting district-level sugarcane yield. Though there was variation in model performance in different states, overall, the study showed the usefulness of VCI, which can be used as an input for operational sugarcane yield forecasting.  相似文献   

Fluid flow related features as an indicator of potential gas hydrate zone: western continental margin of India     

Uma Shankar  N. K. Thakur  B. Ashalatha 《Marine Geophysical Researches》2006,27(3):217-224

Multichannel seismic reflection data from the continental margin of western India suggest the potential presence of fluid expulsion features, which may or may not be associated with gas hydrates. No typical bottom simulating reflector was observed on the reflection seismic section. As a result we look for other evidence in seismic sections in a small corridor of the western continental margin of India in order to establish the presence of gas hydrates. We study features including venting through the seafloor, pockmarks, sea floor collapse, faults acting as migration paths for fluid flow, transparent gas-charged sediment, reduction in amplitude strength, diapirism and mud-volcano. Presence of all these gas-escape features on a seismic section implies the probable presence of methane within the zone of hydrate stability field.  相似文献   

“Man and Biosphere” — Studies on the Sikkim Himalayas. Part 4: Effects of Chelating Agent EDTA on the Acute Toxicity of Copper and Zinc on Tadpoles of the Frog Rana hexadactyla     

B. S. Khangarot  Atam Sehgal  M. K. Bhasin 《洁净——土壤、空气、水》1985,13(1):121-125

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