Search

This study aims to identify distinct small-scale temporary patterns between the river discharge and suspended sediment load for the main tropical rivers using continuous wavelet transform. Strong annual and irregular semi-annual variabilities, with few quarterly and interdecadal variabilities, are observed in river discharge and sediment load. The wavelet coherence reveals that the strongest in-phase coherence relationships exist between total suspended sediment and streamflow. The methodology for identifying the primary climate factors that integrate the partial wavelet coherence (PWC), multiple wavelet coherence (MWC), and quadruple wavelet coherence (QMWC) techniques is presented. The results show that the El-Nino/Southern Oscillation (ENSO) is the major regulator of streamflow followed by Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). The chosen rivers show a statistically significant ($p \le 0.05$p≤0.05) descending trend in sediment load but no significant positive or negative trend in river discharge. This could be due to regional sediment storage and large-scale stream events affecting the sediment transport dynamics. [ABSTRACT FROM AUTHOR]

In this paper, formation of a double layer (DL) is studied in the background plasma (considering only electrons and ions) in the presence of a magnetic field in the context of the Rf operated beam source in India for negative ion research negative ion source by using 2D-3V particle-in-cell Monte Carlo collision kinetic simulations. A rectangular geometry to model the source, expansion, and magnetic filter regions in the negative ion source is considered in the XY plane. A Gaussian shaped magnetic field is applied in the Z-direction (perpendicular to the simulation plane), and a bias voltage is applied on the extraction boundary. Our simulations show the presence of instabilities as reported in the literature. We confirm the formation of a weak DL in the magnetic filter region under some specific combinations of the magnetic field and bias voltage. Initiation of DL leads to ion acceleration in the magnetic filter region. Split in ion velocities is also visible in the phase space plots due to the presence of free and trapped ions in the DL region. Our study highlights the effect of DL on plasma transport, which should be taken into account when interpreting the experimental observations associated with E × B plasma based negative ion sources. [ABSTRACT FROM AUTHOR]

North Indian Ocean witnesses varied dynamical response due to independent climate modes such as Indian Ocean Dipole (IOD)/El Niño Southern Oscillations (ENSO) and their co-occurrences. These modes have a significant impact on ocean productivity, which in turn shows feedback for the strengthening of these patterns. Keeping this in view, the present work attempts to analyze the biological activity during the combined influence of positive IOD with El Niño during 2006–2007 event. To divulge the biological variability along with the dynamical response, the study includes intra-annual variability surface chlorophyll anomaly with D20 anomaly using satellite observations. Here, the individual role of IOD and ENSO on both surface chlorophyll and D20 is segregated through partial regression analysis for a period of 25 years (1993–2017). By the regression method, it can be seen varied chlorophyll response for the 2006–2007 event with the IOD forcing leads to the major spatial and temporal variability with positive anomalies in Eastern Equatorial Indian Ocean (EEIO) (generally oligotrophic), Northwestern Bay of Bengal (NWBoB), and Northwestern Arabian Sea (NAS2) where production begins in fall intermonsoon and peaks up during November. On the other hand, negative anomalies are observed around the southern tip of India (SBoB) and the Northern Arabian Sea (NAS1). While ENSO depicts the high surface chlorophyll variability in the Western Indian Ocean (WIO1, WIO2) with negative anomalies of surface chlorophyll. This study observed an asymmetric response of chlorophyll variability over the North Indian Ocean during the 1997–1998 and 2006–2007 events with a major influence of IOD mode compared with the El Niño. Therefore, understanding the chlorophyll anomalies during different climate modes will help us to better understand the interannual variability and improve the predictability of chlorophyll productivity regions. [ABSTRACT FROM AUTHOR]

The western boundary current in the Bay of Bengal, also known as East India Coastal Current, is northward (southward) and continuous during pre‐ (post‐) Indian Summer Monsoon (ISM) but discontinuous during ISM (June–September). This study investigates the features of this discontinuity and role of eddies, local winds, and southern open boundary lateral forcing using AVISO TOPEX Poseidon, ERS, and Jason1 combined sea surface height anomaly, Ocean Surface Current Analysis Real‐time (OSCAR) surface currents and high‐resolution Regional Ocean Modelling System simulations. The study shows that the discontinuity is governed by westward and southwestward propagating eddies between two opposite facing flows along the boundary, northward of 10°N and southward of 21°N. This northward flow of 10°N is wind driven with lateral influence during September. The southward flow of 21°N is influenced by the Summer Monsoon Current, but the local wind influence starts from July onward. During ISM, about 79% cyclonic and 77% anticyclonic eddies move westward, while 68% cyclonic and 69% anticyclonic eddies move southward. Three highly active eddy genesis areas, having more than 50% activities during ISM, are identified: northern and southwestern bay for cyclonic and off Visakhapatnam (17.68°N, 83.21°E) coast for anticyclonic eddies. The pre‐ISM (post‐ISM) is dominated by anticyclonic (cyclonic) eddies, which are found across the western Bay of Bengal and away from northward (southward) East India Coastal Current. The ISM is dominated by westward and southwestward moving both cyclonic and anticyclonic eddies, which are confined to the boundary, where discontinuity is generally observed. Plain Language Summary: The western boundary current in Bay of Bengal, which is also known as East India Coastal Current, flows northward during February–May and southward during October–December. During Indian Summer Monsoon period (June–September), the boundary current is not consistent and various cyclonic and anticyclonic eddies are generated in the western Bay of Bengal. This study investigates the features of this disorganized boundary currents and the role of eddies, local winds, and southern boundary in making the currents disorganized using measurements and high‐resolution numerical model simulations. The study is important to understand the changes in upper ocean dynamics associated with the inconsistent flow and to assess the contribution of the above said forcings to trigger such inconsistency. The study can further be used to understand the discontinuity induced ocean mixing, upwelling, sea level variability, and energy distribution along the western boundary of Bay of Bengal. Key Points: The discontinuity features are more pronounced along the western boundaryThe discontinuity is governed by westward and southwestward propagating eddies along the boundary between two opposite flows of 10°N and 21°NLocal winds and southern boundary lateral forcing have significant roles in the boundary current discontinuity [ABSTRACT FROM AUTHOR]

Forecasting the Indian summer monsoon is a challenging task due to its complex and nonlinear behavior. A large number of global climatic variables with varying interaction patterns over years influence monsoon. Various statistical and neural prediction models have been proposed for forecasting monsoon, but many of them fail to capture variability over years. The skill of predictor variables of monsoon also evolves over time. In this article, we propose a joint-clustering of monsoon years and predictors for understanding and predicting the monsoon. This is achieved by subspace clustering algorithm. It groups the years based on prevailing global climatic condition using statistical clustering technique and subsequently for each such group it identifies significant climatic predictor variables which assist in better prediction. Prediction model is designed to frame individual cluster using random forest of regression tree. Prediction of aggregate and regional monsoon is attempted. Mean absolute error of 5.2% is obtained for forecasting aggregate Indian summer monsoon. Errors in predicting the regional monsoons are also comparable in comparison to the high variation of regional precipitation. Proposed joint-clustering based ensemble model is observed to be superior to existing monsoon prediction models and it also surpasses general nonclustering based prediction models. [ABSTRACT FROM AUTHOR]

Indian monsoon is an important climatic phenomenon and a global climatic marker. Both statistical and numerical prediction schemes for Indian monsoon have been widely studied in literature. Statistical schemes are mainly based on regression or neural networks. However, the variability of monsoon is significant over the years and a single model is often inadequate. Meteorologists revise their models on different years based on prevailing global climatic incidents like El-Niño. These indices often have degree of severity associated with them. In this paper, we cluster the monsoon years based on their fuzzy degree of associativity to these climatic event patterns. Next, we develop individual prediction models for the year clusters. A weighted ensemble of these individual models is used to obtain the final forecast. The proposed method performs competitively with existing forecast models. [ABSTRACT FROM AUTHOR]

Movement of seasonal eddies in the Bay of Bengal (BOB) and its relation with cyclonic heat potential (CHP) and cyclogenesis points have been investigated in this study using 6 years (2002-2007) of global ocean monthly analysis datasets based on the Simple Ocean Data Assimilation (SODA) package (SODA v2.0.4) of Carton et al. () and Indian Meteorological Department cyclogenesis points. The region dominated by anticyclonic eddies with CHP greater than 70 × 10 J/m as well as good correlations (>0.9) with sea surface height (SSH) and 26°C isothermal depth ( D) can be a potential region of cyclogenesis. The region dominated by cyclonic eddies with CHP greater than 50 × 10 J/m and good correlation (>0.9) with both SSH and D can serve as a potential region of high-level depression. Potential cyclogenesis regions are the southern BOB (5°N-12°N) for the post-monsoon season and the head of BOB (north of 15°N) during southwest monsoon. Seven potential regions are identified for the eddy formation for different seasons, which are consistent with the cyclogenesis points. The CHP distributions alone are able to explain the cyclone tracks for the pre-monsoon and post-monsoon seasons but not for the monsoon season. [ABSTRACT FROM AUTHOR]

The Bay of Bengal circulation features have been analyzed using a three-dimensional Ocean General Circulation Model (OGCM). The northward propagation of eastern boundary coastal Kelvin wave and its movement throughout the entire Bay is evident from the study. The trapping of Kelvin waves in the central Bay for many months causes warming of the central basin, which acts as a potential breeding ground of cyclones. The seasonal variations of circulation, temperature, and salinity have been reproduced by the model. These variations compare favorably with observations. The existence of a salt finger towards north and its eastward movement are two important results of the study. The cyclonic gyres in the Bay of Bengal during different months agree reasonably well with the SeaWiFS chlorophyll observations and indicate the upwelling zones over the basin. The presence of a subsurface Bay-of-Bengal dipole in summer monsoon months is another important result of the study. [ABSTRACT FROM AUTHOR]

This study attempts to investigate the simulation of heavy precipitation events (HPEs) over the West Coast of India associated with atmospheric rivers (ARs) using the Advanced Research Weather Research and Forecasting (ARW-WRF) model. The study evaluates the sensitivity of five microphysical (Lin, WSM6, Goddard, Thompson, and Morrison) and cumulus (KF, BMJ, Grell3D, Tidtke, and GD) parameterization schemes to explore the capability to reproduce the AR associated HPEs. The model simulations were reasonably successful at reproducing key structural and synoptic characteristics of atmospheric rivers, including well-defined corridors of strong water vapor transport, meteorological variables and circulation features. Deviations in Rainfall and Wind profiles were observed in simulations among the different parameterization schemes. The model better simulated the AR related precipitation using the Lin, Thompson MP and KF, Grell3D CU schemes when compared to observations, and attributed to the moisture laden tendency of the schemes. Nonetheless, differences in precipitation distribution and overestimation of winds among the model runs using different microphysical and cumulus physics schemes were noted. The study highlights that simulation of AR associated HPEs using high-resolution mesoscale mode with suitable representations of physical parameterization schemes are useful for disaster management and to minimize the loss of fatalities and property. • Atmospheric rivers (ARs) are linked to the occurrence of heavy precipitation events (HPEs) over West Coast of India. • WRF simulations well represented the key features characteristic of observed AR events. • Sensitivity studied to MP (Lin, WSM6, Goddard, Thompson, Morrison) and CU (KF, BMJ, Grell3D, Tidtke, GD) schemes. • The combination of different model MP and CU schemes reasonably simulated the ARs associated with HPEs. • Lin, Thompson MP and KF, Grell3D CU schemes are better simulated over the other schemes. [ABSTRACT FROM AUTHOR]

The changing climate may adversely affect crop production unless appropriate adaptation strategies are used. The appropriate level of fertilization and sowing dates are some of the simple and most economic but effective strategies which can be developed and applied for specific climatic regions. Keeping the aforesaid fact in mind, varying sowing dates were analyzed as a strategic adaptation to cope with the climate change for maize yield in Eastern India under rainfed and irrigated conditions. Evaluation of sowing dates was performed by the CERES-maize model for estimating the maize yield for the projected time periods 2021–2050 (2050s), and 2051–2080 (2080s) by using different Representative Concentration Pathways (RCP) 2.6, 4.5, 6.0, and 8.5 W m-2 respectively from the 17 Global circulation models (GCM) of CMIP5 (Coupled Model Intercomparison Project Phase 5) climate projection scenarios, and the results projected were compared with the baseline scenario of 1982–2012. The results indicated that the effect of late sowing dates (30 June and 10 July) was more in RCPs 6.0, and 8.5 for both the time periods 2050s and 2080s as during the tasseling stage the intensity of solar radiation decreased, while for the recommended (20 June), and earlier sowing (30 May and 10 June) dates reduced grain yield was recorded for the rainfed condition due to higher temperature stress. In irrigated conditions, the recommended sowing date (15 January) was suitable for time slice 2050s in all the RCP scenarios, while the earlier sowing date (25 December) was found to be suitable in the time slice period of 2080s with RCP 8.5. Thus, shifting sowing dates can be an effective management strategy to cope with climate change with less waste and efficient use of resources. [Display omitted] • Shifting sowing dates is most economical way to decrease climate change impact. • Sowing date 20 Jun was more effective in all RCP scenarios of CMIP5 in rainfed. • Sowing date 30 May was effective in RCP 8.5 in 2080s of CMIP5 in rainfed. • Sowing date 25 Dec was effective for both time period in all RCPs in irrigated. • Holistic approach in crop modelling leads to waste reduction and balanced economy. [ABSTRACT FROM AUTHOR]

• Climate change impact evaluation was done under different RCP Scenarios. • T max affects the maize yield more than the T min for elevated CO 2 levels. • Maize yield was reduced with increasing RCP for irrigated maize. • Dry matter increased with increasing RCP for irrigated and vice versa in rainfed. Global climate change can harm the food production globally by varying intensity and frequency of rainfall, occurrence of extreme weather and increment in greenhouse gases. Increased occurrence of extreme climate events results in greater variability of agricultural production. In this study, the climate change impact evaluation was done by using CERES-maize model for maize yield and yield attributes for the projected time periods 2021–2050, and 2051–2080 by using different Representative Concentration Pathways (RCP) 2.6, 4.5, 6.0, and 8.5 W/m2 respectively for eastern India, and the projected results were compared with the baseline scenario of 1982–2012. On comparison with the baseline (1982–2012) results, the change in yield recorded was −10.58%, −14.80%, −21.02%, and −23.39% respectively for the time slice 2021–2050, and −15.20%, −18.54%, −24.75%, and −26.83% respectively for the time slice 2051–2080 for irrigated condition. But, in rainfed condition, the change in yield recorded was higher of 10.55%, 9.20%, 8.13%, and 7.47% respectively with the time slice 2021–2050, while 10.63%, 6.65%, 7.47%, and 4.31% for the time slice 2051–2080. Study indicates the loss of grain yield is more for time period of 2051–2080 rather than the time period 2021–2050 under irrigated condition in comparison to the baseline yield, while in rainfed condition, the grain yield increased in both the time periods 2021–2050, and 2051–2080 which indicates that the increase in rainfall reduced the negative impact of temperature on the crop yield. [ABSTRACT FROM AUTHOR]

Urban heat island (UHI) phenomena is among the major consequences of the alteration of earth's surface due to human activities. The relatively warmer temperatures in urban areas compared to suburban areas (i.e. UHI) has potential health hazards, such as mortality due to high temperatures and heat waves. In addition, UHI situation demands more energy (e.g. fans and air-conditioners) that would trigger greenhouse gas emissions. Studies on UHI intensity help to assess its impact on urban population, city planning, and urban health planning. This is particularly important for a country like India, where 32% people (~7% of total world population), live in urban areas. We conducted a detailed study on surface UHI intensity (SUHII), which is the difference between urban and surrounding rural land surface temperatures, across all seasons in 44 major cities of India, which shows that mean daytime SUHII is positive (up to 2 °C) for most cities, as analysed from satellite temperature measurements for the period 2000–2017, in contrast to previous studies. However, although statistically insignificant, most cities show a positive trend in SUHII for monsoon and post-monsoon periods, but negative for winter and summer seasons. The increasing night-time SUHII in all seasons for most cities suggest increasing trend in temperature in cities due to the impact of the rapid urbanisation, and thus, suggesting the influence of anthropogenic forcing on SUHII. This is also supported by the analysis of aerosols, night lights, precipitation and vegetation in the study regions. Therefore, this study shall aid planning and management of urban areas by giving insights about the effects of nature and intensity of development, land cover and land use mix and the structure of cities on SUHII. Image 1 • Long-term (18 years) analysis of SUHII for 44 major Indian cities. • Positive SUHII observed during day and night for most cities. • Vegetation plays a key role in determining the daytime SUHII. • Signatures of anthropogenic activities in altering the SUHII analysed. [ABSTRACT FROM AUTHOR]

Indian Test Facility (INTF) is being built in Institute For Plasma Research to characterize Diagnostic Neutral Beam in co-operation with ITER Organization. INTF is a complex system which consists of several plant systems like beam source, gas feed, vacuum, cryogenics, high voltage power supplies, high power RF generators, mechanical systems and diagnostics systems. Out of these, several INTF components are ITER deliverable, that is, beam source, beam line components and power supplies. To ensure successful operation of INTF involving integrated operation of all the constituent plant systems a matured Data Acquisition and Control System (DACS) is required. The INTF DACS is based on CODAC platform following on PCDH (Plant Control Design Handbook) guidelines. The experimental phases involve application of HV power supplies (100 KV) and High RF power (∼800 KW) which will produce energetic beam of maximum power 6MW within the facility for longer durations. Hence the entire facility will be exposed tohigh heat fluxes and RF radiations. To ensure investment protection and to provide occupational safety for working personnel a matured Safety and Interlock system is required for INTF. The Safety and Interlock systems are high-reliability I&C systems devoted completely to the specific functions. These systems will be separate from the conventional DACS of INTF which will handle the conventional control and acquisition functions. Both, the Safety and Interlock systems are based on IEC 61511 and IEC 61508 standards as prescribed by the ITER PCDH guidelines. [ABSTRACT FROM AUTHOR]

The Indian Test Facility (INTF) – a negative hydrogen ion based 100 kV, 60 A, 5 Hz modulated NBI system having 3 s ON/20 s OFF duty cycle. Prime objective of the facility is to install a full-scale test bed for the qualification of all Diagnostic Neutral Beam (DNB) parameters, prior to installation in ITER. The automated and safe operation of the INTF will require a reliable and rugged instrumentation and control system which provide control, data acquisition (DAQ), interlock and safety functions, referred as INTF-DACS. The INTF-DACS has been decided to be design based on the ITER CODAC architecture and ITER-PCDH guidelines since the technical understanding of CODAC technology gained from this will later be helpful in development of plant system I&C for DNB. For complete operation of the INTF, approximately 900 numbers of signals are required to be superintending by the DACS. In INTF conventional control loop time required is within the range of 5–100 ms and for DAQ except high-end diagnostics, required sampling rates in range of 5 sample per second (Sps) to 10 kSps; to fulfill these requirements hardware components have been selected from the ITER slow and fast controller catalogs. For high-end diagnostics required sampling rates up to 100 MSps normally in case of certain events, therefore event and burst based DAQ hardware has been finalized. Combined use of CODAC core software (CCS) and NI-LabVIEW has been finalized due to the fact that full required DAQ support is not available in present version of CCS. Interlock system for investment protection of facility and Safety system for occupational safety of the involved personal, are under design as per ITER-PCDH recommendations, which are based on IEC 61508 standard. This paper described the detail design of INTF DACS based on ITER-PCDH guidelines. [ABSTRACT FROM AUTHOR]

Abstract: The RF based single driver −ve ion source experiment test bed ROBIN (Replica Of BATMAN like source in INDIA) has been set up at Institute for Plasma Research (IPR), India in a technical collaboration with IPP, Garching, Germany. A hydrogen plasma of density 5×1012 cm−3 is expected in driver region of ROBIN by launching 100kW RF power into the driver by 1MHz RF generator. The cesiated source is expected to deliver a hydrogen negative ion beam of 10A at 35kV with a current density of 35mA/cm2 as observed in BATMAN. In first phase operation of the ROBIN ion source, a hydrogen plasma has been successfully generated (without extraction system) by coupling 80kW RF input power through a matching network with high power factor (cos θ >0.8) and different plasma parameters have been measured using Langmuir probes and emission spectroscopy. The plasma density of 2.5×1011 cm−3 has been measured in the extraction region of ROBIN. For negative hydrogen ion beam extraction in second phase operation, extraction system has been assembled and installed with ion source on the vacuum vessel. The source shall be first operated in volume mode for negative ion beam extraction. The commissioning of the source with high voltage power supply has been initiated. [Copyright &y& Elsevier]

Cities are becoming hotter day-by-day because heat is trapped near the earth's surface due to a decrease in green cover, rapid urbanization, energy-intensity activities, and concrete structures. The four major metropolitan cities of India, i.e. Kolkata, Chennai, Delhi and Mumbai, have experienced heat waves and heat stress frequently during the summer season. This study analyses heat wave and heat stress patterns in these cities using 30 years of data from 1990 to 2019 during the summer season. We used daily maximum temperature, relative humidity, wind speed and solar radiation datasets for the above mentioned period in this study. To understand the episode of a heat wave, we have used the 95th percentile method. Furthermore, we have also used Humidity Index (HD) to evaluate the degree of discomfort and the Universal Thermal Climate Index (UTCI) to categorize the level of heat stress. The analysis indicates that the number of heat wave events in the Delhi region is 26.31%, 31.58% and 63.16% higher than Kolkata, Chennai, and Mumbai regions respectively. It is also seen that the risks of extreme heat stress and dangerous-heat stroke events in the Chennai region during heat wave periods are higher than that experienced in other metropolitan cities because of high temperature with higher values of relative humidity. The risk of extreme heat stress is less in Delhi because of lower relative humidity compared to other metropolitan cities although temperature is higher in this region. However, the risk of extreme heat stress is lower in Mumbai region because of relatively lower temperature than Chennai during summer season. The likelihood of experiencing great discomfort during heat wave periods in Kolkata city is higher than that experienced in other metropolitan cities in India, however, during non-heat wave periods the probability of extreme discomfort is higher in Chennai., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

North Indian Ocean witnesses varied dynamical response due to independent climate modes such as Indian Ocean Dipole (IOD)/El Niño Southern Oscillations (ENSO) and their co-occurrences. These modes have a significant impact on ocean productivity, which in turn shows feedback for the strengthening of these patterns. Keeping this in view, the present work attempts to analyze the biological activity during the combined influence of positive IOD with El Niño during 2006-2007 event. To divulge the biological variability along with the dynamical response, the study includes intra-annual variability surface chlorophyll anomaly with D20 anomaly using satellite observations. Here, the individual role of IOD and ENSO on both surface chlorophyll and D20 is segregated through partial regression analysis for a period of 25 years (1993-2017). By the regression method, it can be seen varied chlorophyll response for the 2006-2007 event with the IOD forcing leads to the major spatial and temporal variability with positive anomalies in Eastern Equatorial Indian Ocean (EEIO) (generally oligotrophic), Northwestern Bay of Bengal (NWBoB), and Northwestern Arabian Sea (NAS2) where production begins in fall intermonsoon and peaks up during November. On the other hand, negative anomalies are observed around the southern tip of India (SBoB) and the Northern Arabian Sea (NAS1). While ENSO depicts the high surface chlorophyll variability in the Western Indian Ocean (WIO1, WIO2) with negative anomalies of surface chlorophyll. This study observed an asymmetric response of chlorophyll variability over the North Indian Ocean during the 1997-1998 and 2006-2007 events with a major influence of IOD mode compared with the El Niño. Therefore, understanding the chlorophyll anomalies during different climate modes will help us to better understand the interannual variability and improve the predictability of chlorophyll productivity regions.