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In this study trend analysis and bias correction have been done for dry (January–May) and wet (June–September) seasons under two future climate period 2021–2050 and 2051–2080 with respect to the current climate period 1980–2012 in Eastern India. The different representative concentration pathways (RCPs) of 2.6, 4.5, 6.0, and 8.5 were used to assess the future trend of the study area. Results indicate that the increasing RCP increases temperature (maximum and minimum) in all regions due to higher radiative forces (4–8.5 W/m2) with respect to the baseline temperature during the period 2051–2080. Further, the bias-corrected rainfall has a declined trend with respect to baseline, and RCP’s values for both the time slices (2021–2050 and 2051–2080) showed less scattering in the amount of rainfall for the wet season in comparison to the dry season.

This paper discusses the upgraded data assimilation (DA) wave forecasting system at the Indian National Centre for Ocean Information Services (INCOIS). Significant wave height (SWH) observations from deep and shallow water buoys in the North Indian Ocean are incorporated into the assimilation system in conjunction with satellite observations from SARAL/AltiKa, Jason-3, Sentinel-3a, and Sentinel-3b. In deep water, satellite DA improved the SWH forecast by ~16%, and the inclusion of buoy observations enhanced it up to ~43% in the initial forecast hours. The impact of satellite DA persists throughout the forecast period of 5 days for swell height, with 11–27% improvement. Ingestion of buoy observations further improved it up to ~31.5% at the 3rdhr forecast. For the wind–sea height, buoy DA resulted in an improvement of 9–26% during the initial 12 hr. In general, the positive impact of buoy DA only lasts till the 30thhr forecast. In shallow water, the impact of satellite DA on SWH prediction is moderate, with positive improvements of 4–7.5%. Adding buoy observations significantly improved it to 10–40% in the initial 12 hr, especially for the low wave heights. Although the buoy DA improved the prediction of wave periods compared to the non-assimilated model, it tends to degrade the forecast compared to the model with satellite DA alone. This points to the limitation of the current assimilation approach in correcting the wave energy distribution in the background spectrum, particularly at higher frequencies.

ABSTRACTMadi was a category-2 cyclonic storm formed over the south-western Bay of Bengal (BoB) in December 2013. It formed on 6th December as a depression, and by 8thDecember it became a very severe cyclonic storm. Some unique features of Madi were: (a) an unexpected reduction in the intensity during its north-westward movement, (b) sudden change in track by almost 180oin a south-westerly direction, and (c) swift dissipation in the open ocean while moving over cold-core eddies during its south-westward movement. The rapid weakening in intensity before track reversal occurred mainly due to its passage over cold-core eddies, where the upper-ocean heat content was reduced due to eddy-pumping of cold water from the subsurface. An analysis of the eddy-feedback factor reiterated that the slower movement of the cyclone was due to the cold-core eddy. When the cyclone entered into the cold-core eddy region, it slowed-down and changed its track towards a south-westerly direction under the influence of prevailing north-easterly winds. The biogeochemical response of Madi estimated using the satellite remote sensing and Bio Argo data showed an increase in Chlorophyll-a(Chl-a) concentration from 0.2-0.4–2.7 mg/m3, while the net primary productivity (NPP) increased from 320 to 2500 mg C/m2/day, both of which were about 7 and 8 times respectively higher than the before-cyclone values. The CO2flux showed a 4 times increase from its pre-cyclone value of 3.5 mmol/m2/day, indicating that BoB becomes a strong source to the atmosphere during the cyclone Madi period.

ABSTRACTThis study investigates the seasonal transport variability of the North Indian Ocean (NIO) boundary currents, in particular, the East India Coastal Current (EICC) in the Bay of Bengal (BoB), West India Coastal Current (WICC) in the Arabian Sea (AS) and Somali Current (SC) in the Equatorial Indian Ocean (EIO) using a high-resolution Regional Ocean Modeling System (ROMS) with climatological river input. The simulation result indicates that northward EICC peaks in March and its mean transport is 2.65 Sv during February to April. The southward EICC extends down to 200 m depth and transports 0.67 Sv during October–December. Northward WICC which extends down to 100 m depth transports 0.31 Sv along the west coast of India during the winter monsoon. Southwestward SC flows between 6.5°N to 3°N, and northeastward cross-equatorial SC goes up to 11°N along the Somali coast. Northeastward SC which is the strongest coastal current in the NIO transports 13.05 Sv during the summer monsoon. The average transport of southwestward SC is 2.57 Sv only. The study suggests that wind stress and wind stress curl (WSC) plays a vital role in the semiannual reversal of transport and remote forcing modulated by equatorial wind anomalies dominates the southward EICC transport.

AbstractHigh heat flux components form the primary interface for thermal management of injectors in fusion devices. The requirement for such application varies from 1 to 10 MW/m2. Ultra-high-vacuum compatibility is the inherent characteristic of such components, and manufacturing processes involve the development of specific materials, process qualification of special processes like electron beam welding (EBW), and component performance validation. One such component of active thermal management in a neutral beam injector is the hypervapatron-based heat transfer element (HTE), which is designed to absorb heat flux as high as 10 MW/m2. The route to realization is through a prototype and a one-to-one model and evaluating their performance. The development route of HTEs includes several important areas. One area is development of precipitation-hardened CuCrZr material characterized for its fatigue life (more than 100 000 stress-controlled cycles); mechanical properties at ambient temperature [ultimate tensile strength (UTS) >384 MPa, elongation >13%] and at operational temperature, i.e., 350°C (UTS >263 MPa, elongation >14%); and restricted chemical composition range of Cr, Zr, Cd, and O2to enhance the precipitation effect and weldability of the component. A second area is similar material (CuCrZr to CuCrZr) and dissimilar material (CuCrZr-Ni-SS316L) joining by an advanced technology like EBW in a controlled environment to enhance the localized high heat input over a large weld penetration depth with minimal distortion and thereby overcome the effect of thermal diffusion by typical copper during welding. A third area is validation of these weld joints with respect to international codes/standards. Successful realization of this route establishes HTEs as main baseline components of the high heat flux system or neutral beam system. Similar application areas can be identified in various fusion devices. The paper presents the implementation of this realization route of prototype HTEs including details of the assessment carried out with respect to application.

ABSTRACTHigh voltage bushing is one of the key components of Indian Test Facility. It is designed to provide 100 kV electrical isolation to all high voltage feedlines from the electrically grounded vessel. It also forms vacuum boundary between the vessel and the outer atmosphere. Conventional vacuum compatible porcelain insulator is selected for this purpose. However, to accommodate several high voltage feedlines in a single insulator, diameter of the insulator has been kept as ∼1 m. Further, steps have been provided at both the ends for porcelain-metal vacuum seal transitions which is the challenging step during the fabrication of insulator. This paper describes the design criteria, analysis, manufacturing phases, encountered issues and remedial actions taken to optimize the design, ensuring its manufacturability without compromising operational requirements.

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. 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. 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

An objectively analyzed monthly gridded ocean analysis derived from a combination of satellite and in situ observations is used to describe the seasonal and interannual variability in the barrier layer thickness (BLT) over the maximum variance region in the BLT of the Bay of Bengal (BoB) for the period from 1993 to 2012. The northern BoB acquires a maximum variance in the BLT where a large river discharge flux was observed. The BLT showed strong seasonal variability with minima during April–May and maxima during December–February. An investigation of the variability in the BLT showed large amplitude at annual and semiannual time scales. The relationship between the BLT and the Indian Ocean dipole mode (IOD) reveals that the BLT maximum is relatively high in the negative IOD years when compared to the positive IOD years. A significant relation between the BLT and IOD is inferred with the IOD leading the BLT by 3 months and lagging by 1 month. We show that the 1 month lag in the northern BoB is mainly associated with coastally trapped Kelvin waves that radiate Rossby waves and control the BLT. However, further investigation is required regarding the temporal lead of the IOD with the BLT in the northern BoB. The barrier layer in the Bay of Bengal exhibits strong seasonal and interannual variabilityThe barrier layer maximum is relatively high during negative Indian Ocean dipole years compared to positive Indian Ocean dipole yearsNorthern Bay of Bengal, which receives a large river discharge flux, experiences a maximum variance in the barrier layer

Abstract: An investigation is conducted to study the uncertainty in the cyclonic ocean wind speed (CWS) of Cyclone Global Navigation Satellite System (CYGNSS) satellites over the North Indian Ocean (NIO). For the completion of the assessment, the comparison of CYGNSS wind speed during normal ocean conditions is also carried out with respect to buoy and advanced scatterometer (ASCAT ) data. The de-collocation effect is also studied using the India Meteorological Department’s (IMD) data. The sensitivity of the uncertainty in CWS is evaluated through the soil moisture active passive (SMAP) data. It has been found that the CYGNSS CWS underestimates for CWS > 35.0 m/s. The study shows that the uncertainty for the CWS > 35.0 m/s is dependent on the incidence angle. Therefore, a new incidence angle-based Geophysical Model Function (IGMF) is proposed for CWS. The IMD and SMAP data for the cyclones of the year 2018–2019 have been used for validation of the CWS derived from IGMF. An extremely severe cyclone Fani is analysed in detail. The IGMF reduces the mean error from 1.77 to –0.001 m/s with respect to SMAP for Fani. Overall, the improvement in root mean square difference (RMSD) and the mean error with IGMF are 16.11% and 44.39%, respectively, over CYGNSS for CWS > 35.0 m/s. The maximum CWS from CYGNSS, IGMF, and IMD is 38.8, 52.07, and 54.97 m/s, respectively, for the Bay of Bengal. It can be concluded that IGMF provides better CWS than the CYGNSS CWS. Research highlights:

The uncertainty of the CYGNSS Cyclonic Ocean Wind Speed (CWS) is investigated over the North Indian Ocean for the years 2018-2019.

The Geo-shifting process with the collocation is included to reduce the collocation error due to the cyclone translational speed.

The CYGNSS CWS shows significant under-estimation for the wind speed >35 m/s with the SMAP and the IMD data.

A new Incidence angle-based Geo-physical Model Function (IGMF) is developed to improve the bias in the CWS.

The IGMF model has better agreement with both SMAP and IMD data than CYGNSS CWS over the NIO region.

Polyvinylidene fluoride (PVDF) based, Cellulose acetate (CA), and Graphene oxide (GO) doped membrane acts as a superior cost-effective cation exchange membrane (CEM) for the energy extraction application using microbial fuel cells (MFCs). In this study, the waste sugarcane bagasse was used to prepare CA, and the Tour method was used to prepare GO. CA and GO compositions were varied to prepare CEMs WCA-1, WCA-2, WCA-3, and WCA-4. Doping the functionalized GO material in the hydrophilic membranes enhances the contribution of conducting phase concerning its hydrophilic nature and facilitates its functional characteristics at the surface. Further, adding an adequate amount of GO improves the physicochemical properties of the membrane and its mechanical stability. Also, with the fusion of GO in the membrane, the trend for water uptake ability significantly increases. Post sulfonating the prepared membranes the enhancement in the attained proton conductivity values from 0.025 Scm-1for WCA-1 to 0.4 Scm-1for WCA-4 was observed, which may be attributed to the increase in the GO content in the prepared membranes. Among various prepared membranes, WCA-3 was considered for MFC application. The WCA-3 membrane outperformed several membranes for wastewater treatment and energy extraction using MFC. Columbic efficiency (CE) of 7.1%, chemical oxygen demand (COD) removal efficiency of 97.5 ± 0.8%, and power density of more than 150.22 mW m−2were achieved without any electrode modification. Thus, the prepared low-cost novel PVDF-based, GO and CA membrane (WCA-3) elucidated its appropriateness for proliferating the efficacy of MFC and is recommended for scaling up of MFCs.

In the Arabian Sea, two extremely severe cyclonic storms occurred back to back during October–November 2015. Using a suite of ocean and atmospheric data, we examined the upper ocean responses of tropical cyclones Chapala and Megh, the latter originated immediately after the dissipation of the former. Cyclones Chapala and Megh cooled the sea surface by 1.5°C and 1.0°C, respectively, which was also captured by Bio‐Argo float in the vicinity of their tracks. The cyclone‐induced chlorophyll aenhancement was 6 and 2 times respectively from their precyclone value of 0.36 and 0.30 mg/m3, while the net primary productivity showed an increase of 5.8 and 1.7 times respectively from the precyclone values of 496.26 and 518.63 mg C/m2/day after the passage of Chapala and Megh. The CO2flux showed a sixfold and twofold increase respectively compared to the precyclone value of 2.69–3.58 and 6.78 mmol/m2/day. We show that the anomalous co‐occurrence of the positive phase of Indian Ocean Dipole and the strong El Niño supported large‐scale warming in the western Arabian Sea. Subsequent altered Walker circulation played a decisive role in the preconditioning of both atmosphere and ocean, which led to a situation congenial for cyclogenesis. What triggered the formation of the cyclone Chapala was the arrival of eastward‐propagating atmospheric convection associated with the Madden‐Julian oscillation. The generation of the second cyclone Megh within 8 days appears to be associated with the oceanic Rossby wave that led to an increase in the upper ocean heat content by deepening the 26°C isotherm in the vicinity of the origin of cyclones. The Arabian Sea, situated in the western part of the North Indian Ocean, is prone to cyclones, and it has a profound impact on its biogeochemistry. It is in this context that our study is important as it aims at understanding the response of the back‐to‐back cyclones Chapala and Megh that occurred during October–November 2015, which is a rare phenomenon. Rare because once a cyclone is generated, it utilizes the available heat energy of the upper ocean, and hence, another cyclone cannot be formed immediately in the same region. Through this study, we show that in October–November 2015, an unusual warming occurred in the western Arabian Sea due to a unique co‐occurrence of an ocean‐atmosphere condition that favored the formation of back‐to‐back cyclones. Our study shows that the twin cyclones Chapala and Megh increased the biological productivity of the ocean as well as the emission of CO2gas from ocean to atmosphere 2 to 6 times. The implication of our result is that if the number of cyclones is going to increase in the future, Arabian Sea will become oxygen deficit, and it will give out more CO2to the atmosphere, thereby increasing the chance of more warming. Cyclone formation consumes upper ocean heat and hence cannot support another one right away, making back‐to‐back‐cyclone occurrence specialPreconditioning of ocean‐atmosphere by ENSO‐IOD‐mediated anomalous warming of the western Arabian Sea led to the formation of Chapala and MeghChlorophyll aand CO2flux increased by sixfold and twofold, while SST cooled by 1.5°C and 1°C after cyclones Chapala and Megh, respectively