Western Disturbances: A review Dimri, A. P.; Niyogi, D.; Barros, A. P. ...
Reviews of geophysics (1985),
06/2015, Letnik:
53, Številka:
2
Journal Article
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Cyclonic storms associated with the midlatitude Subtropical Westerly Jet (SWJ), referred to as Western Disturbances (WDs), play a critical role in the meteorology of the Indian subcontinent. WDs ...embedded in the southward propagating SWJ produce extreme precipitation over northern India and are further enhanced over the Himalayas due to orographic land‐atmosphere interactions. During December, January, and February, WD snowfall is the dominant precipitation input to establish and sustain regional snowpack, replenishing regional water resources. Spring melt is the major source of runoff to northern Indian rivers and can be linked to important hydrologic processes from aquifer recharge to flashfloods. Understanding the dynamical structure, evolution‐decay, and interaction of WDs with the Himalayas is therefore necessary to improve knowledge which has wide ranging socioeconomic implications beyond short‐term disaster response including cold season agricultural activities, management of water resources, and development of vulnerability‐adaptive measures. In addition, WD wintertime precipitation provides critical mass input to existing glaciers and modulates the albedo characteristics of the Himalayas and Tibetan Plateau, affecting large‐scale circulation and the onset of the succeeding Indian Summer Monsoon. Assessing the impacts of climate variability and change on the Indian subcontinent requires fundamental understanding of the dynamics of WDs. In particular, projected changes in the structure of the SWJ will influence evolution‐decay processes of the WDs and impact Himalayan regional water availability. This review synthesizes past research on WDs with a perspective to provide a comprehensive assessment of the state of knowledge to assist both researchers and policymakers, and context for future research.
Key Points
Explanation of Western Disturbances dynamics with modeling efforts
Interaction of Western Disturbances with Indian summer monsoon
Increased frequency of Western Disturbances in recent climate change
Indian winter monsoon: Present and past Dimri, A.P.; Yasunari, T.; Kotlia, B.S. ...
Earth-science reviews,
December 2016, 2016-12-00, 20161201, Letnik:
163
Journal Article
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The Indian subcontinent receives most of its annual precipitation due to Indian summer (June, July, August and September) monsoon. Southeastern coastal region of the India receives significant amount ...of precipitation due to the northeast monsoon (October and November). Over northern Indian region almost one-third of annual precipitation is received during winter (December, January and February) by eastward moving extratropical cyclone called ‘western disturbances (WDs)’ in Indian meteorological parlance. Various studies are conducted to understand the Indian summer and northeast monsoons. However, the dynamics and characterization of winter precipitation is not well understood except with reference to the western disturbances (WDs). In this study, wintertime dynamics associated with large-scale flows and WDs influencing winter precipitation is proposed and termed ‘Indian winter monsoon’. In addition, winter precipitation – the Indian winter monsoon – is proposed as eastward traveling WDs embedded in the large-scale subtropical westerlies over the Indian sub-continent. During winter (December, January and February) upper level subtropical westerly jet moves southwards and passes over the Indian sub-continent and provides associated precipitation over the northern Indian region. With concurrent research and changing global context, increased understanding of the Indian winter monsoon is imperative. Equally important is the behavior of WDs showing different patterns in the Peninsular India and the Himalaya particularly during the Holocene. During the Little Ice Age (LIA), it appears that high frequency of El Niño events was responsible for drier conditions in the core monsoon zone but generated more monsoon “breaks” over the Himalaya and thus the climatic conditions in the core Indian summer monsoon area were generally opposite to those in the foothills of the Himalaya during the Holocene period. During this period, a higher frequency of El Niño events might have restricted transport of warm water to the North Atlantic Ocean and brought about a cooling of adjacent continents including Central Asia and this may have amplified the extent of snow over Asia during the winter, and may even have been accounted for early snow in the region at the expanse of reduction in the Indian summer monsoon strength. Thus, this study delineates the Indian winter monsoon at intraseasonal-sub seasonal-interannual-paleoclimate scale and provides comprehensive details on defining the Indian winter monsoon and makes an attempt to understand the WDs particularly from mid-Holocene onwards as well.
In view of unremitting diminution of mineral resources, rising energy economics along with increasing global consumption of Manganese (Mn), development of environment friendly technologies for ...tapping alternate sources of Mn has gained importance lately. Mn recovery from mining residues using conventional approaches is extremely expensive due to high capital and energy costs involved. However lean grade ores present in millions of tons awaits the development of competent and cost effective extractive process. Mn recovery by biomining with diverse microbes is thereby recommended as a superior and green alternative to the current pyro metallurgical techniques. The synergistic effects of different factors are known to influence microbial leaching of mineral ores which includes microbiological, mineralogical, physicochemical and process parameters. Bacterial bioleaching is mostly due to enzymatic influence, however fungal bioleaching is non enzymatic. Genomic studies on microbial diversity and an insight of its metabolic pathways provides unique dimension to the mechanism of biomining microorganisms. The extraction of Mn has a massive future prospective and will play a remarkable role in altering the situation of ever-decreasing grades of ore. This review aims to encompass the different aspects of Mn bioleaching, the plethora of organisms involved, the mechanisms driving the process and the recent trends and future prospects of this green technology.
•Microbial diversity involved in manganese bioleaching has been highlighted.•Mechanism of manganese bioleaching have been described.•Process parameters for efficient Mn recovery has been discussed.•Recent development and future trends in manganese mining has been suggested.
While studying the Western Disturbances (WDs) and associated precipitation forming mechanism in changing time, we found that there is significant amount of precipitation received during Non-WDs days ...too. In addition, it is also highlighted that all the WDs don’t precipitate. And hence cumulative winter precipitation is kind of summation of all the available precipitation and NOT only of WDs days’ precipitation. Thus here understanding of WDs vs Non-WDs days precipitation dynamics, linkages and changes in last three decades are deliberated. Threshold for evaluating non-precipitating and precipitating day(s) is chosen as < 0.1 mm/d and = or > greater than 0.1 mm/d, respectively. The present finding shows decreasing trend (p-value 0.039) of WDs days precipitation and intriguingly increasing trend (p-value 0.57) of Non-WDs days precipitation. These trends, though statistical not significant, are based on Mann–Kendall test. Further, Non-WDs days precipitation over the western Himalayas (WH) is less studied and researched. Thus dynamics of WDs vs Non-WDs precipitating days precipitation is evaluated and corresponding precipitation and moisture sources days are assessed. As knowingly, WDs precipitation is mainly from western sources and Arabian Sea (AS); whereas Non-WDs days precipitation derive moisture from Bay of Bengal (BoB). Present work presents preliminary investigation for Non-WDs days precipitation.
The present investigation reports the isolation, molecular identification and screening of manganese (Mn) solubilizing fungal strains from low-grade Mn mine tailings. Six morphologically distinct Mn ...solubilizing fungal strains were isolated on MnO
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-supplemented agar plates with Mn concentration of 0.1% (w/v). The biochemical characterization of the isolated fungal strains was carried out. The molecular identification by internal transcribed spacer (ITS) sequencing identified the strains as Aspergillus terreus, Aspergillus oryzae, Penicillium sp., Penicillium sp., Penicillium daleae and Penicillium sp. with GenBank accession numbers KP309809, KP309810, KP309811, KP309812, KP309813 and KP309814, respectively. The ability of the isolated fungal strains to tolerate and solubilize Mn was investigated by subculturing them on Mn-supplemented plates with concentration ranging from 0.1 to 0.5% (w/v). Mn solubilizing ability of the fungal isolates is possibly due to the mycelia production of biogenerated organic acids such as oxalic acid, citric acid, maleic acid and gluconic acid as revealed by ion chromatography. Our investigation signifies the role of fungi in biotransformation of insoluble Mn oxide.
Antibiotic resistance is a major public health concern worldwide. The gut microbiota harbours multiple antibiotic resistant genes (ARGs) that contribute to the existing and future microbial ...population in a community or ecosystem. This study aimed to investigate the prevalence of 35 antibiotic resistance genes (ARGs) in the gut microbiota of the tribal people of Nabarangpur, Odisha, India. A total of 83 faecal samples were collected from three different tribes (Bhatra, Gond, and Paraja). Total faecal DNA was extracted, and the simplex polymerase chain reaction was performed to detect selected ARGs. Further analysis was done to estimate the incidence of these ARGs across these tribes based on alcohol consumption habits. We identified a higher prevalence of tetracycline resistance genes (tetW, tetQ and tetM) in the gut microbiota among three populations. Furthermore, a significant (P = 0·024) difference in ARG prevalence against vancomycin in individuals with and without alcohol consumption habits was noticed. The overall distribution of ARGs among the three major tribes of this location was found to be very similar. Together, irrespective of the tribes, the people of this location have gut microbiota harbouring different kinds of ARGs and tetracycline‐resistant genes are the most commonly found ARGs.
Significance and Impact of the Study: This is the first attempt to check the prevalence of different ARGs in the gut microbiota of tribal people of Nabarangpur, Odisha, which is a small contributing step in controlling the evolving antibiotic resistance in India. The results of this study showed the dominance of tetracycline resistance genes (tetW, tetQ and tetM) as well as the similar pattern of distribution of ARGs among the three major tribes of this location. These findings provide a reference to monitor the evolution of antimicrobial resistome in this population in the future.
The effects of outdoor ageing on various compositions of glass fibre reinforced plastic (GFRP) composites were studied. Changes in the interlaminar shear strength (ILSS) of hand-laid samples with ...50–60 wt.% of fibre were determined by three-point bending and glass transition temperature (Tg) measurements. SEM analysis was carried out for exploring the mode of failure. The moisture ingress rate and extent were concentration-dependent at first, but became increasingly dependent on the fibre-matrix interfacial area. The ILSS initially fluctuated and then showed a decreasing trend with time, especially for the higher fibre concentrations. ILSS variations were zigzag initially and showed a lowering trend after the initial periods. Rate of lowering of ILSS was the highest for samples with the highest fraction reinforcement. Weight fraction reinforcement didn’t have any significant effect on the Tg variations. SEM fractograph revealed excessive fracture and fragmentation for the composite samples with the highest weight percentage reinforcement.
The coastal vulnerability to multi-hazard study aims to assess the coastal zones of Andhra Pradesh that really are vulnerable to various oceanogenic hazards. Using high-resolution coastal elevation, ...the maximum extent of coastal inundation during extreme high waves of cyclones & tsunamis, shoreline change, and sea-level rise can be computed. Vulnerability impact up to the village level was assessed based on future projection (return period) of multi-hazard impact using a holistic approach with geospatial techniques. The current study results revealed that 706 villages and 8 towns that are completely falling under CMZ are at risk. A total of 9682 km
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of coastal zones of Andhra Pradesh coast are exposed and prone to inundation as recorded under CMZ. Krishna, Godavari, Guntur and Prakasham districts comprise 70% of the total CMZ area are large low-lying areas exposed to ocean hazards. CMZ area along Andhra Pradesh coast recorded a significant negative correlation of − 0.65 with coastal elevation and a positive correlation of 0.34 with coastal exposure index. Shoreline change assessed from 1972 to 2019 across the study area reveals the 7% under high erosion along the headland and low-lying area of Krishna-Godavari delta. The outputs and maps produced in this study provide vital input for coastal disaster management and necessary policy interventions.
A composite material scores over its metallic counter parts in many aspects and can be tailor-made to suit the specific purpose for which it is conceived. However, during functioning the composite is ...exposed to the severities of the surrounding ambiance and is damaged and degraded by the atmospheric deterrent-reagents like moisture and heat fluctuations. In order to ensure a safe, extended service life-span of the composite material, it is, therefore, pertinent that the behaviour of the material related to its physical, chemical and mechanical characteristics must be analysed and established under different fluctuating ambient conditions. The present report aims at analysing and presenting the degradation/damages caused to the glass-fibre reinforced plastic (GFRP) composites under different ambient conditions and the role played by some inherent factors like the constituent components of the GFRP composites, its pre-existing flaws created during manufacturing/service-life, volume fraction fibres, length and distribution of the fibres in the matrix phase and the curing processes adopted for strengthening and stabilising the matrix structure.
Winter (December, January, and February (DJF)) precipitation over northwest India (NWI) is mainly associated with the eastward moving mid-latitude synoptic systems, western disturbances (WDs), ...embedded within the subtropical westerly jet (SWJ), and is crucial for Rabi (DJF) crops. In this study, the role of winter precipitation at seasonal and monthly scale over NWI and its nine meteorological subdivisions has been analyzed. High-resolution (0.25° × 0.25°) gridded precipitation data set of India Meteorological Department (IMD) for the period of 1901–2013 is used. Results indicated that the seasonal precipitation over NWI is below (above) the long-term mean in most of the years, when precipitation in any of the month (December/January/February) is in deficit (excess). The contribution of December precipitation (15–20%) to the seasonal (DJF) precipitation is lesser than January (35–40%) and February (35–50%) over all the subdivisions. December (0.60), January (0.57), and February (0.69) precipitation is in-phase (correlation) with the corresponding winter season precipitation. However, January precipitation is not in-phase with the corresponding December (0.083) and February (−0.03) precipitation, while December is in-phase with the February (0.21). When monthly precipitation (December or January or December–January or February) at subdivision level over NWI is excess (deficit); then, the probability of occurrence of seasonal excess (deficit) precipitation is high (almost nil). When antecedent-monthly precipitation is a deficit or excess, the probability of monthly (January or February or January + February) precipitation to be a normal category is >60% over all the subdivisions. This study concludes that the December precipitation is a good indicator to estimate the performance of January, February, January–February, and the seasonal (DJF) precipitation.
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