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154 results on '"Rathinasamy, Maheswaran"'

5. Partial wavelet coherence analysis for understanding the standalone relationship between Indian Precipitation and Teleconnection patterns

Author

Rathinasamy, Maheswaran, Agarwal, Ankit, Parmar, Vilakshna, Khosa, Rakesh, and Bairwa, Arvind

Subjects
Physics - Atmospheric and Oceanic Physics, Physics - Data Analysis, Statistics and Probability
Abstract

Hydro-meteorological variables, like precipitation, streamflow are significantly influenced by various climatic factors and large-scale atmospheric circulation patterns. Efficient water resources management requires an understanding of the effects of climate indices on the accurate predictability of precipitation. This study aims at understanding the standalone teleconnection between precipitation across India and the four climate indices, namely, Ni\~no 3.4, PDO, SOI, and IOD using partial wavelet analysis. The analysis considers the cross correlation between the climate indices while estimating the relationship with precipitation. Previous studies have overlooked the interdependence between these climate indices while analysing their effect on precipitation. The results of the study reveal that precipitation is only affected by Ni\~no 3.4 and IOD and a non-stationary relationship exists between precipitation and these two climate indices. Further, partial wavelet analysis revealed that SOI and PDO do not significantly affect precipitation, but seems the other way because of their interdependence on Ni\~no 3.4. It was observed that partial wavelet analysis strongly revealed the standalone relationship of climatic factors with precipitation after eliminating other potential factors. Keywords: Indian Precipitation, wavelet coherency, partial wavelet coherence, teleconnections patterns., Comment: 28 pages, 14 figures, 4 tables, Article submitted to JOH

Published
2017

16. Inter-Comparison of Gauge-Based Gridded Data, Reanalysis and Satellite Precipitation Product with an Emphasis on Hydrological Modeling

Author

Sridhara Setti, Rathinasamy Maheswaran, Venkataramana Sridhar, Kamal Kumar Barik, Bruno Merz, and Ankit Agarwal

Subjects
parameter and prediction uncertainty, IMD, TRMM, CFSR, Nagavali River Basin Region (NRB), Meteorology. Climatology, QC851-999
Abstract

Precipitation is essential for modeling the hydrologic behavior of watersheds. There exist multiple precipitation products of different sources and precision. We evaluate the influence of different precipitation product on model parameters and streamflow predictive uncertainty using a soil water assessment tool (SWAT) model for a forest dominated catchment in India. We used IMD (gridded rainfall dataset), TRMM (satellite product), bias-corrected TRMM (corrected satellite product) and NCEP-CFSR (reanalysis dataset) over a period from 1998–2012 for simulating streamflow. The precipitation analysis using statistical measures revealed that the TRMM and CFSR data slightly overestimate rainfall compared to the ground-based IMD data. However, the TRMM estimates improved, applying a bias correction. The Nash–Sutcliffe (and R2) values for TRMM, TRMMbias and CFSR, are 0.58 (0.62), 0.62 (0.63) and 0.52 (0.54), respectively at model calibrated with IMD data (Scenario A). The models of each precipitation product (Scenario B) yielded Nash–Sutcliffe (and R2) values 0.71 (0.76), 0.74 (0.78) and 0.76 (0.77) for TRMM, TRMMbias and CFSR datasets, respectively. Thus, the hydrological model-based evaluation revealed that the model calibration with individual rainfall data as input showed increased accuracy in the streamflow simulation. IMD and TRMM forced models to perform better in capturing the streamflow simulations than the CFSR reanalysis-driven model. Overall, our results showed that TRMM data after proper correction could be a good alternative for ground observations for driving hydrological models.

Published
2020
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27. Impact of Reynolds number on tracer spreading in porous media

Author

Arvind Bairwa, Manish Shukla, Rakesh Khosa, and Rathinasamy Maheswaran

Abstract

Interfacial transport across the free surface flow and obstructed region is critical for understanding the scalar transport and mixing in physical situations such as proximity of open water with vegetation in the aquatic system, sediment-water interface (SWI) in river and estuaries, tree canopies in the atmospheric boundary layer, mixing in coral reef and biofilm formation over biological systems. This interaction occurs over a wide range of Spatio-temporal scales due to fast and slow flow in the free layer and porous media which is determined by the key parameters such as degree of flow unsteadiness and porosity. In these situations, understanding and predicting the spreading of the scalar is crucial for water quality assessment and the health of aquatic ecosystems. In this study, we conduct a high-resolution numerical simulation of an array of circular cylinders packed with channels at moderate Reynolds number (Re). As the Reynolds number increases gradually, we observe that particle tends to form coherent structures at the interface as well as filamentation of tracer behind the cylinders. It is worthwhile to note that filaments are a good candidate for mixing as they enhance concentration gradient which is easily erased by molecular diffusion. Breakthrough curves (BTCs) are measured at the midpoint and outlet of the domain to investigate the spreading of tracers using a random walk-based particle tracking method. We found that as the Re decreases, BTCs become broader because the tracer spends a longer time near cylinder boundaries and within the coherent structure before exiting the domain. These BTCs are successfully predicted by the continuous-time random walk model.

Published
2022

44. Game-theoretic-based modelling of Krishna waters dispute: equilibrium solutions by Metagame Analysis

Author

Durga Prasad Panday, Rakesh Khosa, Rathinasamy Maheswaran, K. Ravikumar, and Ankit Agarwal

Subjects
0103 physical sciences, 010306 general physics, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Electronic, Optical and Magnetic Materials
Abstract

Conflicts are inevitable concerning sharing of the resources. Most of the time, due to the opacity of the conflict resolution technique, players involved do not accept the final solution. Therefore, any method adopted for resolving a conflict should involve players to get the equilibrium solution. Besides, the conflict resolution technique needs to be transparent, and the procedure must be the same for all the players involved. Metagame Analysis has the potential to accommodate the above conditions. In this study, we have discussed Metagame Analysis and its application to resolve India’s Krishna river basin dispute. Since the environment is an integral part of the river ecosystem, it has also been included as a conflict resolution player. We have also defined and derived Fair and Equitable (F&E) allocation in this regard, considering the factors that form the basis for their right as a rightful owner of the resource. The factors considered for F&E allocation are drainage area, cultivable area, and virgin runoff. The derived F&E allocation is then selected as one of the options for the Metagame Analysis. Metagame Analysis is carried out using two scenarios before and after Andhra Pradesh’s reorganization (in 2014). In scenario 1, equilibrium outcomes are 454, 458, and 469. Our results show that excessive demands may harm the water allocation if it violates the total flow. Outcome 469 is the F&E outcome in which all the players are going for cooperated negotiations which maximize their share. Outcomes 454 and 458 are those outcomes in which Karnataka is benefitted as it is getting its first option share. AP’s demand cannot be accommodated in any strategy as it exceeds the total flow, while there is a strategy available in which Karnataka’s first option can be sustained. The paper shows that the game-theoretic-based techniques can solve real-world disputes and that too as complex as water sharing.

Published
2021

48. Performance of Canna Indica based microscale vertical flow constructed wetland under tropical conditions for domestic wastewater treatment.

Author

Pinninti, Ramdas, Kasi, Venkatesh, Sallangi, L. K. S. V. Prasad, Landa, Sankar Rao, Rathinasamy, Maheswaran, Sangamreddi, Chandramouli, and Dandu Radha, Prasada Raju

Subjects
SEWAGE purification, TROPICAL conditions, WASTEWATER treatment, CONSTRUCTED wetlands, BIOCHEMICAL oxygen demand, GRAYWATER (Domestic wastewater)
Abstract

Constructed wetlands (CWs) have great potential as low-cost natural wastewater treatment in developing countries. The present study appraises the performance of the vertical flow constructed wetland for domestic wastewater treatment. More specifically, the potential of Canna Indica in the removal of carbon, nitrogen, and phosphorus (CNP) from wastewater under tropical conditions. CW cell was fabricated with a vegetative layer of Canna Indica and tested with domestic wastewater. Based on the test results, Canna Indica shows a high Removal Efficiency (RE) of Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5) on the order of 87% and 91%, respectively. Similarly, nutrients removal efficiency for total nitrogen (TN), total phosphorus (TP) was found to be 97% and 98%, respectively. The investigation also revealed that there is considerable removal of sulfates with efficiency equal to 78.4%. Overall, the Canna Indica based CWs were found to be suitable for wastewater treatment in the tropical regions, provided a viable medium for treating the wastewater in peri-urban and rural areas of developing countries. This study investigates the performance of Canna indica based vertical flow wetlands for greywater treatment. The study investigates the results at different hydraulic retention times and loading rates. There are no much studies reporting the performance of this variety of plant species under a tropical humid climate. The results from the study can encourage adoption of this plant variety, indigenous to this part of the country, for wastewater treatment It could emphasize the importance of familiarity with constructed wetlands to comprehend the RE of various climatic zones. It is possible to highlight the Canna-based CW's efficiency in removing organics and nutrients from domestic wastewater. The possibility for field-scale Canna-based CW to remove pollution in tropical climates was investigated, and Decentralization of wastewater treatment at the household level to apply CWs that will improve wastewater quality. [ABSTRACT FROM AUTHOR]

Published
2022
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