Papers by Ganesh Prasad Ghimire
Two-dimensional (2D) layered atomic crystals have received great scientific attention during the ... more Two-dimensional (2D) layered atomic crystals have received great scientific attention during the past decade since the discovery of graphene [1]. Among 2D materials crystal family transition metal dichalcogenides (TMDs) are the most promising candidates for potential applications in optoelectronic devices, and great efforts have been devoted to study their electronic and optical properties [2]. It was shown that single layers of MoS2, WS2, MoSe2 and WSe2 exhibit direct bandgaps ranging from visible to near-infrared (between 1-2 eV), which gives rise to a strong light-matter coupling in these materials. Moreover, beyond the devices consisting of single layer TMDs, atomically-thin van der Waals heterostructures based on 2D TMDs with a varied bandgaps can be synthesized, without a stringent requirement of lattice matching between two constituent materials [3]. Tungsten disulfide (WS2) is a promising representative of the semiconducting TMDs. Unlike its bulk counterpart, WS2 monolayers ...
The Hydropower Energy Storage Capacity (HESC) Dataset catalogues estimates of nominal energy stor... more The Hydropower Energy Storage Capacity (HESC) Dataset catalogues estimates of nominal energy storage capacity based on varying levels of detail. Dams and reservoirs selected were selected based on those reported in the National Inventory of Dams (NID 2019) and/or the Global Reservoir and Dam (GRanD v1.3) datasets. These data provide a foundation for understanding available resources at existing hydropower facilities and their potential to provide storage of energy and more flexible generation. Current estimates include Level 1 (based on maximum storage capacities and hydraulic head) and Level 2 (based on historical models or observations of reservoir volume and hydraulic head). For facilities where installed capacity is known, there are also estimates for discharge duration or the length of time when a facility could provide generation at a given capacity. Essential information used to calculate the energy storage capacity and discharge duration (volume, hydraulic head, and details ...
Earth, 2021
Streamflow and sediment flux variations in a mountain river basin directly affect the downstream ... more Streamflow and sediment flux variations in a mountain river basin directly affect the downstream biodiversity and ecological processes. Precipitation is expected to be one of the main drivers of these variations in the Himalayas. However, such relations have not been explored for the mountain river basin, Nepal. This paper explores the variation in streamflow and sediment flux from 2006 to 2019 in central Nepal’s Kali Gandaki River basin and correlates them to precipitation indices computed from 77 stations across the basin. Nine precipitation indices and four other ratio-based indices are used for comparison. Percentage contributions of maximum 1-day, consecutive 3-day, 5-day and 7-day precipitation to the annual precipitation provide information on the severity of precipitation extremeness. We found that maximum suspended sediment concentration had a significant positive correlation with the maximum consecutive 3-day precipitation. In contrast, average suspended sediment concentra...
Eos, 2021
From its high mountains to its low plains, Nepal faces growing risks from natural hazards. Prepar... more From its high mountains to its low plains, Nepal faces growing risks from natural hazards. Preparing for these risks requires accurate, locally relevant risk assessments and effective communications.
Forecasting, 2020
Improving decision-making in various areas of water policy and management (e.g., flood and drough... more Improving decision-making in various areas of water policy and management (e.g., flood and drought preparedness, reservoir operation and hydropower generation) requires skillful streamflow forecasts. Despite the recent advances in hydrometeorological prediction, real-time streamflow forecasting over the Himalayas remains a critical issue and challenge, especially with complex basin physiography, shifting weather patterns and sparse and biased in-situ hydrometeorological monitoring data. In this study, we demonstrate the utility of low-complexity data-driven persistence-based approaches for skillful streamflow forecasting in the Himalayan country Nepal. The selected approaches are: (1) simple persistence, (2) streamflow climatology and (3) anomaly persistence. We generated the streamflow forecasts for 65 stream gauge stations across Nepal for short-to-medium range forecast lead times (1 to 12 days). The selected gauge stations were monitored by the Department of Hydrology and Meteoro...
Journal of Hydrometeorology, 2021
Incorporating rainfall forecasts into a real-time streamflow forecasting system extends the forec... more Incorporating rainfall forecasts into a real-time streamflow forecasting system extends the forecast lead time. Since quantitative precipitation forecasts (QPFs) are subject to substantial uncertainties, questions arise on the trade-off between the time horizon of the QPF and the accuracy of the streamflow forecasts. This study explores the problem systematically, exploring the uncertainties associated with QPFs and their hydrologic predictability. The focus is on scale dependence of the trade-off between the QPF time horizon, basin-scale, space-time scale of the QPF, and streamflow forecasting accuracy. To address this question, the study first performs a comprehensive independent evaluation of the QPFs at 140 U.S. Geological Survey (USGS) monitored basins with a wide range of spatial scales (~10 – 40,000 km2) over the state of Iowa in the Midwestern United States. The study uses High-Resolution Rapid Refresh (HRRR) and Global Forecasting System (GFS) QPFs for short and medium-rang...
Weather, 2021
Extreme rainfall is one of the major causes of natural hazards (for example flood, landslide, and... more Extreme rainfall is one of the major causes of natural hazards (for example flood, landslide, and debris flow) in the central Himalayan region, Nepal. The performance of strategies to manage these risks relies on the accuracy of quantitative rainfall estimates. Rain gauges have traditionally been used to measure the amount of rainfall at a given location. The point measurement often misrepresents the basin estimates, because of limited density and high spatial variability of rainfall fields across the Himalayas. The Department of Hydrology and Meteorology (DHM), Nepal has planned to install a network of three weather radars that cover the entire country. So far, the first weather radar has been installed in 2019 in the western region of the country. Two more radars will be added for the planned radar network in the near future covering the central and eastern regions of the country. Here we introduce the first installed weather radar in Nepal. We highlight both the opportunities and challenges with the radar observation in the mountainous regions. Radar rainfall estimates across the Himalayas are critical to issue severe weather warnings; forecast floods and landslides; and inform decision making in a broad range of sectors, including water and energy, construction, transportation, and agriculture.
ReS2 exhibits strong anisotropic optical and electrical responses originating from the asymmetric... more ReS2 exhibits strong anisotropic optical and electrical responses originating from the asymmetric lattice. Here, we show that the anisotropy of monolayer (1L) ReS2 in optical scattering and electrical transport can be practically erased by lattice engineering via lithium (Li) treatment. Scanning transmission electron microscopy revealed that significant strain is induced in the lattice of Li-treated 1L-ReS2, due to high-density electron doping and the resultant formation of continuous tiling of nanodomains with randomly rotating orientations of 60°, which produced a nearly isotropic response of polarized Raman scattering and absorption of Li-treated 1L-ReS2. With Li treatment, the in-plane conductance of 1L-ReS2 increased by an order of magnitude, and its angle dependence became negligible. Our result that the asymmetric phase was converted into the isotropic phase by electron injection could significantly expand the optoelectronic applications of polymorphic two-dimensional transition metal dichalcogenides.
Geophysical Research Letters, 2020
Despite efforts to detect and mitigate wind farm clutter in weather radar observations of rainfal... more Despite efforts to detect and mitigate wind farm clutter in weather radar observations of rainfall, these signatures propagate to quantitative precipitation estimates. In this study, the authors investigate the hydrologic impact of wind farm clutter in the Multi-Radar Multi-Sensor rainfall products. The study uses the probability of detection method to identify wind farm clutter in data from Iowa for the years 2016 and 2017. Using the physically based distributed hydrologic model called the Hillslope-Link Model, the authors show that streamflow (flood) prediction errors are generally significant at smaller basin communities where wind farms occupy a large portion of the upstream basins. These errors due to wind farm clutter show systematic decrease with the basin scales. The results from this study have implications for real-time streamflow forecasts provided automatically by the National Water Model at the National Oceanic and Atmospheric Administration, particularly at small riverine communities. Plain Language Summary Wind farms corrupt radar-rainfall estimates used for flood forecasting. Erroneous streamflow forecasts affect small communities where wind farms occupy a large portion of the upstream basins. The effect is difficult to detect at larger scales typically monitored by the USGS streamflow gauging network as the wind farms occupy a small fraction of the basins at those scales.
Frontiers in Water, 2020
Streamflow is a dynamical process that integrates water movement in space and time within basin b... more Streamflow is a dynamical process that integrates water movement in space and time within basin boundaries. The authors characterize the dynamics associated with streamflow time series data from about seventy-one U.S. Geological Survey (USGS) stream-gauge stations in the state of Iowa. They employ a novel approach called visibility graph (VG). It uses the concept of mapping time series into complex networks to investigate the time evolutionary behavior of dynamical system. The authors focus on a simple variant of VG algorithm called horizontal visibility graph (HVG). The tracking of dynamics and hence, the predictability of streamflow processes, are carried out by extracting two key pieces of information called characteristic exponent, λ of degree distribution and global clustering coefficient, GC pertaining to HVG derived network. The authors use these two measures to identify whether streamflow process has its origin in random or chaotic processes. They show that the characterization of streamflow dynamics is sensitive to data attributes. Through a systematic and comprehensive analysis, the authors illustrate that streamflow dynamics characterization is sensitive to the normalization, and the timescale of streamflow time-series. At daily scale, streamflow at all stations used in the analysis, reveals randomness with strong spatial scale (basin size) dependence. This has implications for predictability of streamflow and floods. The authors demonstrate that dynamics transition through potentially chaotic to randomly correlated process as the averaging timescale increases. Finally, the temporal trends of λ and GC are statistically significant at about 40% of the total number of stations analyzed. Attributing this trend to factors such as changing climate or land use requires further research.
Journal of Waterway, Port, Coastal, and Ocean Engineering, 2020
Abstract This study develops a site-specific analysis of sediment transport for the in-the-wet co... more Abstract This study develops a site-specific analysis of sediment transport for the in-the-wet construction of Olmsted Locks and Dam on the Ohio River using the HEC-RAS model. Results from the anal...
In this study, the authors explore three persistence approaches in streamflow forecasting motivat... more In this study, the authors explore three persistence approaches in streamflow forecasting motivated by the need for forecasting model skill evaluation. The authors use stream flow observations with 15 minutes resolution from the year 2008 to 2017 at 140 U.S. Geological Survey (USGS) streamflow gauges monitoring the streams and rivers over the State of Iowa. The spatial scale of the basins ranges from about 7 km2 to 37,000 km2. The study explores three approaches: simple persistence, gradient persistence and anomaly persistence. The study shows that persistence forecasts skill has strong dependence on basin scales and weaker but non-negligible dependence on geometric properties of the river network for a given basin. Among the three approaches explored, anomaly persistence shows highest skill especially for small basins, under about 500 km2. The anomaly persistence can serve as a benchmark for model evaluations considering the effect of basin scales and geometric properties of river ...
JAWRA Journal of the American Water Resources Association, 2018
River flow velocity can be estimated using power law relationships with discharge and drainage ar... more River flow velocity can be estimated using power law relationships with discharge and drainage area providing a framework to develop models for hydraulically similar rivers in the U.S. and the world.
Syntheses of azepinoindole alkaloids cimitrypazepine, fargesine and hyrtioreticulins C & D Ganesh... more Syntheses of azepinoindole alkaloids cimitrypazepine, fargesine and hyrtioreticulins C & D Ganesh Ghimire The Watanabe-Cenini-Söderberg reductive N-heterocyclization has emerged as a powerful tool for the synthesis of a variety of functionalized indoles. Söderberg's elaboration of this methodology has been utilized as a late-stage cyclization protocol for the synthesis of azepinoindole alkaloids, a class of natural products characterized by an azepane skeleton fused with an indole ring. Short syntheses of the naturally occurring azepino[5,4,3-cd]indole alkaloids, cimitrypazepine, fargesine, and the diastereomeric hyrtioreticulins C & D have been completed starting from commercially available tetra-substituted benzene derivatives. The key azepinoindole core in each case was assembled via an intramolecular Mizoroki-Heck reaction followed by a Watanabe-Cenini-Söderberg reductive N-heterocyclization. Synthesis of aurantioclavine using a similar strategy is currently underway.
World Environmental and Water Resources Congress 2016, 2016
Lecture Notes in Computer Science
Much of the world’s knowledge is captured in writing, and shared through writing, and as such is ... more Much of the world’s knowledge is captured in writing, and shared through writing, and as such is inaccessible to the one eighth of the world’s population who are illiterate. We are developing a software system for the use of this population based on speech and images without written text. We have evaluated basic interaction devices and simple interface metaphors to
Tetrahedron Letters, 2016
A short synthetic sequence leading to the tricyclic alkaloids cimitryptazepine and fargesine is r... more A short synthetic sequence leading to the tricyclic alkaloids cimitryptazepine and fargesine is reported. An intramolecular Heck reaction and a palladium catalyzed reductive Nheterocyclization are key steps in the synthesis.
Uploads
Papers by Ganesh Prasad Ghimire