There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The ERA5 global reanalysis

Soil Chemical Analysis

Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

Climate change 2014 - Synthesis Report

Dam construction in developing nations is on the rise. Monitoring these dams is essential to understanding downstream hydrologic impacts and for better planning and management of water resources. Satellite observations and advancements in information technology now present a unique opportunity to overcome the traditional limitations of reservoir monitoring. In this study, a global reservoir monitoring framework was developed as an online tool for near real-time monitoring and impact analysis of existing and planned reservoirs based on publicly available and global satellite observations. The framework used a mass balance approach to monitor 1598 reservoirs in South America, Africa, and Southeast Asia. Simulated streamflow of the developed tool was validated in 25 river basins against a multidecadal record of in-situ discharge. The simulated storage change was validated against in-situ data from 77 reservoirs. The framework was able to capture reservoir state realistically for more than 75% of these reservoirs. At most in-situ gaging locations, the reservoir tool was able to capture streamflow with a correlation of more than 0.9 and a normalized root mean square error of 50% or less. The tool can now be used to study existing or planned reservoirs for short and long-term decision making and policy analysis.

Towards a global Reservoir Assessment Tool for predicting hydrologic impacts and operating patterns of existing and planned reservoirs

Assessment of a stochastic interpolation based parameter sampling scheme for efficient uncertainty analyses of hydrologic models

The safety of large and aging water infrastructures is gaining attention in water management given the accelerated rate of change in landscape, climate and society. In current engineering practice, such safety is ensured by the design of infrastructure for the Probable Maximum Precipitation (PMP). Recently, several numerical modeling approaches have been proposed to modernize the conventional and ad hoc PMP estimation approach. However, the underlying physics have not been fully investigated and thus differing PMP estimates are sometimes obtained without physics-based interpretations. In this study, we present a hybrid approach that takes advantage of both traditional engineering practice and modern climate science to estimate PMP for current and future climate conditions. The traditional PMP approach is modified and applied to five statistically downscaled CMIP5 model outputs, producing an ensemble of PMP estimates in the Pacific Northwest (PNW) during the historical (1970-2016) and future (2050-2099) time periods. The hybrid approach produced consistent historical PMP estimates as the traditional estimates. PMP in the PNW will increase by 50%±30% of the current design PMP by 2099 under the RCP8.5 scenario. Most of the increase is caused by warming, which mainly affects moisture availability through increased sea surface temperature, with minor contributions from changes in storm efficiency in the future. Moist track change tends to reduce the future PMP. Compared with extreme precipitation, PMP exhibits higher internal variability. Thus long-time records of high-quality data in both precipitation and related meteorological fields (temperature, wind fields) are required to reduce uncertainties in the ensemble PMP estimates.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2017WR021094

Probable Maximum Precipitation in the U.S. Pacific Northwest in a Changing Climate

A new era involving both simple and complex hydrologic modeling of un-gauged river basins may now emerge with the anticipated global availability of high resolution satellite rainfall data from the proposed Global Precipitation Measurement (GPM) mission. This era of application pertains to rapid prototyping of GPM-based flood monitoring systems for downstream nations in International River Basins (IRBs) where basin-wide in-situ rainfall data is unavailable due to lack of either an infrastructure or a treaty for real-time data sharing with upstream riparian nations. In this paper, we develop, verify and apply an open-book watershed model for demonstrating the value of a parsimonious modeling scheme in quick prototyping of satellite rainfall-based flood monitoring systems for lowermost nations in flood-prone IRBs. The open-book watershed modeling concept was first formulated by Yen and Chow [1969. A laboratory study of surface runoff due to moving rainstorms. Water Resources Research 5(5), 989-1006] more than 30years ago as a convenient and pragmatic framework to understand the underlying physics behind surface hydrologic phenomena. Our developed model is based on first principles of conservation of mass and momentum that parsimoniously represents the static geophysical features of a basin with minimum calibration. Such a generic and parsimonious representation has the added potential to supplement complex hydrologic models for stakeholder involvement and conflict management in transboundary river basins, among many additional applications. We first demonstrate the physical consistency of our model through sensitivity analysis of some geophysical basin parameters pertinent to the rainfall-runoff transformation. Next, we simulate the stream-flow hydrograph for a 4-month long period using basin-wide radar (WSR-88D) rainfall data over Oklahoma assuming an open-book river basin configuration. Finally, using the radar-simulated hydrograph as the benchmark, and assuming a two-nation hypothetical IRB over Oklahoma, we explored the impact of assimilating NASA's real-time satellite rainfall data (IR-3B41RT) over the upstream nation on the flow monitoring accuracy for the downstream nation. We developed a relationship defining the improvement in flow monitoring that can be expected from assimilating IR-3B41RT over transboundary regions as a function of the relative area occupied by the downstream nation for a semi-arid region. The relative improvement in flow monitoring accuracy for the downstream nation was found to be clearly high (over 35% reduction in root mean squared error) when more than 90% of the basin is transboundary. However, flow monitoring accuracy reduces considerably and even becomes negative when 60% or less of the basin area is transboundary to the downstream nation. Our findings, although hypothetical and very regime-specific, illustrate very clearly the feasibility of utilizing anticipated GPM data to alleviate the current flood monitoring limitations experienced by many nations in IRBs through the application of a generic and parsimonious model.

Faisal Hossain

Papers

Towards a global Reservoir Assessment Tool for predicting hydrologic impacts and operating patterns of existing and planned reservoirs

Assessment of a stochastic interpolation based parameter sampling scheme for efficient uncertainty analyses of hydrologic models

Probable Maximum Precipitation in the U.S. Pacific Northwest in a Changing Climate

An open-book watershed model for prototyping space-borne flood monitoring systems in International River Basins

Impacts of Post-Dam Land-use/Land-cover Changes on Modification of Extreme precipitation in Contrasting Hydro-climate and Terrain Features