74 research outputs found
Satellite-driven downscaling of global reanalysis precipitation products for hydrological applications
Deriving flood hazard maps for ungauged basins typically requires simulating
a long record of annual maximum discharges. To improve this approach,
precipitation from global reanalysis systems must be downscaled to a spatial
and temporal resolution applicable for flood modeling. This study evaluates
such downscaling and error correction approaches for improving hydrologic
applications using a combination of NASA's Global Land Data Assimilation
System (GLDAS) precipitation data set and a higher resolution multi-satellite
precipitation product (TRMM). The study focuses on 437 flood-inducing storm
events that occurred over a period of ten years (2002–2011) in the
Susquehanna River basin located in the northeastern United States. A
validation strategy was devised for assessing error metrics in rainfall and
simulated runoff as function of basin area, storm severity, and season. The
WSR-88D gauge-adjusted radar-rainfall (stage IV) product was used as the
reference rainfall data set, while runoff simulations forced with the stage
IV precipitation data set were considered as the runoff reference. Results
show that the generated rainfall ensembles from the downscaled reanalysis
product encapsulate the reference rainfall. The statistical analysis consists
of frequency and quantile plots plus mean relative error and root-mean-square
error statistics. The results demonstrated improvements in the precipitation
and runoff simulation error statistics of the satellite-driven downscaled
reanalysis data set compared to the original reanalysis precipitation
product. Results vary by season and less by basin scale. In the fall season
specifically, the downscaled product has 3 times lower mean relative error
than the original product; this ratio increases to 4 times for the simulated
runoff values. The proposed downscaling scheme is modular in design and can
be applied on any gridded satellite and reanalysis data set
Viscous Dissipation Impact on Free Convection Flow of Cu-water Nanofluid in a Circular Enclosure with Porosity Considering Internal Heat Source
In this work, free convection of Cu-water nanofluid in an enclosure by considering internally heat generated in the porous circular cavity and the impacts of viscous dissipation are numerically evaluated by control volume finite element method (CVFEM). The outer and inner sides of the circular porous enclosure are maintained at a fixed temperature while insulating the other two walls. The impacts of diverse effective parameters including the Rayleigh number, viscous dissipation, and nanofluid concentration on features of heat transfer and fluid flow are examined. Moreover, a new correlation for the average Nusselt number is developed according to the study’s active parameters. It can be deduced by the results that the maximum value of the temperature is proportional to the viscous dissipation parameter
A (not so) shallow controlled CO2 release experiment in a fault zone
The CSIRO In-Situ Laboratory Project (ISL) is located in Western Australia and has two main objectives related to monitoring leaks from a CO2 storage complex by controlled-release experiments: 1) improving the monitorability of gaseous CO2 accumulations at intermediate depth, and 2) assessing the impact of faults on CO2 migration. A first test at the In-situ Lab has evaluated the ability to monitor and detect unwanted leakage of CO2 from a storage complex in a major fault zone. The ISL consists of three instrumented wells up to 400 m deep: 1) Harvey-2 used primarily for gaseous CO2 injection, 2) ISL OB-1, a fibreglass geophysical monitoring well with behind-casing instrumentation, and 3) a shallow (27 m) groundwater well for fluid sampling. A controlled-release test injected 38 tonnes of CO2 between 336-342 m depth in February 2019, and the gas was monitored by a wide range of downhole and surface monitoring technologies. CO2 reached the ISL OB-1 monitoring well (7 m away) after approximately 1.5 days and an injection volume of 5 tonnes. Evidence of arrival was determined by distributed temperature sensing and the CO2 plume was detected also by borehole seismic after injection of as little as 7 tonnes. Observations suggest that the fault zone did not alter the CO2 migration along bedding at the scale and depth of the experiment. No vertical CO2 migration was detected beyond the perforated injection interval; no notable changes were observed in groundwater quality or soil gas chemistry during and post injection. The early detection of significantly less than 38 tonnes of CO2 injected into the shallow subsurface demonstrates rapid and sensitive monitorability of potential leaks in the overburden of a commercial-scale storage project, prior to reaching shallow groundwater, soil zones or the atmosphere. The ISL is a unique and enduring research facility at which monitoring technologies will be further developed and tested for increasing public and regulator confidence in the ability to detect potential CO2 leakage at shallow to intermediate depth
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