Validation of ICESat-2 Surface Water Level Product ATL13 with Near Real Time Gauge Data
Giribabu Dandabathula,
Sitiraju Srinivasa Rao
Issue:
Volume 8, Issue 2, June 2020
Pages:
19-25
Received:
23 July 2020
Accepted:
3 August 2020
Published:
13 August 2020
Abstract: The NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) mission uses laser altimetry measurements to determine the elevations at point levels of Earth. ICESat-2, which is a successor to the ICESat-1 satellite mission is a continuation of this series and carries a sensor namely Advanced Topographic Laser Altimeter System (ATLAS). The key advancement of ICESat-2 is that it generates individual laser foot prints of nearly 14 m (in diameter) on the Earth’s surface, with each footprint separated by only 70 cm, a much higher resolution and sampling than the earlier mission. ATLAS works under the concept of multi-beam approach containing three pairs of strong and weak beams that produce data products containing global geolocated photon data and height data from land-ice, sea-ice, land/terrain, canopy, ocean surface, and inland water-bodies. From the Level 2 master product called ATL03 numerous sub-data product are generated and are made available to the public through the National Snow and Ice Data Center. One of the products namely ATL13 is a specialized geophysical data product that gives along-track and near-shore water surface height distribution within the water masks. In this article, results after validating ATL13 data product with 46 observations made with near real-time gauged data for 15 reservoirs/water bodies have been presented. The maximum uncertainty observed for this data product is at centimeter-level. A significant observation made from this study is that the heights of surface water level computed from strong beams (gt1r, gt2r, and gt3r) and weak beams (gt1l, gt2l, and gt3l) are occasionally having a variation of 5 to 10 centimeters relatively.
Abstract: The NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) mission uses laser altimetry measurements to determine the elevations at point levels of Earth. ICESat-2, which is a successor to the ICESat-1 satellite mission is a continuation of this series and carries a sensor namely Advanced Topographic Laser Altimeter System (ATLAS). The key advanc...
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A Study of Flow Structure Topology in the Vicinity of a Concave Bed Sill Using Numerical Model
Moslem Sohrabi,
Alireza Keshavarzi,
Mahmood Javan
Issue:
Volume 8, Issue 2, June 2020
Pages:
26-33
Received:
10 August 2020
Accepted:
22 August 2020
Published:
31 August 2020
Abstract: Stabilization of the banks and bed of the river is an important problem in river engineering works. River bed scouring is a major environmental problem for fish and aquatic habitat resources. Using a bed sill is one approach that can be used to prevent waterway bed scouring. In this study, a concave bed sill was tested in an experimental program with movable bed condition. In addition to the experimental program, numerical simulations were undertaken to explore the flow characteristic around concave bed sill. In experiment the results showed that most scouring occurred at the channel sides, while deposition occurred in the middle of channel downstream of the concave bed sill. During the experiment two dimensional flow velocity was measured using particle image velocimetry (PIV). It was found that a vortex formed at the sides and downstream of the concave bed sill and then stretched to the middle of the channel. The results also indicated that there was minimum flow vorticity intensity at the center of the channel where deposition occurred. The numerical results were compared with this experimental data to validate the numerical simulations. The numerical results confirmed that for a concave bed sill, similarly a vortex formed at the side of the channel which created the maximum scouring depth at the side wall and with following deposition of sediment particles in the centerline of the channel.
Abstract: Stabilization of the banks and bed of the river is an important problem in river engineering works. River bed scouring is a major environmental problem for fish and aquatic habitat resources. Using a bed sill is one approach that can be used to prevent waterway bed scouring. In this study, a concave bed sill was tested in an experimental program wi...
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