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The Orinoco low-level jet

Author
Jimenez Sanchez, Jorge Giovanni
Published
[University Park, Pennsylvania] : Pennsylvania State University, 2018.
Physical Description
1 electronic document
Additional Creators
Markowski, Paul, 1974-
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Open Access.
Summary
The low-level jet over the Orinoco River basin is characterized using finer horizontal, vertical, and temporal resolution than possible in previous studies via dynamical downscaling. The investigation relies on a 5-month-long simulation (November 2013- March 2014) performed with the Weather Research and Forecasting model, with initial and boundary conditions provided by the Global Forecast System analysis. Dynamical downscaling is demonstrated to be an effective method to better resolve the horizontal and vertical characteristics of the OLLJ, not only improving its diurnal and austral-summer evolution, the identification and location of low-level jet streaks inside the stream tube, but also in determining the mechanisms leading to its formation.The Orinoco low-level jet (OLLJ) is found to be a single stream tube over Colombia and Venezuela with wind speeds greater than 8 m s-1, and four distinctive cores varying in height under the influence of sloping terrain. The OLLJ has its maximum monthly mean wind speed (13 m s-1) and largest spatial extent (2100 km 400 km) in January. The maxima mean wind speeds (1317 m s-1) in the diurnal cycle occur in the early morning above the nocturnal inversion; wind speeds are a minimum (89 m s-1) in the late afternoon when a deep, approximately unstratified boundary layer is present.The momentum balance analysis performed in a streamwise- and crosswise-rotated coordinate system reveal that the OLLJ is the result of four phenomena acting together to accelerate the wind: a sea-breeze penetration over the Orinoco River delta and Unare River depression, katabatic flow down the Coastal Cordillera, three expansion fans from point wakes in topography, and diurnal variation of turbulent diffusivity. The latter, in contrast to the heavily studied nocturnal low-level jet in the U.S. Great Plains region, plays only asecondary role in OLLJ acceleration. These results suggest that LLJs near the equator may originate from processes other than the inertial oscillation and topographic thermal forcing.
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Dissertation Note
Ph.D. Pennsylvania State University 2018.
Reproduction Note
Microfilm (positive). 1 reel ; 35 mm. (University Microfilms 13871843)
Technical Details
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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