Long-Term Observations and High-Resolution Modeling of Midlatitude Nocturnal Boundary Layer Processes Connected to Low-Level Jets

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Marke , T , Crewell , S , Schemann , V , Schween , J H & Tuononen , M 2018 , ' Long-Term Observations and High-Resolution Modeling of Midlatitude Nocturnal Boundary Layer Processes Connected to Low-Level Jets ' , Journal of Applied Meteorology and Climatology , vol. 57 , no. 5 , pp. 1155-1170 . https://doi.org/10.1175/JAMC-D-17-0341.1

Title: Long-Term Observations and High-Resolution Modeling of Midlatitude Nocturnal Boundary Layer Processes Connected to Low-Level Jets
Author: Marke, Tobias; Crewell, Susanne; Schemann, Vera; Schween, Jan H.; Tuononen, Minttu
Contributor: University of Helsinki, Department of Physics
Date: 2018-05
Language: eng
Number of pages: 16
Belongs to series: Journal of Applied Meteorology and Climatology
ISSN: 1558-8424
URI: http://hdl.handle.net/10138/308369
Abstract: Low-level-jet (LLJ) periods are investigated by exploiting a long-termrecord of ground-based remote sensing Doppler wind lidar measurements supported by tower observations and surface flux measurements at the Julich Observatory for Cloud Evolution (JOYCE), a midlatitude site in western Germany. LLJs were found 13% of the time during continuous observations over more than 4 yr. The climatological behavior of the LLJs shows a prevailing nighttime appearance of the jets, with a median height of 375 m and a median wind speed of 8.8 ms(-1) at the jet nose. Significant turbulence below the jet nose only occurs for high bulk wind shear, which is an important parameter for describing the turbulent characteristics of the jets. The numerous LLJs (16% of all jets) in the range of wind-turbine rotor heights below 200 m demonstrate the importance of LLJs and the associated intermittent turbulence for wind-energy applications. Also, a decrease in surface fluxes and an accumulation of carbon dioxide are observed if LLJs are present. A comprehensive analysis of an LLJ case shows the influence of the surrounding topography, dominated by an open pit mine and a 200-m-high hill, on the wind observed at JOYCE. High-resolution large-eddy simulations that complement the observations show that the spatial distribution of the wind field exhibits variations connected with the orographic flow depending on the wind direction, causing high variability in the long-term measurements of the vertical velocity.
Subject: GREAT-PLAINS
DOPPLER LIDAR
WIND
CLIMATOLOGY
WEATHER
PRECIPITATION
PERFORMANCE
NETWORK
SYSTEM
ENERGY
114 Physical sciences
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