Atmospheric Boundary Layer Classification With Doppler Lidar

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Manninen , A J , Marke , T , Tuononen , M & O'Connor , E J 2018 , ' Atmospheric Boundary Layer Classification With Doppler Lidar ' , Journal of Geophysical Research : Atmospheres , vol. 123 , no. 15 , pp. 8172-8189 . https://doi.org/10.1029/2017JD028169

Title: Atmospheric Boundary Layer Classification With Doppler Lidar
Author: Manninen, A. J.; Marke, T.; Tuononen, M.; O'Connor, E. J.
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2018-08-16
Language: eng
Number of pages: 18
Belongs to series: Journal of Geophysical Research : Atmospheres
ISSN: 2169-897X
URI: http://hdl.handle.net/10138/299689
Abstract: We present a method using Doppler lidar data for identifying the main sources of turbulent mixing within the atmospheric boundary layer. The method identifies the presence of turbulence and then assigns a turbulent source by combining several lidar quantities: attenuated backscatter coefficient, vertical velocity skewness, dissipation rate of turbulent kinetic energy, and vector wind shear. Both buoyancy-driven and shear-driven situations are identified, and the method operates in both clear-sky and cloud-topped conditions, with some reservations in precipitation. To capture the full seasonal cycle, the classification method was applied to more than 1year of data from two sites, Hyytiala, Finland, and Julich, Germany. Analysis showed seasonal variation in the diurnal cycle at both sites; a clear diurnal cycle was observed in spring, summer, and autumn seasons, but due to their respective latitudes, a weaker cycle in winter at Julich, and almost non-existent at Hyytiala. Additionally, there are significant contributions from sources other than convective mixing, with cloud-driven mixing being observed even within the first 500m above ground. Also evident is the considerable amount of nocturnal mixing within the lowest 500m at both sites, especially during the winter. The presence of a low-level jet was often detected when sources of nocturnal mixing were diagnosed as wind shear. The classification scheme and the climatology extracted from the classification provide insight into the processes responsible for mixing within the atmospheric boundary layer, how variable in space and time these can be, and how they vary with location. Key Points
Subject: LOW-LEVEL JETS
VELOCITY-VARIANCE
DISSIPATION RATE
MIXING HEIGHT
CLOUD
WIND
TURBULENCE
FINLAND
TRANSITION
PARAMETERS
114 Physical sciences
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