observed structure of the atmospheric boundary layer (2)
DESCRIPTION
Observed Structure of the Atmospheric Boundary Layer (2). Review of last lecture. Vertical structure of the atmosphere and definition of the boundary layer Vertical structure of the boundary layer Definition of turbulence and forcings generating turbulence - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Observed Structure of the Atmospheric Boundary Layer (2)](https://reader035.vdocuments.mx/reader035/viewer/2022062323/56815cbf550346895dcac494/html5/thumbnails/1.jpg)
Observed Structure of the Atmospheric Boundary Layer
(2)
![Page 2: Observed Structure of the Atmospheric Boundary Layer (2)](https://reader035.vdocuments.mx/reader035/viewer/2022062323/56815cbf550346895dcac494/html5/thumbnails/2.jpg)
Review of last lecture• Vertical structure of the atmosphere and
definition of the boundary layer• Vertical structure of the boundary layer • Definition of turbulence and forcings
generating turbulence• Static stability and vertical profile of virtual
potential temperature: 3 cases. Richardson number
• Boundary layer over ocean
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Boundary Layer depth:Lidar
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Boundary Layer depth:Lidar
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Turbulence inside the boundary layer
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Boundary Layer depth:Effects of diurnal forcing over land
• Daytime convective mixed layer + clouds (sometimes)• Nocturnal stable boundary layer + residual layer
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Convective mixed layer (CML):Growth
The turbulence (largely the convectively driven thermals) mixes (entrains) down potentially warmer, usually drier, less turbulent air down into the mixed layer
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Convective mixed layer (CML):Vertical profiles of state variables
Well-mixed (constant profile)
Super-adiabatic
Nearly adiabatic
Strongly stable lapse rate
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Nocturnal boundary layer over land: Vertical structure
• The residual layer is the left-over of CML, and has all the properties of the recently decayed CML. It has neutral stability.
• The stable boundary layer has stable stability, weaker turbulence, and low-level (nocturnal) jet.
Strongly stable lapse rate
Nearly adiabatic
Weakly stable lapse rate
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Comparison between day and night
Kaimal and Finnigan 1994
• Subtle difference between convective mixed layer and residual layer: Turbulence is more vigorous in the former
Super-adiabatic
Nearly adiabatic
Strongly stable lapse rate
Strongly stable lapse rate
Nearly adiabatic
Weakly stable lapse rate
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Summary• Daytime: convective mixed layer + clouds
(sometimes)• Nocturnal: stable boundary layer + residual
layer