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# Boundary Layer Meteorology - PowerPoint PPT Presentation

Boundary Layer Meteorology. Prof. Daniel Kirk-Davidoff Rm. 3423 CSS (301)-270-3704 [email protected] Lecture 1 8/31/04. Course Syllabus: discuss requirements, schedule, readings. Starting Point Exam Introduction to the Boundary Layer Hand out readings.

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### Boundary Layer Meteorology

Prof. Daniel Kirk-Davidoff

Rm. 3423 CSS

(301)-270-3704

• Course Syllabus: discuss requirements, schedule, readings.

• Starting Point Exam

• Introduction to the Boundary Layer

Definitions:

Stull:“that part of the troposphere that is directly influenced by the presence of the earth’s surface, and responds to surface forcings with a timescale of about an hour or less”

Definitions:

Garratt:“the layer of air directly above the Earth’s surface in which the effects of the surface (friction, heating and cooling [and moistening]) are felt directly on time scales of less than a day, and in which significant fluxes of momentum, heat or matter are carried by turbulent motions on a scale of the order of the depth of the boundary layer or less.”

• Large diurnal temperature variations (relative to the free troposphere above).

• Turbulence

• Sources of turbulence:

• Thermal forcing (thermals: buoyant eddies forced by solar heating of the surface)

• Vertical wind shear (due to frictional drag by the surface on geostrophic flow aloft)

• Horizontal wind shear (due to flow of wind around obstacles: trees, mountains, islands)

• Waves (gravity)

• Spiraling Winds

• Katabatic (drainage) Winds

• Nocturnal Jet

• Clouds:

• Fair weather cumulus clouds (whose roots are in the BL)

• Trade cumulus (which may rain)

• Stratocumulus clouds (which may rain)

• Fog

• Stable

• Near-Neutral

• Convective

• Why is the mean structure of the boundary layer “very much dependent on the season”?

• When and why is the structure of the boundary layer over the ocean similar to that over land “in extra-tropical latitudes”?

• Otherwise, why is the marine boundary layer usually shallower than over the land?

• Why is “information on the likely growth of the shallow mixed layer” of particular importance to the dispersal of smog and low-level pollutants?

• How does dewfall and frost formation depend on the state of the atmospheric boundary layer (ABL)?

• Why is w’ anticorrelated with any other property fluctuation in figure 1.4?