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Boundary Layer Meteorology

Boundary Layer Meteorology. Prof. Daniel Kirk-Davidoff Rm. 3423 CSS (301)-270-3704 dankd@atmos.umd.edu. 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

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  1. Boundary Layer Meteorology Prof. Daniel Kirk-Davidoff Rm. 3423 CSS (301)-270-3704 dankd@atmos.umd.edu

  2. Lecture 1 8/31/04 • Course Syllabus: discuss requirements, schedule, readings. • Starting Point Exam • Introduction to the Boundary Layer • Hand out readings

  3. 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”

  4. Introduction to the Boundary Layer 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.”

  5. Things that happen in the boundary layer • 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)

  6. Things that happen in the boundary layer • Horizontal wind shear (due to flow of wind around obstacles: trees, mountains, islands) • Waves (gravity) • Spiraling Winds • Katabatic (drainage) Winds • Nocturnal Jet

  7. Things that happen in the boundary layer • Clouds: • Fair weather cumulus clouds (whose roots are in the BL) • Trade cumulus (which may rain) • Stratocumulus clouds (which may rain) • Fog

  8. Kinds of atmospheric boundary layers • Stable • Near-Neutral • Convective

  9. Kinds of atmospheric boundary layers

  10. Read ch. 1 of Garratt, and answer: • 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?

  11. Read ch. 1 of Garratt, and answer: • 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)?

  12. Read ch. 1 of Garratt, and answer: • Why is w’ anticorrelated with any other property fluctuation in figure 1.4?

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