1. Boundary Layer Meteorology
Prof. Daniel Kirk-Davidoff
Rm CSS
(301)

2. Lecture /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
Marine
Continental
Little diurnal variability
Strong diurnal variability
1-2 km (3 max, maybe)
Up to 5 km over deserts
Low Bowen ratio
High Bowen ratio
Wave state important
Surface shape fixed, but important

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?