7. Topographic Eeffects and Sea Breezes

Question 1

Laminar boundary layer (vs. turbulent)

Answer 1

Laminar = no mixing of different speed layers, linear reduction in wind speed from free flow to surface

Question 2

Laminar boundary layer thickness vs. turbulent layer

Answer 2

Turbulent: 2,000 feet, Laminar: 1000-1500 feet (surface wind speed in laminar layer lower than in turbulent for same free flow wind speed)

Question 3

Surface wind “slack and back” over land day (direction and speed)

Answer 3

• 30 degrees, 50% of free low

Question 4

Surface wind “slack and back” over sea / day (direction and speed)

Answer 4

• 10 degrees, 70% of free flow wind

Question 5

Mountain breeze / valley breeze

Answer 5

Cooling (night) and warming (day) of upslope air leads to denser higher presser and downslope breeze (night), lower pressure and upslope breeze (day) -

Question 6

Foehn Winds

Answer 6

warm wind on lee side of mountain, air blows over mountain, coo,s reaches dew point, looses moisture, descends on lee side and warms up, ends up warmer than before

Question 7

Calculate temperature rise of Foehn wind on lee side

Answer 7

1.2 (difference between DALR and SALR) x difference of cloudbase (windward side vs lee side) in 1,000s of feet

Question 8

Katabatic winds

Answer 8

Air flowing down mountains at night (as surface cools, air parcels become denser and slide down the mountain)

Question 9

Anabatic winds

Answer 9

Airflow up the side of mountains as surface heats during day (air goes straight up, though, rather than following mountain profile)

Question 10

Hazards with wind blowing over hills

Answer 10

• Air cooling / icing on windward side
• Venturi effects can make altimeter overread
• Foehn on lee side + katabatic effects can create a temperature inversion

Question 11

Sea breeze

Answer 11

Forms during day with a slack pressure gradient, increase in strength during day, if strong enough coriolis force makes it veer (in northern hemisphere), small cold front and cloud may form inland