Geoscience Reference
In-Depth Information
12.13 Explain why second-order closure can be more reliable in the SBL than the
CBL.
Problems
12.1 The surface energy balance has a term involving heat transfer at the top of the
surface slab. Discuss its nature and explain why this is sometimes referred
to as
convective
heat transfer.
12.2 A surface is cooler than the air above and is evaporating water so that the
vertical flux of water vapor is positive. The virtual temperature flux is zero.
What is the stability index
z/L
? Using M-O similarity, write the expression
for the vertical gradient of potential temperature.
12.3 Explain why the late-afternoon change in direction of the surface heat flux
occurs before sunset.
12.4 Explain and discuss why the nocturnal ABL is less likely to provide quasi-
steady conditions than its daytime counterpart.
12.5 Under what conditions would you expect to find an inertial subrange in stably
stratified turbulence?
12.6 Sketch the vertical profile of the length scale of the energetic eddies of the
w
-field in the inversion-capped neutral ABL of
Figure 9.7
.
12.7 The change in mean wind direction across the ABL tends to be least in the
convective case and greatest in the stable case. Why? (Hint: Consider the
streamwise mean equation of motion.)
12.8 Explain why the nocturnal jet can be particularly strong following the late-
afternoon decay of a baroclinic convective ABL.
12.9 Discuss some of the differences between the daytime and nocturnal ABLs
as potential sources of wind power.
12.10 Explain why the mean wind speed in the surface layer typically decreases in
late afternoon in clear weather. (Hint: use the forms of the M-O functions for
dimensionless mean wind shear, and assume the mean horizontal pressure
gradient does not change.)
12.11 Which term in the horizontal equation of mean motion also contributes to the
post-transition decrease in mean wind speed in the surface layer? Interpret
the mechanism physically.
12.12 Show that the indicated solution to
Eq. (12.48)
for the complex stress profile
is consistent with
Eq. (12.6)
.
12.13 Derive
Eq. (12.14)
and the solution
(12.15)
.
12.14 Derive
Eqs. (12.16
)and
(12.17)
.
