Geoscience Reference
In-Depth Information
●
Averaging rules
:
simplifying rules apply when the time-average is taken of
decomposed atmospheric variables, decomposed variables multiplied by a
constant, and derivatives and combinations of decomposed variables
(Table 15.2).
●
Reynolds averaging
:
the cross product of two atmospheric variables is equal
to the product of their mean values plus the time-average of the instantane-
ous product of their fluctuating components: the time-average of the product
of two or more turbulent fluctuations cannot be assumed to be zero.
●
Mean and turbulent kinetic energy
:
Mean Kinetic Energy (MKE) and
Turbulent Kinetic Energy (TKE) per unit mass of air are given by the sum of
the squares of the mean wind speed components and sum of the squares of
the turbulent wind speed components, respectively: TKE is not conserved.
●
Correlation of variables
:
in the ABL there are substantial height- and time-
dependent correlations between the fluctuations in atmospheric variables
(e.g., virtual potential temperature, specific humidity, and vertical wind speed)
that are associated with the transport of turbulent fluxes within the ABL.
●
Kinematic fluxes
:
to simplify the development of equations describing
atmospheric flow described in later chapters it is convenient to work in terms
of kinematic fluxes (e.g.,
H
k
,
E
k
,
,
t
k
,
,
etc
), these being the fluxes in natural
c
p
).
●
Advective and turbulent flux
:
a
kinematic
flu
x
is the time-average of the
product of an atmospheric variable with the velocity component in the
direction of interest.
Reynolds averaging
identifies
kinematic
flu
x
as the sum
of an
advective flux
(the product of their mean values), and a
turbulent flux
(the time-average of the instantaneous product of their fluctuating
components).
units (e.g.,
H
,
E
,
t
, etc
) divided by
r
or, in the case of sensible heat, by (
r
References
Gash, J.H.C. and Dolman, A.J. 2003. Sonic anemometer (co)sine response and flux meas-
urement: I. The potential for cosine error to affect flux measurements.
Agricultural and
Forest Meteorology
,
119
, 195-207.
Stull, R.B. (1988)
An Introduction to Boundary Layer Meteorology
(Atmospheric Sciences
Library). Kluger Academic Publishers, Dordrecht, Netherlands.
