Compute the kinematic flux from two time series.
Compute the kinematic flux from the time series of two variables vel
and b. Note that to be a kinematic flux, at least one variable must be
a component of velocity.
vel (array_like) – A component of velocity
b (array_like) – May be a component of velocity or a scalar variable (e.g. Temperature)
perturbation (bool, optional) – True if the vel and b variables are perturbations. If False, perturbations
will be calculated by removing the mean value from each variable. Defaults to False.
array_like – The corresponding kinematic flux
axis (int, optional) – The index of the time axis, along which the calculations will be
performed. Defaults to -1
A kinematic flux is computed as
where at the prime notation denotes perturbation variables, and at least
one variable is perturbation velocity. For example, the vertical kinematic
momentum flux (two velocity components):
or the vertical kinematic heat flux (one velocity component, and one
If perturbation variables are passed into this function (i.e.
perturbation is True), the kinematic flux is computed using the equation
However, the equation above can be rewritten as
which is computationally more efficient. This is how the kinematic flux
is computed in this function if perturbation is False.
For more information on the subject, please see [Garratt1994].