Data Shortcuts (Properties)
DOLfYN datasets also contain shortcuts to other variables that can be obtained from simple operations of its data items. Certain shortcuts require variables calculated using the DOLfYN API.
Name |
units |
Description/Notes |
---|---|---|
u |
m/s |
|
v |
m/s |
|
w |
m/s |
|
U |
m/s |
Horizontal velocity as a complex quantity (u + 1j * v) |
U_mag |
m/s |
Magnitude of the horizontal velocity |
U_dir |
deg |
Direction of the horizontal velocity (CCW from X, East, or streamwise direction, depending on coordinate system) |
I |
— |
Turbulence Intensity: ratio of horizontal velocity standard deviation (U_std) to mean (‘U_mag’) |
I_tke |
— |
TKE Intensity: Ratio of sqrt(2*tke) to horizontal velocity magnitude |
tke |
m2/s2 |
Turbulent kinetic energy (half the sum of the data in ‘tke_vec’) |
E_coh |
m2/s2 |
Coherent TKE (root-sum-square of Reynold’s stresses) |
upup_ |
m2/s2 |
|
vpvp_ |
m2/s2 |
|
wpwp_ |
m2/s2 |
|
upvp_ |
m2/s2 |
|
upwp_ |
m2/s2 |
|
vpwp_ |
m2/s2 |
|
Important Note: The items listed in Table 4 are not stored in the dataset but are provided as attributes (shortcuts) to the dataset itself. They are accessed through the xarray accessor velds.
For example, to return the magnitude of the horizontal velocity:
>> import dolfyn
>> dat = dolfyn.read_example('AWAC_test01.wpr')
>> dat.velds.U_mag
<xarray.DataArray 'vel' (range: 20, time: 9997)>
array([[1.12594587, 0.82454599, 0.96503734, ..., 3.40359042, 3.34527587,
3.44412805],
[0.86688534, 1.05108722, 1.12899632, ..., 0.72053462, 6.47548786,
0.49120468],
[0.88066635, 0.97954744, 0.63123135, ..., 4.37153751, 2.77540426,
1.81550287],
...,
[1.00013206, 1.21381814, 1.14834231, ..., 5.89236205, 1.44082763,
2.7157082 ],
[0.7759962 , 0.89600228, 1.02900833, ..., 2.39949021, 2.18758737,
4.41797285],
[0.95729835, 1.15594339, 1.15038508, ..., 3.11517746, 3.79158362,
2.66788512]])
Coordinates:
* range (range) float32 1.41 2.41 3.4 4.4 5.4 ... 17.36 18.36 19.35 20.35
* time (time) float64 1.34e+09 1.34e+09 1.34e+09 ... 1.34e+09 1.34e+09
Attributes:
units: m/s
description: horizontal velocity magnitude