geodata.wind.extrapolate_wind_speed#

geodata.wind.extrapolate_wind_speed(ds, to_height, extrap_fn=log_ratio, from_height=None, var_height=None)#

Extrapolate the wind speed from a given height above ground to another.

If ds already contains a key refering to wind speeds at the desired to_height, no conversion is done and the wind speeds are directly returned.

Otherwise, extrapolates according to (1) extrap_fn and (2) heights

Parameters:

ds (xarray.Dataset) – Dataset containing the wind speed time-series
to_height (int|float) – Height (m) to which the wind speeds are extrapolated
extrap_fn (function for wind speed extrapolation) – log_ratio : wind speed follows the logarithmic ratio law as desribed in [1] log_law : wind speed follows logarithmic (integration) law described in [3] power_law : wind speed follows power law (with fixed alpha), e.g., in [4]
from_height (int) – (Optional) Height (m) from which the wind speeds are interpolated to ‘to_height’. If not provided, the closest height to ‘to_height’ is selected.
var_height (str) – (Optional) suffix of variables in ds corresponding to variable height e.g., lml => height contained in hlml, wind speed contained in wndlml

Returns:

da – DataArray containing the extrapolated wind speeds. Name of the DataArray is ‘wnd{to_height:d}’.

Return type:

xarray.DataArray

References

[1] Equation (2) in Andresen, G. et al (2015):: ‘Validation of Danish wind time series from a new global renewable energy atlas for energy system analysis’.
[2] https://en.wikipedia.org/w/index.php?title=Roughness_length&oldid=862127433,: Retrieved 2019-02-15.

[3] S. Emeis, Wind Energy Meteorology (Springer, Berlin, 2013). [4] Archer, C.L., Jacobson, M.Z., 2005. Evaluation of global wind power.

Journal of Geophysical Research 110, D12110.

geodata.wind.extrapolate_wind_speed