def tn_days_below(tasmin, thresh="-10.0 degC", freq="YS"):
r"""Number of days with tmin below a threshold in
Number of days where daily minimum temperature is below a threshold.
Parameters
----------
tasmin : xarray.DataArray
Minimum daily temperature [℃] or [K]
thresh : str
Threshold temperature on which to base evaluation [℃] or [K] . Default: '-10 degC'.
freq : str, optional
Resampling frequency
Returns
-------
xarray.DataArray
Number of days Tmin < threshold.
Notes
-----
Let :math:`TN_{ij}` be the daily minimum temperature at day :math:`i` of period :math:`j`. Then
counted is the number of days where:
.. math::
TX_{ij} < Threshold [℃]
"""
thresh = utils.convert_units_to(thresh, tasmin)
f1 = utils.threshold_count(tasmin, "<", thresh, freq)
return f1
def test_simple(self, tas_series):
ts = tas_series(np.arange(365))
out = utils.threshold_count(ts, "<", 50, "Y")
np.testing.assert_array_equal(out, [50, 0])