Fixed doc broken reference and added more tests to wind chill

tests/test_scalars.py

@@ -154,11 +154,26 @@ def test_apparent_temperature(self):
         # print(f"at {at}")
         assert at == pytest.approx(299.86678322384626, abs=1e-6)
 
-    def test_windchill(self):
+    def test_wind_chill(self):
         t2_k = np.array([270])
         va = np.array([10])
-        wc = np.array([tmf.calculate_wind_chill(t2_k, va)])
-        assert wc == pytest.approx(261.92338925380074, abs=1e-6)
+        wc_k = np.array([tmf.calculate_wind_chill(t2_k, va)])
+        assert wc_k == pytest.approx(261.92338925380074, abs=1e-6)
+        # reference result from from wikipedia article https://en.wikipedia.org/wiki/Wind_chill
+        t2_k = np.array([tmf.celsius_to_kelvin(-20)])  # -20C to K
+        va = np.array([5 / 3.6])  # 5 km/h to m/s
+        wc_k = np.array([tmf.calculate_wind_chill(t2_k, va)])
+        wc_c = tmf.kelvin_to_celsius(wc_k)
+        assert wc_c == pytest.approx(
+            -24.27850328, abs=1e-6
+        )  # around ~ -24C for wind chill (not exact)
+        va = np.array([30 / 3.6])  # 30 km/h to m/s
+        wc_k = np.array([tmf.calculate_wind_chill(t2_k, va)])
+        wc_c = tmf.kelvin_to_celsius(wc_k)
+        print(f"wc_c {wc_c}")
+        assert wc_c == pytest.approx(
+            -32.56804448, abs=1e-6
+        )  # around ~ -33C for wind chill (not exact)
 
     def test_heat_index_simplified(self):
         t2_k = np.array([tmf.celsius_to_kelvin(21.0)])

thermofeel/thermofeel.py

@@ -711,11 +711,11 @@ def calculate_wind_chill(t2_k, va):
         :param t2_k: (float array) 2m Temperature [K]
         :param va: (float array) wind speed at 10 meters [m/s]
         returns wind chill [K]
-        Temperature must be between -50°C and 5°C; wind speed must be between 5km/h and 80km/h
-        Wind chill from input values outside those ranges are not to be considered valid
+        Computation is only valid for temperatures between -50°C and 5°C and wind speeds between 5km/h and 80km/h.
+        For input values outside those ranges, computed results not be considered valid.
     Reference: Blazejczyk et al. (2012)
     https://doi.org/10.1007/s00484-011-0453-2
-    See also: http://www.ec.gc.ca/meteo-weather/default.asp?lang=n&n=5FBF816A-1#wc6
+    See also: https://web.archive.org/web/20130627223738/http://climate.weatheroffice.gc.ca/prods_servs/normals_documentation_e.html  # noqa
     """
     t2_c = kelvin_to_celsius(t2_k)  # kelvin_to_celsius(tk)
     v = va * 3.6  # convert to kilometers per hour