add tests for mean sea level pressure

Author: tjwixtrom

src/metpy/calc/basic.py

@@ -1205,7 +1205,7 @@ def _check_radians(value, max_radians=2 * np.pi):
 
 
 @exporter.export
-@preprocess_xarray
+@preprocess_and_wrap(wrap_like='pressure')
 @check_units('[pressure]', '[temperature]', '[length]', '[pressure]')
 def mean_sea_level_pressure(pressure, temperature, geopotential_height, vapor_pressure):
     """Reduce surface pressure to mean sea level.
@@ -1231,15 +1231,15 @@ def mean_sea_level_pressure(pressure, temperature, geopotential_height, vapor_pr
 
     Notes
     -----
-    This function is an implementation of the method used in [NWS1963]_, Ch. 7. The humidity correction term has been
-    fitted to be continuous and the local station correction has been ignored. See also [Pauley1998]_.
+    This function is an implementation of the method used in [NWS1963]_, Ch. 7. The humidity
+    correction term has been fitted to be continuous and the local station correction has been
+    ignored. See also [Pauley1998]_.
     """
     # define function for empirical humidity correction
     def humidity_correction(height):
-        """
-        Calculate humidity correction term
+        """Calculate humidity correction term.
 
-        Fitted from table of empirically derived values found in NWS Manual of Barometry, Ch. 7.
+        Fitted from table of empirically derived values found in NWS Manual of Barometry.
         """
         const = np.array([5.04969979e-6, 1.30236277, 1.96926239e-1])
         return (const[0] * (height.to('meter').m**const[1]) + const[2]) * units('degF / hPa')
@@ -1249,8 +1249,9 @@ def humidity_correction(height):
     lapse_rate = 6.5 * units('kelvin / kilometer')
 
     # calculate mean temperature for extrapolation
-    mean_temp = (temperature.to('kelvin') + ((lapse_rate * geopotential_height) / 2.).to('kelvin') +
-                 (vapor_pressure * humidity_correction(geopotential_height)).to('kelvin'))
+    mean_temp = temperature.to('kelvin') + \
+        ((lapse_rate * geopotential_height) / 2.).to('kelvin') + \
+        (vapor_pressure * humidity_correction(geopotential_height)).to('kelvin')
 
     # calculate mslp from hypsometric equation
     return pressure * np.exp(geopotential_height / (k * mean_temp))

tests/calc/test_basic.py

@@ -12,9 +12,9 @@
                         altimeter_to_sea_level_pressure, altimeter_to_station_pressure,
                         apparent_temperature, coriolis_parameter, geopotential_to_height,
                         heat_index, height_to_geopotential, height_to_pressure_std,
-                        pressure_to_height_std, sigma_to_pressure, smooth_circular,
-                        smooth_gaussian, smooth_n_point, smooth_rectangular, smooth_window,
-                        wind_components, wind_direction, wind_speed, windchill)
+                        mean_sea_level_pressure, pressure_to_height_std, sigma_to_pressure,
+                        smooth_circular, smooth_gaussian, smooth_n_point, smooth_rectangular,
+                        smooth_window, wind_components, wind_direction, wind_speed, windchill)
 from metpy.testing import (assert_almost_equal, assert_array_almost_equal, assert_array_equal)
 from metpy.units import units
 
@@ -796,3 +796,23 @@ def test_altimeter_to_sea_level_pressure_hpa():
     res = altimeter_to_sea_level_pressure(altim, elev, temp)
     truth = 1016.246 * units.hectopascal
     assert_almost_equal(res, truth, 3)
+
+
+def test_mean_sea_level_pressure():
+    """Test mean sea level pressure."""
+    p = 1013.25 * units('hPa')
+    T = 20. * units.degC
+    es = 3 * units('hPa')
+    z = 0. * units.meter
+    p0 = mean_sea_level_pressure(p, T, z, es)
+    assert_almost_equal(p, p0, 7)
+
+
+def test_mean_sea_level_pressure_1000m():
+    """Test mean sea level pressure with height above sea level."""
+    p = 920. * units('hPa')
+    T = 20. * units.degC
+    es = 1 * units('hPa')
+    z = 3270. * units.feet
+    p0 = mean_sea_level_pressure(p, T, z, es)
+    assert_almost_equal(1011.9606088890467 * units('hPa'), p0, 7)