diff --git a/src/metpy/calc/thermo.py b/src/metpy/calc/thermo.py index fd7dc34b1be..2a166f874ea 100644 --- a/src/metpy/calc/thermo.py +++ b/src/metpy/calc/thermo.py @@ -3293,7 +3293,6 @@ def mixed_parcel(pressure, temperature, dewpoint, parcel_start_pressure=None, Pressure of the mixed parcel `pint.Quantity` Temperature of the mixed parcel - `pint.Quantity` Dewpoint of the mixed parcel @@ -4354,7 +4353,8 @@ def lifted_index(pressure, temperature, parcel_profile, vertical_dim=0): Calculation of the lifted index is defined as the temperature difference between the observed 500 hPa temperature and the temperature of a parcel lifted from the - surface to 500 hPa. + surface to 500 hPa. As noted in [Galway1956]_, a low-level mixed parcel is often used + as the surface parcel. Parameters ---------- @@ -4379,29 +4379,38 @@ def lifted_index(pressure, temperature, parcel_profile, vertical_dim=0): Examples -------- - >>> from metpy.calc import dewpoint_from_relative_humidity, lifted_index, parcel_profile + >>> from metpy.calc import lifted_index, mixed_parcel, parcel_profile >>> from metpy.units import units - >>> # pressure - >>> p = [1008., 1000., 950., 900., 850., 800., 750., 700., 650., 600., - ... 550., 500., 450., 400., 350., 300., 250., 200., - ... 175., 150., 125., 100., 80., 70., 60., 50., - ... 40., 30., 25., 20.] * units.hPa - >>> # temperature - >>> T = [29.3, 28.1, 23.5, 20.9, 18.4, 15.9, 13.1, 10.1, 6.7, 3.1, - ... -0.5, -4.5, -9.0, -14.8, -21.5, -29.7, -40.0, -52.4, - ... -59.2, -66.5, -74.1, -78.5, -76.0, -71.6, -66.7, -61.3, - ... -56.3, -51.7, -50.7, -47.5] * units.degC - >>> # relative humidity - >>> rh = [.85, .65, .36, .39, .82, .72, .75, .86, .65, .22, .52, - ... .66, .64, .20, .05, .75, .76, .45, .25, .48, .76, .88, - ... .56, .88, .39, .67, .15, .04, .94, .35] * units.dimensionless - >>> # calculate dewpoint - >>> Td = dewpoint_from_relative_humidity(T, rh) - >>> # compute the parcel temperatures from surface parcel - >>> prof = parcel_profile(p, T[0], Td[0]) - >>> # calculate the LI - >>> lifted_index(p, T, prof) - + >>> from numpy import concatenate + >>> + >>> # Define pressure, temperature, dewpoint temperature, and height + >>> p = [1002., 1000., 993., 925., 850., 846., 723., 632., 479., 284., + ... 239., 200., 131., 91., 72.7, 54.6, 41., 30., 22.8] * units.hPa + >>> T = [28.2, 27., 25.4, 19.4, 12.8, 12.3, 4.2, 0.8, -12.7, -41.7, -52.3, + ... -57.5, -54.9, -57.8, -58.5, -52.3, -53.4, -50.3, -49.9] * units.degC + >>> Td = [14.2, 14., 12.4, 11.4, 10.2, 10.1, -7.8, -16.2, -37.7, -55.7, + ... -58.3, -69.5, -85.5, -88., -89.5, -88.3, -88.4, -87.3, -87.9] * units.degC + >>> h = [139, 159, 221, 839, 1559, 1599, 2895, 3982, 6150, 9933, 11072, + ... 12200, 14906, 17231, 18650, 20474, 22323, 24350, 26149] * units.m + >>> + >>> # Calculate 500m mixed parcel + >>> parcel_p, parcel_t, parcel_td = mixed_parcel(p, T, Td, depth=500 * units.m, height=h) + >>> + >>> # Replace sounding temp/pressure in lowest 500m with mixed values + >>> above = h > 500 * units.m + >>> press = concatenate([[parcel_p], p[above]]) + >>> temp = concatenate([[parcel_t], T[above]]) + >>> + >>> # Calculate parcel profile from our new mixed parcel + >>> mixed_prof = parcel_profile(press, parcel_t, parcel_td) + >>> + >>> # Calculate lifted index using our mixed profile + >>> lifted_index(press, temp, mixed_prof) + + + See Also + -------- + mixed_parcel, parcel_profile """ # find the measured temperature and parcel profile temperature at 500 hPa.