lifted_index#
- metpy.calc.lifted_index(pressure, temperature, parcel_profile, vertical_dim=0)[source]#
Calculate Lifted Index from the pressure temperature and parcel profile.
Lifted index formula derived from [Galway1956] and referenced by [DoswellSchultz2006]:
\[LI = T500 - Tp500\]where:
\(T500\) is the measured temperature at 500 hPa
\(Tp500\) is the temperature of the lifted parcel at 500 hPa
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. As noted in [Galway1956], a low-level mixed parcel is often used as the surface parcel.
- Parameters:
pressure (
pint.Quantity
) – Atmospheric pressure level(s) of interest, in order from highest to lowest pressuretemperature (
pint.Quantity
) – Atmospheric temperature corresponding to pressureparcel_profile (
pint.Quantity
) – Temperature profile of the parcelvertical_dim (int, optional) – The axis corresponding to vertical, defaults to 0. Automatically determined from xarray DataArray arguments.
- Returns:
pint.Quantity
– Lifted Index
Examples
>>> from metpy.calc import lifted_index, mixed_parcel, parcel_profile >>> from metpy.units import units >>> 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) <Quantity([2.4930656], 'delta_degree_Celsius')>
See also