lifted_index

metpy.calc.lifted_index(pressure, temperature, parcel_profile, vertical_dim=0)

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 pressure

• temperature (pint.Quantity) – Atmospheric temperature corresponding to pressure

• parcel_profile (pint.Quantity) – Temperature profile of the parcel

• vertical_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

mixed_parcel, parcel_profile

Examples using metpy.calc.lifted_index

Sounding Calculation Examples

Sounding Calculation Examples