cross_totals#

metpy.calc.cross_totals(pressure, temperature, dewpoint, vertical_dim=0)#

Calculate Cross Totals from the pressure temperature and dewpoint.

Cross Totals formula derived from [Miller1972]:

\[CT = Td850 - T500\]

where:

  • \(Td850\) is the dewpoint at 850 hPa

  • \(T500\) is the temperature at 500 hPa

Calculation of the Cross Totals is defined as the difference between dewpoint at 850 hPa and temperature at 500 hPa. This is a part of the Total Totals Index.

Parameters:

  • pressure (pint.Quantity) – Pressure level(s), in order from highest to lowest pressure

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

  • dewpoint (pint.Quantity) – Dewpoint temperature corresponding to pressure

  • vertical_dim (int, optional) – The axis corresponding to vertical, defaults to 0. Automatically determined from xarray DataArray arguments.

Returns:

pint.Quantity – Cross Totals

Examples

>>> from metpy.calc import dewpoint_from_relative_humidity, cross_totals
>>> 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 cross totals index
>>> cross_totals(p, T, Td)
<Quantity(19.7741081, 'delta_degree_Celsius')>

Examples using metpy.calc.cross_totals#

Sounding Calculation Examples

Sounding Calculation Examples