cross_totals#
- metpy.calc.cross_totals(pressure, temperature, dewpoint, vertical_dim=0)[source]#
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 pressuretemperature (
pint.Quantity
) – Temperature corresponding to pressuredewpoint (
pint.Quantity
) – Dewpoint temperature corresponding to pressurevertical_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')>