sweat_index#
- metpy.calc.sweat_index(pressure, temperature, dewpoint, speed, direction, vertical_dim=0)[source]#
Calculate SWEAT Index.
SWEAT Index derived from [Miller1972]:
\[SWEAT = 12Td_{850} + 20(TT - 49) + 2f_{850} + f_{500} + 125(S + 0.2)\]where:
\(Td_{850}\) is the dewpoint at 850 hPa; the first term is set to zero if \(Td_{850}\) is negative.
\(TT\) is the total totals index; the second term is set to zero if \(TT\) is less than 49
\(f_{850}\) is the wind speed at 850 hPa
\(f_{500}\) is the wind speed at 500 hPa
\(S\) is the shear term: \(sin{(dd_{850} - dd_{500})}\), where \(dd_{850}\) and \(dd_{500}\) are the wind directions at 850 hPa and 500 hPa, respectively. It is set to zero if any of the following conditions are not met:
\(dd_{850}\) is between 130 - 250 degrees
\(dd_{500}\) is between 210 - 310 degrees
\(dd_{500} - dd_{850} > 0\)
both the wind speeds are greater than or equal to 15 kts
Calculation of the SWEAT Index consists of a low-level moisture, instability, and the vertical wind shear (both speed and direction). This index aim to determine the likeliness of severe weather and tornadoes.
- 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 pressurespeed (
pint.Quantity
) – Wind speed corresponding to pressuredirection (
pint.Quantity
) – Wind direction corresponding to pressurevertical_dim (int, optional) – The axis corresponding to vertical, defaults to 0. Automatically determined from xarray DataArray arguments.
- Returns:
pint.Quantity
– SWEAT Index