9.1.2. metcalcpy.diagnostics.land_surface.calc_humidity_index

metcalcpy.diagnostics.land_surface.calc_humidity_index(pressure, temperature, dewpoint, station_index, start_pressure_hpa=-1, bot_pressure_hpa=50.0, top_pressure_hpa=150.0, interp=True, db=False)
Function for computing the Humidity Index defined as:

\(\mathrm{HI_{low}} = (T_{950\,\text{hPa}} - D_{950\,\text{hPa}}) + (T_{850\,\text{hPa}} - D_{850\,\text{hPa}})\)

Parameters

  • pressure (pint.Quantity or xarray.DataArray) – the pressure variable with units of Hectopascals (hPa).

  • temperature (pint.Quantity or xarray.DataArray) – the temperature variable with units of Kelvin (K).

  • dewpoint (pint.Quantity or xarray.DataArray) – the dewpoint temperature variable with units of Kelvin (K).

  • station_index (int) – the integer index of the station currently being processed. Use -1 if a single station is being passed.

  • start_pressure_hpa (float, optional) – the starting pressure to use. Default: -1 (bottom level in profile).

  • bot_pressure_hpa (float, optional) – bottom pressure value of the layer, subtracted from start_pressure_hpa. Default: 50 hPa.

  • top_pressure_hpa (float, optional) – top pressure value of the layer, subtracted from start_pressure_hpa. Default: 150 hPa.

  • interp (bool) – perform vertical interpolation to bot_pressure_hpa and top_pressure_hpa or use closest. Default: True.

  • db (bool) – Print debugging statements. Default: False

Returns

float32

Reference:

Findell, K. L., and E. A. B. Eltahir, 2003: Atmospheric Controls on Soil Moisture–Boundary Layer Interactions. Part I: Framework Development. J. Hydrometeor., 4, 552–569, https://doi.org/10.1175/1525-7541(2003)004<0552:ACOSML>2.0.CO;2.

Also see: https://www.pauldirmeyer.com/coupling-metrics for a summary of this and other land-atmosphere coupling metrics.

Notes

Pressure and temperature can either be a 1D profile or a 3D array of data. If a 3D array, station_index needs to be a non-negative value indicating the single column to extract from the 3D data. If they are 1D profiles, use -1 for the station_index as that will be the only profile to use.

Note also that the equation denotes 950 and 850 hPa, but the starting pressure in vertical profiles is not always 1000 hPa. Thus, the function is designed to focus on a consistent layer depth of 100 hPa starting at 50 hPa above the bottom pressure value and ending at 150 hP above the bottom pressure value rather than a 100 hPa layer spanning 950 hPa to 850 hPa.