List of metrics

TropD_Metric_EDJ(U, lat[, lev, method, n, n_fit]) TropD Eddy Driven Jet (EDJ) metric
TropD_Metric_OLR(olr, lat[, method, Cutoff, n]) TropD Outgoing Longwave Radiation (OLR) metric
TropD_Metric_PE(pe, lat[, method, ...]) TropD Precipitation minus Evaporation (PE) metric
TropD_Metric_PSI(V, lat, lev[, method, ...]) TropD Mass streamfunction (PSI) metric
TropD_Metric_PSL(ps, lat[, method, n]) TropD Sea-level pressure (PSL) metric
TropD_Metric_STJ(U, lat, lev[, method, n]) TropD Subtropical Jet (STJ) metric
TropD_Metric_TPB(T, lat, lev[, method, n, ...]) TropD Tropopause break (TPB) metric
TropD_Metric_UAS(U, lat[, lev, method, ...]) TropD near-surface zonal wind (UAS) metric

Description of metrics

metrics.TropD_Metric_EDJ(U, lat, lev=array([1]), method='peak', n=0, n_fit=1)[source]

TropD Eddy Driven Jet (EDJ) metric

Latitude of maximum of the zonal wind at the level closest to the 850 hPa level

Parameters:
  • U (lat,lev) – Zonal mean zonal wind. Also takes surface wind
  • lat – latitude vector
  • lev – vertical level vector in hPa units
  • method (str, optional) –

    ‘peak’ (default) | ‘max’ | ‘fit’

    peak (Default): Latitude of the maximum of the zonal wind at the level closest to the 850 hPa level (smoothing parameter n=30)

    max: Latitude of the maximum of the zonal wind at the level closest to the 850 hPa level (smoothing parameter n=6) fit: Latitude of the maximum of the zonal wind at the level closest to the 850 hPa level using a quadratic polynomial fit of data from gridpoints surrounding the gridpoint of the maximum

  • n (int, optional) – If n is not set (0), n=6 (default) is used in TropD_Calculate_MaxLat. Rank of moment used to calculate the position of max value. n = 1,2,4,6,8,...
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of EDJ in SH and NH
Return type:

tuple
metrics.TropD_Metric_OLR(olr, lat, method='250W', Cutoff=50, n=6)[source]

TropD Outgoing Longwave Radiation (OLR) metric

Parameters:
  • olr (lat,) – zonal mean TOA olr (positive)
  • lat – equally spaced latitude column vector
  • method (str, optional) –

    ‘250W’(Default): the first latitude poleward of the tropical OLR maximum in each hemisphere where OLR crosses 250W/m^2

    ‘20W’: the first latitude poleward of the tropical OLR maximum in each hemisphere where OLR crosses the tropical OLR max minus 20W/m^2

    ‘cutoff’: the first latitude poleward of the tropical OLR maximum in each hemisphere where OLR crosses a specified cutoff value

    ‘10Perc’: the first latitude poleward of the tropical OLR maximum in each hemisphere where OLR is 10# smaller than the tropical OLR maximum

    ‘max’: the latitude of maximum of tropical olr in each hemisphere with the smoothing paramerer n=6 in TropD_Calculate_MaxLat

    ‘peak’: the latitude of maximum of tropical olr in each hemisphere with the smoothing parameter n=30 in TropD_Calculate_MaxLat

  • Cutoff (float, optional) – Scalar. For the method ‘cutoff’, Cutoff specifies the OLR cutoff value.
  • n (int, optional) – For the ‘max’ method, n is the smoothing parameter in TropD_Calculate_MaxLat
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of near equator OLR threshold crossing in SH and NH
Return type:

tuple
metrics.TropD_Metric_PE(pe, lat, method='zero_crossing', lat_uncertainty=0.0)[source]

TropD Precipitation minus Evaporation (PE) metric

Parameters:
  • pe (lat,) – zonal-mean precipitation minus evaporation
  • lat – equally spaced latitude column vector
  • method (str) – ‘zero_crossing’: the first latitude poleward of the subtropical minimum where P-E changes from negative to positive values. Only one method so far.
  • lat_uncertainty (float, optional) – The minimal distance allowed between the first and second zero crossings along lat
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of first subtropical P-E zero crossing in SH and NH
Return type:

tuple
metrics.TropD_Metric_PSI(V, lat, lev, method='Psi_500', lat_uncertainty=0)[source]

TropD Mass streamfunction (PSI) metric

Latitude of the meridional mass streamfunction subtropical zero crossing

Parameters:
  • V (lat,lev) – zonal-mean meridional wind
  • lat – latitude vector
  • lev – vertical level vector in hPa units
  • method (str, optional) –

    ‘Psi_500’(default): Zero crossing of the stream function (Psi) at the 500hPa level

    ‘Psi_500_10Perc’: Crossing of 10# of the extremum value of Psi in each hemisphre at the 500hPa level

    ‘Psi_300_700’: Zero crossing of Psi vertically averaged between the 300hPa and 700 hPa levels

    ‘Psi_500_Int’: Zero crossing of the vertically-integrated Psi at the 500 hPa level

    ‘Psi_Int’ : Zero crossing of the column-averaged Psi

  • lat_uncertainty (float, optional) – The minimal distance allowed between the first and second zero crossings. For example, for lat_uncertainty = 10, the function will return a NaN value if a second zero crossings is found within 10 degrees of the most equatorward zero crossing.
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of Psi zero crossing in SH and NH
Return type:

tuple
metrics.TropD_Metric_PSL(ps, lat, method='peak', n=0)[source]

TropD Sea-level pressure (PSL) metric

Latitude of maximum of the subtropical sea-level pressure

Parameters:
  • ps (lat,) – sea-level pressure
  • lat – equally spaced latitude column vector
  • method (str, optional) – ‘peak’ (default) | ‘max’
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of subtropical sea-level pressure maximum SH and NH
Return type:

tuple
metrics.TropD_Metric_STJ(U, lat, lev, method='adjusted_peak', n=0)[source]

TropD Subtropical Jet (STJ) metric

Parameters:
  • U (lat,lev) – zonal mean zonal wind
  • lat – latitude vector
  • lev – vertical level vector in hPa units
  • method (str, optional) –

    ‘adjusted_peak’: Latitude of maximum (smoothing parameter n=30) of the zonal wind averaged between the 100 and 400 hPa levels minus the zonal mean zonal wind at the level closes to the 850 hPa level, poleward of 10 degrees and equatorward of the Eddy Driven Jet latitude

    ‘adjusted_max’ : Latitude of maximum (smoothing parameter n=6) of the zonal wind averaged between the 100 and 400 hPa levels minus the zonal mean zonal wind at the level closes to the 850 hPa level, poleward of 10 degrees and equatorward of the Eddy Driven Jet latitude

    ‘core_peak’: Latitude of maximum of the zonal wind (smoothing parameter n=30) averaged between the 100 and 400 hPa levels, poleward of 10 degrees and equatorward of 70 degrees

    ‘core_max’: Latitude of maximum of the zonal wind (smoothing parameter n=6) averaged between the 100 and 400 hPa levels, poleward of 10 degrees and equatorward of 70 degrees
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of STJ SH and NH
Return type:

tuple
metrics.TropD_Metric_TPB(T, lat, lev, method='max_gradient', n=0, Z=None, Cutoff=15000)[source]

TropD Tropopause break (TPB) metric

Parameters:
  • T (lat,lev) – temperature (K)
  • lat – latitude vector
  • lev – pressure levels column vector in hPa
  • method (str, optional) –

    ‘max_gradient’ (default): The latitude of maximal poleward gradient of the tropopause height

    ‘cutoff’: The most equatorward latitude where the tropopause crosses a prescribed cutoff value

    ‘max_potemp’: The latitude of maximal difference between the potential temperature at the tropopause and at the surface

  • Z (lat,lev) – geopotential height (m)
  • Cutoff (float, optional) – geopotential height (m) cutoff that marks the location of the tropopause break
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of tropopause break SH and NH
Return type:

tuple
metrics.TropD_Metric_UAS(U, lat, lev=array([1]), method='zero_crossing', lat_uncertainty=0)[source]

TropD near-surface zonal wind (UAS) metric

Parameters:
  • U (lat,lev) –
  • lat – latitude vector
  • lev – vertical level vector in hPa units. lev=np.array([1]) for single-level input zonal wind U(lat,)
  • method (str) – ‘zero_crossing’: the first subtropical latitude where near-surface zonal wind changes from negative to positive
  • lat_uncertainty (float, optional) – the minimal distance allowed between the first and second zero crossings
Returns:

PhiSH (ndarray), PhiNH (ndarray) Latitude of first subtropical zero crossing of the near surface zonal wind in SH and NH
Return type:

tuple