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Compute the human discomfort index due to excessive heat and humidity using the Stull wet bulb temperature (wetbulb_stull).

Available in version 6.4.0 and later.


load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/heat_stress.ncl"  ; This library is automatically loaded
                                                             ; from NCL V6.5.0 onward.
                                                             ; No need for user to explicitly load.

	function heat_discoi_stull (
		t          : numeric,  
		twb_stull  : numeric,  
		rh         : numeric,  
		iounit [2] : integer,  
		opt    [1] : logical   

	return_val [dimsizes(t)] :  float or double



Scalar or array containing 2-m temperature(s) [ units see iounit ].


Scalar or array containing the Stull wet bulb temperature (wetbulb_stull).


Scalar or array containing relative humidity (%).


An integer array of length 2 which specifies the units of the input t and returned heat_index:

  • iounit(0)=0 input t (degC)
  • iounit(0)=1 input t (degK)
  • iounit(0)=2 input t (Farenheit)

  • iounit(1)=0 returns units degC
  • iounit(1)=1 returns units degK
  • iounit(1)=2 returns units Farenheit


Variable of type logical. Currently not used. Set to False.

Return value

A scalar or an array of the same size and shape as t. The output will be double if t or rh is of type double. The units are specified by iounit(1).


    Epstein, Y., and D.S. Moran (2006) 
            Thermal comfort and the heat stress indices,
            Ind. Health, 44, 388-398.

    Buzan, J.R. et al (2015): 
           Implementation and comparison of a suite of heat stress metrics
              within the Community Land Model version 4.5
           Geosci. Model Dev., 8, 151-170, 2015

See Also

Heat and Stress functions


Example 1:

   t   = 30.5
   twb = 24.25   ; Stull wetbulb
   rh  = 75.3

   discoi_stull = heat_discoi_stull(t, twb, rh, (/0,0/), False)

The output is:

    Variable: discoi_stull
    Type: float
    Total Size: 4 bytes
                1 values
    Number of Dimensions: 1
    Dimensions and sizes:	[1]
    Number Of Attributes: 2
      long_name :	discomfort index with Stull wet bulb temperature
      units :	degC
      NCL :     heat_discoi_stull

    (0)	52.9