 NCL Home > Documentation > Functions > Heat stress

# heat_discoi

Compute a simplified human discomfort index. Available in version 6.4.0 and later.

## Prototype

```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 (
t          : numeric,
twb        : numeric,
iounit  : integer,
opt        : integer
)

return_val [dimsizes(t)] :  float or double
```

## Arguments

t

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

twb

Scalar or array containing vapor pressure (Pa).

iounit

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

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

opt

Currently not used. Set to zero.

## 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. This is a unitless quantity.

## Description

This is the discomfort index (DI) calculated via equation 10 in Buzan et al (2015). Specifically:

```     DI = 0.5*t + 0.5*twb

The DI values are an indicator of threats to populations:

DI of 21-24 less than 50% of population is in discomfort
DI of 24-27 more than 50% of population is in discomfort
DI of 27-29 most of the population is in discomfort
DI of 29-32 severe stress
DI of 32+   state of emergency

REFERENCES:
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
www.geosci-model-dev.net/8/151/2015/    doi:10.5194/gmd-8-151-2015
```

## Examples

Example 1:

```   t      = 30.5
twb    = 24.25
discoi = heat_discoi(t, twb, (/0,0/), 0)
print(discoi)
```
The output is:
```
Variable: discoi
Type: float
Total Size: 4 bytes
1 values
Number of Dimensions: 1
Dimensions and sizes:	
Coordinates:
Number Of Attributes: 4
long_name :	discomfort index
units :	degC
info :	human discomfort due to heat and humidity: eqn 10 of Buzan et al (2015)
NCL :	heay_discoi
(0)	27.375
```