NCL Home> Documentation> Functions> Heat stress, Meteorology

fire_index_haines

Computes the Haines fire index (aka: Lower Atmosphere Severity Index) from a sounding.

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 fire_index_haines (
		p [*] : numeric, 
		t [*] : numeric, 
		td [*] : numeric, 
		opt [1] : logical 
	)
	return_val [3] : float or double

Arguments

A one-dimensional array containing pressures (hPa).

t
td

One-dimensional arrays containing temperatures (degC) and dew point temperatures (degC), respectively.

opt

Currently not used. Set to False.

Return value

The return value is a one-dimensional array of length 3. Elements 0, 1, 2 pertain to low, mid and high elevation.

Description

See: Haines paper and Haines Index.

The Haines_Index is technically the "Lower Atmosphere Severity Index" ==> LASI. It consists of two parts:

(i) Stability Term: (Tpl - Tp2)
(ii) Moisture Term : (Tp1 - TDp1)

The Haines Index can range between 2 and 6. The drier and more unstable the lower atmosphere the higher the index. Let ROS mean 'Risk Of Spread'. Then a Haines Severity Index of

2-3= a very low ROS
4= low ROS
5= moderate ROS, and
6= high ROS

The Climate Analysis Center uses the low-level Haines for the Coastal and Midlands zones, and the mid-level Haines for the Upstate zones.

The Haines Index is intended to be used all over the United States it is adaptable for three elevation regimes: Low Elevation, Middle Elevation and High Elevation. [See http://www.k3jae.com/wxHaines.php]

Low Elevation is for fires occurring at or very near sea level.
Middle Elevation is for fires burning in the 1000-3000 foot elevation range.
High Elevation is intended for fires burning above 3000 feet elevation.

Examples

 ; PRESSURE (MB; hPa)
 p =(/ 1008.,1000.,950.,900.,850.,800.,750.,700.,650.,600., \
 550.,500.,450.,400.,350.,300.,250.,200., \
 175.,150.,125.,100., 80., 70., 60., 50., \
 40., 30., 25., 20. /)
 
 ; TEMPERATURE (C)
 t =(/ 29.3,28.1,23.5,20.9,18.4,15.9,13.1,10.1, 6.7, 3.1, \
 -0.5,-4.5,-9.0,-14.8,-21.5,-29.7,-40.0,-52.4, \
 -59.2,-66.5,-74.1,-78.5,-76.0,-71.6,-66.7,-61.3, \
 -56.3,-51.7,-50.7,-47.5 /)
 
 ; MIXING RATIO (g/kg)
 q =(/ 20.38,19.03,16.14,13.71,11.56,9.80,8.33,6.75,6.06,5.07, \
 3.88, 3.29, 2.39, 1.70,1.00,0.60,0.20,0.00,0.00, \
 0.00, 0.00, 0.00, 0.00,0.00,0.00,0.00,0.00,0.00, \
 0.00, 0.00 /)
 
 ; Haines Index (HI) requires dew point temperature so it must be derived
 
 ; Change units to those requires by 'relhum' function
 q = q/1000. ; (kg/kg)
 t = t+273.15 ; K
 
 rh = relhum(t, q, p*100) ; p*100 => mb => Pa
 td = dewtemp_trh(t,rh) ; dew pt temperature [K]
 td = td-273.15 ; [C] ; return to units required by 'fire_haines_index'
 t = t -273.15 ; [C]
 
 ;print(p+" "+t+" "+q+" "+rh+" "+td)
 
 ; assign metadata
 
 ; units [ @ ]
 p@units = "hPa"
 t@units = "degC"
 
 ; name dimensions [ ! ]
 p!0 = "p"
 t!0 = "p"
 td!0 = "p"
 
 ; assign coordinate values [ & ] to named dimensions
 p&p = p
 t&p = p
 td&p = p
 
 ; look at data
 ; printVarSummary(p)
 ; printVarSummary(t)
 ; printVarSummary(td)
 
 printMinMax(t,0)
 
 HI = fire_index_haines(p, t, td, False)
 print(HI)

A sample output

 Variable: HI
 Type: float
 Total Size: 12 bytes
 3 values
 Number of Dimensions: 1
 Dimensions and sizes:	[elevation | 3]
 Coordinates: 
 Number Of Attributes: 5
 long_name :	Haines Index
 reference :	http://www.nwas.org/digest/papers/1988/Vol13-Issue2-May1988/Pg23-Haines.pdf
 info :	Lower Atmosphere Severity Index (LASI)
 elevation :	( Low, Medium, High )
 details :	http://www.erh.noaa.gov/cae/haines.htm
 (0)	 3
 (1)	 3
 (2)	 2