mixhum_convert
Convert mixing ratio to specific humidity or vice-versa.
Available in version 6.5.0 and later.
Prototype
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl" ; This library is automatically loaded
; from NCL V6.2.0 onward.
; No need for user to explicitly load.
function mixhum_convert (
wq : numeric, ; float, double, integer only
wqType [1] : string,
iounit [2] : integer
)
return_val [dimsizes(wq)] : float or double
Arguments
wqA scalar or array containing mixing ratio or specific humidity (units: kg/kg, g/kg).
wqType- wqType="w" or "W" means that wq is mixing ratio and a conversion to specific humidity is desired.
- wqType="q" or "Q" means that wq is specific humidity and a conversion to mixing ratio is desired.
An integer array of length 2 which specifies the units of the input wq and returned variable
- iounit(0)=0 input wq are kg/kg
- iounit(0)=1 input wq are g/kg
- iounit(1)=0 returned units are kg/kg
- iounit(1)=1 returned units are g/kg
Return value
A variable of the same size and shape as wq.
Description
The mixing ratio and specific humidity are commonly denoted as w and q, respectively. As noted in the Glossary of Meteorology, these quantities are nearly identical. Hence, w and q are often used interchangeably. Still, for certain applications, it may be appropriate to make the conversion. Specifically:
q = w/(1+w) [switch=True] <===> w = q/(1-q) [switch=False]
See Also
mixhum_ptd, mixhum_ptrh, relhum
Examples
Example 1: Convert mixing ratio to specific humidity and vice-versa.
W = 15.2 ; g/kg iounit(0)=1 q = mixhum_convert(W, "w", (/1,1/) ; q = 14.97; return g/kg, iounit(1)=1 printVarSummary(q) w = mixhum_convert(q, "q", (/1,1/) ; w = 15.2 ; return g/kg, iounit(1)=1 printVarSummary(w)Example 2: Read specific humidity (Q; kg/kg). Convert to mixing ratio and vice-versa.
a = addfile("cam35.h0.0008-07.nc","r") Q = a->Q ; kg/kg iounit(0)=0 w = mixhum_convert(Q, "q", (/0,0/); return kg/kg, iounit(1)=0 printVarSummary(w) ; w(time,lat,lon) q = mixhum_convert(w, "w" , (/0,1/); return kg/kg, iounit(1)=1 printVarSummary(q) ; q(time,lat,lon)The edited output:Variable: Q Type: float Total Size: 1437696 bytes 359424 values Number of Dimensions: 4 Dimensions and sizes: [time | 1] x [lev | 26] x [lat | 96] x [lon | 144] Coordinates: time: [3132..3132] lev: [3.54463800000001..992.5560999999998] lat: [ -90..89.99999999999999] lon: [ 0..357.5] Number Of Attributes: 3 units : kg/kg long_name : Specific humidity cell_method : time: mean (0) Specific humidity (kg/kg) : min=4.95837e-07 max=0.0220418 Variable: w Type: float Total Size: 1437696 bytes 359424 values Number of Dimensions: 4 Dimensions and sizes: [time | 1] x [lev | 26] x [lat | 96] x [lon | 144] Coordinates: time: [3132..3132] lev: [3.54463800000001..992.5560999999998] lat: [ -90..89.99999999999999] lon: [ 0..357.5] Number Of Attributes: 4 long_name : mixing ratio equation : w=q/(1-q) units : kg/kg NCL : mixhum_convert (0) mixing ratio (kg/kg) : min=4.95838e-07 max=0.0225386 Variable: q Type: float Total Size: 1437696 bytes 359424 values Number of Dimensions: 4 Dimensions and sizes: [time | 1] x [lev | 26] x [lat | 96] x [lon | 144] Coordinates: time: [3132..3132] lev: [3.54463800000001..992.5560999999998] lat: [ -90..89.99999999999999] lon: [ 0..357.5] Number Of Attributes: 4 long_name : specific humidity equation : q=w/(1+w) units : g/kg NCL : mixhum_convert (0) specific humidity (kg/kg) : min=4.95837e-04 max=2.20418