;*********************************************************
;  sphum_to_mxrat.pro converts specific humidity to mixing ratio
;
;  INPUT
;  sphum = specific humidity in kg/kg
;        = kg vapor/kg total air
;
;  OUTPUT
;  mxrat = mixing ratio in kg/kg  
;        = kg vapor/ kg dry air
;*********************************************************

pro sphum_to_mxrat,sphum,mxrat,missing

;  Make a mxrat array the same size as sphum
mxrat=sphum

;  Convert specific humidity to mixing ratio using this equation:
;  w = q/(1-q)   w=mxrat, q=sphum

result=where(sphum ne missing,count)
if count gt 0 then begin
  mxrat[result]=sphum[result]/(1.0-sphum[result])
endif

return
end