In this paper we describe the characteristics of the optical hygrometer spectral channels and main features of the spectroscopic method to measure moisture content in the atmosphere in the NIR (λ= 0.94 μm). Different measurement approaches are analyzed taking into account the influence of the variability of spectral behavior of aerosol optical thickness. We also deal with the error estimates and calibration results of the two— and three—channel techniques based on the aerological sounding data.