High precision atmospheric hygrometry using the solar infrared spectrum

An infrared hygrometer of high precision is described. The procedure for calibrating the hygrometric ratio in terms of atmospheric water vapour content is based on comparisons and extrapolations from data resulting from high accuracy measurements of vertical water vapour content in a relatively narrow range of values. The resulting calibration curve extends from 0.3 to 40 cm STP of water vapour content. The applications of the instrument are discussed. A comparison of our calibration curve with others presented in previous papers shows that a great improvement has been achieved in this field.