Abstract

Water vapor is the main responsible atmospheric gas that regulates the weather and climate and contributes with about 90% of the Earth’s natural greenhouse effect. The continuous cycle of evaporation, vapor transport, cloud formation, and precipitation distributes water and energy around the globe. In this connection, it is a natural desire to know the laws of the phenomena, occurring in the atmosphere and determining the conditions of our lives. High-precision Fourier Transform Infrared (FTIR) spectrometer is one of the most suitable instruments to measure the concentration of greenhouse gases, including water vapors from remote-sensing techniques. As a result, a number of infrared spectrometers from different laboratories have been used for atmosphere monitoring. The present chapter gives a detailed description of these spectrometers, including their designs and operating principles. Examples of FTIR spectrometers designed specifically for water vapor monitoring are also considered. The IR range is surely the most suitable spectral region for analyzing the water vapor in the atmosphere. However, as it is shown in the present chapter, the measurements in the visible range are also possible and may be effective.