Measuring Atmospheric Water Vapor

The two-channel water vapor instrument shown here is physically identical to the two-channel visible light sun photometer for measuring aerosol optical thickness. It uses two near-IR detectors instead of the LEDs used in the visible-light version. Protocols for using this instrument were written for the GLOBE program in the mid-1990's. However, the GLOBE program no longer actively supports this protocol. IESRE currently has no independent source of data for calibrating these instruments. If you are near a NOAA GPS-MET or NASA AERONET site, you can calibrate them yourself. (See the link to "Participate in the GLOBE water vapor instrument calibration project." Even though this is no longer a GLOBE project, the procedure remains the same.) These instruments can be purchased from IESRE, aligned but not calibrated, for $180.