Water vapor measurements by raman lidar and balloon sonde at Mauna Loa Observatory

Water vapor measurements have been added to the aerosol/temperature lidar operated by the NOAA/Climate Monitoring and Diagnostics Laboratory at Mauna Loa Observatory (MLO). The 532 nm light from an Nd:YAG laser is used and two channels measure the raman shifted light at 607 nm (nitrogen) and 660 nm (water vapor). The receiver is a 74 cm diameter parabolic mirror with the two detectors at the prime focus. An interference filter and two high pass filters achieve a rejection of the 532 nm light of about IE9, which is needed for measurements of water in the upper troposphere where the water mixing ration can be a few parts per million. Radiosonde flights from the observatory were used for both the calibration constant and the low altitude overlap corrections. The sonde flights used both Vaiasala humidity sensors and chilled mirror hygrometers. The Vaiasala sensors were accurate to about 11 km (-50 C). The chilled mirro hygrometer detection limit is determined by the temperature depression attainable by the cooler. The lidar system has been used for validation of the Atmospheric Infrared Sounder (AIRS) on the NASA/Aqua satellite launched in May, 2002.