This paper describes DIAL techniques for water vapor measurements in the atmosphere usingtwo narrowband (<500MHz) Ti: sapphire lasers pumped with a frequency doubled Nd: YAG laser. Photoacoustic spectroscopy (PAS) cells are designed for tuning the laser line tothe water vapor absorption line. Moreover, a quasi-simultaneous DIAL system with a time lagof 100ms between a pair of an on-line laser shot and an off-line laser shot is developed. The result of water vapor DIAL measurement was consistent with one measured by a Raman lidar atthe same lidar site simultaneously. The goal of the present investigation is an airborne watervapor DIAL.