Recent measurements by laser hygrometers in the upper troposphere and lower stratosphere.

We have recently developed a new water vapor instrument with improved electronics, and new calibration techniques for laser hygrometers. This has resulted in more accurate and precise aircraft water vapor measurements in the upper troposphere and lower stratosphere. This is critically important for studies of climate, cloud microphysics, and radiation balance, all of which depend on knowing water vapor concentrations and relative humidity in the tropical tropopause layer. This presentation will show the quantitative figures of merit and recent lab and field measurements from the Unmanned Aerial System Laser Hygrometer (ULH) to demonstrate its accuracy and precision. ULH is a new laser hygrometer developed by JPL for faster, more precise measurements of atmospheric water vapor. ULH data rates as fast as 20 Hz allow spatial resolution of 10 meters or less, which is particularly important for ice cloud studies. ULH has been flight tested on the NASA WB-57F high-altitude aircraft during the NASA Newly- Operating and Validated Instruments Comparison Experiment (NOVICE), in preparation for future science flights on the Global Hawk Unmanned Aerial System (UAS). This presentation will also show measurements from the JPL Laser Hygrometer (JLH), which has flown on the WB-57F aircraft since 1999. JLH recently participated in the AquaVIT international water vapor instrument intercomparison in Karlsruhe, Germany. In this experiment, JLH was mounted inside the AIDA aerosol chamber, for a series of blind comparisons of hygrometer measurements at pressures, temperatures, and water mixing ratios representative of the troposphere and lower stratosphere.