The CAMEX-4 JPL Laser Hygrometer dataset contains water vapor volume and mixing ratio concentractions collected during the CAMEX-4 campaign to study tropical cyclones. The Laser Hygrometer measures in situ water vapor content using a tuneable laser emitting at 1.37 microns. Absorption at that wavelength is a function of water vapor content, thus measuring the amount of absorption in an open path beyond the aircraft boundary layer, a value of water vapor pressure is made. The maximum sampling rate is 8 Hz, but the instrument is normally configured through the software for a 1Hz sampling rate.