This dataset provides the concentrations of water measured by the Diode Laser Hygrometer (DLH) during airborne campaigns conducted by NASA's Atmospheric Tomography (ATom) mission from 2016 - 2018. The DLH measures the water vapor (H2O(v)) in the atmosphere by wavelength modulated differential absorption spectroscopy of an isolated rovibrational line. The measurements include water vapor mixing ratio in parts-per-trillion-by-volume (pptv) and relative humidity in percent.