Ground-based water vapor atmospheric vertical profiler

Detailed accurate data on temperature variations and water vapor concentration distributions are needed for weather and climate forecasting. Water vapor is particularly important for predicting precipitation amounts from storms. Measurements are needed from the ground to the top of the troposphere at about 10 km altitude. Existing ground-based instruments often have measurement uncertainties due to the complexities of data analysis. Ground-based laser heterodyne radiometers will be developed for quantitative measurements of water vapor and oxygen (O2) optical absorbances in transmitted sunlight. Oxygen column retrievals are simplified because O2 concentrations are nearly invariant throughout the troposphere. This simplifies temperature and pressure retrievals that can then be used to improve the quality of the H2O retrievals. The Phase I project met or exceeded all objectives. A suitable wavelength region was identified for simultaneous measurements of water vapor and oxygen, the wavelength region was validated experimentally, and software development began for retrieving concentration and temperature profiles from the ground-based heterodyne measurements. Improvements identified in Phase I will be implemented with an emphasis on improving wavelength precision and accuracy. Up to three instruments will be assembled and field tested. The technology will be tested and validated in field tests including deployment at the Atmospheric Radiation Measurement Southern Great Plains site and the Smithsonian Environmental Research Center. Our technology is (1)a lower-cost method for validating data from more complicated and expensive instruments that generate data complicated by multiple scattering and distributed emission volumes and (2)a new method for remote sensing of natural gas leakage.