The Alpenglow All-Phase Water Probe (Final Report)

Abstract

used in remote sensing applications. This project explored the use of the same approach in an in situ probe to measure all three phases of water in the atmosphere. The prototype device developed in this Phase 1 DOE SBIR proposal was used to demonstrate proof of concept for using Raman scattering to detect signals from water vapor, liquid water, and ice water. The prototype instrument consisted of the transmitting laser (355 nm, 7ns pulse), collector optics and receiver body, and data system. The receiver section body split the return signal into four channels, one for nitrogen plus channels dominated by water vapor, liquid water, and ice. Tests were conducted over a range of conditions ranging from ambient conditions in the lab (low water vapor mixing ratio, no liquid or ice water content), through a cool but saturated plume produced by an off-the-shelf humidifier (moderate water vapor mixing ratio plus some liquid water content), and hot, saturated stream containing extremely high water vapor mixing ratios with liquid water. Data from these tests, which was recorded using a Licel photon-counting data system, demonstrated the sensitivity of the system to varying water vapor mixing ratios ranging from ~5 g m-3 to > 20 g m-3. Signals in the water vapor and ice channels were observed during the humidifier and hot vapor tests, as expected given the overlap between the ice and water vapor Raman spectra, with the relative contributions to each channel varying as expected with temperature.