Calibration of advanced DOE oceanic and atmosphericchemistry models requires synoptic scale global data sets ofatmospheric-oceanic fluxes of water vapor. However, currentinstrumentation and sensing techniques appear incapable ofyielding accurate data over an extended period of time in the harshmarine boundary layer. The major problem lies in the area offast-response humidity sensors that will survive the marineenvironment. This project explores an innovative laser hygrometerthat will be combined with either a sonic anemometer or a laserDoppler anemometer to provide an all-solid-state sensor system withno moving parts for measuring marine boundary layer water vaporflux. The key elements of the laser hygrometer are similar tothose used in undersea fiber optic cables designed for 10 years ofautonomous operation. Use of a noncontact humidity-sensingtechnique means that the sapphire windows are the only sensorelements that require contact with the harsh marine environment. Reponse times of 10 to 20 Hz are typical, and the response time isfundamentally limited only by the speed at which the ambient windflushes the small sample volume. The humidity measurementtechnique is sufficiently stable and reliable to allow a singlesensor to be used for measurements of both water vapor flux andsteady-state humidity. The Phase I work plan includes laboratoryand atmospheric testing of a proof-of-concept water vapor fluxsensor, marine testing for investigation of potential opticalwindow problems, and the drafting of a Phase II sensor design andPhase II work plan.Anticipated Results/Potential Commercial Applications as described by the awardee:This new measurement capability could make asignificant contribution to DOE's overall program goals ofachieving a better understanding of the ocean's role in globalclimate change and the environmental consequences of energy use. While being responsive to DOE scientific program interests, thisline of research could also result in a new generation ofpractical, cost-effective, ultrasensitive, very rugged hygrometersfor the industrial sector. Industrial applications will benefitthe Nation's economic competitiveness in manufacturing systems.
