A MARINE BOUNDARY LAYER WATER VAPOR FLUX SENSOR

CALIBRATION OF ADVANCED DOE OCEANIC AND ATMOSPHERIC CHEMISTRY MODELS REQUIRES SYNOPTIC SCALE GLOBAL DATA SETS OF ATMOSPHERIC-OCEANIC FLUXES OF WATER VAPOR. HOWEVER, CURRENT INSTRUMENTATION AND SENSING TECHNIQUES APPEAR INCAPABLE OF YIELDING ACCURATE DATA OVER AN EXTENDED PERIOD OF TIME IN THE HARSH MARINE BOUNDARY LAYER. THE MAJOR PROBLEM LIES IN THE AREA OF FAST-RESPONSE HUMIDITY SENSORS THAT WILL SURVIVE THE MARINE ENVIRONMENT. THIS PROJECT EXPLORES AN INNOVATIVE LASER HYGROMETER THAT WILL BE COMBINED WITH EITHER A SONIC ANEMOMETER OR A LASER DOPPLER ANEMOMETER TO PROVIDE AN ALL-SOLID-STATE SENSOR SYSTEM WITH NO MOVING PARTS FOR MEASURING MARINE BOUNDARY LAYER WATER VAPOR FLUX. THE KEY ELEMENTS OF THE LASER HYGROMETER ARE SIMILAR TO THOSE USED IN UNDERSEA FIBER OPTIC CABLES DESIGNED FOR 10 YEARS OF AUTONOMOUS OPERATION. USE OF A NONCONTACT HUMIDITY-SENSING TECHNIQUE MEANS THAT THE SAPPHIRE WINDOWS ARE THE ONLY SENSOR ELEMENTS THAT REQUIRE CONTACT WITH THE HARSH MARINE ENVIRONMENT. RESPONSE TIMES OF 10 TO 20 HZ ARE TYPICAL, AND THE RESPONSE TIME IS FUNDAMENTALLY LIMITED ONLY BY THE SPEED AT WHICH THE AMBIENT WIND FLUSHES THE SMALL SAMPLE VOLUME. THE HUMIDITY MEASUREMENT TECHNIQUE IS SUFFICIENTLY STABLE AND RELIABLE TO ALLOW A SINGLE SENSOR TO BE USED FOR MEASUREMENTS OF BOTH WATER VAPOR FLUX AND STEADY-STATE HUMIDITY. THE PHASE I WORK PLAN INCLUDES LABORATORY AND ATMOSPHERIC TESTING OF A PROOF-OF-CONCEPT WATER VAPOR FLUX SENSOR, MARINE TESTING FOR INVESTIGATION OF POTENTIAL OPTICAL WINDOW PROBLEMS, AND THE DRAFTING OF A PHASE II SENSOR DESIGN AND PHASE II WORK PLAN.