ALL NON-STATIONARY EARTH-SENSING SATELLITES SPEND MOST OF THEIR TIME OVER THE OCEAN. IF THE SENSED VARIABLES ARE TO BE ACCURATE OVER THE OCEAN EFFECTS OF OCEAN SURFACE WAVES MUST BE UNDERSTOOD AND TAKEN INTO ACCOUNT. THE PRIMARY QUANTITY USED TO SPECIFY THE STATE OF OCEAN WAVES IS THE DIRECTIONAL WAVE SPECTRUM. FROM THIS SPECTRUM PHILLIPS LAMBDA FUNCTION DESCRIBING THE PROPERTIES OF BREAKING SURFACE WAVES CAN BE DERIVED. OTHER THAN CONTINUOUS SIMULTANEOUS DIRECT MEASUREMENTS WHICH ARE BEYOND OUR REACH AT PRESENT THERE ARE TWO METHODS OF SPECIFYING THE FORM OF THE SPECTRUM OF DOMINANT WAVES ON THE OCEAN OVER THE WHOLE GLOBE. ONE USES THE ACTION BALANCE EQUATION AND EMPIRICALLY DEVELOPS FORMS FOR THE TERMS OF WIND INPUT DISSIPATION NON-LINEAR TRANSFER AND WAVE BREAKING THAT APPEAR ON THE RIGHT HAND SIDE OF THE EQUATION. THESE TERMS THEN DETERMINE IN THE BEST CASE THE FORM OF THE WAVE SPECTRUM AND ITS CHANGES IN SPACE AND TIME. THE OTHER METHOD IS TO MAKE DIRECT EMPIRICAL DETERMINATIONS OF THE FORM OF THE MEAN WAVE SPECTRUM AT VARIOUS LOCATIONS THROUGH MEASUREMENTS OF WIND AND WAVES. THIS PROPOSAL FALLS INTO THIS SECOND CATEGORY. PAST WORK OF THIS TYPE HAS FITTED ANALYTIC FORMS TO SPECTRA MEASURED IN CAREFULLY CONSTRAINED AIR/SEA CONDITIONS WITH LIMITED FETCHES AND THEN APPLIED THESE FORMS EVERYWHERE ON THE OCEAN. BUT THE CONCEPTS OF FETCH AND DURATION IMPLY THAT THE WIND HAS NOT ACTED ON THE OCEAN UNTIL SOME POINT IN SPACE OR TIME WHEN IT SUDDENLY BEGINS TO EXERT ITS INFLUENCE. REAL WIND DOES NOT BEHAVE THIS WAY. ON THE OPEN OCEAN IT WAXES AND WANES TWISTS AND TURNS. WE WILL EXTEND THIS TYPE OF STUDY TO MORE REALISTIC OPEN OCEAN CONDITIONS WHERE FETCH AND DURATION ARE GENERALLY UNDEFINED AND WIND SPEED AND DIRECTION ARE SELDOM CONSTANT. WE WILL DO THIS BY INCLUDING RATES OF CHANGE OF SPEED AND DIRECTION INTO OUR SPECIFICATION OF THE FORM OF THE DIRECTIONAL WAVE SPECTRUM. WHEN THE WIND VELOCITY AND FETCH ARE CONSTANT WE WILL REQUIRE THAT THIS FORM REDUCE APPROXIMATELY TO THOSE PRESENTLY IN USE. HAVING SUCH AN IMPROVED SPECTRAL FORM WE WILL DETERMINE TO THE EXTENT THE DATA ALLOW ITS GEOGRAPHIC VARIATION ITS EFFECT ON PHYSICAL MODELS OF MICROWAVE SIGNATURES OF THE OCEAN ITS IMPORTANCE IN CORRECTING ALTIMETER AND RADIOMETER MEASUREMENTS FOR SURFACE ROUGHNESS AND WHAT IT IMPLIES FOR THE STUDY OF BREAKING WAVES WITH THEIR ATTENDANT EFFECTS ON HEAT MOMENTUM AND GAS TRANSFER AT THE AIR/SEA INTERFACE. WE WILL USE BUOY DATA IN THIS STUDY TO DEVELOP OUR SPECTRAL FORMS SO THE LOCATIONS WHERE THESE FORMS CAN BE TESTED FOR ACCURACY WILL BE LIMITED. HOWEVER A SATELLITE CFOSAT WITH AN INSTRUMENT ONBOARD TO MEASURE DIRECTIONAL WAVE SPECTRA WILL SOON BE LAUNCHED AND THIS WILL ALLOW OUR SPECTRAL FORMS TO BE TESTED EVERYWHERE ON THE OCEAN. CFOSAT WITH A POSSIBLE LAUNCH DATE AS SOON AS 2018 WILL CONTAIN SCATTEROMETERS CAPABLE OF MEASURING BOTH WIND VECTORS AND DIRECTIONAL SURFACE WAVE SPECTRA. IN THIS STUDY WE WILL PRIMARILY UTILIZE WIND MEASUREMENTS MADE ON THE BUOYS TO DETERMINE RATES OF CHANGE OF THE WIND VECTOR SINCE SPATIAL RESOLUTION IN SATELLITE MEASUREMENTS OF WIND IS STILL RELATIVELY LOW. WE UTILIZE SATELLITE WIND MEASUREMENTS TO LOOK AT OVERALL PATTERNS OF WIND VECTORS. SINCE THE TREND OF SATELLITE WIND MEASUREMENTS IS TOWARD HIGHER SPATIAL RESOLUTION WE FORESEE A TIME WHEN SATELLITE WINDS ALONE COULD SPECIFY OUR WAVE SPECTRA. THE SPECTRAL FORMS DEVELOPED HERE FOR PARTICULAR TIME VARIATIONS IN THE WIND VECTOR COULD BE CONVERTED TO SPATIAL VARIATIONS UTILIZING TAYLOR S HYPOTHESIS.
$235,122FY2017National Aeronautics and Space AdministrationNASA
University Of Washington, Seattle WA