THE CYCLONE GLOBAL NAVIGATION SATELLITE SYSTEM (CYGNSS) MISSION TO BE LAUNCHED NOVEMBER 2016 WILL PROVIDE OCEAN SURFACE WIND SPEED MEASUREMENTS FROM AN EIGHT SATELLITE CONSTELLATION USING GPS REFLECTOMETRY OBSERVATIONS. THE WIND SPEED DATA OBTAINED WILL PROVIDE UNPRECEDENTED SPATIAL AND TEMPORAL COVERAGE OF THE TROPICS AND SHOULD BE AVAILABLE EVEN IN REGIONS OF HIGH PRECIPITATION. THESE PROPERTIES MOTIVATE THE USE OF CYGNSS MEASUREMENTS FOR STUDYING ATMOSPHERIC VARIABILITY IN REGIONS OF HIGH PRECIPITATION AND ON A VARIETY OF TIME SCALES RANGING FROM RAPID REVISIT MEASUREMENTS SEPARATED BY EVEN LESS THAN 1 HOUR TO INVESTIGATIONS OF DIURNAL VARIABILITY TO STUDIES OF SURFACE WINDS ON THE TIME SCALES OF THE MADDEN-JULIEN OSCILLATION (MJO) OR LONGER. UNDER THE PREVIOUS SUPPORT OF THE WEATHER AND ATMOSPHERIC DYNAMICS PROGRAM THE PROJECT TEAM HAS USED SIMULATED CYGNSS DATA TO INVESTIGATE THE POTENTIAL UTILITY OF CYGNSS MEASUREMENTS FOR OBSERVING THE ATMOSPHERE OVER ALL OF THESE TIME SCALES. THE PROPOSED PROJECT WILL CONTINUE THESE STUDIES INTO THE POST-LAUNCH PERIOD AND WILL EXPAND THE INVESTIGATION TO ADDRESS THE FOLLOWING QUESTIONS: 1) HOW DO THE SURFACE WINDMEASUREMENTS OBTAINED BY CYGNSS CAPTURE THE MJO WHAT DIFFERENCES IN CHARACTERIZING MJO PHASES RESULT FROM USING SURFACE WINDS VERSUS THE MORE TRADITIONAL LONG WAVE RADIATION OR HIGHER ALTITUDE WIND PRODUCTS? 2) HOW ARE DIURNAL VARIATIONS IN SURFACE WINDS AFFECTED BY THE MJO? DO COMBINED CYGNSS AND SCATTEROMETER OBSERVATIONS POST-LAUNCH CONFIRM PRE-LAUNCH EXPECTATIONS? 3)WHAT IS THE INFLUENCE OF PRECIPITATION ON CYGNSS WIND MEASUREMENTS? 4) CAN THE RAPID REVISIT OBSERVATIONS OF CYGNSS PROVIDEUSEFUL INFORMATION ON EXTREME WEATHER EVENTS?CYGNSS PRODUCTS ARE EXPECTED TO BECOME AVAILABLE SHORTLY AFTER THE PROJECT START AND WILL BE ANALYZED WITH OTHER SATELLITE WIND PRODUCTS AND MODEL DATA THROUGHOUT THE PROJECT. CYGNSS WINDS WILL ALSO BE COMBINED WITH PRECIPITATION INFORMATION FROM THE GLOBAL PRECIPITATION MISSION (GPM) AND OTHER SATELLITE AND IN-SITU WIND OBSERVATIONS TO ASSESS THE INFLUENCE OF PRECIPITATION ONCYGNSS MEASUREMENTS. FOCUSED INVESTIGATIONS WILL INCLUDE ASSESSMENTS OF MJO INFORMATION OBTAINED FROM CYGNSS SURFACE WINDS ANALYSIS OF DIURNAL WIND VARIABILITY CHARACTERIZATION OF THE INFLUENCE OF PRECIPITATION ON CYGNSS MEASUREMENTS AND THE CREATION AND USE OF CYGNSS RAPID-REVISIT PRODUCTS.THIS PROPOSAL DIRECTLY ADDRESSES A.23 WEATHER AND ATMOSPHERIC DYNAMICS TOPIC 2.2-CYGNSS ON INVESTIGATING MULTI-SCALE ATMOSPHERIC INTERACTIONS WITH THE TROPICAL OCEAN USING CYGNSS WIND DATA. SPECIFIC BENEFITS INCLUDE (1) IMPROVEMENT IN UNDERSTANDING THE PROCESSES THAT LEAD TO ORGANIZATION OF CONVECTION ON LARGE SCALES WITH A FOCUS ON THE DIURNAL CYCLE IN THE TROPICAL OCEAN AND ITS LINK TO THE MJO AND SEASONAL VARIABILITY (2) USE OF CYGNSS SURFACE WIND SPEED DATA IN STUDIES OF THE MJO AND OTHER WEATHER AND CLIMATE APPLICATIONS AND (3) THE CREATION OF A RAPID REVISIT CYGNSS PRODUCT TO INDICATE SUDDEN CHANGES IN WINDPROPERTIES.