OUR OVERARCHING SCIENCE GOAL IS TO EXPLORE AND UNDERSTAND THE INTRASEASONAL RESPONSE OF THE MESOSPHERE/LOWER THERMOSPHERE/ IONOSPHERE REGION (MLTI 80-150 KM) TO DIURNAL TIDAL VARIABILITY CAUSED BY THE MADDEN-JULIAN OSCILLATION (MJO) IN THE TROPICAL TROPOSPHERE. THE MJO SHIFTS DEEP CONVECTIVE AND CIRCULATION PATTERNS WITH 30-90 DAY TIME PERIODS AND AS SUCH MODULATES TIDAL FORCING AND PROPAGATION CONDITIONS ON AN INTRASEASONAL TIME SCALE. IN THIS INVESTIGATION WE WILL (I) DIAGNOSE THE MJO SIGNAL IN MLTI TIDES OBSERVED BY SABER/TIMED (II) DELINEATE THE PHYSICAL PROCESSES THAT TRANSMIT THE MJO SIGNAL INTO THE TIDES AND (III) QUANTIFY THE IMPACT OF MJO-RELATED TIDAL VARIABILITY ON THE MEAN STATE OF THE THERMOSPHERE (TEMPERATURE WINDS INFRARED COOLING RATES). STUDYING THE IMPACT OF THE MJO ON THE MLTI WAS HAMPERED BY THE INSUFFICIENT (60-DAY RUNNING MEAN FOR SABER) TIME RESOLUTION OF SATELLITE-BASED TIDES. RECENT PROGRESS IN SHORT-TERM TIDAL DIAGNOSTICS NOW ALLOWS US TO CONCLUSIVELY IDENTIFY AND CHARACTERIZE THE MJO SIGNAL IN MIGRATING AND NONMIGRATING DIURNAL TEMPERATURE TIDES FROM SABER (50-110 KM) AND TO CONDUCT THE PROPOSED STUDY. A PRELIMINARY DIAGNOSTICS INDICATES THAT THE MJO IMPOSES AN ABOUT 20% MODULATION (W.R.T. TO 60-DAY RUNNING MEAN AMPLITUDES) ON THE DIURNAL TIDES. WE WILL EMPLOY AND EXPAND OUR EXISTING (2002-2016) SHORT-TERM (DAILY) TIDAL VARIABILITY DIAGNOSTICS FROM SABER TO THE YEAR 2018 AND POSSIBLY BEYOND DEPENDING ON INSTRUMENT HEALTH FOR MIGRATING AND NONMIGRATING DIURNAL TIDES. THIS BASELINE DATA SET WILL THEN BE ANALYZED FOR MJO SIGNALS DEPENDING ON MJO STRENGTH AND PHASE USING COMPLEMENTARY SPECTRAL AND STATISTICAL APPROACHES. TRMM/TMPA DATA WILL BE USED TO ANALYZE PRECIPITATION AS AN INDICATOR OF CONVECTIVE TIDAL FORCING. MERRA-2 DATA WILL BE USED TO EXAMINE RADIATIVE FORCING AND THE LOWER AND MIDDLE ATMOSPHERE BACKGROUND WINDS THROUGH WHICH THE TIDES PROPAGATE. A SERIES OF SD-WACCM SIMULATIONS WILL BE EMPLOYED TO IDENTIFY THE RELATIVE ROLES OF TIDAL FORCING WIND FILTERING TIDAL ADVECTION AND GW MOMENTUM FORCING IN TRANSMITTING THE MJO SIGNAL INTO THE MLTI TIDES OBSERVED BY SABER. FINALLY WE WILL DRIVE THE TIE-GCM WITH THE OBSERVED TIDES WITH AND WITHOUT THE MJO SIGNAL TO DIAGNOSE THE IMPACT ON THE MEAN STATE OF THE THERMOSPHERE. THE TIEGCM RESULTS WILL BE VALIDATED WITH NO 5.3 UM (100-180 KM) AND CO2 15 UM (100-135 KM) INFRARED COOLING RATES IN THE THERMOSPHERE OBSERVED BY SABER. OUR INVESTIGATION WILL PROVIDE NOVEL INSIGHT INTO HOW INTRASEASONAL WEATHER OSCILLATIONS MODULATE UPWARD PROPAGATING TIDES AND IMPACT THE VARIABILITY AND MEAN STATE OF THE MLTI. THIS DIRECTLY PERTAINS TO THE TIMED PRIMARY SCIENCE OBJECTIVE TO EXPLORE ENERGY TRANSFER INTO THE MLTI REGION. THE PROPOSAL DIRECTLY ADDRESSES THE DECADAL SURVEY HIGH LEVEL SCIENCE GOAL 2: DETERMINE THE DYNAMICS AND COUPLING OF EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS. THE MLTI RESPONSE TO METEOROLOGICAL DRIVING FROM BELOW IS HIGHLIGHTED AS ONE OF THE FIVE LEADING SCIENCE GOALS IN THE AIMI CHAPTER OF THE DECADAL SURVEY.