THE OVERARCHING OBJECTIVE OF THIS PROPOSAL IS TO INVESTIGATE THE SHORT-TERM VARIABILITY (ON THE ORDER OF 4 DAYS) OF ATMOSPHERIC TIDES FROM ABOUT THE TROPOSPHERE TO THE IONOSPHERIC E-REGION DYNAMO REGION (20-110 KM). EMPHASIS IS ON THE MIGRATING AND NONMIGRATING DIURNAL TIDES FROM WESTWARD PROPAGATING WAVENUMBER 5 TO EASTWARD PROPAGATING WAVENUMBER 5 (DW5 TO DE5). TOWARDS THIS GOAL, THE PROJECT WILL SYNERGISTICALLY EMPLOY AN EXISTING 30-YEAR SIMULATION (1979-2010) FROM THE EXTENDED CANADIAN MIDDLE ATMOSPHERE MODEL (ECMAM) DRIVEN BY REANALYSIS DATA AND EXISTING SHORT-TERM TIDAL VARIABILITY DIAGNOSTICS FROM THE SABER INSTRUMENT ON THE TIMED SATELLITE. THE INVESTIGATION WILL EXAMINE THE STATISTICAL CHARACTERISTICS OF THE TIDAL SHORT-TERM VARIABILITY, HOW IT VARIES AS A FUNCTION OF YEAR, SEASON, LATITUDE AND ALTITUDE, DEVELOP A STATISTICAL EMPIRICAL MODEL OF THE TIDAL SHORT-TERM VARIABILITY, AND QUANTIFY THE RELATIVE IMPORTANCE OF VARIOUS CAUSES FOR THE SHORT-TERM TIDAL VARIABILITY AND THEIR RESPECTIVE ATMOSPHERIC IMPACTS. AS SUCH, THE PROPOSAL MAKES THE STEP FROM "SEASONAL/CLIMATOLOGICAL TIDES" TO "TIDAL WEATHER". THE PROPOSAL RESPONDS TO THREE OF THE PRIORITY INVESTIGATIONS OUTLINED IN THE 2009 HELIOPHYSICS ROADMAP: "WHAT GOVERNS THE COUPLING OF NEUTRAL AND IONIZED SPECIES?"; "HOW DO COUPLED MIDDLE AND UPPER ATMOSPHERES RESPOND TO EXTERNAL DRIVERS AND EACH OTHER??; AND "WHAT IS RESPONSIBLE FOR THE DRAMATIC VARIABILITY IN MANY OF THE STATE VARIABLES DESCRIBING THE IONOSPHERE THERMOSPHERE AND MESOSPHERE (ITM) REGION?". IT ALSO ADDRESSES PRIORITY GOAL 2 "DETERMINE THE DYNAMICS AND COUPLING OF EARTH'S MAGNETOSPHERE, IONOSPHERE, AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS" OF THE DECADAL SURVEY AND SPECIFICALLY ADDRESSES THE ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS (AIMI) SCIENCE PRIORITY 2 "UNDERSTAND HOW TROPOSPHERIC WEATHER INFLUENCES SPACE WEATHER". THE PROPOSAL IS TIMELY BECAUSE (I) IT MAKES USE OF RECENT PROGRESS IN SATELLITE DATA ANALYSIS AND GENERAL CIRCULATION MODELING AND (II) ITS RESULTS WILL BE IMPORTANT FOR THE INTERPRETATION OF THE UPCOMING ICON AND GOLD MISSIONS.