SCIENCE GOALS AND OBJECTIVES: THE OVERALL GOAL OF THIS PROPOSAL IS TO IMPROVE OUR UNDERSTANDING OF THE ATMOSPHERIC COUPLING BETWEEN THE LOWER ATMOSPHERE AND MESOSPHERE SPECIFICALLY THE COUPLING BETWEEN THE LOW-LATITUDE STRATOSPHERE AND HIGH-LATITUDE MESOSPHERE VIA OBLIQUE GRAVITY WAVE (GW) PROPAGATION. WE PROPOSE TO STUDY THE CONNECTION BETWEEN THESE ATMOSPHERIC REGIONS BY UNDERSTANDING THE INFLUENCE OF GWS GENERATED OVER THE MONSOON REGION (~10-30 N ~50 KM) ON THE HIGH-LATITUDE SUMMER MESOSPHERE (~54-85 N ~82-86 KM). SINCE POLAR MESOSPHERIC CLOUDS (PMCS) ARE SENSITIVE INDICATORS OF THE CHANGES IN THE HIGH-LATITUDE SUMMER MESOSPHERE WE WILL EVALUATE THIS INFLUENCE OF OBLIQUELY PROPAGATING GWS (ALSO KNOWN AS LATERAL OR NON-VERTICAL PROPAGATION) BY INVESTIGATING THE DIRECT LINK BETWEEN PMCS AND LOW-LATITUDE LOW-ALTITUDE GWS. PMCS FORM IN THE HIGH LATITUDE SUMMER MESOSPHERE AT ~83 KM AND ARE OF SCIENTIFIC INTEREST SINCE THEY PROVIDE IMPORTANT INFORMATION ABOUT THE MESOSPHERIC ENVIRONMENT BY RESPONDING TO CHANGES IN SOLAR FORCING INTER- AND INTRA- HEMISPHERIC COUPLING AND METEOROLOGY INCLUDING INFLUENCE OF GWS PLANETARY WAVES AND TIDES. OF IMPORTANCE IS THE STUDY OF GWS OWING TO THE FACT THAT THESE SMALL SCALE WAVES ARE OFTEN PARAMETERIZED IN GLOBAL CIRCULATION MODELS. THESE WAVES CAN HAVE TWO DIFFERENT EFFECTS ON PMCS. IN SUMMER VERTICALLY PROPAGATING GWS INDUCE A RESIDUAL CIRCULATION THAT COOLS THE SUMMER MESOSPHERE SUPPORTING THE FORMATION OF PMCS. HOWEVER OBSERVATION AND MODELING STUDIES HAVE SHOWN THAT SHORT PERIOD GWS CAN DESTROY PMCS. GWS ARE OFTEN CONSIDERED TO BE EITHER VERTICALLY AND HORIZONTALLY PROPAGATING WAVES OR GENERATED IN-SITU. HOWEVER RECENT CASE STUDIES SUGGEST THAT THE SLANTED STRUCTURE OF THE EASTERLY WINDS ASSOCIATED WITH THE MONSOON CIRCULATION WOULD ALLOW EASTWARD PROPAGATING GWS FROM LOW-LATITUDES AND LOWALTITUDES TO ENTER THE HIGH-LATITUDE MIDDLE ATMOSPHERE. WE PROPOSE THE FIRST COMPREHENSIVE STUDY TO UNDERSTAND THIS OBLIQUE PROPAGATION OF GWS AND THEIR EFFECT ON THE POLAR SUMMER MESOSPHERE USING DATA FROM THE SABER INSTRUMENT ON THE TIMED SATELLITE THE CIPS AND SOFIE INSTRUMENT ON THE AIM SATELLITE AND THE GROGRAT RAY-TRACING MODEL. DATA AND METHODOLOGY: - THE SABER INSTRUMENT ON THE TIMED SATELLITE HAS BEEN TAKING MEASUREMENTS OF LOWER AND UPPER ATMOSPHERIC TEMPERATURE SINCE 2002. WE WILL USE THIS LONG-TERM TEMPERATURE DATA TO DERIVE THE GW PARAMETERS (MOMENTUM FLUX AMPLITUDE VERTICAL WAVELENGTH HORIZONTAL WAVELENGTH) IN THE MONSOON REGION. - THE CIPS AND SOFIE INSTRUMENTS ON THE AIM SATELLITE HAVE BEEN OBSERVING PMCS SINCE APRIL 2007. THE PMC VARIABILITY WILL BE USED AS AN INDICATOR OF THE CHANGES IN THE POLAR SUMMER MESOSPHERE. CIPS DATA WILL PROVIDE PMC PROPERTIES (CLOUD OCCURRENCE FREQUENCY ALBEDO ICE WATER CONTENT) AND SOFIE WILL PROVIDE PMC PROPERTIES AND HIGH-LATITUDE GW PARAMETERS (AMPLITUDE AND VERTICAL WAVELENGTH). - GROGRAT IS A FOUR DIMENSIONAL RAY-TRACING MODEL THAT IS WIDELY USED TO STUDY THE GW PROPAGATION. WE WILL USE THE GW AND PMC DATA FROM 16 PMC SEASONS TO QUANTIFY THE ROLE OF MONSOON GWS ON THE POLAR SUMMER MESOSPHERIC ENVIRONMENT THUS IMPROVING OUR UNDERSTANDING OF THE OFTEN OVERLOOKED EQUATOR TO POLE NON-VERTICAL GRAVITY WAVE PROPAGATION. THE RAY TRACING MODEL WILL BE USED TO VALIDATE OUR OBSERVATIONAL RESULTS. RELEVANCE: THE RESULTS FROM OUR ANALYSIS WILL PROVIDE OBSERVATIONAL EVIDENCE OF A POTENTIAL NEW SOURCE OF MESOSPHERIC GRAVITY WAVES AND HAS IMPLICATIONS FOR IMPROVING GLOBAL CIRCULATION MODELS. THIS PROJECT IS RELEVANT TO THE HELIOPHYSICS DECADAL SURVEY PRIORITY #2 TO DETERMINE THE DYNAMICS AND COUPLING OF THE EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND THEIR RESPONSE TO SOLAR AND TERRESTRIAL INPUTS