The investigators will continue measurements of mesospheric winds using a medium frequency (MF) radar on Kauai, Hawaii. The data will be used to study the interannual, seasonal, and short-term variability of the waves and mean winds at equatorial and subtropical latitudes. The MF radar technique is ideally suited for continuous measurements of the mean, tidal, and planetary wave structures, but it has also proven valuable in statistical and mechanistic studies of gravity wave modulation, seasonal and short-term variability, source sensitivity, and propagation character at mesospheric altitudes. Specific science objectives include 1) definition of the zonal mean circulation, 2) a more complete definition of the structure and variability of tides, 3) a better understanding of planetary wave structures, and 4) studies of gravity wave propagation, source responses, and filtering. The effort requires an upgrade to the Hawaii radar consisting of a new 12-bit receiver system and improved analysis software. When combined with other comparably upgraded systems at Christmas Island, Rarotonga, and other latitudes, the data will contribute significantly to understanding of mesosphere and lower thermosphere dynamics and its implications for global atmospheric structure
