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Abstract. The global-scale wave model (GSWM) is used to investigate the effects of mean winds and realistic dissipation on upward propagating nonmigrating diurnal tidal components. We explore the signatures of two plausible tropospheric sources of these waves, namely, latent heat release associated with deep convective activity and the absorption of solar infrared radiation which varies zonally with longitudinal variations in tropospheric water vapor. Our calculations suggest that while nonmigrating components are up to a factor of 3 times smaller than the migrating diurnal tide, they modulate the latter and introduce measurable (•10 m/s) longitudinal variability in the mesosphere and lower thermosphere. These effects are most pronounced in the GSWM for the latent heat source and during northern hemisphere winter.

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Abstract. The importance of gravity wave effe. cts on various dynamical processes has been well documented in the upper and middle atmosphere. However, less is known about these waves in the lower atmosphere. Whereas many studies of longer-period waves have previously been conducted using wind profiler data, this paper is an effort to quantify the short-term motions of the troposphere. We will present some of the initial tropospheric gravity wave horizontal variance and momentum flux estimates calculated from Christmas Island wind profiler data collected during 1994. A coplanar antenna beam configuration was used for this analysis. In addition to the high-frequency results, we will discuss some of the difficulties we encountered while processing the data. In order to determine the robustness of applying a coplanar beam analysis method to tropospheric data, we have compared the results of two data sets that were created using two independently developed cleaning algorithms on the same original raw data. These results show that the high-frequency calculations are sensitive to the quality of the cleaned data used for this analysis. As long as the uncertainties associated with cleaning the data are considered, it is possible to establish the magnitude of the vertical momentum fluxes and the resulting accelerations in the troposphere.

Abstract. Solar heating of the atmosphere is responsible for most of the diurnal oscillations in the neutral wind velocities and temperatures of the mesosphere and lower thermosphere. When these oscillations are global-scale waves, they are called atmospheric tides. Excited in the lower atmosphere, tides can propagate up into the upper atmosphere where they can break and deposit considerable energy and momentum into the mean flow. Ground-based estimates of the diurnal winds over Christmas Island have been made using a narrow-beam meteor radar system. Previously, data collected using the three-beam antenna configuration of the meteor radar were processed under the assumption that the vertical wind component was at least 2 orders of magnitude smaller than the horizontal component for all temporal scales of motion. The addition of two oblique beams to the radar configuration in late 1993 made it possible to estimate the horizontal wind field without applying the negligible vertical wind assumption, by using a coplanar analysis technique. Not only did the diurnal fits of the horizontal coplanar winds agree better with the results of the collocated mediumfrequency radar and model predictions, but also the Christmas Island meteor radar appears to be measuring a significant vertical velocity. This velocity has a diurnal amplitude of 10-15 m s -1 and maximizes at midnight across all heights. Under the assumption that this strong vertical motion is produced by geophysical phenomena, two hypotheses to explain this velocity are presented: the vertical motion associated with gravity wave breaking and the influence of strong electric fields on the ionized meteor trails.