First results of tropospheric gravity wave momentum flux measurements over Christmas Island

Abstract

The importance of gravity wave effects 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. For periods shorter than 8 hours, the monthly vertical fluxes of zonal and meridional momentum were estimated to be between ±0.02 kg m−1 s−2 and ±0.01 kg m−1 s−2, respectively. The resulting net accelerations of the mean flow were in the range of ±0.1 m s−1 d−1. 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.