Analysis of the Seasonal and Spatial Structure of the Gravity Waves Over the Central USA Using Data From the NOAA Wind Profiler Network

Gravity waves are important atmospheric phenomenon, as they transport momentum and energy, affecting the dynamic structure of the troposphere, stratosphere and mesosphere. However, the spatial and seasonal distribution, and sources of generation of the tropospheric gravity waves are not completely understood. The high-resolution (6 min in time and 250m in height domain) wind data from the NOAA wind profiler network (NPN) for 2002-2005 were used to analyze the seasonal and height structure of gravity waves in midlatitudes. For altitudes from 1 km to 14-16 km, the distribution of high frequency (periods of 12 minutes-1 hour), medium-frequency (periods of 12 minutes-3 hours) and low-frequency (periods of 3 hours-12 hours) oscillations of zonal, meridional and vertical components of the wind vector were calculated, and compared to variations of profilers' mean wind, wind shear and reanalysis' rainfall data. In the observed seasonal structure, the of maximums of low- and mid-tropospheric wave activity generally coincide with maximums in reanalysis rainfall rate data, suggesting a convective source for high- and medium-frequency waves, while for low frequency waves in mid- and upper troposphere the source seems to be associated with variations in the mean horizontal wind. We speculate that the part of the variance of gravity wave activity between different locations that is not explained by variations in the horizontal wind and precipitation fields can be attributed to the difference in the topography with resulting orographic generation of gravity waves.