Gravity Waves and Turbulence as Seen in the Radiosonde-Thermosonde Observations

Abstract

Atmospheric gravity waves (GWs) are ubiquitous and play an essential role in the dynamics, temperature and constituent structure of the lower and middle atmosphere. The importance of the effect of gravity wave on various dynamical and chemical processes has been well documented in the upper and middle atmosphere. However, less is known about these waves in the lower atmosphere, as well the importance of various source mechanisms and their propagation characteristics. It is well accepted that they transport energy and momentum from the region where they are generated to others regions where they are dissipated and interact with mean circulation, contributing to the shape and structure of atmosphere circulation, thermal structure and the chemistry of the atmosphere. Quasicontinuous GW breaking at a range of heights around the globe maintains body forces and turbulent diffusion that drives winds, temperatures, and chemical constituent distributions that are quite different from those of an atmosphere lacking these processes. Gravity waves are generated by a variety of processes, especially in the lower atmosphere. Therefore for the comprehensive understanding of the global atmosphere dynamics and structure it is of significant importance to study the primary features of gravity wave activity in the lower atmosphere. The chief mechanisms by which they are generated are thought to be flow over orography 27, , convection , shear instability , or by developing fronts and upper tropospheric jets. However, knowledge of wave source distribution and properties remains poor, which is a major uncertainty in GW parameterizations in atmospheric models. The theoretical understanding of gravity wave sources is in some way worse than our observational knowledge of them, which is not considered to be very complete. For instance we have little idea how important gravity wave emission from tropopause jets might be, or whether the observed correlation with tropopause jetstream activity is mainly due to correlations of the jet-stream activity with surface winds or with orographic and frontal gravity-wave generation. These facts have stimulated considerable effort toward observations and theoretical characterizations of gravity waves as well as the development of numerical algorithms which simulate gravity wave source characteristics and generation, wave propagation, breaking and their interaction with mean atmospheric flows.