CEDAR: Lower-Upper Atmosphere Coupling via Acoustic Wave Energy

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) program, a broad-based, community-guided, upper atmospheric research program, is aimed at understanding the behavior of atmospheric regions from the lower atmosphere upward through the mesosphere and lower thermosphere (MLT) region near 80-120 km. Of particular interest is the energy transfer into the mesosphere lower thermosphere (MLT) region resulting from the coupling to the lower atmosphere, where there are violent phenomena such as thunderstorms, convective frontal activity, tornados, and other violent storm weather phenomena, as well as anthropogenic sources such as heating and air conditioning units, that will produce strong acoustic wave signals. Such energy transfer might have importance regarding a contribution to the MLT energy budget. This award provides support for the balloon flight measurements over four campaigns (one for each season) of acoustic wave activity using instrumented zero pressure balloon payloads flown to stratosphere heights near 35 km. The project is aimed at establishing the extent to which acoustic wave structures generated within the troposphere will propagate to the MLT region and produce MLT heating through acoustic wave dissipation. The balloon microphone sensors would measure the acoustic wave energy flux for frequencies within the range of 1 to 10 Hz. A PhD graduate student and a postdoctoral associate would be supported in this award. These observations would take place with launches from the University of North Carolina Chapel Hill campus, which will create considerable public interest in these experiments. Each campaign would feature morning and evening flights of two balloons carrying aloft two microphones mounted in each balloon payload that would obtained acoustic waveform data that would be used in ray tracing software of acoustic wave structures to determine trajactories, occurrence rates, and wave frequency. These measurements would be obtained in four separate campaigns to measure the seasonal and diurnal variation of the aooustic energy background. Determination of the possible effects upon the MLT region would be based upon the application of linear sound wave absorption theory following the lines of previous published work. In the case of possible complex sound waveforms as might be generated by anthropogenic sources (e.g., air conditioning systems, a more sophisticated treatment of the analysis would be carried out to determine the impact upon the MLT temperature in a quantitative way.