Infrasound and Gravity Waves Over the Andes Observed by a Pressure Sensor on Board a Stratospheric Balloon

Abstract

The study of infrasound (acoustic) and gravity waves sources and propagation in the atmosphere of a planet gives us precious insight on atmosphere dynamics, climate, and even internal structure. The implementation of modern pressure sensors with high rate sampling on stratospheric balloons is improving their study. We analyzed the data from the National Aeronautics and Space Administration Ultra Long Duration Balloon mission (16 May to 30 June 2016). Here, we focus on the balloon's transit of the Andes Mountains. We detected gravity waves that are associated to troposphere convective activity and mountain waves. An increase of the horizontal wavelengths from 50 to 70 km with increasing distance to the mountains is favoring the presence of mountain waves. We also report on the detection of infrasounds generated by the mountains in the 0.01–0.1 Hz range with a pressure amplitude increase by a factor 2 relative background signal. Besides, we characterized the decrease of microbaroms power when the balloon was flying away from the ocean coast. These observations suggest, in a way similar to microseisms for seismometers, that microbaroms are the main background noise sources recorded in the stratosphere even far from the ocean sources. Finally, we observed a broadband signal above the Andes, between 0.45 and 2 Hz, probably associated with a thunderstorm. The diversity of geophysical phenomena captured in less than a day of observation stresses the interest of high rate pressure sensors on board long‐duration balloon missions.

A “Floatilla” of Airborne Seismometers for Venus

“…After all, the planet we know best is Earth and so far, our approach of relying on physical rules that govern the Earth to predict what we might see on other planets has served us well, at least in the seismic realm. Several confirmed detections of the non-seismic sources mentioned above from stratospheric balloons are already extant in literature (see e.g., Lamb et al (2018) for thunderstorms, and Poler et al (2020) for mountain waves). Long-duration data collection from balloons can help in further expanding this catalog, so that patterns can begin to emerge that would allow independent association of infrasound signals to originating events.…”

Natural and Anthropogenic Sources of Seismic, Hydroacoustic, and Infrasonic Waves: Waveforms and Spectral Characteristics (and Their Applicability for Sensor Calibration)

“…The waveform characteristics of the detected events depended on the distance from the source terrain, as more distant mountain ranges apparently resulted in lower frequencies at the sensors than nearer sources. MAWs have also been measured by infrasound sensors on a balloon when crossing the southern Andes (Poler et al 2020 ). An example waveform recording and its associated spectrogram is shown in Fig.…”

Airborne Infrasound Makes a Splash

“…By placing infrasound microbarometers on a high altitude balloon, Bowman and Lees (2015) showed that airborne sensors were able to capture sound fields very different from that of the Earth's surface, and that background noise levels were very low when the instruments were properly protected against electromagnetic interference. A 19 days infrasound sensing mission on a long duration balloon in the southern hemisphere then captured hitherto unsampled acoustic radiation above the ocean microbarom source region (Bowman & Lees, 2018), thunderstorms (O. Lamb et al., 2018), and wind/mountain interactions (Poler et al., 2020). The balloon circled Antarctica, at one point crossing through a 7,000 km gap between ground infrasound stations.…”

“…sensing mission on a long duration balloon in the southern hemisphere then captured hitherto unsampled acoustic radiation above the ocean microbarom source region , thunderstorms (O. Lamb et al, 2018), and wind/mountain interactions (Poler et al, 2020). The balloon circled Antarctica, at one point crossing through a 7,000 km gap between ground infrasound stations.…”