This is a 3-year observation and modeling project to be undertaken as part of the Coupling, Energetics and Dynamics of Atmospheric Regions (CEDAR) program. Atmospheric gravity waves are believed to play a vital role in the transport of energy and momentum between atmospheric layers. This project concerns the ubiquitous wave field in the thermosphere at the low latitude Arecibo Observatory (AO) site. Observing campaigns with the Arecibo incoherent scatter radar that employ a newly developed and tested innovative measurement technique will be used together with ray tracing, and first principles models. The goal is to self-consistently determine all of the parameters needed for reverse ray tracing for the gravity waves observed at the AO, to identify the most likely lower atmospheric and thermospheric sources for dozens of these gravity wave events, to determine the temporal evolution of the F region neutral wind, and to determine the neutral wind acceleration caused by select sources.
Gravity waves are a significant forcing source on mesosphere and lower thermosphere dynamics and their effects strongly impact general circulation and climate models. In addition, numerical weather prediction models, despite their tropospheric focus, have been shown to make better predictions when the upper-atmospheric dynamics are more accurately modeled. The project is collaboration between a female PI at North West Research Associates and an early career scientist at SRI International and also involves scientists at the NSF AO facility.
Atmospheric gravity waves (GWs) are created by many different processes, including thunderstorms, ocean waves, wind over the mountains, etc. For this project, we examined the GWs moving in the Earth's atmosphere 100 to 260 km (60 to 165 miles) above the Earth's surface using data from the Arecibo Observatory and modeling. This highly-sensitive observatory is located on the main island of Puerto Rico, and has been peering up into the Earth's atmosphere for more than 50 years. Drs. Nicolls and Vadas designed a novel rotating dual-beam experiment which was able to not only see the waves, but determine which direction they were moving and how large they were. It was found that the GWs propagated southward, eastward, or northward, but not westward, and varied day-to-day. Possible sources were thunderstorms and ocean waves. These results were described in a paper published in a peer-reviewed journal In order to understand the amplitudes and properties of the GWs from ocean waves in the Earth's atmosphere, Dr. Vadas developed a new ocean wave/atmosphere coupling model. This model and first results were described in a paper which will soon be sent to a peer-reviewed journal for possible publication. It was found that GWs with many different frequencies are excited by an ocean wave packet, and that they propagate at different speeds into the upper atmosphere. It was also found that significant temperature fluctuations occur in the Earth's atmosphere 250 km above the ground. The excited GWs travel in distinct packets, and arrive for many hours after being excited. More precise modeling in the future will allow researchers to better-understand the influence of ocean waves on the Earth's atmosphere above the Arecibo Observatory. If ocean waves end up being an important source of GWs, this would be an important discovery, because 71% of Earth is covered by oceans. Thus, this project has and will lead to a better understanding of the perturbations in the Earth's atmosphere far above the Arecibo Observatory.
