Lidar observations of neutral Fe layers and fast gravity waves in the thermosphere (110-155 km) at McMurdo (77.8°S, 166.7°E), Antarctica

Abstract

We report the first lidar observations of neutral Fe layers with gravity wave signatures in the thermosphere from 110–155 km at McMurdo, Antarctica in May 2011. The thermospheric Fe densities are low, ranging from ∼200 cm−3 at 120 km to ∼20 cm−3 at 150 km. The measured temperatures from 115–135 km are considerably warmer than MSIS and appear to be related to Joule heating enhanced by aurora. The observed waves originate in the lower atmosphere and show periods of 1.5–2 h through 77–155 km. The vertical wavelength increases from ∼13 km at 115 km to ∼70 km at 150 km altitude. These wave characteristics are strikingly similar to the traveling ionospheric disturbances caused by internal gravity waves. The thermospheric Fe layers are likely formed through the neutralization of vertically converged Fe+ layers that descend in height following the gravity wave downward phase progression.

Simultaneous, common‐volume lidar observations and theoretical studies of correlations among Fe/Na layers and temperatures in the mesosphere and lower thermosphere at Boulder Table Mountain (40°N, 105°W), Colorado

“…In the remaining five nights, neither Fe nor Na converged layer is above 100 km. In light of the recent discovery of neutral Fe layers in the thermosphere up to 155 km at McMurdo, Antarctica [Chu et al, 2011b], the thermosphere metal layers above 100 km become an interesting topic. Following the McMurdo discovery, Friedman et al [2013] report a thermosphere K layer up to 150 km at Arecibo Observatory, Tsuda et al [2012] report a thermosphere Na layer reaching 130 km at Syowa, Antarctica, and J. report an intensive Na layer up to 130 km at Beijing.…”

Short-period mesospheric gravity waves and their sources at the South Pole

“…As such, because of their significance to the dynamics of the middle atmosphere, gravity waves have been a focus of active and ongoing research, particularly at high latitudes. However, while some studies have looked at gravity waves near the poles (Chu et al, 2011;Chen et al, 2013;Kaifler et al, 2015), observations at high latitudes are often difficult to obtain due to experimental logistics. This is even more of an issue in the Antarctic region, where few manned stations exist to operate gravity wave instrumentation during the austral winter.…”

Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding

“…The advantage of the RMR lidar at Kühlungsborn is the ability to measure under nighttime as well as under daytime conditions, resulting in a continuous temperature time series over the whole day (Gerding et al, 2013(Gerding et al, , 2016Kopp et al, 2015). Most other lidar instruments which can measure during the day cover only a small altitude range (Chu et al, 2011), while other RMR lidars measure only during nighttime conditions (Gardner and Voelz, 1987;Wilson et al, 1991). This paper presents main features of wave activity at midlatitudes for an altitude range from the lower stratosphere to the upper mesosphere on short timescales of 10 days in May 2016.…”