First measurement of horizontal wind and temperature in the lower thermosphere (105–140 km) with a Na Lidar at Andes Lidar Observatory

Abstract

We report the first measurement of nighttime atmospheric temperature and horizontal wind profiles in the lower thermosphere up to 140 km with the Na lidar at Andes Lidar Observatory in Cerro Pachón, Chile (30.25°S, 70.74°W), when enhanced thermospheric Na was observed. Temperature and horizontal wind were derived up to 140 km using various resolutions, with the lowest resolution of about 2.7 hr and 15 km above 130 km. Thus, the measurements span 60 km in vertical, more than double the traditional 25 km. On the night of 17 April 2015, the horizontal wind magnitude in the thermosphere exceeds 150 ms−1, consistent with past rocket measurements. The meridional wind shows a clear transition from the diurnal‐tide‐dominant mesopause to the semidiurnal‐tide‐dominant lower thermosphere. A lidar with a 100 times the power aperture product will be able to measure wind and temperature above 160 km and cover longer time span, providing key measurements for the study of atmosphere‐space interactions in this region.

The First Concurrent Observations of Thermospheric Na Layers From Two Nearby Central Midlatitude Lidar Stations

“…Although we are unable to compare with those in the polar region or tropic, as no statistics is available, it is much lower than the 33% (22%) reported from Lijiang (Cerro Pachón) observations (Gao et al, 2015;Liu et al, 2016). Gao et al (2015) and Liu et al (2016) also reported thermospheric layers in April, the latter with 46% occurrence. In addition to 15 April 2018 and 27 April 2018, we also observed a thermospheric layer on 27 April 2017 at Pingquan station (included as entry 12 in Table 1; there are no data at Yanqing).…”

“…Although we are unable to compare with those in the polar region or tropic, as no statistics is available, it is much lower than the 33% (22%) reported from Lijiang (Cerro Pachón) observations (Gao et al, 2015;Liu et al, 2016). Although we are unable to compare with those in the polar region or tropic, as no statistics is available, it is much lower than the 33% (22%) reported from Lijiang (Cerro Pachón) observations (Gao et al, 2015;Liu et al, 2016).…”

“…The rare layers above the main layers extending to below 130 km were reported (mostly in Na) over the past 20 years (see, for example, Collins et al, 1996) have received renewed interest by Gong et al (2003) and others with different names. Since then, there are five additional publications reporting layers to beyond 130 km, one (Tsuda et al, 2015) from another Antarctic station over Syowa Station (69.0°S, 39.6°E); two (Friedman et al, 2013;Raizada et al, 2015) from the same tropic station, Arecibo (18.35°N, 66.75°W); and two from lower midlatitude stations at Lijiang, China (26.7°N, 100.0°E) by Gao et al (2015), and Cerro Pachón, Chile (30.25°S, 70.74°W) by Liu et al (2016). Fe layers between 110 and 155 km over McMurdo,Antarctica (77.8°S,166.7°E) by Chu et al (2011) was the first report of this type.…”

A Numerical Investigation on Tidal and Gravity Wave Contributions to the Summer Time Na Variations in the Midlatitude E Region

“…At the same time, the wave also induces extremely low Na number density centered around 100 km: once during early evening and once more during late morning period. While the tidal wave contributions to Na s are quite limited due to their large temporal and spatial scales, large‐amplitude GW and the associated dynamic features can indeed generate small‐scale Na variations in the E region, such as Na s . In addition, the significant enhancement of eddy diffusion coefficient above the GW saturation level can change the Na s spatial and temporal structures dramatically. The tidal wind vertical wind component is found to be mainly responsible for the large‐scale Na layer extension into the thermosphere of midlatitude, which likely contributes to the Na layer observed in the thermosphere above low latitudes as well (Gao et al, ; Liu et al, ), where the tidal wave modulations are much stronger than those near midlatitude.…”

“…Indeed, Plane et al () “pushed” an intense ion layer downward mathematically below 100 km in an Na chemistry model, and a sporadic Na layer was formed out of the E s . However, the formation of the Na layer/cloud above 100 km in the thermosphere reported around the globe (Clemesha, Batista, et al, ; Gao et al, ; Liu et al, ; Sarkhel et al, ) is puzzling, while the existing models currently do not generate these Na structures in the thermosphere. The Na ion‐molecular chemistry in the literatures limits the Na + neutralization above this altitude; thus, other mechanisms have to play significant roles in the Na variations in the E region, unless the current metal chemistry is missing some critical reactions.…”