Search

Wind shear has important implications for Kelvin–Helmholtz instability (KHI) and gravity waves (GWs) in the mesosphere–lower thermosphere (MLT) region where its momentum transport process is dominated by short-period (<1 h) GWs. However, the sub-hourly variation in wind shear is still not well quantified. This study aims to improve current understanding of vertical wind shear by analyzing multi-year meteor radar measurements at the Mohe (MH, 53.5°N, 122.3°E), Beijing (BJ, 40.3 ° N , 116.2 ° E ), Wuhan (WH, 30.5 ° N , 114.6 ° E ), and Fuke (FK, 19.5°N, 109.1°E) stations in China. The wind field is estimated by a new algorithm, e.g., the damped least squares fitting. Taking the wind shear estimated by normal products as a criterion, the shear produced by the new algorithm has more statistical convergence as compared to the traditional algorithm, e.g., the least squares fitting. Therefore, we argue that the 10 min DLSA wind probably produces a more reasonable vertical shear. Both intensive wind shears and GW kinetic energy can be simultaneously captured during the 0600–1600 UTs of May at MH and during the 1300–2400 UTs of March at FK, possibly implying that the up-propagation of GWs could contribute to the production of large wind shears. The sub-hourly variation in wind shears is potentially valuable for understanding the interrelationship between shear (or KHI) and GWs. [ABSTRACT FROM AUTHOR]

In this study, we analyze the observations of the ionosondes at Wuhan (30.4°N, 114.4°E, 82.4% obscuration), Xiamen (24.2°N, 118.07°E, 97.8% obscuration), and Nanning (22.7°N, 109.25°E, 81.1% obscuration), as well as the total electron content (TEC) from the global ionosphere maps (GIMs) to examine the ionospheric behaviors in the F‐region on 21 June 2020 solar eclipse day. The observations show that a TEC enhancement occurred after the major depression near the center path of the solar eclipse, and it lasts to midnight on the solar eclipse day. Notes that the occurrence of the TEC enhancement is accompanied by the prominent TEC depletion in the southern side of the center path in the nighttime. The independent in situ electron density (Ne) observation from the Swarm‐B satellite and the calibrated TEC profile from the radio occultation technique onboard the FORMOSAT‐7/Constellation Observing System for Meteorology, Ionosphere, and Climate‐2 satellites also observed the long‐lasting enhancement in the F2 region near midnight. The solar eclipse‐induced convergence effects can result in the long‐lasting ionospheric perturbations, which may further cause the spread‐F in the nighttime. Key Points: The long‐lasting ionospheric enhancement can be attributed to the eclipse‐induced convergence effects near the center pathThe eclipse‐induced convergence effects cause the secondary density depletion in the southern side of the center pathThe solar eclipse perturbed the ionosphere from the obscuration to midnight and may further influence the nighttime irregularities [ABSTRACT FROM AUTHOR]