| Summary: | We report on the first observation of mesospheric cloud (MC) at the altitude range of 50-65 km with lidars at Yanqing (40.5°N, 116°E) and Pingquan (41°N, 118.7°E) on 30 October 2018. The MC occurred at the 51-56 km altitude range during the hours of dawn. It had an obvious double-layer structure, but the cloud layer was sparse. The MC was re-observed at the 56-62 km altitude range in the twilight, and the double-layer structure was still obvious. However, the cloud layer became thicker with a maximum volume backscatter coefficient (BSC) 3.1×10−10m−1sr−1. Atmospheric temperature structure was derived according to the lidar observations, and it was found that, several hours before the MC occurrence, a temperature anomaly with coldest temperature ~185 K was propagating downward at the altitudes of 50-65 km. This MC layer was simultaneously observed with lidar at Pingquan in the twilight. It could be a regional MC event and possibly formed locally by a transient cooling due to small-scale disturbances in the mesosphere.
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