Signature of a Quasi 30‐Day Oscillation at Midlatitude Based on Wind Observations From MST Radar and Meteor Radar

• Published in: Journal of geophysical research. Atmospheres 2019-11, Vol.124 (21), p.11266-11280
• Main Authors: Huang, Kai Ming, Xi, Yu, Wang, Rui, Zhang, Shao Dong, Huang, Chun Ming, Gong, Yun, Cheng, Hao
• Format: Article
• Language: English
• Subjects: Amplitude; Amplitudes; Atmosphere; Atmospheric oscillations; Back propagation; Decay; Geophysics; Intraseasonal oscillation; Latitude; Lower atmosphere; Mesosphere; Meteors; Oscillations; Polar environments; Polar regions; quasi 30‐day oscillation; Radar; Radar observation; reflection; Refractive index; Refractivity; Stratosphere; Tropical environments; Troposphere; Wind; Wind observation; Zonal winds
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2019JD031170

Lots of works make contributions to revealing propagation features and excitation mechanisms of intraseasonal oscillations (ISOs) in the tropics; however, there are few reports on ISOs at higher latitudes. By using measurements of mesosphere‐stratosphere‐troposphere radar at Xianghe (39.8°N, 116.5°E) and meteor radar at Beijing (40.3°N, 116.2°E) and reanalysis data for 105 days from 16 November 2013 to 28 February 2014, we study an ISO with about 30‐day period at midlatitude and high latitude. Radar observations indicate that in the troposphere, the oscillation attains an amplitude peak in zonal wind at about 9 km and propagates downward below 9 km. At about 9–16 km, the oscillation gradually decays with height and then strengthens again as it propagates upward in the stratosphere. In the mesosphere, the oscillation obviously appears at 78–86 km with a maximum amplitude at 80 km. Reanalysis data show that in the troposphere, the oscillation propagates southward. At about 100 (~16 km)‐ to 10 (~32 km)‐hPa levels, the oscillation is gradually reflected back to propagate northward, and then propagates poleward at higher altitude. Refractive index can explain its complex propagation characteristics very well. Consistence and coherence of its phase progression indicate that in the lower atmosphere, the oscillation comes from the polar region. Hence, ISOs can not only originate from but also propagate in the atmosphere at mid and high latitudes. Key Points MST radar and meteor radar observations show that a quasi 30‐day ISO is robust in the troposphere, stratosphere, and mesosphere over 40°N The 30‐day ISO originates from polar lower atmosphere and shows the features of reflection in the vertical and meridional directions Lasting negative squared index at 9–16 km and between 30 and 45°N can explain ISO reflection and amplitude decay in different directions