Planetary Wave Characteristics in the Lower Atmosphere Over Xianghe (117.00°E, 39.77°N), China, Revealed by the Beijing MST Radar and MERRA Data

Abstract

AbstractUsing observation data from the Beijing mesosphere‐stratosphere‐troposphere radar from December 2013 to November 2014, together with the Modern Era Retrospective analysis for Research and Applications data, the dominant planetary waves (PWs) in the lower atmosphere over Xianghe (117.00°E, 39.77°N), for example, quasi‐16‐day and quasi‐10‐day oscillations, were identified and investigated. These two kinds of PWs displayed similar seasonal and height variations, indicating that they may have similar generation sources and dissipation processes. For both of them, near the tropospheric jet, significant zonal amplitudes could be observed in winter and spring months; quasi‐constant phase or partial vertical wavelength larger than 100 km was present in the zonal wind in December, March, and April, indicating that they were quasi vertical standing waves near the tropospheric jet. The calculated refractive indexes of these two PWs were significantly negative in the lower troposphere (3.5–5 km) and near the tropopause (15–20 km), and the resulted strong wave evanescence or even wave reflection could explain the observed quasi standing structure of these two PWs and height variations of their wind amplitudes. Their estimated zonal wave numbers in every month both showed the prevailing eastward propagation. Furthermore, we investigated the impact of PWs on the background wind by Eliassen‐Palm fluxes and divergences, which indicate that both the quasi‐16‐day and the quasi‐10‐day PWs, especially the latter, may contribute significantly to the construction and maintenance of the tropospheric jet. We also found that the tropospheric jet magnitude and height were both intensively modulated by the quasi‐16‐day and quasi‐10‐day PWs.