资源环境科技发展态势分析平台

Continuous observations of polar mesosphere summer echoes at heights from 81-93 km were performed using the first Mesosphere-Stratosphere-Troposphere/Incoherent Scatter radar in the Antarctic over the three summer periods of 2013/2014, 2014/2015, and 2015/2016. Power spectra of horizontal and vertical wind fluctuations, and momentum flux spectra in a wide-frequency range from (8 min)(-1) to (20 days) (-1) were first estimated for the Antarctic summer mesosphere. The horizontal (vertical) wind power spectra obey a power law with an exponent of approximately -2 (-1) at frequencies higher than the inertial frequency of (13h)(-1) and have isolated peaks at about 1 day and a half day. In addition, an isolated peak of a quasi-2 day period is observed in the horizontal wind spectra but is absent from the vertical wind spectra, which is consistent with the characteristics of a normal-mode Rossby-gravity wave. Zonal (meridional) momentum flux spectra are mainly positive (negative), and large fluxes are observed in a relatively low-frequency range from (1 day)(-1) to (1h)(-1). A case study was performed to investigate vertical profiles of momentum fluxes associated with gravity waves and time mean winds on and around 3 January 2015 when a minor stratospheric warming occurred in the Northern Hemisphere. A significant momentum flux convergence corresponding to an eastward acceleration of similar to 200ms(-1)d(-1) was observed before the warming and became stronger after the warming when mean zonal wind weakened. The strong wave forcing roughly accorded with the Coriolis force of mean meridional winds.