Large-amplitude gravity waves above the southern Andes, the Drake Passage, and the Antarctic Peninsula

• Main Authors: De La Torre, Alejandro Eduardo, Alexander, Pedro M., Hierro, Rodrigo Federico, Llamedo Soria, Pablo Martín, Rolla, Alfredo Luis
• Language: unknown
• Published: 2012
• Subjects: Atmospherics; Computer simulation; Gravity waves; Remote sensing; Research; Upper atmosphere; Wave energy conversion; Wavelet transforms; Weather forecasting; Antarctic Peninsula; Background winds; Constant pressures; Continuous Wavelet Transform; Different mechanisms; Dominant mode; Down-scaling; Drake passage; Equipartition; European Centre for Medium-Range Weather Forecasts; In-situ; Kinetic waves; Lower stratosphere; Mesoscale model simulation; Momentum flux; Partial waves; Pressure level; Reinitialization; Research programs; Satellite observations; Spin-up; Temperature fluctuation; Upper troposphere; Vertical fluxes; Wave amplitudes; Wave crest; Weather research and forecasting; Shear flow; air-sea interaction; amplitude; gravity wave; in situ measurement; mesocosm; mesoscale motion; mountain region; wave energy; wavelength; wind shear; zonal wind; Andes; Antarctic; Drake Passage; The Antarctic; Antarc*
• Online Access: https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_01480227_v117_n2_p_DeLaTorre; https://hdl.handle.net/20.500.12110/paper_01480227_v117_n2_p_DeLaTorre

Above the southern Andes range and its prolongation in the Antarctic Peninsula, large-amplitude mountain and shear gravity waves observed with Weather Research and Forecasting (WRF) mesoscale model simulations during winter 2009 are analyzed. Two specific reasons motivated this study: (1) a decade of satellite observations of temperature fluctuations in the stratosphere, allowing us to infer that this region may be launching the largest-amplitude gravity waves into the upper atmosphere, and (2) the recent design of a research program to investigate these features in detail, the Southern Andes Antarctic Gravity wave Initiative (SAANGRIA). The simulations are forced with ERA-Interim data from the European Centre for Medium-Range Weather Forecasts. The approach selected for the regional downscaling is based on consecutive integrations with weekly reinitialization with 24 h of spin-up, and the outputs during this period are excluded from the analysis. From 1 June to 31 August 2009, five case studies were selected on the basis of their outstanding characteristics and large wave amplitudes. In general, one or two prevailing modes of oscillation are identified after applying continuous wavelet transforms at constant pressure levels and perpendicularly to the nominal orientation of the dominant wave crests. In all cases, the dominant modes are characterized by horizontal wavelengths around 50 km. Their vertical wavelengths, depending on a usually strong background wind shear, are estimated to be between 2 and 11 km. The corresponding intrinsic periods range between 10 and 140 min. In general, the estimated vertical wavelength (intrinsic period) maximizes (minimizes) around 250-300 hPa. The synoptic circulation for each case is described. Zonal and meridional components of the vertical flux of horizontal momentum are shown in detail for each case, including possible horizontal wavelengths between 12 and 400 km. Large values of this flux are observed at higher pressure levels, decreasing with increasing height after a ...