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Volume 4, issue 9 | Copyright

Special issue: Observing atmosphere and climate with occultation techniques...

Atmos. Meas. Tech., 4, 1777-1784, 2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Sep 2011

Research article | 08 Sep 2011

A method to improve the determination of wave perturbations close to the tropopause by using a digital filter

P. Alexander1, A. de la Torre2, P. Llamedo2, R. Hierro2, T. Schmidt3, A. Haser3, and J. Wickert3 P. Alexander et al.
  • 1Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
  • 2Facultad de Ingeniería, Universidad Austral, Av. J. de Garay 125, 1063 Buenos Aires, Argentina
  • 3Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg A17, Potsdam, 14473, Germany

Abstract. GPS radio occultation satellite data allowed to analyze in the last decade for the first time a large amount of atmospheric temperature profiles including both the troposphere and the stratosphere all over the globe. Wave amplitude enhancements have been systematically observed around tropopause levels, which are apparently due to artifacts generated by any digital filter used to isolate the wave components from these data. We present a new filtering method which can be equally applied to temperature or refractivity profiles. It was tested with synthetic temperature data based on NCEP reanalyes and observed wave climatologies and it was also statistically validated with GPS radio occultation profiles from the COSMIC mission. The suggested technique significantly reduces artificial enhancements around the tropopause, mainly at low latitudes, where a sharp lapse rate change usually exists. This represents an improvement in comparison to previous applications of standard filters. In addition it would allow the study of longer vertical wavelengths than previously done with other filtering procedures.

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