Equatorial wave analysis from SABER and ECMWF temperatures

[摘要] Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravitywaves are excited by convective processes in the troposphere.In this paper an analysis for these and other equatorialwave modes is carried out with special focus on the stratosphereusing temperature data from the SABER satellite instrument as well as ECMWFtemperatures.Space-time spectra of symmetric and antisymmetric spectral powerare derived to separate the different equatorial wave types andthe contribution of gravity waves is determinedfrom the spectral background of the space-time spectra.

Both gravity waves and equatorial planetary scale wave modes are main driversof the quasi-biennial oscillation (QBO) in the stratosphere. Temperaturevariances attributed to the different wave types are calculated for theperiod from February 2002 until March 2006 and compared to previous findings.A comparison between SABER and ECMWF wave analyses shows that in the lowerstratosphere SABER and ECMWF spectra and temperature variances agreeremarkably well while in the upper stratosphere ECMWF tends to overestimateKelvin wave components. Gravity wave variances are partly reproduced by ECMWFbut have a significant low-bias. For the examples of a QBO westerly phase(October–December 2004) and a QBO easterly phase (November/December 2005,period of the SCOUT-O3 tropical aircraft campaign in Darwin/Australia) in thelower stratosphere we find qualitatively good agreement between SABER andECMWF in the longitude-time distribution of Kelvin, Rossby (n=1), andRossby-gravity waves.

[学科分类] 大气科学