Planetary wave coupling from the stratosphere to the thermosphere during the 2002 Southern Hemisphere pre‐stratwarm period

Abstract

Temperature observations between 20 and 120 km from the SABER instrument on the TIMED spacecraft are used to investigate the nature of planetary wave activity during the 60 days prior to the midwinter stratospheric warming that commenced on 26 September, 2002 in the Southern Hemisphere. The primary wave components consist of eastward‐propagating quasi‐10‐day waves with zonal wave numbers s = 1 and s = 2, and a stationary planetary wave with s = 1. The waves are found to extend from the lower stratosphere to the 100–120 km height region with surprisingly little amplitude attenuation, although wave amplitudes oscillate with altitude like a standing wave pattern. Time evolution of the waves is also addressed with emphasis on 86 km altitude, where temperature observations from three Antarctic stations at Davis (69°S, 78°W), Rothera (68°S, 68°W) and Syowa (69°S, 40°E) are available during the same period. We demonstrate that the temporal evolution of temperature obtained by superposition of the waves derived from SABER measurements accounts for nearly all the temperature variability observed at the longitudes of the three Antarctic stations.

Large-scale planetary disturbances in stratospheric temperature at high-latitudes in the southern summer hemisphere

“…All these recent studies Jarvis, 2001, 2003;Palo et al, 2005;Chshyolkova et al, 2006) consider the stratospheric dynamics during the Antarctic winter and spring seasons, including periods of major stratospheric warmings. Yet, although similar planetary wave signatures are revealed in the COSMIC data, they are for a period when no major stratospheric warming event was registered and for a season when planetary wave activity should be negligible in the Southern Hemisphere (e.g.…”

“…However, the wave 2 had a traveling component similar to that of wave 1, but did not have a stationary wave component. Palo et al (2005) examined the planetary wave dynamics prior to the major stratospheric warming in the winter of 2002 in the Southern Hemisphere employing SABER temperature data. They started from the premise that wave forcing plays a key role in the preconditioning of the atmosphere prior to stratospheric warming and examined the wave interaction between eastward-propagating waves with a period of 10 days, quasi-stationary waves and the zonal mean atmospheric state.…”

“…Hirooka, 2000;Palo et al, 2005;Ern et al, 2007). However, the spatial and temporal coverage of these observations has been restricted by orbit configurations, viewing geometry and vertical resolution.…”

Method for assessing the amplitude modulation of the stationary planetary waves

“…SPWs (Forbes et al, 2002) or some of the normal modes (Wu et al, 1994;Talaat et al, 2002;Palo et al, 2005;Azeem et al, 2005). Recently however, Pancheva et al (2008b) have suggested a data analysis method where all types of planetary wave (stationary, zonally travelling and zonally symmetric) with zonal wavenumbers up to 3 have been simultaneously extracted from the UKMO data.…”

“…Analysis of the global stratosphere data like UK Met Office (UKMO) assimilated fields (Swinbank and Ortland, 2003) or the National Centre for Environmental Prediction (NCEP) reanalysis data (Randel, 1992) provided observational evidence for interactions between the zonally propagating planetary waves, quasistationary planetary waves and the zonal mean flow (Krüger et al, 2005;Pancheva et al, 2007Pancheva et al, , 2008a. The satellite measurements as those of the HRDI and WINDII instruments onboard the UARS satellite and particularly recent measurements of the SABER and TIDI instruments onboard the TIMED satellite were employed to explore not only the temporal behavior and spatial structures of the planetary waves from lower stratosphere to the lower thermosphere (Wang et al, 2000;Forbes et al, 2002) but the coupling processes as well (Palo et al, 2005;Merzlyakov and Pancheva, 2007).…”