Extracting gravity wave parameters during the September 2002 Southern Hemisphere major sudden stratospheric warming using a SANAE imaging riometer

Nkanyiso Mbatha (1, 2) , Venkataraman Sivakumar (2) , Hassan Bencherif (3) , Sandile B. Malinga (2)

1 SANSA - South African National Space Agency
2 UKZN - University of KwaZulu-Natal [Durban, Afrique du Sud]
3 LACy - Laboratoire de l'Atmosphère et des Cyclones

Using absorption data measured by imaging ri-ometer for ionospheric studies (IRIS) located at the South Africa National Antarctic Expedition (SANAE), Antarctica (72 • S, 3 • W), we extracted the parameters of gravity waves (GW) of periods between 40 and 50 min during late win-ter/spring of the year 2002, a period of the unprecedented major sudden stratospheric warming (SSW) in the Southern Hemisphere middle atmosphere. During this period, an unprecedented substantial increase of temperature by about 25– 30 K throughout the stratosphere was observed. During the period of the occurrence of the major stratospheric warming , there was a reduction of both the GW horizontal phase speeds and the horizontal wavelengths at 90 km. The GW phase speeds and horizontal wavelengths were observed to reach minimum values of about 7 m s −1 and 19 km, respectively , while during the quiet period the average value of the phase speed and horizontal wavelength was approximately 23 m s −1 and 62 km, respectively. The observed event is discussed in terms of momentum flux and also a potential interaction of gravity waves, planetary waves and mean circulation.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Nkanyiso Mbatha, Venkataraman Sivakumar, Hassan Bencherif, Sandile B. Malinga. Extracting gravity wave parameters during the September 2002 Southern Hemisphere major sudden stratospheric warming using a SANAE imaging riometer. Annales Geophysicae, 2013, 31 (10), pp.1709 - 1719. ⟨10.5194/angeo-31-1709-2013⟩. ⟨hal-01387268⟩