The summertime 12-h wind oscillation with zonal wavenumber s = 1 in the lower thermosphere over the South Pole

• Main Authors: Portnyagin, Y. I., Forbes, J. M., Makarov, N. A., Merzlyakov, E. G., Palo, S.
• Other Authors: Institute for Experimental Meteorology, Department of Aerospace Engineering Sciences, University of Colorado Boulder
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1998
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; South Pole; Scott Base; Molodezhnaya; South pole
• Online Access: https://hal.science/hal-00316411; https://hal.science/hal-00316411/document; https://hal.science/hal-00316411/file/angeo-16-828-1998.pdf

International audience Meteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one ( s =1). The wind measurements are confined to the periods from 19 January 1995 through 26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s =1 oscillation is found to be a predominantly summertime phenomenon, and is replaced in winter by a spectrum of oscillations with periods between 6 and 11.5 h. Both summers are characterized by minimum amplitudes (5?10 ms ?1 ) during early January and maxima (15?20 ms ?1 ) in November and late January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of order 4?6 h occur during the course of the summer. In addition, there is considerable day-to-day variability (±5?10 ms ?1 in amplitude) with distinct periods (i.e., ~5 days and ~8 days) which suggests modulation by planetary-scale disturbances. A comparison of climatological data from Scott Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near 78°S is s =1, but that at 68°S there is probably a mixture between s =1 and other zonal wavenumber oscillations (most probably s =2). The mechanism responsible for the existence of the 12-h s =1 oscillation has not yet been identified. Possible origins discussed herein include in situ excitation, nonlinear interaction between the migrating semidiurnal tide and a stationary s =1 feature, and thermal excitation in the troposphere.