K. Sato et al., SHORT-PERIOD DISTURBANCES IN THE EQUATORIAL LOWER STRATOSPHERE, Journal of the Meteorological Society of Japan, 72(6), 1994, pp. 859-872
Temperature and horizontal wind fluctuations with periods shorter than
3 days in the equatorial lower stratosphere are examined by using dat
a from routine rawinsonde observations at Singapore (1N, 104E) during
1978-1993. Internal wave-like structures having a period of about 2 da
ys and a short vertical wavelength of 5 km are occasionally observed b
oth in temperature and wind fluctuations. The result of power spectral
analysis indicates that short-period fluctuations have significant en
ergy, separated from Kelvin waves and mixed Rossby-gravity waves. Long
-term variations of the spectral characteristics are investigated in r
elation to the quasi-biennial oscillation (QBO). Zonal wind and temper
ature variances due to the short-period fluctuations are generally lar
ge and particularly enhanced in the QBO phase when the direction of me
an wind changes from easterly to westerly. Co-spectra of temperature a
nd zonal wind fluctuations at short periods are significantly larger t
han the quadrature spectra, and the sign of co-spectra changes accordi
ng to the phases of the QBO. These results indicate strong connection
of the short-period disturbances with the QBO.