Space-time variations of Equatorial Kelvin wave Activity around the tropical tropopause region

The equatorial Kelvin wave around the TTL plays a critical role in dehydrating air entering the lower stratosphere from the upper troposphere [Fujiwara et al., 2001]. In this study, the longitudinal and seasonal variations of the Kelvin wave around the TTL are examined using ERA-40. On the basis of the spectral analyses around the TTL, the Kelvin waves are extracted using a filter with the zonal wavenumber 1-10, the frequency 0.043-0.25 [1/day], and the equivalent depth 8-240 [m]. The Kelvin waves in the zonal wind around the TTL are most active from the Indian Ocean to the western Pacific. The area where the Kelvin waves disappear and its basic state are also investigated with the composite analysis. It is found that the waves are disappearing in the eastern hemisphere around a convective region in the strong easterly wind, but that they are receding in the western hemisphere around the westerly wind region.