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is calculated from the radiosonde temperature data and the EAR horizontal wind data.A continuous updraft (>0.025 m s 1 ) is clearly seen in the region 0–1 km above thecold-point tropopause determined by the radiosonde soundings (Figure 3(a)). Temporalvariation of the tropopause height is affected by equatorial Kelvin waves [Fujiwara et al.,2003]. The echo power in the westward beam is continuously stronger than that in theeastward beam in the updraft region (Figure 3(b)). A strong eastward wind shear orwestward wind which decreases with altitude from the tropopause (10–50 m s 1 km 1 )is also continuously observed in the same region (Figure 3(c)). Ri is almost continuously< 0.5 and sometimes < 0.25. (Figure 3(d)).KHI is considered to occur frequently, even if observed Ri is > 0.25. One reason is thatRi is not always < 0.25 in all. Another reason is that occurrence and non-occurrence ofKHI recurred, on average, in one hour. The contamination of horizontal wind to verticalwind velocity which is measured in the vertical beam easily occurs, if the echo layer istilted by billows generated by KHI (KH billows). If the layer is tilted by KH billows, theeffective direction of the vertical beam becomes tilted toward the perpendicular axis ofthe refractivity surface, because the effective direction of the radar beam is determinedby the convolution of angle dependence of radar wave scattering with the antenna beampattern. Under this condition, the horizontal wind component, which is extremely greaterthan the vertical wind component, contaminates the Doppler shift in the vertical beam.Figure 3(d) shows that Ri is almost continuously < 0.5 in the updraft region due to thestrong zonal wind shear, and the condition for KHI generation is satisfied. The positivevalues of zonal EPI in the updraft region (Figure 3(b)) indicate that the echo layer istilted downward to the west and suggest continuous existence of KH billows under thestrong eastward wind shear (Figure 3(c)). Therefore, the updraft in the region 0–1 kmabove the tropopause is not real nut a spurious one resulting from the contamination ofwestward winds under the condition of the echo layer tilted downward to the west, whichis generated by KH billows. Under this condition, the spurious vertical wind should beupward, which agrees with the observed result. These features consistently suggest thatKHI is continuously generated in the TTL.ConclusionIn this paper, we have shown the enchanced turbulence by the Kelvin wave and theKHI occurence, both of which exist in the tropical tropopause region. Existence of KHIaround the tropopause may play a role in tropical stratosphere-troposphere exchange.Further studies on the turbulence in the tropical tropopause layer (TTL) is performedby EAR observations, and will be shown in the near future.ReferencesFujiwara, M., M. K. Yamamoto, H. Hashiguchi, T. Horinouchi, and S. Fukao,Turbulence at the tropopause due to breaking Kelvin waves observed by the EquatorialAtmosphere Radar, Geophys. Res. Lett., 30(4), 1171, doi:10.1029/2002GL016278, 2003.Fukao, S., H. Hashiguchi, M. Yamamoto, T. Tsuda, T. Nakamura, M. K. Yamamoto,T. Sato, M. Hagio, and Y. Yabugaki, The Equatorial Atmosphere Radar (EAR): Systemdescription and first results, Radio Sci., 38(3), 1053, doi:10.1029/2002RS002767, 2003.Gage, K. S., B. B. Balsley, W. L. Ecklund, D. A. Carter, and J. R. McAfee, Windprofiler-related research in the tropical Pacific, J. Geophys. Res., 96, 3209-3220, 1991.Yamamoto, M. K., M. Fujiwara, T. Horinouchi, H. Hashiguchi, and S. Fukao,Kelvin-Helmholtz instability around the tropical tropopause observed with theEquatorial Atmosphere Radar, Geophys. Res. Lett., 30(9), 1476,doi:10.1029/2002GL016685, 2003.219