Dynamical Properties of the Tropical Atmosphere Derived from Radiosonde Observations at San Cristobal and Singapore

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Operational radiosonde data at San Cristo´bal (0.90°S, 89.62°W; eastern Pacific) are compared with those at Singapore (1.37°N, 103.98°E; western Pacific) intending to explore the differences in the dynamical properties of the tropopause region and in the activities of atmospheric waves between the eastern and the western tropical Pacific. The interannual variations in the meteorological parameters of the tropopause region are found to be almost synchronized between the two stations and do not show direct correspondence with the time evolution of El Niño. These evidences, as opposed to the general expectation of the strong influence of sea surface temperature variations on the tropopause properties, suggest that the tropospheric dynamical forcing is not a prevailing factor that drives the interannual variation of the tropical tropopause properties for these stations. The dynamical parameters of the tropopause region are affected by passages of vertically propagating atmospheric waves that characterize the time evolution of daily sounding data. The variations with the time scales of 15 to 20 days are identified as equatorial Kelvin waves of zonal wave number 1, which is consistent with the observed out-ofphase relationship between the two stations. The perturbations in the tropospheric temperature and wind are also brought about by those waves with the typical time scales of several days. These waves are more pronounced over San Cristo´bal than in Singapore. As the convections are more active and reach higher altitude in the western than in the eastern Pacific, this evidence implies that the altitude rather than the strength of convection is more important in characterizing the daily fluctuations of the tropical troposphere. The differences between the two stations in the time evolution and magnitude of the quasibiennial oscillation in the equatorial stratosphere are found to be marginal, although occasional differences in the onset time and the magnitude of zonal wind acceleration could be pointed out.<br>

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  • 気象集誌. 第2輯

    気象集誌. 第2輯 82 (4), 1129-1145, 2004

    公益社団法人 日本気象学会

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