Extended Abstract (820K)P2.2
Red Shift Phenomena Revealed in the Zonal Winds Oscillations Probably Induced by the Sunspot Cycle
G.-H. Lim, Seoul National University, Seoul, Korea; and A. -. S. Suh and Y. Suh
Comprehensive wavelet analysis was applied to the averaged zonal winds for the latitudes from ?5 degree to 15 degree at all the standard pressure levels from 1000 hPa to 10 hPa. The winds are based on the monthly values of the NCEP reanalyses for months from January 1948 to June 2003. The same analysis was also used for investigating the time dependent frequency characteristics of the principal component time series of the first mode of the empirical orthogonal function analysis of the global GPCP precipitations for the regions extending from ?0 latitude to +60 latitude for 22 years from 1979 to 2000. The well-defined oscillations are annual, semiannual, and El Nino and La Nina related components in the troposphere. Among these for the various levels, the strongest signature was found at 850 hPa. At the level, there also exists significant power related to the frequency components of 2-3 years periodicities and 13-16 years periodicities. These components are observable with ease in the lower troposphere on the other hand in the upper troposphere there is no clear signature of 2-3 years periodicity oscillation but a relatively weak signature of the 10-12 year oscillation is observed with maximum amplitudes at 150 hPa. In the stratosphere, up to 10 hPa level in our analysis, the stratospheric QBO, annual, semiannual, and the 10-12 year oscillations are well defined. Except for the QBO with large amplitudes at 70 hPa, the other oscillations are conspicuous near the tropopause level, approximately 150 hPa in the tropics. For the QBO oscillation, the amplitude and frequency range is pretty consistent with the previously proposed theories about it. Strikingly enough we found a strong correspondence between the amplification of the semi and annual components of 70 hPa level and the occurrence of the El Nino and La Nina virtually for the entire analysis period. The TBO oscillation has a bit longer periodicity than the QBO's. The same relationship holds for the 10-12 year oscillation appeared in the upper troposphere, and the 13-16 year oscillation in the lower troposphere. These oscillations might be related to the sun spot cycles. The above observations might be abstracted as followings. The semi and annual components are the intrinsic oscillation from the lower troposphere dynamics, mainly solar induced thermal effects, and the QBO results from the wave mean flow interactions, so far accepted. The El Nino and La Nina phenomena are also from the internal dynamics of the ocean and atmosphere couplings. However, the TBO oscillation might be induced by the QBO rather than from the internal dynamics. The slight frequency discrepancy of the two oscillations may arise from a damping effect that will play during the response of the lower troposphere to the QBO. In such case, the associated frequency will decrease or the length of the periodicity will increase to a certain degree according to the magnitude of damping coefficient involved in the process. The counter acting forcing against damping might come from the corresponding oscillations. The assumption may not be so irritable if we consider the relative amplitudes of the 10-12 and 13-16 year oscillations at the 150 and 850 hPa levels in order. The remote forcing mechanism, of course, has not been given here. The related topics should be dealt in future And finally the band-pass filtered time series of 850 hPa zonal winds are compared with the corresponding time series of the first mode of the EOF analysis of global precipitation for latitudes from ?0 degree to +60 degree. They are virtually equal in their time evolution and phase relations for the frequency bands with periodicities of 2-3 years. The low frequency components of the pc time series are in good agreement with the occurrences of El Nino and La Nina in general.
Poster Session 2, Atmospheric Oscillations and Boundary Layer Processes (Hall 4AB)
Wednesday, 14 January 2004, 2:30 PM-4:00 PM, Hall 4AB
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