Extended Abstract (924K)9A.2
Evolution and Structures of Tropical Instability Waves in the Pacific Ocean and Its Interannual Variation
Toshiaki Shinoda, NRL, Stennis Space Center, MS; and G. Kiladis and P. E. Roundy
Sea surface height (SSH), sea surface temperature (SST), winds and surface currents derived from satellite observations are analyzed to investigate intraseasonal variability of upper ocean and atmosphere in the eastern tropical Pacific. Wavenumber-frequency spectral analyses of SSH and SST anomalies were performed in order to examine space and time variations of these variables. Significant spectral peaks along the dispersion curve of first baroclinic mode Rossby and Kelvin waves are found in the SSH spectrum, indicating that the analysis can effectively identify the signals of equatorial waves in the upper ocean. A prominent peak in SSH fields at around 33 days and 1500 km wavelength along the Rossby wave dispersion curve is evident, and a similar peak is also found in SST fields. This upper ocean variability on these space and time scales is shown to be associated with tropical instability waves (TIWs). The spatial and temporal structures of 33-day TIWs are further examined based on an analysis of time series filtered in the frequency-wavenumber domain. The maximum variability of SSH associated with TIW is located around 5N, 130W, while that of SST is found around 2N, 100W. The evolution of SSH, SST, surface velocity, winds and cloudiness associated with TIWs and their phase relationships are described based on the cross correlation analysis. These statistical analyses are able to isolate salient features of TIWs and their associated air-sea interaction signals. The interannual variation of TIW activity is also described by the statistical analysis of these data.
Session 9A, General Climate Studies: Climate Dynamics
Wednesday, 23 January 2008, 8:30 AM-10:00 AM, 215-216
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