Analisis Penjalaran Gelombang Kelvin di Atas Kototabang Berbasis Data EAR (Equatorial Atmosphere Radar)

Abstract

Indonesian geographical condition, maritime continent, contribute significant effects in atmosphere dynamics both macro and micro scale. One of equatorial atmospheric waves which play an important role is the Kelvin wave. It was suspected as the trigger of the Intraseasonal Variability phenomenon especially MJO (Madden Julian Oscillation). Studies on propagation and vertical structure of Kelvin wave were still limited on OLR data, GPS, RO, NCEP / NCAR reanalysis and radiosonde. EAR data were expected to explain about propagation and vertical structure of Kelvin wave better. To analyze the Kelvin wave propagation above Kototabang, spectral analysis method were used with both the FFT (Fast Fourier Transform) and the Wavelet technique. Statistical analysis was also done with cross-correlation technique (Cross Corelation Function) and cross Spectral (Cross Spectrum) to see the relevance between Kelvin wave and the KTTL (Kototabang Tropical Tropopause Layer). Based on EAR data over period of 1 December 2007 – 31 December 2008, Kelvin wave was detected above Kototabang with eastward zonal propagation and downwards vertically. Spectral analysis during this period showed that the Kelvin wave appeared periodic every 18 days at 17.41 km altitude near the Tropopause layer (~17 km). Power spectrum analysis indicate that the Kelvin wave energy was stronger during wet season than during dry season. During wet months, the Kelvin wave is dominant at 16.97 km in altitude and appear periodic every 15 days. While in dry months, it is more dominant at 16.52 km in altitude and appeared every 18 days. Statistical analysis results during wet and dry season indicate a correlation between zonal wind dynamics with the fluctuation of Tropopause height, spontaneously and inspontaneously. Cross-spectrum analysis showed that zonal wind dynamics activity affected the height fluctuation of the Tropopause where the Kelvin wave tend to rise the KTTL height during wet season, while in dry season it will lower the KTTL height. Keywords : Kelvin waves, Propagation, EAR, KTTL, Spectral analysis.