Interannual variability of precipitation in Sri Lanka

Abstract

Abstract: Two different spectral analysis methods, the multitaper method (MTM) and the maximum entropy method (MEM) were applied to investigate the presence of low-frequency periodicities in precipitation records of 14 climatological stations in Sri Lanka. The spectral analysis revealed statistically significant periodicities in the range of 2 – 3 year and 3 – 6 year periods in all parts of Sri Lanka irrespective of the climatic variability. The 2 – 3 year band corresponds to the Quasi-Biennial oscillation (QBO), while the 3 – 6 year band corresponds to the El-Nino/Southern oscillation (ENSO) higher and lower frequency bands. Cross spectrum analysis showed statistically significant (at 5 %) coherencies for the Indian Ocean dipole (IOD) and Southern oscillation index (SOI) in the 2 – 3 year band and the 3 – 6 year band, respectively for most of the regions. Thus, it is concluded that the IOD and SOI play important roles as modulators of precipitation in Sri Lanka