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
