Interannual variability of precipitation in Sri Lanka

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.