Rainfall variations of Sri Lanka Part 1: Spatial and temporal patterns

  • R. Suppiah
  • M. M. Yoshino


In order to study the spatial and temporal patterns in Sri Lanka, monthly rainfall data at 29 stations for the period 1881–1980 were analysed in this study. First, Empirical Orthogonal Function analysis method was applied for the monthly rainfall anomalies. The result indicated clear dominant spatial patterns. The first eigenvector accounts for 40.2% and the second for 11.1% of the total variance explain the most apparently existing patterns with orographic influences. In particular, the former is explained by the rainfall patterns in the period between October and February (northeast monsoon), and the later by that in May to September (southwest monsoon) period. Power spectra of first eigenvector's time coefficients revealed cycles at 40, 24 and 14–15 months, while the second eigenvector's time coefficients indicated at 120 and 40 months. Lastly, a regional division by rainfall fluctuations is presented for Sri Lanka based on the space coefficients of first two eigenvectors.


Power Spectrum Temporal Pattern Rainfall Data Empirical Orthogonal Function Rainfall Pattern 
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Variationen des Niederschlags in Sri Lanka. Teil 1: Räumliche und zeitliche Verteilungsmuster


Zur Untersuchung der räumlichen und zeitlichen Verteilungsmuster des Niederschlags in Sri Lanka werden Monatswerte von 29 Stationen aus der Periode 1881–1980 analysiert. Die Methode der Hauptkomponentenanalyse wurde auf monatliche Niederschlags-anomalien angewendet. Der erste Eigenvektor zu 40,8% und der zweite Eigenvektor zu 11,1% der totalen Varianz erklaren die am wahrscheinlichsten existierenden Muster mit orographischen Einflüssen. Im besonderen ist ersterer durch Niederschlagsmuster in der Periode zwischen Oktober und Februar (NE-Monsun) erklärt und letzterer durch die in der Periode Mai bis September (SW-Monsun). Die Spektralanal ysen der Zeitkoeffizienten des ersten Eigenvektors weisen Zyklen von 40, 24 and 14–15 Monaten auf, während die des zweiten Eigenvektors 120 and 40 Monate anzeigen. Schließlich wird, basiert auf die ersten zwei Eigenvektoren, eine regionale Einteilung von Niederschlagsfluktuationen für Sri Lanka vorgelegt.


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Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • R. Suppiah
    • 1
  • M. M. Yoshino
    • 1
  1. 1.Institute of GeoscienceThe University of Tsukuba, Sakura-muraNiihari-gun, Ibaraki-kenJapan

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