Changes in the Southwest Monsoon mean daily rainfall intensity in Sri Lanka: Relationship to the El Niño-Southern Oscillation

E. Ranatunge, B. A. Malmgren, Y. Hayashi, T. Mikami, W. Morishima, Masayuki Yokosawa, M. Nishimori

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Daily rainfall data for 187 stations in Sri Lanka spanning the period 1960-1996 were analyzed to investigate the spatial and temporal characteristics of the mean rainfall intensity (MRI) through this time interval with special focus on the Southwest Monsoon (May-September). Particular emphasis was laid on temporal changes in the MRI series. The mean and standard deviation (SD) of the MRI data showed considerable spatial variation. Regression analysis expressing precipitation as a function of time at the various stations revealed distinct spatial trends; the results point to high MRI in lowland areas and low MRI in mountain areas. Principal Components Analysis of the temporal relationships among a reduced set of stations located in an equal-sized grid showed that the three dominant principal components (PCs) are characterized by the maximum and minimum mean and SD of the MRI series together with the mean number of rainy days. The first, second and third PC modes show significant patterns of the MRI data series over the northern half, southern half and southwestern coastal belt of Sri Lanka, respectively. The time series pattern of the dominant PC modes revealed distinct changes in MRI over time. A noticeable higher value in MRI was found from 1977 to 1996; this tendency is most pronounced for the first PC mode. The time series of the Southern Oscillation Index was found to be closely related to changes in the MRI patterns associated with the first PC mode. In addition, El Niño years coincide with low values of the first PC mode. Some La Niña years show a positive response for the first and third PC modes, while there is no clear response for the MRI pattern identified by the second PC.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume197
Issue number1-2
DOIs
Publication statusPublished - 2003 Aug 15
Externally publishedYes

Fingerprint

rain intensity
Southern Oscillation
Sri Lanka
precipitation intensity
oscillation
monsoon
time series analysis
time series
meteorological data
spatial variation
lowlands
principal component analysis
regression analysis
mountains

Keywords

  • El Niño/La Niña
  • Mean rainfall intensity
  • Principal components analysis
  • Southern Oscillation Index
  • Southwest Monsoon
  • Sri Lanka

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

Cite this

Changes in the Southwest Monsoon mean daily rainfall intensity in Sri Lanka : Relationship to the El Niño-Southern Oscillation. / Ranatunge, E.; Malmgren, B. A.; Hayashi, Y.; Mikami, T.; Morishima, W.; Yokosawa, Masayuki; Nishimori, M.

In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 197, No. 1-2, 15.08.2003, p. 1-14.

Research output: Contribution to journalArticle

Ranatunge, E. ; Malmgren, B. A. ; Hayashi, Y. ; Mikami, T. ; Morishima, W. ; Yokosawa, Masayuki ; Nishimori, M. / Changes in the Southwest Monsoon mean daily rainfall intensity in Sri Lanka : Relationship to the El Niño-Southern Oscillation. In: Palaeogeography, Palaeoclimatology, Palaeoecology. 2003 ; Vol. 197, No. 1-2. pp. 1-14.
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