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, M. Yokozawa, M. Nishimori

*この研究の対応する著者

研究成果: Article査読

27 被引用数 (Scopus)

抄録

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.

本文言語English
ページ(範囲)1-14
ページ数14
ジャーナルPalaeogeography, Palaeoclimatology, Palaeoecology
197
1-2
DOI
出版ステータスPublished - 2003 8月 15
外部発表はい

ASJC Scopus subject areas

  • 海洋学
  • 生態、進化、行動および分類学
  • 地表過程
  • 古生物学

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