Applied Environmental Research

Publication Date



Rainfall variability is a critical factor for Thailand’s socio-economic development. Thus, enhancing understanding of rainfall mechanisms and its variability is of paramount importance for effective strategies for tackling the severe droughts/floods which are memorable and a recurring problem in Thailand. Through this study, we examined the variability of total annual rainfall (Rtotal) and the annual total number of rainy days (Rday) in Thailand during 1951-2003, using an Empirical Orthogonal Function (EOF) analysis. The primary objective is to determine the dominant spatiotemporal patterns, and to illustrate their connection with the El Nino-Southern Oscillation (ENSO). The results revealed that the first two EOF modes, which explained nearly half of the total variance, showed a good coherence of spatio-temporal structures. A salient feature of the leading modes of Rtotal and Rday in Thailand is that their day temporal coefficients exhibit significant relations to the ENSO. In an interannual timescale, the leading modes tended to be greater than normal during the La Nina and lower than normal during the EL Nino phases of the ENSO. Changes in the Walker circulation appeared to be the dominant mechanism whereby the ENSO exerts its influence on rainfall variability in Thailand. For an interdecadal timescale, there was evidence of the unusual and persistent deficit in Rtotal accompanied by a concomitant reduction of Rday over the day last three decades. The recent droughtlike condition closely associated with the shift in the ENSO towards more El Nino events since the late 1970s, and coincided with high global mean temperature. These natural/anthropo-genic-induced climatic changes are important implications for rainfall forecasting, and consequently for water resources and agricultural planning and management in Thailand.

First Page


Last Page




To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.