Hydroclimate variability and long-lead forecasting of rainfall over Thailand by large-scale atmospheric variables
Nkrintra Singhrattna a , Mukand S. Babel a & Sylvain R. Perret a b
a Water Engineering and Management , Asian Institute of Technology , Pathumthani , Thailand
b Centre de Coopération Internationale en Recherche Agronomique pour le Développement, UMR G-Eau , Montpellier , France
Published online: 20 Jan 2012.
Editor Z.W. Kundzewicz
Citation Singhrattna, N., Babel, M.S. and Perret, S.R., 2012. Hydroclimate variability and long-lead forecasting of rainfall over
Thailand by large-scale atmospheric variables. Hydrological Sciences Journal, 57 (1), 26–41.
Abstract
The development of statistical relationships between local hydroclimates and large-scale atmospheric variables enhances the understanding of hydroclimate variability. The rainfall in the study basin (the Upper Chao Phraya River Basin, Thailand) is influenced by the Indian Ocean and tropical Pacific Ocean atmospheric circulation. Using correlation analysis and cross-validated multiple regression, the large-scale atmospheric variables, such as temperature, pressure and wind, over given regions are identified. The forecasting models using atmospheric predictors show the capability of long-lead forecasting. The modified k-nearest neighbour (k-nn) model, which is developed using the identified predictors to forecast rainfall, and evaluated by likelihood function, shows a long-lead forecast of monsoon rainfall at 7–9 months. The decreasing performance in forecasting dry-season rainfall is found for both short and long lead times. The developed model also presents better performance in forecasting pre-monsoon season rainfall in dry years compared to wet years, and vice versa for monsoon season rainfall.
Key words rainfall; hydroclimate variability; ENSO; large-scale atmospheric variables; long-lead forecasting; statistical approach; modified k-nn model; cross-validated multiple regression; Chao Phraya River Basin; Ping River Basin; Thailand
Hydrological Sciences Journal
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