Formulation of Monthly Rainfall Forecast Model based on Large-Scale Atmospheric Variables: A Case Study in Tapee River Basin, Thailand

It has been noticed That Thailand experiences flood and drought more frequently in the east three decades. It has been claimed that global climate change is one of a major cause of such high interannual variation of rainfall. Various researches have been conducted to investigate impact of climate change on these rainfall variations. It is necessary to develop rainfall forecast model that is able to forecast at least seasonal rainfall with sufficient precision for well-planned water resource allocation over a river basin. This study aims to formulate a monthly Rainfall Forecast Model, based on large-scale atmospheric variables (LAV) by using Tapee river basin, located in the Southern part of Thailand, as a case study. The four main variables of LAV, which are surface air temperature (SAT), sea level pressure (SLP), surface zonal (u) and meridian wind (v) were investigated their relationships with seasonal rainfall over the Tapee river basin during 1976-2011. It has been found that SAT over Pacific Ocean and SLP over South China Sea have correlation with 3 months rainfall and can be used as predictors in seasonal rainfall forecast model with 12 month leading time of forecast. Such tool developed in this study can be used in water resource planning to allocate water resources appropriately under constraint of high water demand and high variable water supply. (C) 2016 INT TRANS J ENG MANAG SCI TECH.