Weather and Climate Extremes (Sep 2022)
Regional extreme precipitation index: Evaluations and projections from the multi-model ensemble CMIP5 over Thailand
Abstract
Various climate extreme events in Thailand such as more recurrent and more intense floods, droughts, tropical storms, and extreme rainfall events pose increasing threats to the environment, water resources, and agricultural production. To assess the occurrence and impacts of extreme climate events, we have overviewed and investigated the changes of indices characterizing extreme precipitation provided by the Expert Team on Climate Change Detection and Indices (ETCCDI) across the country. Ten precipitation extreme indices (PRCPTOT, SDII, R10mm, R20mm, R95p, R99p, Rx1day, Rx5day, CDD, and CWD), including the strength of Asian monsoon (SWMR and NEMR) were calculated from the station data, then comparisons and projections were made with CMIP5 models. The SWMR displays high values (South and East) and low values (North, Northeast, and Central), implying high potential flood and drought hazard areas similar to the distributions of precipitation intensity extreme indices (PRCPTOT, SDII, R95p, R99p, Rx1day, and Rx5day). Most GCMs display similar spatial distribution pattern of high intensity of extreme precipitation indices to observations while there are much greater variety of results between the models and observations for the frequency indices. The multi-model ensemble (MME) projects increase in most precipitation extreme indices, indicating stronger precipitation events (by R95p and R99p) across the country notably in the west, Central, and South. Though, the MME delivers better results, some individual GCMs display high uncertainties among different RCP scenarios. Therefore, selection of suitable GCMs along with bias-correction method for regional impact study under extreme climate have to be done carefully.
