[M-IS06] Extreme Weather and Water Related Disasters in Asia

[MIS06-P01] Projected changes to monsoon season heavy rainfall events in Davao River, Philippines and associated weather patterns under global warming

★Invited Papers

*Ralph Allen Elpa Acierto¹、Tomoki Ushiyama¹、Toshio Koike¹ (1.The International Centre for Water Hazard and Risk Management, Public Works Research Institute)

キーワード：heavy rainfall events, super high-resolution AGCM, Davao River, monsoon, composites

Assessments of future heavy rainfall events (HREs) in river basins is key in developing adaptation strategies for sustainable development. This study presents a framework on assessing the projected changes of HREs in Davao River basin, Philippines, by a high-resolution 20-km general circulation model (GCM) called MRI-AGCM 3.2S. We defined the HREs using 99th percentile peak-over-threshold method on area-averaged rainfall in Davao river basin in June-July-August (JJA) and December-January-February (DJF) seasons for past and RCP 8.5 scenario. We calculated composites of synoptic-scale conditions and anomalies to understand the mechanism of the conditions and its projected changes. We found that the HRE mean rainfall are projected to increase by 1.85 (1.5) in JJA (DJF) under the future scenario indicating 0.1% confidence level for both seasons. The projected increase in JJA are due to the higher anomalous moisture conditions induced by the southward migration of inter-tropical convergence zone (ITCZ) in the future despite the projected weakening of the western north Pacific subtropical high (WNPSH). While, projected increase in DJF are due to the higher anomalous northeasterlies from an inclined mean sea level pressure (mslp) anomaly structure despite reduced mslp anomaly from Siberian High that tend to intensify the cyclonic circulation of ITCZ. In summary, we have assessed the projected changes of seasonal HRE in the river basin and expounded on the mechanism of large-scale conditions and the projected changes under the RCP 8.5 scenario. These results are useful in understanding the mechanism of the changes basin hydroclimate in relation to the large-scale synoptic features from GCMs. These results are useful for future hydrological risk and climate change studies before and in conjunction to downscaling the projections.