Publication Date:
2023-08-24
Description:
Makassar, the provincial capital on the South Peninsula of Sulawesi, which is an island in Indonesia, experienced its largest flood in 20 years in January 2019. Total rainfall accumulated for the 4-day event exceeded 350 mm with devastating impacts on the community, including 53 perished and over 14 thousand evacuated. In this study, we use the COAMPS adjoint model to identify specific components of the mesoscale and environmental flow that affected the flooding event and implications for predictability. Previous studies have highlighted that both a convectively coupled Kelvin wave (CCKW) and convectively coupled equatorial Rossby wave (CCERW) associated with the active phase of the Madden-Julian Oscillation occurred concurrently and were likely contributors to the onset of the mesoscale convective system and the low-level westerlies that enhanced the orographically-forced precipitation and subsequent flooding. The adjoint analysis indicates that enhancing the moisture and low-level convergence associated with the mesoscale convective system, as well as the low-level westerlies that contribute to upslope winds, can substantially increase the precipitation. However, the sensitivity patterns are quite complex, with low-level convergence and low-level vorticity sensitivity in quadrature and projecting onto the larger-scale CCKW and CCERW. Small adjoint-based perturbations made to the initial forecast state can increase the South Peninsula 36-h precipitation maximum by more than 30%, with perturbations made only to the initial moisture field accounting for much of this increase. The sensitivity analysis supports the importance of both the mesoscale convective system and components of the equatorial waves in contributing to the South Peninsula flood.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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