Detecting Source Regions of Spatial Drought Propagation and Quantitative Assessment of Their Potential Influence in South Korea

Compared to other natural disasters, drought is a disaster that continues and accumulates over time, with its impacts depending on the spatial extent of droughts over prolonged periods. Droughts propagate in time and space. Especially, the spatial drought propagation refers to expansion of drought from specific regions to other regions due to increased magnitude or transition of drought center. This study aims to conduct quantitative assessment of spatial drought propagation that has been relatively understudied in South Korea. We identified the seasonal source regions and analyzed the impacts of spatial drought propagation of meteorological droughts in South Korea, using propagation potential (PP) and potential influence of source region (PISR). The PP indicates the difference in intensity between drought propagation from a specific grid to other grids and from other grids to the specific grid. A grid with positive PP values is defined as a source region, while a grid with negative PP values is defined as a sink region. A source region refers to the region of early drought onset that propagates to other regions within the basin, and a higher PP value represents a higher intensity of drought propagation. The PISR is the proportion of drought events propagated from drought onset of source regions within the basin. In this study, the highest absolute values of PP exist in spring, which has the highest risk of drought due to the climate in South Korea, and this result indicates a frequent occurrence of spatial propagation. On the other hand, the lowest absolute values of PP exist in autumn. We estimate that drought onset in sink region is more likely influenced by propagation from source regions, rather than individual drought occurrence. In conclusion, the PP is considered for detecting the source regions of meteorological drought and assessing the seasonality of spatial propagation. In addition, the PISR quantitatively assesses the impact of source regions, determining that sink regions are high hazard influenced by source regions, rather than individual drought occurrence. The results of this study can contribute to detecting the areas where the drought can propagate ahead of time to minimize the impact of droughts.

Acknowledgement: This research was supported by a grant (2022-MOIS63-001) of Cooperative Research Method and Safety Management Technology in National Disaster funded by Ministry of Interior and Safety (MOIS, Korea).