| Abstrak/Abstract |
Extreme weather occurs when meteorological conditions in a specific location are unusually lower or higher than the average pattern, for example, tropical cyclones and extreme rain events. The southern margin of Yogyakarta, a province in Indonesia, abuts the Indian Ocean as one of the active tropical cyclone basins on Earth. Therefore, tropical cyclones potentially affect the rainfall characteristics in the region. This study aimed to ascertain the threshold values and frequencies of extreme rainfall and the impact of tropical cyclones on daily rainfall in Yogyakarta. It used 30-year rainfall data (1991‒2020) from the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) and three methods for determining extremes: the percentile method and two fixed thresholds set by Indonesia’s Meteorological, Climatological, and Geophysical Agency (BMKG) and World Meteorological Organization (WMO). Details on tropical cyclone occurrences were obtained from Australia’s Bureau of Meteorology. The results showed that the 99th percentile made the nearest threshold values to the fixed ones set for extreme rainfall by WMO and heavy rain by BMKG (R50mm). Extreme rainfall occurred in the west more often than in other parts of the province. In 1991‒2020, four tropical cyclones entered the Yogyakarta area, including Tropical Cyclone Cempaka on November 28, 2017, which induced inordinately high rainfall that exceeded the percentile threshold and the WMO’s fixed threshold of 50 mm (R50mm) for extremes and fell in the category Heavy Rainfall by the BMKG standard. |
