Rainy season drought severity trend analysis of the Indonesian maritime continent

Drought is generally associated with a long-term reduction in total precipitation. However, changes at shorter time-scales can also induce drought conditions. This study analyses trends of meteorological drought severity during the rainy season in the Indonesian maritime continent. We propose a new dry spell index to characterize this drought severity. The anomalous accumulation definition was used to define a single most intense rainy season for region with one or two rainy seasons per year. The Mann–Kendall test was applied for trend analysis of the index. Temporal and spatial drought characterisations were compared between the dry spell index and standardized precipitation index. The results show that in semi-annual and anti-monsoonal regimes the rainy season precipitation increases, the number of dry days decreases, and long dry spell contribution decreases, overall causing a decrease in drought severity. Over the same period, the number of dry days, duration of the extreme dry spell, and long dry spell contribution increased in the monsoon regime, indicating a tendency towards a drier condition. In contrast, standardized precipitation index showed a strong tendency towards a wetter condition during the rainy season over this region.