Fig 1.
Study area: Java Island and the eight districts of the largest rice producer in Indonesia as the region of interest.
The greener areas on the map indicate paddy fields of the region of interest.
Table 1.
The rice fields and yields of the eight districts in 2019 [34].
Table 2.
Summary of the datasets used in this study.
Table 3.
Drought severity based on SPI values [53].
Fig 2.
Comparison of the annual total precipitation (left), mean monthly precipitation in the rainy season (middle), and mean monthly precipitation in the dry season (right) over the study area according to 20 years of climatological data from CHIRPS, TRMM, PERSIANN, and SA-OBS.
The rainy season corresponds to December, January, and February (DJF); the dry season corresponds to June, July, and August (JJA). Dots on the map indicate the largest rice-producing districts of Indonesia.
Fig 3.
SPI-3 derived from CHIRPS, TRMM, PERSIANN, and SA-OBS for June (left), August (middle), and October 2015 (right) during the drought event due to the 2015–16 El Niño.
Dots on the map indicate the largest rice-producing districts of Indonesia.
Fig 4.
Six-month SPI (SPI-6) derived from CHIRPS, TRMM, PERSIANN, and SA-OBS for June 2015 (left), August 2015 (middle), and October 2015 (right) during the drought event due to the 2015–16 El Niño.
Dots on the map indicate the largest rice-producing districts of Indonesia.
Fig 5.
Time series for the monthly precipitation (left) and SPI-3 (right) of the eight largest rice-producing districts in Java grouped by province: West Java (top), Central Java (middle), and East Java (bottom).
The monthly precipitation and SPI-3 were determined from CHIRPS (blue), TRMM (green), PERSIANN (red), and SA-OBS (black).
Fig 6.
Scatterplot of the regional pooled precipitation (left) and SPI-3 (right) for 2001–2017.
CHIRPS, TRMM, and PERSIANN were each plotted against SA-OBS.
Fig 7.
Time series of the Oceanic Nino Index (ONI) and Dipole Mode Index (DMI) for climate events during 1981–2020 (top), the monthly precipitation derived from all datasets (middle), and SPIs (bottom).
For the SPI results, the colored bar shows the average from multiple sources, and the lines show the values derived from individual datasets: CHIRPS (blue), TRMM (green), PERSIANN (red), and SA-OBS (black). For each time series, the vertical orange solid line indicates a year with El Niño, and a vertical light-blue line indicates a year with La Niña. The horizontal gray dashed lines indicate the levels of ENSO (top), precipitation (middle), and SPI (bottom).
Fig 8.
Scatter and density plot of the (A) Oceanic Nino Index (ONI) and (B) Dipole Mode Index (DMI) against SPI classified as dry, normal, and wet conditions.
The SPI and its classification are determined from the averaged multiple source SPI as in Fig 7.