- Heavy Rainfall Criterion
The heavy rainfall criterion is the top 10% precipitation intensity (90th percentile) over the 21 years (April 2000 to March 2021).
- Extreme Rainfall
An area where "mean rainfall amount exceeds the criterion" and "the heavy rainfall criterion is 1 mm/day or more" is colored as an area of extreme rainfall. The value is the corresponding from 90th to 99th percentile values.
Drought Index (SPI)
Standardized Precipitation Index (SPI) is a drought index that is able to calculate using only precipitation. The larger the negative value, the stronger the drought tendency.
NOAA/CPC Drought Indices Web site
The SPI calculation program was provided by NOAA/CPC.
The long-term average of precipitation (statistics period: April 2000 to March 2021). The unit is [mm / day].