用于气象学，或者其他领域，计算标准降水化指数，用以研究，以及预测。-Meteorology, or other areas used to calculate the standard precipitation index for research, as well as forecast.

SPI是一个标准化指数，相对于当地雨量的长期气候状况，反映某观测雨量可能出现之机会率。(PI is a standardized index, relative to the local rainfall of the long-term climate conditions, reflecting the observed rainfall may occur in the opportunity rate.)