Rainfall and Temperature Anomaly Indices for Climate Analysis

Computes rainfall anomaly indices and a standardised temperature anomaly from monthly or annual precipitation and temperature data supplied by the user. The rainfall indices are the Rainfall Anomaly Index (RAI; Van Rooy, 1965), the Modified Rainfall Anomaly Index (MRAI) and the Standardized Rainfall Anomaly Index (SRAI) of Ekpetere (2025) , the Simplified Standardized Precipitation Index (SSPI) of Raziei (2021) , and the Standardized Precipitation Index (SPI; McKee et al., 1993). The temperature anomaly is a z-score computed within each calendar month. All indices are computed group-wise, so the user can stratify by any combination of spatial units (state, district, grid cell) and calendar month, and each value can be classified into a descriptive severity class.