Evaluating the correlation of SPI, SPEI, and SSI with climatic and socioeconomic factors for drought monitoring

Droughts have become more severe and prolonged in recent years, causing significant social and environmental impacts. Analysing drought conditions with various climatic and socio-economic factors is critical for effective drought monitoring. This study investigated the correlation between drought severity and climatic and socio-economic changes in a study area – San Diego County, CA, USA. The drought severity was quantified using three drought indices: standardised precipitation index, standardised precipitation evapotranspiration index and standardised streamflow index. These indices were also used to describe the variation of the drought severity in the study area. The study employed Spearman’s correlation coefficient analysis to evaluate the correlations between the drought indices and climatic and socio-economic factors. The results showed that the drought indices indicated similar variations of the droughts in the study area. However, the severity, duration and frequency of the droughts varied with the timescales in the drought index analysis. Additionally, this study found that the drought conditions based on the three indices had strong negative correlations with precipitation, soil moisture, agricultural area and forest area, which were more pronounced as the timescale increased. The findings will provide insights into effective drought monitoring and management, particularly targeting severe droughts.