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Univariate drought indices do not reflect the integrated process through which droughts develop and occur. Therefore, developing a multivariate drought index that accounts for precipitation, evapotranspiration, and soil moisture is crucial for comprehensive drought prediction and evaluation. In this study, a comprehensive agricultural drought index (CADI) was developed using a combination of five commonly used binary copulas by considering evapotranspiration factors based on the Multivariate Standardized Drought Index (MSDI), which is based on both precipitation and soil moisture, and the drought monitoring capability of CADI was evaluated. The relationship between the CADI and the yield anomalies of winter wheat and summer maize in the rainfed and irrigated croplands of the North China Plain (NCP) was analyzed, and the drought evolution characteristics and trends in rainfed and irrigated croplands were examined. The results indicated that compared with the Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Soil Moisture Index (SSI), and MSDI, the proposed CADI accurately reflected the integrated process of meteorological and agricultural drought occurrence and evolution. In addition, the strength of the correlation between the CADI and the yield anomalies of winter wheat and summer maize in the rainfed and irrigated croplands of the NCP surpassed that of the SPEI, SSI, and MSDI, thereby confirming the validity and reliability of the proposed CADI for drought monitoring. Over the past four decades, droughts in the rainfed and irrigated croplands of the NCP have demonstrated a decreasing trend, and severe droughts have been concentrated in winter. Overall, the results of this study can be used in agrometeorological drought early warning and agricultural impact assessment and can provide theoretical guidance for drought monitoring in other regions.
Yang et al. (Fri,) studied this question.