Study on the agricultural crop drought index based on weights of growth stages

Drought is one of the main natural disasters affecting economic development and food security. Drought monitoring and identification are the premise of disaster risk management, and the drought index is the main means of monitoring and identifying drought. The paper proposes a new drought index, the agricultural crop drought index (ACDI), which is suitable for rainfed agriculture in arid areas. ACDI calculates water deficit from precipitation and evapotranspiration and considers the weight of crop growth stage. The weight of growth stage and water deficit constitute the weighted data series. The fitting distribution is optimized by Kolmogorov–Smirnov test, and the data are standardized to obtain ACDI. The weight of growth stage is determined by the multiple correlation coefficient between meteorological factors and grain yield. A large weight is equivalent to a large coefficient, large coefficient means that meteorological factors in this growth stage will have a greater impact on grain yield, so the water deficit in this growth stage should play a more important role in defining drought index to better identify agricultural drought from the perspective of crops. Finally, Qiqihar, a semiarid area in Northeast China, is selected as the research area for the case study. Comparing ACDI with standard precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI) and crop water deficit index (CWDI), the standard deviation of ACDI is larger, which indicates that the difference between index values is larger and it is relatively good in distinguishing the degree of drought. In addition, the correlation coefficient between ACDI and climate grain yield passed the test with a significance level of 0.05, while the other three indexes did not pass the test, which shows that the relationship between ACDI and grain yield is higher than the other three drought indexes. For arid areas, grain yield can reflect the impact of drought. Therefore, ACDI looks more promising to identify agricultural drought from the perspective of crops. ACDI provides a reference for monitoring agricultural drought from the perspective of crop growth stage, and enriches the drought index theory.