Process-based evaluation indicators of grape drought and risk characteristics in the Bohai Rim Region, China

Drought stress is a major environmental limiting factor for grape growth in the Bohai Rim Region (BRR) in China. The investigation of process-based meteorological evaluation indicators is of particular interest to precisely understand the spatiotemporal characteristics of grape drought processes, providing substantial support for grape drought monitoring, prevention, and mitigation. In this study, a daily grape drought index (GDI) was constructed based on a rolling calculation of water profit and deficit. The characteristics of the GDI in historical drought disaster samples were analyzed and drought evaluation level indicators were constructed, facilitating the assessment of process-based grape drought risk. The results showed that duration days with GDI <  − 0.4 could be used as drought level indicators, and the thresholds of grape drought in germination to new shoot (P1), flowering to fruit setting (P2), fruit expansion (P3), and coloring to maturity (P4) were 14, 13, 12, and 13 days with GDI <  − 0.4, respectively. The identification results calculated by grape drought indicators were basically consistent with historic occurrence levels of grape drought, with 76.9% of the calculated grape level being completely consistent with the historical records and 15.4% being within one level. The process-based grape drought risk gradually decreased with the advancement of grape process, with grape drought risk in the order of P1 > P2 > P3 > P4. Beijing, Tianjin, Hebei, and western Liaoning exhibited the highest grape drought risk.