Increasing frequency of warm-dry climate-year type in Northeast China: A major contributor to maize yield shocks

Under the context of climate change, the climatic conditions for maize during different growth stages in Northeast China (NEC) exert a markedly varying influence on the final yield. We define nine Climate-Year Types (CYTs) based on the probability density functions of temperature and precipitation, aiming to explore the underlying drivers of climatic factors contributing to yield shocks. By incorporating a panel regression model, we quantitatively analyze the key compound climate conditions that influence maize yield across different growth stages. The results indicate that the main CYTs are biased towards drier conditions (Cold-Dry, Rainless, Warm-Dry) from 1992 to 2021, while the probability of warmer conditions (Normal-Warm, Warm-Wet, Warm-Dry) is expected to increase throughout the whole growth stage in the future. The overall yield shock is approximately 20 % in the historical period, with projected exacerbation under the future warming scenarios. At present, the dominant CYTs that determines the final yield of maize is changing from colder and wetter conditions in the growing stage to drier and warmer conditions in the reproductive stage. Moreover, the Warm-Dry CYT emerges as the most significant climatic factor influencing maize yield, with each occurrence associated with a 3.70 % decrease in yield throughout the whole growth stage in the historical period. Notably, the frequency of Warm-Dry CYT is expected to increase in most cities of NEC, which remains a major contributor to yield shocks, with the magnitude of its impact likely to intensify in the future. In summary, these studies identify the key climate types affecting maize yield at different growth stages in NEC, emphasizing the impact of compound heat and drought. This will provide a scientific basis for targeted measures to enhance yield and mitigate risks.