Abstract:

The middle and lower reaches of the Yangtze river (MLYR) are the main areas for double cropping rice in China, where cold dew wind is a significant agricultural meteorological hazard. Scientific assessment of its risk is of great significance for guiding agricultural production. Based on daily average temperature and sunshine hours data from 220 national meteorological stations in the late rice planting areas of the middle and lower reaches of the Yangtze river from 1961 to 2023 during the late rice heading and flowering period, growth stage data from 31 agro−meteorological observation stations , alongside yield per unit area and planting area data of late rice in major producing counties (cities, districts), the intensity index of cold dew wind process was established by comprehensively considering the equivalent cold accumulated temperature, duration of low temperature, and sunshine hours during the process. The cumulative effect of multiple cold dew wind events within a year was further incorporated to construct an annual cold dew wind intensity index. On this basis, high−resolution land use information was integrated, and a risk assessment model was established based on the hazardousness of disaster−inducing factors , exposure, and vulnerability of the affected system. The results showed that: (1) the process intensity index effectively quantified the severity of cold dew wind events. Higher average index values were observed in most areas of Hunan, central Hubei and western and southern Zhejiang, while lower values were noted in other regions. (2) Annual cold dew wind intensity levels were classified using the kernel density estimation method. Annual cold dew wind intensity index values ≤3 were defined as light cold dew wind years, values from 3 to 10 as moderate years, and values >10 as severe years. This classification was found to be highly consistent with historical disaster records, verifying the reliability of the index. (3) The natural breaks (Jenks) method was applied to determine comprehensive risk levels of cold dew wind in the middle and lower reaches of the Yangtze river. High and moderately high−risk zones were identified in northern and central Hunan, as well as southwestern Hubei. Low and moderately low−risk zones were located in southern Hunan, eastern Hubei, northern and southern Jiangxi, southern Anhui, and most parts of Zhejiang. Other areas were categorized as medium−risk zones.

Key words: The middle and lower reaches of the Yangtze river, Double?cropping late rice, Cold dew wind, Intensity index, Risk assessment