Abstract: Based on the daily meteorological data of 40 weather stations and the observed cotton yield data of agro-meteorological station in cotton planting regions of Hebei province from 1981 to 2015,the characteristics and the impacts of continuous rainfall (CR) process on the cotton yield were analyzed,and the index of CR disaster was revised and optimized.Then,through the mathematical statistics,the yield loss rate caused by CR was calculated and the key disaster-causing factors of CR were filtered.Furthermore,using the weight coefficient of factors,the intensity indices of CR during the cotton growth stage were designed.Moreover,based on the relationship between the intensity index and yield loss rate,the evaluation model of yield loss was established.According to the analytical method of the ordered sample cluster,the disaster grade was ranked.Finally,based on risk analysis principle of disaster,the indices and characteristics of risk were established and analyzed.The results show that the intensity index of CR can objectively reflect the intensity of CR and the effect of yield loss evaluation model is satisfactory.The occurrence probability and the yield loss caused by CR during the seeding stage are both small and are 0.076 and 0.09%,respectively.The growth of cotton is mainly affected by the CR during squaring to boll opening stage and the orders of probability and the yield loss caused by CR changing from large to small are flower-boll stage (0.447,17.1%),squaring stage (0.394,11.7%) and boll opening stage (0.237,7.2%).In recent years,the amount of CR decreases during the squaring stage,and increase during the flower-boll and the boll opening stages,especially during the boll opening stage which is the most major stage when the cotton growth is affected by CR.The high-risk area of CR during the squaring stage distributes in the north of Baoding and its northward areas,while that during the flower-boll stage distributes in the north of Baoding and its northward areas as well as the west of three cities including Shijiazhuang,Xingtai and Handan.The above-mentioned areas are non-major cotton planting area.The high-risk area of CR during the boll opening stage distributes in the southwest of Baoding,the west of Hengshui,Shijiazhuang and its southward areas.

Key words: Cotton, Continuous rainfall, Quantitative evaluation, Risk analysis