Abstract: Low-temperature and rainy weather during the rape flowering period is one of the meteorological disasters affecting the rape-yield in the Sichuan Basin region. In this study, the daily meteorological data from 101 weather stations in the Sichuan Basin from 1961 to 2020, as well as the rape yield data and the disaster information (drought, low-temperature cold damage, consecutive rainy weather, gale and hail) from 1983 to 2000, are utilized. The years with low-temperature and rainy weather disasters during the rape flowering period are selected, and then the yield loss rate and disaster-inducing factors of low-temperature rainy weather during the rape flowering period are obtained by utilizing mathematical-statistical methods. Furthermore, the disaster-inducing indicators of low-temperature and rainy weather disasters during the rape flowering period are determined through correlation analysis, and are validated by using the disaster information data from 2001 to 2020. Based on the selected key disaster-inducing factors of low-temperature and continuous rainy weather, an assessment model on the losses caused by low-temperature and rainy disasters during the rape flowering period by using the regression analysis method was built. Then, the back substitution and prediction test are conducted to analyze the disaster risk zoning and variation trends. The results indicate that the daily average temperature ≤7°C and the duration of disaster events ≥1d are the disaster-inducing indicators of low-temperature during the rape flowering period in the Sichuan Basin. The ≤7°C negative accumulated temperature and the accumulated precipitation of the persistent rainfall event with ≥3d duration are the key disaster-inducing factors of low-temperature and rainy weather disasters. The indicators are examined with the low-temperature cold damage data during the rape flowering period from 2001 to 2020, and the results align with the actual situation. Based on the meteorological data, rape yield and disaster information from 1983 to 2000, an assessment model on the losses caused by low-temperature and rainy weather during the rape flowering period in the Sichuan Basin is established. The back substitution results indicate that for the light and moderate assessed levels, the assessment accuracy (the difference between assessed level and actual level is one or zero) is over 96%. For the severe and extremely severe assessed levels, the assessment accuracies with zero level difference are both 0, and the assessment accuracies with one level difference are 75% and 0, respectively. Then, by using the assessment model the low-temperature and rainy weather disasters during the rape flowering period in each year of 2001–2020 are predicted, and the results are consistent with the actual situation. From 1961 to 2020, in the southwestern, southern and northeastern parts of the basin, the risk levels of low-temperature and rainy weather disasters are mainly medium or high. The regions with lower risk level (low or sub-low) are mainly concentrated in the northwestern and central parts of the Sichuan Basin. Under the background of climate warming, the high-risk areas for low-temperature and rainy weather disasters during the rape flowering period in the Sichuan Basin show a decreasing trend, while low-risk areas show an increasing trend. In summary, the indicators for low-temperature cold damage during the rape flowering period in the Sichuan Basin are reliable. The loss assessment model of low-temperature and rainy weather disasters can effectively evaluate disaster losses and can be applied in agricultural meteorological service operations. The results of disaster risk zoning can provide a reference for the rape production layout in Sichuan Province.

Key words: Sichuan Basin, Rape flowering period, Low-temperature and rainy weather, Hazard loss assessment, Risk zoning