渭北苹果花期冻害气象指数保险设计

Design and Analysis of Weather Index Insurance Product for Frost Injury in Apple Florescence in Weibei

为科学设计渭北苹果花期冻害气象指数保险产品,提供气象指数保险技术参考。研究选取旬邑县作为陕西省渭北地区苹果代表县,利用1991—2020年气象、苹果花期物候、产量等数据,选取苹果花期冻害极端低温和过程累积危害指数作为备选气象指数,采用滑动平均-灰色预测法分离苹果气象产量。通过气象指数与苹果减产率的相关分析,确定苹果花期冻害气象指数,构建苹果花期冻害气象指数与减产率之间的关系模型。利用苹果单产风险分布特点,选取6种分布模型利用参数分布法进行拟合,并根据Anderson-Darling(A-D)检验结果和概率密度函数图筛选最优分布。最后根据保险触发值,厘定不同赔付触发条件下的保险纯费率。结果表明:代表县苹果花期冻害过程累积危害气象指数Ts与减产率的相关性显著强于苹果花期冻害极端低温气象指数Tc;Ts与减产率之间存在正向线性关系模型;苹果单产风险分布符合柯西分布;当赔付触发条件对应2%、4%、6%、8%减产率时,旬邑县各乡镇苹果花期冻害气象指数保险产品纯费率区间为0.40%~1.84%。相较传统苹果农业保险产品,苹果花期冻害气象指数保险产品可实现差异化费率,有利于发挥气象指数保险优势。

To design and improve the weather index insurance product for frost injury in apple florescence,Xunyi is selected as the representative apple planting county in the Weibei region of Shaanxi Province.The data of meteorology,apple flowering phenophase and yields from 1991 to 2020 are used for design and analysis.The meteorological yield of apples is separated by using moving average and grey prediction methods.The weather index based on extremely low temperatures and the frost injury process cumulative hazard during apple flowering is constructed for selection.The weather index for frost injury in apple florescence is determined by correlation analysis between weather index and yield reduction rate.The regression model between weather index and yield reduction rate is constructed.According to apple yield risk distribution characteristics,using the parameter distribution method,a variety of distribution models are selected to fit apple yield risk distribution.The optimal distribution model is selected by A-D test results and probability density function diagram.The pure premium rates are determined under different compensation trigger conditions.Results show that the correlation between cumulative hazard weather index in the frost injury process and yield reduction rate is higher than that between extremely lowtemperature weather index in representative counties and yield reduction rate.The yield reduction rate has a linear relationship with the∑T_(s)weather index.Apple yield risk distribution fit to Cauchy distribution.The pure premium rates of weather index insurance products for frost injury in apple florescence are from 0.40 to 1.84 percent when yield reduction rates are 2,4,6 and 8 percent in Xunyi.The rationality and applicability of the weather index insurance product have been enhanced compared to traditional agricultural insurance products,which is beneficial to giving full advantages to weather index insurance.