陕西省苹果花期冻害风险评估

Assessment of freezing risk at apple florescence in Shaanxi Province

以Tmin≤-1℃为冻害指标，基于模糊数学和信患扩散理论，把1970—2008年38a间日最低气温Tmin≤-1℃的低温天气事件作为风险源，计算陕西省27个苹果主要生产基地县在每年4月各时段发生花期冻害的风险水平，并确定各基地县花期冻害的重点防御时间及开始疏花的时阃。结果表明，4月全省苹果基地县出现Tmin≤-1℃的风险概率均大干十年八遇，而4月10日和20日后出现Tmin≤-1℃的风险概率均小于两年一遇及十年一遇；此外，分别用50％和20％的风险概率作为指标，确定各基地县花期重点防御结束时间和安全疏花起始时间，两个时间均从东南向西北逐渐推迟。

Using Tmin≤-1℃ as freezing index, by taking the information of freezing weather events of 27 major apple growing counties in Shaanxi Province form 1970 - 2008 as the background, fuzzy mathematics and information diffusion theory are applied to analyze quantitatively the risk level in different time and to ascertain the priority prevention time and flower thining time. The results indicate that in the whole 27 major apple growing counties, the risk probability in April is always greater than $0%, but is lower than 1/2 and 1/10 after Apr. 10 and Apr. 20. In addition, the end of key prevention time and initiation of safe flower thinning time are ascertained by using risk probability in 50 % and 20 % as index, both of which are postponed gradually form southeast to northwest.