研究气温极值的分布以预测重现期是客观评价出现在农作物关键期的极端气象灾害强度的一种方法.本研究以苹果为例,根据苹果严重气象灾害指标,利用陕西种植区代表站逐日气温数据,建立了苹果开花期严重冻害(4月最低气温＜ -2℃)和果实膨大期严重高温热害(6～8月最高气温＞40℃)气温极值的分布模型及重现期预测,对北扩地区苹果树越冬期冻害频次进行了分析.结果表明:陕北、渭北局部10 a的重现期出现开花期严重冻害,在100a的重现期中不会出现严重高温热害；关中、渭北大部分地区40～ 50 a的重现期出现严重冻害,30～80a的重现期出现严重高温热害；相同重现期陕北、渭北局部极端最低气温和极端最高气温均明显低于关中、渭北大部分地区；在苹果北扩基地县中,甘泉、米脂、吴起、志丹、子洲平均每年越冬期都出现低温,米脂、吴起、志丹越冬期低温频次出现较多,达2～3次/a.%To study the probability distribution of air temperatures' extreme value thus to predict its recurrence interval is a method to objectively evaluate the intensity of extreme meteorological disasters during the critical period of crops. Taking apple as an example, based on the index of extreme meteorological disasters, by using daily air temperature data, a probability distribution and recurrence interval predicting model was set up for the extreme value of air temperature about critically freezing injury during blooming period (the lowest temperature on Aprs 40℃ ) , Analysis was also conducted of the frequency of freezing injury during wintering period on the northern enlarged area of apple planting. The results show that: To Shaanbei and Weibei areas, the critically freezing injury during blooming period will arise at l0a's recurrence interval, but critically high temperature damage during apple fruit swelling period will not arise at 100a's recurrence interval; To Guanzhong and most part of Weibei areas, and the same type recurrence interval is 40 -50 a and 30~80 a, respectively. To the same recurrence interval, both the lowest and the highest temperature of Shaanbei and Weibei areas are apparently lower than Guanzhong and most part of Weibei areas; In the northern enlarged apple planting area, freezing injury will appeare in Ganquan, Mizhi, Wuqi, Zhidan and Zizhou during wintering period every year on average, and the frequency of freezing injury in Mizhi, Wuqi and Zhidan during wintering period will be even higher, as many as 2 ~ 3 times every year.
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