由于气候变化无常 ,我国北方地区每年都有寒流发生 ,因其侵袭的范围和强度不同 ,所以经常程度不同地对果树造成一定的冻害 ,轻则伤芽 ,重则死树 ,严重时可毁灭全园。 1999年冬季我市最低气温达- 14 .7℃ ,并且持续 3～ 4天 ,因而造成近 4 0 0ｈｍ2葡萄发生冻害 ,直接经济损失达 Because of the climate change, the cold current occurs in the northern part of our country every year. Because of the different extent and intensity of invasion, the frost damage is often caused to the fruit trees in varying degrees, garden. In the winter of 1999, the lowest temperature in our city reached -14.7 ℃ and lasted for 3 ~ 4 days, resulting in the freezing damage of nearly 400hm2 grape and direct economic loss of up to