一、前言冬季的低温冻害,是我国柑桔生产的主要农业气象灾害。由于柑桔对低温的反应极其敏感,所以评价一地区的气候条件是否适宜栽种柑桔,主要应分析该地区冬季低温的寒冷程度如何。当冬季出现了柑桔所不能忍受的低温时,即使历时很短,也会使柑桔遭受冻害。因此,用一地区的年极端最低气温来衡量柑桔的越冬条件是可行的。其中,分析一地区年极端最低气温的历史资料,对评定该地区柑桔的越冬条件尤为重要。当冻害指标确定后,经常看到人们用“低温指标T平均x年一遇”作为分析的依据。x值大,则 I. Preface The cold frost damage in winter is the main agricultural meteorological disaster in the production of citrus in our country. Because citrus is extremely sensitive to low temperatures, it is important to evaluate the suitability of climatic conditions in a region for citrus cultivation, primarily to assess the degree of colder winter temperatures in the area. When the winter appears low temperature orange can not tolerate, even a short duration, will also make citrus frost damage. Therefore, it is feasible to measure the overwintering condition of citrus with the annual minimum temperature in a region. Among them, the analysis of the historical data of the annual minimum temperature in a region is particularly important for assessing the winter conditions of citrus in the area. When the frost damage index is determined, it is often seen that people use “low temperature index T average x year case” as the basis for analysis. x value is large