【摘要】 本文根据平凉地区1973—1979年的冰雹灾情报告,分析了平凉地区的降雹特征及其与前期（降雹日当天早晨）环境场气象要素的关系。分析结果说明:（1）平凉地区的雹灾日,平均为18.3天,其中蚕豆大小（雹直径约1.5厘米）以上的降雹占总数的42％。降雹的地理分布呈波长约42公里的波动形,明显地表现出六盘山的背风坡作用。（2）水平风的垂直切变对雷暴发展的影响主要表现在强切变层(平均3×10^-3/秒)所在的高度不同,无雹雷暴日的强切变层出现在对流层上层（海拔7—9公里）,位于强回波(η=10^-7/厘米)中心高度（4.6公里）以上,大冰雹降雹日的强切变层则在对流层中层（5—7公里）,位于强回波中心高度（8.6—10.1公里）以下;中、小冰雹降雹日的强切变层大致与强回波中心高度相一致（7公里左右）。（3）降雹强度与负温区的厚度有很大关系,负温区越厚降雹强度越大。（4）降雹日当天早晨的水汽条件为低层较湿,中、高层较干燥,如果整层水汽含量都比较大,有雷暴发展,但不利于降雹。更多还原

【Abstract】 In this paper,basing on the hail damage data of May-Sept, of 1973-1979 in the Ping Liang region, we have analysed the characteristics of hailfall and its relation with the environment meteorological elements. The results shows:l.The average hail damage days over Ping-Liang area are 18.3 days in a year.The geographical distribution of occurrence of hail appears in the wave feature with a wavelength about 42 km.The lee effects of Liu-pan mountain behave obviously.2.The thermodynamic instability of stratification in the atmosphere is an important factor for hailfall in Ping Liang region.3.The effect of the vertical shear of horizontal wind on the development of thunderstorm differs with its various heights of intensive shear.The intensive shears of thunderstorm days appear in the upper troposphere (7-9 km M.S.L.), which is above the centrum of intensity echo(4. 6km). The intensive shear of large-hail days is located at the middle troposphere (5-7km M.S.L.), which is delow the centrum of intensity echo(8. 6-10.1km). The intensive shear of morderate and small hail days are corresponded wi-th the centrum height of intensity echo(abont 7km).4.The intensity of hailfall bears a close relation to the thickness of the negative temperature zone, the greater is the thickness of the negative temperature zone, the more the hailfall is intensive.5.The water vapour in the morninng of hail days requires much moist-ure in lower troposphere but less and drier in the middle and upper ones. The thunderstorm is possible to develop when more moisture content exis-ts in all tropospheres, but it will be of no benefit to hailfall.更多还原