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Covadonga Palencia Claude Berthet Marta Massot Amaya Castro Jean Dessens Roberto Fraile 《Atmospheric Research》2007,83(2-4):493-504
This paper is a comparative study between the two most common hailpad calibration systems: one annual calibration of a whole consignment of material, and the individual calibration of each plate after a hailfall. Individual calibration attempts to minimize errors due to differences in sensitivity to the impact of hailstones between plates from the same consignment, or due to differences in the inking process before the actual measurement.The comparison was carried out using calibration data from the past few years in the hailpad network in south-western France, and data from an individual calibration process on material provided by the hailpad network in Lleida (Spain). The same type of material was used in the two cases.The results confirm that the error in measuring hailstone sizes is smaller in the case of an individual calibration of hailpads than when one single calibration process was carried out for a whole consignment. The former is approximately 80% of the latter. However, this error could have been higher if it had not been the same person carrying out the single calibration process and the measuring of the dents: it has been found that differences in the inking process may account for up to 20% of the error in the case of small hailstones. Calibration errors affecting other variables, e.g. energy or parameter λ of the exponential size distribution are generally higher (5% and 18%, respectively) than errors due to the spatial variability of the hailstones. However, the calibration method does not influence the maximum size, since the relative error attributed to the spatial variability is about 8 times the calibration error.In conclusion, if errors in determining energy or parameter λ are to be reduced to a minimum, it is highly advisable to be consistent in applying the measuring procedure (if possible with the same person carrying out the measurements all the time), and even to use individual calibration on each plate, always bearing in mind that technicians have to be trained appropriately in order to achieve the highest possible degree of uniformity. 相似文献
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本文分析了2005年8月26日傍晚太原市尖草坪区降雹过程的急流、冷暖平流、形势背景,并通过对降雹过程的多普勒雷达资料的强度场、速度场及其它产品的分析,结合块状冰雹云出现特点,得出降雹过程不同阶段临近预报的较好预报和识别指标。 相似文献
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In this work, the hailstone size distributions at the ground in the plain of Friuli-Venezia Giulia are presented, as revealed through a network of polystyrene pads (hailpads), managed by volunteers, which has been active since 1988. The aim of this work is to highlight possible differences in the diurnal and seasonal behavior of hail at the ground, both from Friuli-Venezia Giulia and other countries, in order to improve the knowledge of this meteorological phenomenon.In the comparison between different countries, differences are found between the yearly size distributions of Friuli-Venezia Giulia and those of North-East Colorado, measured during the National Hail Research Experiment (NHRE). The size distributions obtained in South West France and in Friuli-Venezia Giulia are quite similar and they are slightly different from those of the Grossversuch experiment.In the comparison between different periods of the year, relevant differences are found between April and May and the other months. In particular, thunderstorms are less efficient in producing big hailstones during the former months. The most prolific month in producing hailstones is June, followed by September. This feature is interpreted as due to a form of synergy between the frequency of the synoptic forcing of storms and the amount of available energy at the ground.Analyzing the size distributions at different times of the day, the greatest differences are found in the intervals [00–06] and [06–12] in local time (respectively, [22–04] and [04–10] in UTC). These differences cannot be ascribed to the melting of the hailstones during their fall. 相似文献
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Time-resolved hailstone samples have been collected in the region of maximum radar echo (=10 cm) from four severe hailstorms in Central Switzerland. Thin sections of 1220 hailstones have been prepared and their embryos were classified according to their bubble structure and crystallography. From this embryo trajectories were deduced. Thick sections of seven hailstones were then prepared in order to measure the deuterium content of the different growth layers. This allows an independent check of the embryo and hailstone trajectories as well as an approximate calculation of the updraft velocities. The deuterium content of the vapor feeding the cloud (R
0) has been determined from structural features of the stones as well as from the heightH
–10: in this latter, new method the lowest deuterium values are attributed to those isotherms at which the top of the region of high radar reflectivity (Z
m–10 dBZ) is observed. It is shown that both embryo and hailstone trajectories determined by the two methods are generally in good agreement and that deuterium measurements in conjunction with structural analyses and radar data result in realistic updraft velocities which are in substantial agreement with results from a numerical cloud model. In the temperature interval –10<T
c<–25C upward motion of the hailstones generally corresponds to accretion of clear layers and downward motion to accretion of opaque layers at the same temperature. This is thought to be due to higher liquid water contents in the stronger updrafts resulting in growth near the wet limit.Dedicated to Prof. H. U. Dütsch on the occasion of his 60th anniversary. 相似文献
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满城冰雹微结构的观测研究 总被引：2，自引：0，他引：2
根据河北满城１９８６—１９９０年４０００多个冰雹样品和８４３个冰雹切片的观测资料，对冰雹微结构特征（即冰雹胚胎、层次、冰晶和气泡）进行了统计分析，并推论出冰雹生长（即环境温度和海拔高度）的情况。 相似文献
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青海东部一次强冰雹的微结构及生长机制研究 总被引：3，自引：2，他引：3
2004年8月18日青海省东北部大通、互助出现一次强降雹过程,利用多普勒雷达观测资料分析了冰雹云生长过程并利用现场观测的雹谱和收集的雹块进行了冰晶、气泡结构和同位素研究分析。结果表明:雹谱呈双峰型,雹块呈锥状,少数为椭圆体。冰雹切片中,雹胚以霰为主;雹块按生长方式分为四层,中间两层冰晶最长、厚度较大,表明这两个层次是这次降雹雹块的主要生长区,其生长高度较低、温度较高,生长厚度较大。锥形雹块的气泡以径向纹理为主,近似于椭圆形的雹块中的气泡以纬向纹理为主。雹块中的气泡浓度分布皆呈单峰型,气泡谱宽不超过100μm。雹块透明、不透明层气泡浓度不完全一致,有所起伏。对各层氘同位素的测量结果表明,雹块生长温度相应在-10.0~-24.0℃,生长高度相应在4.5~9.0 km(海拔高度),雹块在相对湿融的气层中,上、下翻滚增长,与冰晶分析的结果基本一致。 相似文献
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近年天津地区冰雹和雷暴天气特征研究 总被引：1，自引：1，他引：0
基于天津地区13个观测站的1990～2009年冰雹资料和2000～2009年雷暴资料,分析了近年来天津地区降雹、雷暴的时空分布特点,并总结出当前雷暴云移动路径,以及引发此类天气的主要影响系统.主要结论为:(1)近20年天津地区年平均雹日是12.6 d,北部蓟县为冰雹天气多发区,冰雹天气常出现在春夏秋季节,集中出现在每年3～9月;(2)全市13个测站在13:00(北京时间,下同)到20:00之间雷暴的发生概率较大,且西北路径,西南路径的雷暴云出现频率较高,占到了65.2％;(3)引发天津地区冰雹及雷暴天气的主要影响系统为高空冷涡和高空槽,所占比例为49.54％和43.12％. 相似文献