ISOTOPIC STUDY OF HAILSTONES ON THE PLATEAU

Five hailstones from two severe storms which occurred in the Qinghai area on 23 July and 6 August,1983 have been examined on their deuterium content and crystal structures,and an absolute temperature scale against deuterium values is discussed.The deuterium concentration on 23 July had values ranging from-65.8 to-76.6‰ and on 6 August from-6.1 to-58.6‰,which correspond to the ambient temperatures of forming hailstones in the range-18-23℃ (altitude 7.7-8.6km) and -1.3-27℃ (5.4-9.0 km),respectively.The hailstone embryos are of a type of conical graupel.The analysis of deuterium values indicates that the graupel embryos were formed in the temperature ranges-16.8-19.5℃(on 23 July) and -11.8-20℃ (on 6 August).It is found that hailstones grew at the middle or upper part of the cloud:some grew in the updraft on 23 July and some grew in an up and down motion on 6 August.In this paper,the updraft is calculated by two methods and the trajectory of hailstones is also discussed.