冰雹生长物理过程参数化研究

PARAMETERIZATION OF PHYSICAL PROCESSES FOR HAILSTONE GROWTH

对冰雹生长物理过程的理论与实验研究都表明 ,冰雹生长过程中表面热量与质量传输决定了冰雹生长率及其结构特征。然而 ,许多模式研究者在冰雹的热量平衡方程中 ,关键的热传输系数一直引用Ranz和Marshall在小雷诺数下对水滴蒸发的测定结果进行外推 ,与实际的冰雹状况差距较大。本文利用郑国光在与实际冰雹尺度相对应的雷诺数范围内 ,对热传输系数的测定结果 ,进行参数化处理 ,应用于胡志晋等的一维及三维冰雹生长模式 ,结果发现冰雹的融化、蒸发、干湿增长都有很大不同。其中冰雹的融化率比原模式大 12 %～ 5 0 % ;冰雹的蒸发率比原模式大 10 %～ 2 0 0 % ;冰雹的干湿增长率增大 10 %～ 40 %。

The theoretical and experimental researches on the process of hail growth have expressed that the mass and heat transfer of hail's surface decided the rate of hail's growth and structure, the hail's dynamic character decided its movement, time of stopping in cloud and the disaster degree after the hail landed on ground, in a word, decided the hail's growth. The hail's mass and heat transfer affects growth, melting and evaporation of hail. But many researchers used the transfer coefficient which Ranz and Marshall measured on water drop evaporation under small Renold number (Re≤200) and expanded it to 104×Re≤107(the actual hail's mass and heat transfer coefficient), it exists bigger difference. Zheng (1994) measured accurately the surface temperature of cooling ice particle using AGMA system under the range of 1.1×104≤Re≤5.2×104 and developed the numerical model to compute the Nusset number. On the basis of the experiment mentioned above, the paper parameterized the experiment result in the range of Renold numbers corresponding to natural hail's Re number, then put it in 1D and 3D cumulus model to compute the hail's growth situation of 4 different areas of China under various parameterization schemes.we found that the hail' growth, melting and evaporation difference from that of Provo scheme. The hail' melting rate is 12%—50% bigger than the previous model and the hail's evaporation rate is 10%—200%bigger than the previous model,the dry and wet growth rate is 10%—40% bigger than the previous model.