| 北上台风强降水形成机制及微物理特征 |
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| 引用本文： | 李欣,张璐.北上台风强降水形成机制及微物理特征[J].应用气象学报,2022,33(1):29-42. |
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| 作者姓名： | 李欣 张璐 |
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| 作者单位： | 青岛市气象局, 青岛 266003 |
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| 基金项目： | 青岛市气象局数值模式产品应用技术创新团队;山东省自然科学基金项目(ZR2021QD028);青岛市气象局面上课题(2018qdqxm01)。 |
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| 摘 要： | 利用NCEP FNL分析资料、青岛降水现象仪和双偏振雷达观测资料, 对北上台风利奇马(1909)和巴威(2008)引发的局地对流性强降水微物理特征进行分析, 结果表明: 在台风外围的东南暖湿气流内, 受地形或边界层锋区触发形成的强对流单体后向传播或原地合并加强造成了局地强降水; 雨滴的质量加权平均直径(Dm)和对数归一化浓度(lgNw)分别为1.89 mm和3.86, 与典型台风降水相比平均直径更大、浓度更低, 形状参数μ和斜率Λ的μ-Λ关系也有明显不同; 随着雨强增强, 小雨滴占比下降而中到大雨滴比例明显上升, 直径1~4 mm雨滴对短时强降水的贡献超过90%;雨滴的碰并增长和对云水的聚集作用在对流性降水中占主导地位, 同时深厚的凇附过程对极端强降水的出现也起到了重要作用。
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| 关 键 词： | 北上台风 双偏振雷达 雨滴谱 降水微物理过程 |
| 收稿时间： | 2021-08-08 |
Formation Mechanism and Microphysics Characteristics of Heavy Rainfall Caused by Northward-moving Typhoons |
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| Li Xin,Zhang Lu.Formation Mechanism and Microphysics Characteristics of Heavy Rainfall Caused by Northward-moving Typhoons[J].Quarterly Journal of Applied Meteorology,2022,33(1):29-42. |
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| Authors: | Li Xin Zhang Lu |
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| Affiliation: | Qingdao Meteorological Bureau, Qingdao 266003 |
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| Abstract: | Local torrential rain and short-term heavy rainfall of small spatial-temporal scale are caused by northward-moving Typhoon Lekima (1909) and Typhoon Bavi (2008) in Qingdao area, with the maximum hourly rainfall of 60.3 mm·h-1 and 130.1 mm·h-1, respectively, while the prediction performance of numerical weather prediction model is very poor. Using NCEP FNL analysis data, raindrop spectrum and polarimetric radar data, the microphysics characteristics of the heavy rainfall are analyzed. The rainfall mainly occurs in a narrow belt region extending northwestward from the coastal mountainous area. The warm and humid air is transported by the southeast wind strengthens the instability. Convective cells are constantly triggered by topography or boundary layer front, and then move northwestward and form linear multicell storms under strong wind condition, or merges into local strong storms when the wind is weak. Both can cause local heavy rainfall. The mass weighted average diameter (Dm) and logarithmic normalized intercept (lgNw) are 1.89 mm and 3.86, respectively, which are between tropical marine-time and continental convective precipitation, indicating a larger mean diameter and lower number concentration compared to the typhoon rainfall in East China and South China. The μ-Λ slope is also significantly different, indicating the dominant microphysical processes are different. With the increase of rainfall intensity, the proportion of small particles below 1 mm decreases significantly, and the proportion of medium-large particles increases, indicating significant collision-coalescence process. Particles with 1-4 mm diameters contribute more than 90% to short-term heavy rainfall. When hourly rainfall is more than 50 mm·h-1, the proportion of small particles increases and particles with 2-3 mm diameter changes little, indicating that breakup and collision-coalescence process reaches equilibrium. Aggregate process and dry snow is dominant above -20℃ level and grapuel produced by riming process is dominant between -10℃ and 0℃ level. With the decrease of height, the values of ZH, ZDR and KDP increase, and raindrops change from light rain to heavy rain particles. At the same time, the liquid water content is significantly greater than ice water content, indicating that the collision-coalescence and accretion process play a critical role in the formation of heavy rainfall. Riming process also plays an important role in extreme heavy rainfall, during which its height can reach near -20℃ layer. The positive feedback of latent heat release leads to the strengthening of convective activity, resulting in more graupel particles and greater ice water content. The melting of graupel directly increases the rainfall. On the other hand, it produces big droplets, which enhance the warm-rain processes and leads to the increase of rainfall intensity. |
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| Keywords: | northward-moving typhoon polarimetric radar raindrop size spectrum precipitation microphysics |
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