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Simulation Study About the Influence of Atmospheric Stratification on Lightning Activities
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A 2D model about charging and discharging processes in thundercloud is used to simulate three differential atmospheric stratifications resulting in discrepant thunderstorm processes in Beijing region. The dynamic and microphysical processes in thunderstorm and their influence on lightning activities are also discussed.The results indicate that ascending velocity and water vapor axe the most important factors to influence lightning activities. At the same time, they affect each other and are together controlled by atmospheric stratification. The magnitude of the ascending velocity determines the intensity of storm and the time when the thunderstorm matured. The thunderstorm with strong updrafts can reach a large height in a short time. Strong persistent updrafts and sufficient water vapor which help to generate more ice phase hydrometeors that directly influence charging and discharging process will prolong the mature stage of the thunderstorm and thereby enhance lightning activities. Though the big density of ice phase hydrometeors can be formed, it is difficult to sustain a long time in the condition of strong updrafts and scant water vapor. Under the condition of weak updrafts and suffcient water vapor in the whole levels, it is easy to form warm cloud process in which the ice phase process and lightning activities are weak. The favorable stratification conditions for strong lightning activities are the sufficient vapor in the lower atmosphere,moderate humidity in the mid troposphere, big instability energy and some suitable convective inhibition.Through calculating some atmospheric instability parameters, it is indicated that convective instability index smaller than -10℃ (negative means instable), convective available potential energy larger than 1000 J kg-1,convective inhibition larger than 40 J kg-1, the 700-hPa potential equivalent temperature larger than 340 K and the 35%-85% humidity in the mid troposphere (700-400 hPa) are the advantageous conditions for strong lightning activities. 相似文献
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LIU Qi & FU Yunfei School of Earth Space Sciences University of Science Technology of China Hefei China 《中国科学D辑(英文版)》2007,50(3):430-441
A 6-year dataset of summer monthly mean precipitation derived from Tropical Precipitation Measure-ment Mission (TRMM)-Microwave Imager (TMI) was used to delineate the spatial distribution patterns of precipitation throughout Asian areas, which indicates that there are three rainfall centers located at the northern coast of the Bay of Bengal, the South China Sea and the western equatorial Pacific Warm Pool, respectively. Based upon the analysis of horizontal distribution, the capability of TMI for characterizing terrestrial and maritime precipitation has been evaluated and compared with Global Precipitation Climatology Project (GPCP) dataset. It was found that TMI and GPCP are well consistent with each other, while a few significant differences occur at several regions over land. By investigating rainfall esti-mates over six specific locations in Asia, a systematic underestimation of TMI was demonstrated, which could be explained by the inherent deficiency within TMI terrestrial algorithm relying on scat-tering signal from ice particles in a precipitation system. A further analysis shows that the highly in-homogeneous distribution of rain gauges employed by GPCP contributes a great deal to the significant discrepancy between GPCP and TMI, especially over regions surrounding the Tibetan Plateau where rain gauges are quite scarce. 相似文献
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In this study, the correlation between simulated and measured radar velocity spectrum width(σv) is investigated. The results show that the dendrites growth zones(DGZs) and needles growth zones(NGZs) mostly contain dendrites(DN) and needles(NE), respectively.Clear σv zones(1.1 < σv(m s–1) < 1.3 and 0.3 < σv(m s–1) < 0.7 for the DGZ and NGZ, respectively) could be identified in the case studies(27 and 28 February 2016) n... 相似文献
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为提升我国多普勒双偏振雷达水凝物分类的应用水平,在美国强风暴实验室(NSSL)研发的水凝物分类算法(HCA)基础上,通过增加冰雹区与三体散射区水凝物类型的订正识别、选用数值模式温度分析场识别融化层、引入水凝物类型垂直分布限制条件等,建立了优化方法(HCA-Opt)。利用HCA-Opt分析了2021年7月9日济南市章丘区一次雹暴云的水凝物分布特征,对冰雹落区与水凝物分类结果进行比对检验,得到如下主要结论:HCA-Opt可以正确识别冰雹与三体散射区的水凝物类型,修正了HCA将其识别为地物的问题;HCA-Opt利用模式温度分析场可准确识别融化层高度,解决了强对流天气下HCA使用的融化层自动识别算法(MLDA)无法有效识别融化层的缺陷;与HCA相比,HCA-Opt识别的水凝物在垂直分布上更加合理。HCA-Opt给出的水凝物分类结果较好描述了雹暴初生、降雹不同阶段的水凝物空间分布,初步揭示了不同高度水凝物粒子相态转化特征。HCA-Opt识别的水凝物分类中,中(小)雨与霰的可信度最高,冰晶与湿雪的可信度较低,且容易与干雪混淆;总体而言,HCA-Opt提高了水凝物分类识别技巧,对冰雹预警和落区判别具... 相似文献
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A heavy rainfall event in south China was simulated by the Weather Research and Forecasting (WRF) model
with three microphysics schemes, including the Morrison scheme, Thompson scheme, and Milbrandt and Yau scheme
(MY), which aim to evaluate the capability to reproduce the precipitation and radar echo reflectivity features, and to
evaluate evaluate their differences in microphysics and the associated thermodynamical and dynamical feedback. Results
show that all simulations reproduce the main features crucial for rainfall formation. Compared with the observation, the
MY scheme performed better than the other two schemes in terms of intensity and spatial distribution of rainfall. Due to
abundant water vapor, the accretion of cloud droplets by raindrops was the dominant process in the growth of raindrops
while the contribution of melting was a secondary effect. Riming processes, in which frozen hydrometeors collect cloud
droplets mainly, contributed more to the growth of frozen hydrometeors than the Bergeron process. Extremely abundant
snow and ice were produced in the Thompson and MY schemes respectively by a deposition process. The MY scheme
has the highest condensation and evaporation, but the lowest deposition. As a result, in the MY scheme, the enhanced
vertical gradient of condensation heating and evaporation cooling at low levels produces strong positive and weak
negative potential vorticity in Guangdong, and may favor the formation of the enhanced rainfall center over there. 相似文献
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模糊逻辑法在双线偏振雷达识别降水粒子相态中的研究 总被引:25,自引:3,他引:22
根据不同相态降水粒子的散射和空间取向等特征建立了基本形式为不对称的T型函数的模糊逻辑识别的隶属函数, 完善了该识别方法的流程, 并利用美国KOUN雷达的观测资料, 详细讨论了利用双线偏振雷达观测资料识别降水粒子相态的方法, 并对其在实际业务运用中的合理性和可行性进行分析探讨.通过分析, 作者认为: (1)利用模糊逻辑方法处理双线偏振雷达测量到的偏振参数, 可以识别降水区域的降水粒子相态, 反映降水区域的相态结构, 识别的结果基本合理, 但还需要资料作进一步的研究.(2)从实际资料的分析结果来看, 虽然利用模糊逻辑法识别降水粒子相态得到的结果比较粗, 没有明确的数据特征值, 但是它基本上能反映各种降水粒子的相态结构, 其识别的结果对目前日常的天气预报参考和人工影响天气的作业指挥和效果评估来说还是符合可用的.为中国国内未来的双线偏振雷达业务运行提供参考和帮助.(3)根据有限的观测资料分析表明, 降水区域中出现60 dBZ以上的回波强度, 并不一定就会出现冰雹, 还有可能是大粒子的液态降水.综合考虑双线偏振雷达的测量参数, 可以得到更合理的结果. 相似文献
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2015年4月28日,在高空冷涡的天气背景下,一个伴有较长生命史中气旋的超级单体在上海南汇双线偏振多普勒雷达观测范围内经历了发展减弱阶段,并产生了冰雹、雷雨大风、短时强降水等灾害性天气。利用常规天气观测、南汇双线偏振多普勒雷达、双雷达反演风场等资料分析发现,超级单体在发展成熟阶段呈现出回波悬垂、低层入流缺口、中气旋以及三体散射等经典特征,以及表示雷暴处于发展加强阶段的差分反射率因子柱。差分反射率因子柱通常意味着雷暴中上升气流的加强,同时说明大量的水滴可以被强上升气流托举到0℃层以上,形成过冷水滴,从而有利于冰雹的形成。超级单体经过的区域0~6 km垂直风切变达到了22~26 m·s~(-1),强垂直风切变环境有利于水平涡度发展,南汇雷达观测范围内中气旋维持了100 min左右,有利于雷暴的发展维持。此外,基于模糊逻辑法对此次降雹强对流天气过程开展了相态识别,结果表明,模糊逻辑法对此次强对流天气过程中的冰雹、降水等不同性质的降水能够进行有效的识别,有助于对雷暴降水相态本质的认识。 相似文献
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Influence of Graupel/Hail Parameters on the Simulation of a Convective System over Coastal South China in Summer
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This paper discusses the effect of graupel/hail parameters on a convective system in Yangjiang, Guangdong Province. The simulation results using the original model settings were similar to observations in terms of radar reflectivity and sea level pressure, as well as the identification of hydrometeor particle classification by X-band dual-polarization radar data. Sensitivity tests using changed parameters of graupel/hail indicated that a size distribution with larger and denser but fewer hail hydrometers resulted in a weaker development of the convective system in the horizontal and vertical directions. With a large terminal velocity of hail, the melting rate of graupel and evaporation rate of rain were the lowest. Hail could reach the ground and the mixing ratio of rain was the largest near the ground. Precipitation, including rainwater and hail, was the largest. However, a size distribution with smaller and lighter but numerous graupel hydrometers resulted in a stronger development of the convective system. The melting rate of graupel and evaporation rate of rain were the largest. More graupel particles were stranded in the air for a longer time—and the maximum mixing ratio of rain was the largest. The precipitation amount, including rainwater only, was the smallest. The changes to graupel parameters also led to differences in microphysical processes. 相似文献
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