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利用三维雷暴云动力-电耦合数值模式,通过对青藏高原地区2003年8月13日一次雷暴过程进行模拟,分析了高原雷暴的电荷结构特征并从微物理角度讨论了其主要形成原因。结果表明,高原雷暴以三极性结构为主,在消散阶段电荷结构转变为偶极性,结构整体电荷密度较小,主正电荷区与主负电荷区深厚,下部次正电荷区范围较大,持续时间较长。其中三极性结构主要是由于云内冰相粒子通过非感应起电机制作用形成;后期偶极性构是由霰粒子下落固态降水的增强导致。云内暖云区厚度较小,混合相区域内有效液态水含量较高,对流层顶较低,导致冰晶、雪所在的高度更低,与霰、雹这样的大粒子重合的区域更大,形成了下部范围较大持续时间较长的正电荷区。 相似文献
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平凉一次雷暴云内的降水粒子分布及其电学特征的探讨 总被引：2，自引：0，他引：2
利用X波段多普勒双偏振雷达在甘肃平凉地区获取的一次雷暴过程资料,采用模糊逻辑判断法详细分析了该过程云内降水粒子的时空演变特征,同时结合该地区雷暴的电学特征,探讨了雷暴云电荷结构与云内降水粒子之间的关系。结果表明,在雷暴发展的不同阶段,各种降水粒子的数量存在较大的差异,霰粒子和干雪的演变特征与雷暴的发展、成熟到减弱过程对应比较一致。结合地面电场和雷达推断,冰相粒子特别是霰粒子和冰晶粒子与雷暴云的起电存在密切的关系。从各种粒子的垂直分布特征来看,中国内陆高原雷暴云下部正电荷区的强弱最有可能由霰粒子的多少来决定;同时利用霰粒-冰晶起电机制可以较好地解释雷暴云内三极性电荷结构的形成。 相似文献
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为了进一步印证以往观测反推得到的广东地区雷暴云多偶极性电荷结构的结论,利用加入了起放电参数化方案的WRF模式,模拟了广东在2017年5月8日发生的一次飑线过程,并对这次飑线过程中一个雷暴单体成熟期的电荷结构演变特征进行分析,通过分析动力、云水含量、各水成物粒子混合比及携带电荷情况,讨论了电荷结构的形成及演变机制。结果表明,成熟阶段的单体,电荷结构从三极性逐渐演变为偶极性。这是因为在成熟初期,霰粒子在有效液态水含量适中且温度较高的地方与冰晶/雪花粒子发生了非感应碰撞,因此底部霰粒子携带正电,雷暴云底部形成次正电荷区,电荷结构为三极性。而在成熟后期,由于丰富的云水含量,使冰粒子的凇附过程增强,霰不断增加,冰晶和雪花不断被消耗,温度较暖区域与霰共存的冰晶和雪花急剧减少,使得该区域大小冰粒子的非感应碰撞起电急剧减少,此处霰粒子不能再通过非感应碰撞获得正电荷,底部次正电荷区随之消失,雷暴云的电荷结构转变为偶极性。此结果和以往观测反推得到的结论不同,这表明,对南方雷暴电荷结构还需继续深入认识。 相似文献
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西北内陆高原雷暴云电活动与微物理场特征的相关性 总被引：3，自引：3，他引：0
选取甘肃平凉地区2005年和2007年3次典型的雷暴过程,根据X波段多普勒双偏振雷达提供的偏振参量ZH、ZDR、KDR、ρHV和高度H,利用分层决策法对雷暴云内的水凝物粒子进行识别。在此基础上,分析甘肃平凉地区夏季雷暴云微物理和电过程之间的关系,尤其是地面电场、闪电类型与水凝物粒子分布之间的关系,推测了雷暴云内不同类型的水凝物粒子携带的电荷极性,并对该地区的电荷结构特征做了进一步解释。 相似文献
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青藏高原雷暴的闪电特征及其成因探讨 总被引：2，自引：10，他引：2
通过对2003—2004年夏季青藏高原那曲地区30次雷暴过程的地面电场及闪电电场变化的分析,发现高原雷暴具有三极性电荷结构特征,其中73%(22次)的雷暴过程在其成熟阶段地面电场呈正极性,表明在雷暴云下部存在较常规雷暴范围广、电荷量大的正电荷区(LPCC),其余27%(8次)的雷暴同样具有三极性电荷结构特征,但LPCC相对要小得多。高原雷暴平均闪电频数一般只有1 fl.min-1,相对其它地区要小几十倍。对雷暴云闪电特征的进一步分析发现,具有较大LPCC的雷暴按照闪电特征可分为以云闪(IC)、负地闪(-CG)和正地闪( CG)为主的三类雷暴。结合气象参量分析发现IC型雷暴对应较高的地气温差和地表温度,相对湿度较小,而 CG型雷暴发生在傍晚,因此对应的地气温差偏小。 相似文献
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《高原气象》2017,(6)
为了验证雷暴单体中是否会由于降水退屏蔽作用导致正地闪的发生,建立了典型的雷暴云三极性电荷结构模型,利用现有的闪电放电参数化方案,通过改变中负和下正电荷区的高度和电荷密度进行的对比试验,对雷暴单体中降水退屏蔽作用和正地闪发生之间的关系进行研究。结果表明,在雷暴单体中发生降水时,引起的雷暴云中负和下正电荷区高度下降以及电荷密度的减小会使雷暴云中电场和电势的分布发生变化。当中负和下正电荷区的高度降低时,模拟域内最大电场强度降低,最大电场强度处电势增大,最大电场强度处和地面之间电势差增大,使正先导更容易发展到地面形成正地闪。当中负和下正电荷区的电荷密度减小时,模拟域内最大电场强度降低,最大电场强度处电势的绝对值先减小后增大,在电势增大过程中最大电场强度处和地面之间电势差增大,正先导也更容易发展到地面形成正地闪。因此,雷暴单体中降水退屏蔽作用对正地闪的发生是有利的。 相似文献
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为了进一步认识闪电和固、液态降水的关系,本文利用三维雷暴云动力-电耦合数值模式,通过设置敏感性试验组,模拟了一次雷暴过程,分析雷暴中闪电和降水的特征,以及闪电和固、液态降水对垂直风速的依赖关系,探讨闪电与固、液态降水的时空分布关系和单次闪电表征的降水量(RPF:rainyields per flash)。结果表明:对流云降水中,液态降水占主要部分,但固态降水比液态降水对于垂直风速的依赖性更强。随着对流的增强,固态降水在总降水中占的比重越来越大。首次放电时间不断提前,闪电峰值落后垂直风速峰值,总闪数一开始随对流的增强而增加,对流一旦增强到一定程度,总闪数则逐渐减小。固态降水和液态降水的开始时间和峰值时间均随着对流的增强而不断提前,而液态降水出现时间和峰值时间均提前于固态降水。雷暴云首次放电的时间滞后于液态降水,而闪电峰值提前固态降水峰值或与固态降水峰值同时产生。雷暴云中的放电活动集中在强降水区域前缘的较弱降水区,强降水区对应的闪电较少,对流的增强会使降水区域面积、降水量和降水强度增加。由于液态降水总量远大于固态降水总量,固、液态RPF的数值相差达到一个量级,但单位时间内固态降水和液态降水增加的速率相近。在单位时间内闪电次数越多,RPF则越小,而固态RPF和闪电次数的线性相关性明显好于液态RPF,所以利用固态降水可以更好地预报闪电。这些结果有助于进一步认识闪电和降水的关系,并可为闪电预报提供新的思路。 相似文献
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通过分析中国内陆高原西藏那曲、 青海大通、 甘肃中川和平凉4个不同海拔高度地区雷暴的电学特征发现, 不同地区间雷暴电学特征有其共性, 但也存在一定的差异。根据过顶雷暴的地面电场演变特征, 内陆高原地区雷暴可以分为特殊型和常规型两类\.特殊型雷暴在当顶阶段地面电场呈正极性, 即雷暴下部存在范围较大的正电荷区（LPCC）, 且特殊型雷暴所占比例随海拔高度的增加有所增加; 常规型雷暴在当顶阶段地面电场为负极性, 与低海拔地区常规雷暴引起的地面电场类似。结合4个地区的地面气象要素以及探空资料的分析, 发现不同地区对应的部分热动力参量以及大气层结参数存在显著差异\.分析表明, 地气温差和暖云区厚度对雷暴云LPCC的强弱有显著的指示意义, 当地气温差越大、 暖云区厚度越薄时, 雷暴云LPCC的强度相对较大; 反之, 雷暴云LPCC的强度及范围都较小。数值模拟结果表明, 特殊型雷暴云内最大上升气流区存在的范围以及总比含水量大于常规型雷暴, 上升气流的强弱以及WCD的大小在很大程度上决定了云内水成物粒子的浓度。 相似文献
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青藏高原东北部地区夏季雷电特征的观测研究 总被引：28，自引：9，他引：19
介绍了2002年夏季在海拔2650m的青海东部地区所进行的雷电综合观测实验及初步研究结果。实验中采用了GPS同步的6个站闪电快、慢电场变化和平均电场的同步观测,配合1ms的高速摄像对该地的雷暴电荷结构、闪电放电特征等进行了研究。初步研究结果表明,青海东部的雷暴云当顶时,地面电场既可受云内的负电荷所控制,也可能受正电荷所控制,揭示了雷暴电荷结构的复杂性。同时,闪电特征也存在一定的特殊性,所发生的地闪先导常以多分叉的形式慢速向地面行进,并在地面形成两个或两个以上的接地点;梯级先导的发展速度约为0.8～1.18×105m·s-1。同时在地闪发生之前和之后常有持续时间较长、闪道清晰的云内放电过程发生。高速摄像观测首次发现,在一次云内正电荷控制地面电场的雷暴条件下,云内放电过程呈现出双层结构特征。放电首先从上部负电荷区和下部正电荷之间的地方激发,然后上、下同时发展。在开始阶段只能看到向下的负流光通道,当上、下发展的通道分别到达负、正电荷区时,明亮的的主通道形成。之后放电在下部正电荷区以多分叉的形式水平扩展,下部的水平扩展停止后,主通道上部的放电开始水平扩展,是一种反极性的云内放电过程。 相似文献
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2012年盛夏山东西部一次短时强降水天气的形成机制 总被引：1，自引：0，他引：1
利用常规观测资料、自动站加密观测资料、卫星云图和雷达资料,对2012年7月4日山东省西部一次短时强降水的天气形势、物理量条件、云图和雷达回波特征进行分析。结果表明：在有利降水的大尺度天气系统背景下,低层冷空气和中尺度天气系统造成了本次短时强降水天气;低层925hPa和1 000 hPa的充沛水汽和辐合上升运动有利于强降水天气的发生,正涡度中心对应强降水中心;地面辐合线和低压环流造成本次短时强降水天气;中尺度对流云团和地面中尺度系统相对应,其位置和维持时间与强降水的落区和时间基本一致。雷达组合反射率因子〉45 dBZ的强回波区与强降水落区基本吻合;雷达平均径向速度产品逆风区中辐合流场的出现和维持及回波顶高的上升对应地面中尺度气旋式环流的形成和维持;逆风区中辐散流场的出现和维持及回波顶高的下降,对应地面中尺度气旋式环流的减弱;短时强降水出现的初期,垂直累积液态水含量出现了一个峰值,峰值出现时间提前于较强降水时段。 相似文献
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The convective charging mechanism of thunderclouds is based on the vertical transport of space charge generated by corona from ground irregularities under the influence of the surface electric field. The present work estimates the amount of charge which is expected to reach cloud base by conduction and convection processes during the lifetime of a thunderstorm. This estimate is made using the numerical model PICASSO, previously designed to characterize the evolution of this corona space charge between ground level and cloud base. Experimentally determined values of surface electric field are introduced into the model in order to initiate the computation. These values are based on six events documented during four different field experiments carried out in Florida and in France. As an upper limit, the convective transport is uniformly applied as a linearly increasing vertical air speed profile and competes with the conductive transport. The fraction of the positive charge generated at the surface by corona which finally reaches the upper limit of the layer varies between 26 and 86%, essentially depending on the electric field evolution at altitude. Assuming that the vertical transport conditions remain the same over an area of 10 km×10 km, the overall charge amount can be roughly estimated. It ranges between about 63 and over 300 C. Because the present assumptions probably lead to an overestimate of these amounts, such a range suggests that the convective charging mechanism is unlikely to be able to account for the major electrification process of the thundercloud. However, it could be considered as a relevant mechanism contributing to the lower positive charge center of the thundercloud, often observed close to cloud base. 相似文献
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A. A. Sin’kevich Yu. A. Dovgalyuk N. E. Veremei A. B. Kurov Yu. P. Mikhailovskii E. V. Bogdanov M. L. Toropova A. A. Ignat’ev A. Kh. Adzhiev A. M. Malkarova A. M. Abshaev V. Gopalakrishnan P. Murugavel S. D. Pawarr 《Russian Meteorology and Hydrology》2017,42(8):494-502
The three-dimensional nonstationary model of a convective cloud is used for investigating a thunderstorm with hail which developed over Pyatigorsk on May 29, 2012 and produced a severe hailstorm. The values of cloud characteristics (liquid water content, ice content, vertical velocity, etc.) are obtained. The importance ofconsidering wind shear is noted. The simulation results are used to analyze the transformation of precipitation field and the electric charge structure of the analyzed cloud during its development. 相似文献
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Numerical studies have been made of the importance of cloud saturation to the sign of charge transfer during graupel/ice crystal interactions in thunderstorms. Previous laboratory studies led to the idea that the diffusional growth rates of the interacting ice surfaces may influence the sign of the charge transferred during brief collisional contact. The ice crystals grow by vapour diffusion in a supersaturated environment while the graupel surface grows by diffusion under low accretion rate conditions, but will sublimate when heated sufficiently by riming. The graupel surface is also influenced, even under net sublimation conditions, by the vapour released to it from droplets freezing on its surface. In a cloud, the diffusional growth rates are also affected by ventilation when the supercooled droplets and their local environment flow past the riming surface.The diffusional growth rates of ice crystals and riming graupel particles are calculated for various cloud saturation ratios, then the sign of electric charge transferred during crystal/graupel collisions is determined according to the concept of the relative vapour diffusional growth rates, according to Baker et al., 1987 [Baker, B., Baker, M.B., Jayaratne, E.J., Latham, J., Saunders, C.P.R., 1987. The influence of diffusional growth rates on the charge transfer accompanying rebounding collisions between ice crystals and soft hailstones. Quart. J. Roy. Met. Soc. 113, 1193–1215]. It is found necessary, in order to account for the observation of positive charging of riming graupel at high accretion rates, to modify the assumptions of Baker et al. in order to increase the flux of vapour to the graupel surface. The variable growth parameters available may be adjusted to represent the environmental saturation conditions in various laboratory experiments, including the mixing of clouds from regions having different growth conditions, and are used to determine charge sign sensitivity to cloud saturation ratio, temperature and accretion as measured by the cloud effective liquid water content. 相似文献
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N. E. Veremei Yu. A. Dovgalyuk V. Gopalakrishnan K. F. Komarovskikh P. Murugavel S. D. Pawar A. A. Sinkevich 《Russian Meteorology and Hydrology》2015,40(12):777-786
Studied are the effects of severe aerosol pollution of the atmosphere on the parameters of a cumulonimbus cloud (including its charge structure) and on precipitation. Considered is the example of the cloud that developed on May 11, 2009 near the town of Kharagpur (India) under conditions of severe aerosol pollution of the atmosphere due to dust transport from the desert. The in situ observations of the evolution of the cumulonimbus cloud of large vertical and horizontal extent and of its electric conditions were carried out on that day. It is found that the distribution of electric charges in the cloud was characterized by inverted polarity (i.e., the main positive charge is in the bottom of the cloud and the negative one is in the upper part of the cloud that contradicts usually observed cases). Using the small-dimension numerical model conducted are numerical experiments on the simulation of aerosol effects produced on the evolution of dynamic, microphysical, and electric structure of the cloud under study, namely, the cloud development under background conditions and in case of high aerosol concentration. It is assumed that aerosol particles possess ice-forming properties. It is obtained that the dynamic, microphysical, and electric structures of the cloud are significantly transformed under the influence of high aerosol concentrations; precipitation generation also significantly intensifies; polarity in the distribution of electric charge varies that agrees with the data of in situ observations. 相似文献
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嵌有对流的层状云系兼有两种云的特征并且降水效率较高, 具有重要的研究意义。本文结合观测资料, 利用中尺度数值模式WRF(Weather Research and Forecast)模拟了2010年7月1日发生在东北地区的一次大范围强降水天气过程, 并对其中两个较典型的嵌入对流个例进行了详细分析。分析发现这两个嵌入对流都是由低层对流嵌入到高层云系所形成, 其中由对流云和位于其正上方的层云所形成的嵌入对流发展更加旺盛并给地面带来更强降水。以这两个个例为基础, 通过其与模拟区域内的普通对流云和层云相比较发现:相对于孤立对流云, 嵌入对流内的对流云生命期更长、低层水汽辐合更强、云内液水含量更大, 不稳定能量更多集中在低层;而在液水含量相当的两个嵌入对流中固态水含量的不同对降水强度影响较大;另一方面, 在嵌入对流发展的过程中嵌入对流内层云的垂直尺度扩大、含水量增加、降水强度增强, 从降水机制来看其云内固态和液态水含量都随嵌入对流发展逐渐增大, 而单纯层云内的上述变化均不明显。 相似文献
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W. David Rust Donald R. MacGorman Eric C. Bruning Stephanie A. Weiss Paul R. Krehbiel Ronald J. Thomas William Rison Timothy Hamlin Jeremiah Harlin 《Atmospheric Research》2005,76(1-4):247
Balloon-borne electric field soundings and lightning mapping data have been analyzed for three of the storms that occurred in the Severe Thunderstorm Electrification and Precipitation Study field program in 2000 to determine if the storms had inverted-polarity electrical structures. The polarities of all or some of the vertically stacked charge regions in such storms are opposite to the polarities observed at comparable heights in normal storms. Analyses compared the charge structures inferred from electric field soundings in the storms with charges inferred from three-dimensional lightning mapping data. Charge structures were inferred from electric field profiles by combining the one-dimensional approximation of Gauss's law with additional information from three-dimensional patterns in the electric field vectors. The three different ways of inferring the charge structure in the storms were found to complement each other and to be consistent overall. Charge deposition by lightning possibly occurred and increased the charge complexity of one of the storms.Many of the cloud flashes in each case were inverted-polarity flashes. Two storms produced ground flash activity comprised predominantly of positive ground flashes. One storm, which was an isolated thunderstorm, produced inverted-polarity cloud flashes, but no flashes to ground. The positive and negative thunderstorm charge regions were found at altitudes where, respectively, negative and positive charge would be found in normal-polarity storms. Thus, we conclude that these storms had anomalous and inverted-polarity electrical structures. Collectively, these three cases (along with the limited cases in the refereed literature) provide additional evidence that thunderstorms can have inverted-polarity electrical structures. 相似文献