共查询到17条相似文献，搜索用时 296 毫秒
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闪电回击过程物理机制研究 总被引：2，自引：0，他引：2
阐述了云地闪发生的物理过程,并根据国外一些类比实验对云地闪发生的物理机制进行了分析,主要就先导过程中电晕套的形成机制和回击过程中电晕套中空间电荷的中和机理作出解释。 相似文献
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《干旱气象》2017,(4)
为了计算鲁西南地区年云地闪密度的历史平均值,选取雷暴日数据及闪电日数据进行相关性分析,将雷暴日与可闻范围内云地闪密度进行拟合,并进一步进行分组拟合,分析相对误差,最后绘制出鲁西南地区云地闪密度历史平均值分布图。结果表明:在距离观测台站6~22 km范围内,雷暴日与闪电日密切相关,两者的相关系数在距离观测站不同半径范围内呈单峰状分布,确定雷声可闻距离为14 km;雷暴日与云地闪密度拟合得出的关系式优于规范公式,更能代表云地闪密度历史平均值,且具有相同成雷机制的邻近区域,由雷暴日通过拟合公式计算得到的云地闪密度与实际发生的云地闪密度一致性更好;云地闪密度历史平均值总体呈现出西南、东北大,中间小的漏斗形,区域差异明显。 相似文献
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城区与郊区不同地形地貌下云地闪分布规律初步研究 总被引：2，自引：0，他引：2
利用上海3台SAFIR3000闪电定位仪的测量数据、计算机软件技术和数据统计方法对上海地区云地闪的分布规律进行了研究,得出了以下结论：①受地形地貌及高大建筑的影响,上海地区的云地闪分布规律是南北多,东西少,城区多,郊区少;②在郊区发生的云地闪密度虽然低于城区,但是其雷电流的平均强度要高于城区;③上海地区14：00-21：00是云地闪发生最为频繁的时间段。雷暴日是用于表征某地雷电活动的频繁程度并据此进行风险评估及确定雷电防护等级的一个重要参数,但此参数在实际应用过程中存在着一些问题,文章提出了用＂闪电密度＂或者＂地闪密度＂代替雷暴日的设想。 相似文献
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湖北省两类强对流天气云地闪特征及其环境条件对比研究 总被引：1，自引：0，他引：1
选取30次短时强降水天气和10次冰雹、雷雨大风天气个例,对云地闪特征及其环境条件进行对比分析。结果表明:以降水为主的强对流天气,负地闪占绝大多数,闪电频数较多,其10分钟云地闪频数过程最大值在50次以上,云地闪与雷达强回波区吻合得较好,且分布比较集中,而以冰雹、雷雨大风为主的强对流天气,正地闪与负地闪频次相当,甚至超过负地闪,闪电频数较少,云地闪并非分布在雷达强回波区,而是零散地分布在冰雹回波下风方向的云砧处。两者在环境条件上也存在差别,以冰雹、雷雨大风为主的强对流天气较之以降水为主的强对流天气,具有较低的整层比湿,较厚的零度以下层结厚度(冷云厚度)以及较大的垂直风切变。 相似文献
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为了得到金属尖端在发生电晕放电时尖端处的电场强度,该文首先采用实验室实验得到不同高度、不同形状、不同材质的金属尖端发生电晕放电时的环境电场阈值;再采用有限元法计算二维泊松方程,得到尖端处电晕触发阈值,由此得出以下结论:环境电场阈值随金属尖端高度的增大基本呈线性减小趋势,随着尖端越来越尖,环境电场阈值呈先减小后增大的变化趋势;高度、形状对金属物尖端处电晕触发阈值无影响,尖端处电晕阈值为定值;给出尖端处电晕触发阈值为158.75 kV·m-1与空间分辨率的拟合公式,可为今后电晕放电数值模拟中判断电晕放电的起始时刻提供参考。 相似文献
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对造成“96·7”大暴雨过程的主要天气系统进行天气学和动力学诊断，初步探讨了这次大降水过程中主要天气系统发生、发展的物理机制。 相似文献
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脉冲电晕与地闪负先导梯级性机制模式探讨 总被引：3，自引：0，他引：3
根据新的观测事实，提出了地闪负先导明亮脉冲可能不是被－慢而弱的流光（引路流光）所此导，而是被一快而短暂的电晕（脉冲电晕）所引导的梯级性流光机制的不同观点。由此出发，对流光间歇时间、梯级长度等重要特征参数进行了新的分析；结合对梯级先导辐射特征脉冲产生机制的进一步分析，提出并论证了明亮脉冲的双向传输，通过一个简单的数值模式对梯级过程进行了计算模式，得到了一些与观测特征基本符合的结果。 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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消雷器电晕电流的测量和理论分析 总被引：1，自引：1，他引：0
迄今为止,“消雷器”产生的电晕电流及其“消雷”机理尚有争论。本文利用一种“消雷器”实测电晕电流和电场强度,并根据一次闪电后地面电场恢复特征,从理论上估算了恢复时段内电晕电流密度。结果表明,即使在电场恢复到较为稳定的时刻,测量值仍比理论值约大一个量级,而理论值和地面自然尖端产生的电晕电流在量级上相当,“消雷器”产生的电晕电流不会高于自然尖端的作用。此外,“消雷器”结构（强局地表面电场、较大电晕有效面 相似文献
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通过对球面正压粘性大气非线性扰动的研究表明:由于波动之间的弱非线性相互作用，球面小扰动的波包演变是由一种较为简单的方程形式控制，当此粘性力消失时，该方程为非线性Schr?dinger方程。研究结果还表明:非线性Schr?dinger孤立波的形成，有两个因子非常重要，一是运动的球面性，另一个则是基本风场的经向切变。前者反映了球面运动的特殊性。本文还从另一个角度证明了粘性力的作用对波动起着加强能量的耗散作用，不利于这种几率波（Schr?dinger 孤立波）的形成。 相似文献
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E.M. Bazelyan Yu.P. Raizer N.L. Aleksandrov F. D'Alessandro 《Atmospheric Research》2009,94(3):436-447
A simple model of a glow corona occurring near the tip of a grounded electrode in a thundercloud electric field that can be enhanced by an approaching downward leader has been studied analytically and numerically with regard to the effect of wind. We obtained an approximate expression for corona current taking into account the (i) removal of space charge from the coronating point due to ion drift and wind and (ii) image of the charge in the ground. As the wind velocity decreases to zero, the expression tends to that obtained previously in the absence of wind. It was shown analytically and numerically that, in a thundercloud electric field, even moderate wind velocities lead to hundreds of percent increase in the corona current. This current decreases with time only slightly in a steady thundercloud electric field, as opposed to the current behavior in the absence of wind. However, even strong wind is not sufficient to affect the properties of a corona intensified in the electric field of an approaching downward leader. The occurrence of wind does not affect the conditions for initiation of an upward connecting leader from grounded objects and consequently the efficiency of lightning rods of ordinary height. 相似文献
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卷云与水云的短波透射与反射特性 总被引：8，自引：1，他引：7
利用矩阵算法计算了对不同太阳天顶角下不同光学厚度的卷云与水云,在4π空间内0～360o的不同方位与0～90o不同天顶角下的波长为1.39 μm太阳短波波段的透射与反射,其天顶角间隔为5.6o,方位角间隔为5.0o。可以看出两种云透射和反射辐射的差别及它们随着光学厚度变化而变化的情况。同时,将其与波长为0.55 μm的可见光波段的透射和反射进行了比较。 相似文献
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Corona ion discharge is responsible for a flux of small ions emanating from an overhead power line capable of modifying the ambient electrical environment. The ensuing space charge can be detected as a change in magnitude of the earth's natural DC electric field at ground level. DC field mill meters were used to measure the vertical component of electric fields upwind and downwind of 132 and 400 kV power lines. Evidence of space charge blowing downwind of power lines was observed in 21 out of 22 cases. Time series measurements recorded in the downwind direction were highly variable with fields of higher magnitude compared to those recorded upwind. Model DC field profiles were used to estimate a lower limit to the space charge density at body height arising from power lines. The average lower limit was 3000 cm−3 excess unipolar charges. The result suggests that between 10% and 60% of outdoor aerosols gain excess charge by the attachment of corona ions. Downwind of a 400 kV line in Somerset that was prone to excessive corona discharge, the estimated mean lower limit excess unipolar space charge density was 6000 cm−3, suggesting that up to 100% of aerosols gain excess charge by the attachment of corona ions. Investigations into the time variation of DC electric fields around motorways and the natural diurnal variation of the earth's DC field were also undertaken and compared to the power line data. The results show that the power line time series are clearly distinguishable from typical examples of both types of field variation, demonstrating the relatively highly charged atmospheres that generally exist around high-voltage power lines. The results are of potential public health concern, because they suggest a degree of aerosol charging that may result in a non-trivial increase in lung deposition of inhaled pollutant aerosols. 相似文献