On 16 November 2023, UK and international researchers gathered at the University of Bath for the 11th CTR Wilson Meeting on atmospheric electricity. The CTR Wilson Institute for Atmospheric Electricity honours the Nobel Prize winner who also pioneered the global circuit concept and published extensively on atmospheric electrical topics. It is integrated with the Special Interest Group of the Royal Meteorological Society, to advance understanding of atmospheric electricity. (Atmospheric electricity concerns diverse and varied electrical phenomenon in the atmosphere, including lightning, atmospheric ionisation and the global electric circuit.) There were 39 registrants for this meeting, which was organised by Martin Fullekrug, Karen Aplin, Alec Bennett, Keri Nicoll and Giles Harrison. A photograph of meeting attendees is shown in Figure 1.

The first session was chaired by Martin Fullekrug and opened by Tamás Bozóki (Institute of Earth Physics and Space Science, Sopron, Hungary), who presented on transient signals from Schumann Resonances (SRs, resonant radio waves in the earth-ionosphere cavity produced by lightning) and their applications in lightning location. He introduced the topic of SR transients, which exceed the ELF (extremely low frequency) radio noise generated by global lightning strikes. They indicate a large change in vertical electric charge moment in large lightning strikes, and there are several methods to geolocate their source strikes. Using a network of 30 sites across the globe, he presented several case studies, including for the Tonga volcano eruption of 2022.

An online presentation was given by Yoav Yair (Reichman University, Israel), who discussed lightning geolocation data showing that lightning superbolt incidence rates were increased over ship tracks in the Mediterranean. This behaviour was argued to result from aerosol pollution from ship exhausts, increasing storm activity and lightning. He was able to find evidence that lightning superbolts (defined by the highest percentiles in the energy distribution of detected strikes) were enhanced in the eastern Mediterranean, in areas with known heavy shipping traffic.

Next, Graeme Marlton (Met Office), presented material on the use of radio telescope VHF (very high frequency) lightning imaging data (at the LOFAR radio telescope, which is able to create images of lightning formation from radio waves). These data were used to study lightning events also detected by the new Met Office lightning detection system, LEELA. They analysed a particular flash in the latest version of the LEELA software and captured by LOFAR, allowing examination of different portions of the lightning event: the dart leader, an inter-cloud strike and a cloud-to-ground strike.

After a short break, the next session (chaired by Jon Wilkinson) was opened by a presentation from Abdullah Kahraman (Newcastle University), on a study of the expected changes in lightning incidence following climate predictions from the RCP8.5 greenhouse gas emission scenario. His study covered all of Europe and was based on a convection-permitting numerical scheme from the Met Office. The general trends suggested more convective instability but less cloud ice, which resulted in a complicated picture across different regions of Europe. He noted that the United Kingdom would see a summertime increase in lightning in RCP8.5, based on his results.

Masashi Kamogawa (University of Shizuoka, Japan) discussed the variation in a long-term set of thunder day data from Japan. He found a very weak correlation between the number of thunder days and the number of cloud-to-ground strikes. The number of thunder days, which had been reconstructed from old records, including diaries, showed similar values from about 1810 to 1950, before an increase in sea surface temperatures and other factors seemed to lead to an increase in thunder.

Next, Isabel Smith (University of Reading) presented her work on whether lightning intensity (i.e. discharge current) will be affected by climate change. In a storm system from 2012, she had found that lightning increased where increased CAPE occurred, although there was a non-linear relationship. She also reported that an increase in CAPE had occurred between 1940 and 2010, noting that it was therefore likely that thresholds for increased lightning currents would be achieved increasingly often.

After lunch, in the session chaired by Alec Bennett, Giles Harrison (University of Reading) spoke on datasets of historical PG (potential gradient) records which are newly available. PG measurements were made for most of the twentieth century at several UK Met Office observatories: Eskdalemuir, Lerwick and Kew. Techniques included a Kelvin water dropper equaliser, which uses a spray of water droplets to continuously measure the PG. Such data can be useful for understanding local pollution and global circuit effects; monthly datasets are now available online.1

Blair McGinness (University of Reading) shared his study on a point-discharge sensor for measurements of atmospheric electricity. He noted that, despite a long history of usage, their operation is not fully understood. He described his methods of calibrating measurements of point discharge current with simultaneous electric field measurements. In his data, there was a phase shift between the current and electric field, which he was able to align by using both static and dynamic components in the calibration. Although retrieving electric fields from point discharge sensor currents is non-trivial, the sensors are still useful for monitoring variability.

Next, Caleb Miller (University of Reading) shared a presentation on his work concerning the behaviour of PG in fog, especially as a method for fog prediction. He noted that there was general inconclusiveness in the previous work, which could be resolved by using a larger dataset of many years' data, such as the measurements from the Reading University Atmospheric Observatory. Using this data, he identified significant PG increases which occurred during fog events, remarking that, in many cases, this increase happened sufficiently early to provide useful information for fog prediction beyond that possible from visibility measurements alone.

The final session (chaired by Keri Nicoll) was opened by David Reid (University of Bristol), who talked on modelling the electric and magnetic fields likely to be produced by dust devils on Mars. With simplifications such as assuming circular motion of the dust particles, he was able to produce a simulation which used the radius profile, height profile, charge profile, rotation frequency and particle loading. His results were approximately consistent with (extremely rare) real-world dust devil measurements made in Arizona, USA.

This session included a presentation from Justin Tabbett (University of Bristol) on a balloon-borne radioactivity detector. He shared that this CsI(Tl) scintillator-based particle detector, which is a small instrument which could be deployed on a weather balloon, could be used to measure ionising particles which are important to the study of atmospheric electricity. He presented results from tests in different environments, including a passenger airline flight and a thermal environment chamber. A microcontroller system is used for formatting the data transmitted to the launch site.

The final presentation was online, from Ronald Holle and Daile Zhang, from Holle Meteorology & Photography and the University of Maryland, respectively, about a recently published book entitled Flashes of Brilliance: The Science and Wonder of Arizona Lightning. They described the chapters of this book, which includes information about the science of lightning, the history of lightning research in Arizona (including interviews with Philip Krider, Kenneth Cummins and Richard Orville), and beautiful photographs of lightning in Arizona. Books describing the progress of lightning research for a single state or country are rare.

The meeting concluded with a lively poster discussion. Posters were presented by Gayane Karapetyan (University of Magdeburg) on lightning climatology, Hripsime Mkrtchyan (University of Reading) on fair weather PG classification methods, Keri Nicoll (University of Reading) on an aircraft charge emitter system and Gregory Marsden (University of Bristol) on volcanic ash charging.

2023 年 11 月 16 日，英国和国际研究人员齐聚巴斯大学，参加关于大气电的第 11 届 CTR 威尔逊会议。CTR 威尔逊大气电研究所向这位诺贝尔奖获得者致敬，他也是全球电路概念的先驱，并发表了大量有关大气电主题的文章。它与皇家气象学会特别兴趣小组合作，以增进对大气电的了解。（大气电涉及大气中多种多样的电现象，包括闪电、大气电离和全球电路。）本次会议有 39 名注册者，由 Martin Fullekrug、Karen Aplin、Alec Bennett、Keri Nicoll 和 Giles 组织哈里森. 与会者照片如图 1 所示。

第一场会议由Martin Fullekrug主持， Tamás Bozóki （匈牙利肖普朗地球物理与空间科学研究所）宣布开幕，他介绍了舒曼共振（SR，闪电在地球电离层空腔中产生的共振无线电波）的瞬态信号）及其在闪电定位中的应用。他介绍了SR瞬变的主题，该瞬变超过了全球雷击产生的ELF（极低频）无线电噪声。它们表明大型雷击中垂直电荷矩的巨大变化，并且有多种方法可以对其雷击源进行地理定位。他利用全球 30 个地点的网络，介绍了多个案例研究，包括 2022 年汤加火山喷发的案例研究。

Yoav Yair（以色列赖克曼大学）进行了在线演示，他讨论了闪电地理定位数据，该数据显示地中海船舶轨道上的闪电超级闪电发生率有所增加。这种行为被认为是由船舶尾气造成的气溶胶污染、风暴活动增加和闪电造成的。他找到了证据，证明超级闪电（由检测到的闪电能量分布中的最高百分位数定义）在地中海东部已知航运交通繁忙的地区增强。

接下来，Graeme Marlton（英国气象局）介绍了如何使用射电望远镜 VHF（甚高频）闪电成像数据（在 LOFAR 射电望远镜上，它能够通过无线电波创建闪电形成的图像）​​。这些数据被用来研究由新的英国气象局闪电探测系统 LEELA 探测到的闪电事件。他们分析了最新版本的 LEELA 软件中并由 LOFAR 捕获的特定闪电，从而可以检查闪电事件的不同部分：飞镖先导、云间雷击和云对地雷击。

短暂休息后，下一场会议（由 Jon Wilkinson 主持）由Abdullah Kahraman （纽卡斯尔大学）的演讲拉开帷幕，该演讲涉及 RCP8.5 温室气体排放情景气候预测后闪电发生率预期变化的研究。他的研究覆盖了整个欧洲，并基于英国气象局的允许对流数值方案。总体趋势表明对流不稳定性增加，但云冰减少，这导致欧洲不同地区的情况变得复杂。他指出，根据他的结果，英国夏季 RCP8.5 闪电将会增加。

Masashi Kamokawa（日本静冈大学）讨论了来自日本的一组长期雷日数据的变化。他发现雷日数与云地雷击次数之间的相关性非常弱。根据包括日记在内的旧记录重建的雷日数在 1810 年至 1950 年间显示出相似的值，之后海面温度升高和其他因素似乎导致雷电增加。

接下来，伊莎贝尔·史密斯（雷丁大学）介绍了她关于闪电强度（即放电电流）是否会受到气候变化影响的工作。在 2012 年的风暴系统中，她发现 CAPE 增加的地方闪电也会增加，尽管存在非线性关系。她还报告说，1940 年至 2010 年间，CAPE 有所增加，并指出，因此，雷电电流增加的阈值很可能会越来越频繁地达到。

午餐后，在Alec Bennett主持的会议上，Giles Harrison（雷丁大学）谈到了最新可用的历史 PG（潜在梯度）记录数据集。二十世纪的大部分时间里，PG 测量都是在英国气象局的几个天文台进行的：埃斯克代尔缪尔 (Eskdalemuir)、勒威克 (Lerwick) 和邱园 (Kew)。技术包括开尔文水滴均衡器，它使用水滴喷雾来连续测量 PG。此类数据可用于了解局部污染和全球电路效应；每月数据集现已在线提供。1

Blair McGinness（雷丁大学）分享了他对用于测量大气电力的点放电传感器的研究。他指出，尽管使用历史悠久，但其操作方式尚未完全了解。他描述了他通过同步电场测量来校准点放电电流测量的方法。在他的数据中，电流和电场之间存在相移，他能够通过在校准中使用静态和动态组件来对齐该相移。尽管从点放电传感器电流中检索电场并非易事，但传感器对于监测变化仍然很有用。

接下来，Caleb Miller（雷丁大学）分享了他关于 PG 在雾中行为的工作，特别是作为雾预测方法的工作。他指出，之前的工作普遍存在不确定性，这可以通过使用多年数据的更大数据集来解决，例如雷丁大学大气观测站的测量结果。利用这些数据，他确定了雾事件期间发生的显着 PG 增加，并指出，在许多情况下，这种增加发生得足够早，可以为雾预测提供有用的信息，超出了仅通过能见度测量所能提供的信息。

最后一场会议（由 Keri Nicoll 主持）由David Reid （布里斯托大学）宣布开幕，他谈到了对火星尘暴可能产生的电场和磁场进行建模。通过假设灰尘颗粒的圆周运动等简化，他能够使用半径分布、高度分布、电荷分布、旋转频率和颗粒载荷进行模拟。他的结果与在美国亚利桑那州进行的（极为罕见的）现实世界尘暴测量结果大致一致。

本次会议包括Justin Tabbett（布里斯托大学）关于气球载放射性探测器的演讲。他分享说，这种基于 CsI(Tl) 闪烁体的粒子探测器是一种可以部署在气象气球上的小型仪器，可用于测量对大气电研究非常重要的电离粒子。他展示了不同环境下的测试结果，包括客运航班和热环境室。微控制器系统用于格式化传输到发射场的数据。

最终的演示是在线的，由分别来自 Holle Meteorology & Photography 和马里兰大学的 Ronald Holle 和 Daile Zhu 介绍，内容涉及最近出版的一本名为《Flashes of Brilliance: The Science and Wonder of Arizona Lightning》的书。他们描述了本书的各个章节，其中包括有关闪电科学的信息、亚利桑那州闪电研究的历史（包括对菲利普·克莱德、肯尼思·康明斯和理查德·奥维尔的采访）以及亚利桑那州闪电的美丽照片。描述单个州或国家闪电研究进展的书籍很少见。

会议在热烈的海报讨论中结束。Gayane Karapetyan（马格德堡大学）展示了闪电气候学， Hripsime Mkrtchyan（雷丁大学）展示了晴天 PG 分类方法，Keri Nicoll（雷丁大学）展示了飞机电荷发射器系统，Gregory Marsden（布里斯托大学）展示了海报关于火山灰充电。