The occurrence ratio of intracloud (IC) to cloud‐to‐ground (CG) discharges, which is denoted by Z‐ratio, is the crucial parameter for the studies on the global electric circuit. However, the latitudinal and regional dependences of Z‐ratio are not fully clarified. Therefore, using optical data obtained by the Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM‐GLIMS), we distinguished the lightning discharge type, that is, IC, positive CG (+CG), and negative CG (−CG) discharges, and statistically estimated the Z‐ratio. We analyzed 8,354 lightning events that obtained by JEM‐GLIMS observation and succeeded in identifying 4,431 IC discharges, 597 +CG discharges, and 3,326 −CG discharges. From this result, we calculated the Z‐ratio over many regions around the world and estimated its latitudinal and regional dependences. It is found that the Z‐ratio over the continental area is larger than the oceanic area. We also found that the Z‐ratio significantly decreases with the latitude, which is generally comparable to the results shown in the previous studies. The estimated Z‐ratio varies from 2.9–0.29 from the equator to 50° latitude, and the global mean value is 1.6. The regional dependence of Z‐ratio derived from this study can be combined with the CG lightning data provided by the ground‐based lightning detection networks to estimate the occurrence number of IC discharges. Then, the occurrence number of both IC and CG discharges can be used for calculating a more accurate estimation of the total lightning currents in the global electric circuit.

中文翻译：

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使用JEM‐GLIMS和地面闪电网络数据估算IC与CG的比率

用Z比率表示的云内（IC）与云对地（CG）放电的发生率是研究全局电路的关键参数。但是，Z比率的纬度和纬度依存度尚未完全阐明。因此，使用通过日本实验模块（JEM-GLIMS）上的“全球闪电和子午线测量”获得的光学数据，我们区分了闪电放电类型，即IC，正CG（+ CG）和负CG（-CG）放电，并以统计方式估算Z比率。我们分析了通过JEM-GLIMS观测获得的8,354次雷电事件，并成功地识别了4,431次IC放电，597次+ CG放电和3,326次-CG放电。根据此结果，我们计算了Z在全球许多地区的比率，并估计其纬度和地区依赖性。发现大陆区域的Z比大于海洋区域。我们还发现Z比率随纬度显着降低，这通常与以前的研究结果相当。估计的Z比率从赤道到纬度50度在2.9-0.29之间变化，全球平均值为1.6。Z的区域依赖性可以将本研究得出的比率与地面雷电检测网络提供的CG雷电数据结合起来，以估计IC放电的发生次数。然后，IC和CG放电的发生次数可用于计算全局电路中总雷电电流的更准确估计。