Estimation of the IC/CG Ratio Using JEM-GLIMS and Ground-based Lightning Network Data and Its Effect on the Global Electric Circuit

Using optical data obtained by the JEM-GLIMS mission and the ground-based lightning data provided by the JLDN, NLDN, WWLLN, and GEON, we have developed a new method to distinguish the lightning discharge type, i.e., intracloud (IC) discharges, positive cloud-to-ground (+CG) discharges, and negative CG (-CG) discharges. We have analyzed a total of 8354 JEM-GLIMS lightning events and succeeded in identifying 4997 IC discharges, 767 +CG discharges, and 2590 -CG discharges. From this result, we further estimated the IC/CG ratio (Z-value) and clarified its latitudinal, regional, and seasonal dependences. It is found that the Z-value seems to be higher over the continent than the ocean, especially at the areas where the lightning activity is high, i.e., Southeast Asia, Central Africa, and Central America. In addition, the average Z-values in the local summer season is higher than that in the local winter season. The clear latitudinal dependence of the Z-value was found, which is reasonable agreement with previous studies. The estimated Z-value varies from 2.95 - 0.51 from the equator to 50^o latitude, and the global mean of the Z-values is 1.51. The decrease of the Z-value from the equator to the higher latitude is confirmed both in the northern and the southern hemispheres. As a next step, the result of the Z-value and WWLLN lightning data were used to estimate the occurrence number of IC discharges with the time resolution of 1 minute and with the spatial resolution of 0.2^ox0.2^o. Then, the estimated occurrence number of IC an CG discharges and the precipitation data obtained by the GPM satellites are used as the input parameters in the global electric circuit (GEC) model, which we are now developing. In this GEC model, the average column resistance including the influence of the cloud coverage is assumed. Using this GEC model, we estimated the total GEC current and the fair weather electric field with the time resolution of 1 minute on June 1, 2014. At the presentation, we will show the preliminary result derived from this simulation analysis in detail.