Global distribution of intense lightning discharges and their seasonal variations

Abstract

In order to study the temporal and regional variation of lightning occurrences and their relation to sprite activity and climate variability, we have analysed the 1–100 Hz ELF magnetic field waveform data obtained at the Syowa station in Antarctica, Onagawa in Japan and Esrange in Sweden for a one year period from September 2003 to August 2004. We have selected totally 1.7 × 105 events of transient Schumann resonances from the ELF magnetic field data whose amplitude exceeds 40 pT at all stations. Then, the lightning locations are estimated by a triangulation method with an estimation error of 0.5 Mm. It is found that in the summer season (from June to August) the lightning occurrence rates are higher in the northern hemisphere than in the southern hemisphere with large enhancements in North America, South-East Asia and the northern part of Africa. On the other hand, in the winter season (from December to February) these rates are higher in the southern hemisphere with large enhancements in South America, Australia and the southern part of Africa. These features are consistent with the results of global lightning measurements from space conducted by the Optical Transient Detector and the Tropical Rainfall Measuring Mission satellite. Then, we have also calculated the charge moment value (Q · dl) of lightning discharges using ELF magnetic field waveform data and have estimated the distribution function of charge moments for positive cloud-to-ground (+CG) discharges and for negative cloud-to-ground (−CG) discharges. It is found that the shape of the distribution function for both +CG and −CG discharges is almost the same for all seasons and that the distribution function of −CG discharges has a steeper slope at high Q · dl than that of +CG discharges.

Solar Activity, Lightning and Climate

“…However, the distribution over the land surface peaks in the months of July and August, varying between 31 and 49 flashes per second; the maximum flash rate for the northern hemisphere is significantly larger than for the southern hemisphere. Sato et al (2008) showed that thunderstorms/lightning are mainly continental phenomena and occur more often in the Fig. 7 Global distribution of lightning (annual flash rate) from 9 years of observations of the NASA OTD (1995)(1996)(1997)(1998)(1999)(2000) and LIS (1998LIS ( -2003 instruments (http://sprg.ssl.berkeley.edu/atmos/tgf/UCB-TGF.pdf) northern hemisphere summer than in the southern hemisphere summer.…”

Lightning and middle atmospheric discharges in the atmosphere

“…4a) and positive (b) CG discharges in the summer season (June-August, 2004) show that the ÀCG discharges occur mainly in the middle America, Africa, India and Southeast Asia both over the land and oceanic regions (Sato et al, 2008). The occurrence of À CG discharge over the oceanic region seems to be more dominant compared with that over the land region.…”

Sprite possibly produced by two distinct positive cloud-to-ground lightning flashes

“…More detailed information can be found in Huang et al (1999), Füllekrug and Constable (2000), , and Sato et al (2008). The Syowa station ELF system uses two orthogonal search coil magnetometers directing magnetic north-south (H-comp) and east-west (D-comp).…”