Characteristics of near-earth thunderstorm electric fields at LHAASO observatory

Thunderstorms are common weather phenomena at high altitudes, accompanying with lightning, strong winds and other disasters. During thunderstorms, the strength of atmospheric electric fields could be up to 1000 V/cm or even higher. The intensity fluctuates violently and the polarity could change multiple times. So, direct measurement of the thunderstorm electric field is a quite challenging work. The Large High Altitude Air Shower Observatory (LHAASO), under the construction of a project at Daocheng (4410 m a.s.l., Sichuan, China), is featured with frequent thunderstorms, especially in summer. The distribution of thunderstorm parameters is presented by analyzing the near-earth atmospheric electric field of the LHAASO station in this work. The polarity and intensity variation characteristics of the electric field in the cumulus, mature and dissipating stages of thunderstorm are also discussed. The results show that the thunderstorms mainly occur in the period of a time from late afternoon to evening. They are more frequent and stronger in summer. During the mature stage, the field changes more dramatically. Our results could be helpful in understanding the variations of cosmic rays at LHAASO during thunderstorms,and provide valuable information for studying global thunderstorm activity.