资源环境科技发展态势分析平台

Data from an S-band Doppler radar system and a three-dimensional very high frequency (VHF) radiation source location system in Chongqing, China, were combined to analyze the characteristics of stratiform lightning flashes associated with the charge layer near the 0 degrees C isotherm (SL0s) in 10 mesoscale convective systems during the summers of 2014-2015. Most of the SL0 events occurred during the dissipating stage of two thunderstorms. The bright band was found to have a very close relationship with the initiation of the SL0 events. The noninductive and inductive charging mechanisms associated with the process of melting ice particles were inferred to contribute to the charge of the bright band area. The reflectivity at the first located VHF radiation source (FirstS) of the SL0s was always weaker than that in the reflectivity core within the lightning area. The stronger the reflectivity core, the greater the difference between the reflectivity and the reflectivity core. The SL0s generated by the thunderstorms with low SL0 frequency tended to have weaker reflectivity at the FirstS but a stronger reflectivity core in the lightning area than that of the thunderstorms with high SL0 frequency. In the storms with low SL0 frequency, SL0s occurred only when the initiation height of the stratiform lightning flashes decreased gradually toward the height range of the SL0s; but in one storm with high SL0 frequency, the SL0s were generated simultaneously with the stratiform lightning flashes initiated at a high level. It gives a clue that the melting charging mechanisms may enhance the charge density of the bright band area.