Comparison of positive and negative compact intracloud discharges

Prior studies have found that positive and negative compact intracloud discharges (+CIDs and -CIDs, according to the physics sign convection) occur at distinctly different altitudes, which correspond to different regions in a thunderstorm. On the basis of a large number of CIDs of both polarities recorded by our VLF/LF lightning location network, characteristic differences between +CIDs and -CIDs are discussed in this study. The results reveal that -CID is a more special type of discharge. Compared with +CIDs, -CIDs produce larger electric field changes on average, and they are more isolated from other discharge processes. A locating method based on ionospheric reflection pairs of CIDs is developed, which confirms that -CIDs do occur at higher altitudes. The relationship between CIDs and convective strength is also analyzed. Out of nine storms analyzed in this study, eight produce fewer -CIDs than +CIDs. The percentage of -CIDs seems to increase with the convective strength. Although -CIDs are relatively rare, their occurrences are more temporally compact; that is, a large portion of -CIDs are produced in a very short period. +CIDs also have this characteristic, but it is not as pronounced as that of -CIDs.