Sprites over a Mesoscale Convective System in North China and the Corresponding Characteristics of Radar Echo and Lightning

Sprites were observed over a mesoscale convective system (MCS) on 31 July 2013 in North China using a low-light video camera. The characteristics of sprite morphology, sprite parent lightning, and the corresponding radar echo in the MCS were analyzed based on coordinated Beijing Lightning NETwork (BLNET) data and weather radar data. Among the eight sprites produced in this MCS, two were columnar sprites, three were carrot sprites, one was a dancing sprite, and two were wishbone sprites (underdeveloped carrot sprites). The estimated channel bottom of the sprites was lower than 61.8±3.5 km, and the channel top was at 84.3±6.8 km on average. The arithmetic mean (AM) and geometric mean (GM) of sprite duration were 25.7±9.8 ms and 32.7 ms, respectively. All of the parent lightning strokes of these sprites were positive cloud-to-ground (+CG) strokes, with an AM peak current of +77.1 kA, ranging from +62.5 kA to +106.2 kA, which was 1.4 times larger than that of the total +CGs in this MCS. The estimated GM value of impulse charge moment change was +571.0 C km, ranging from +475 to +922 C km. In this MCS, sprites were produced above the trailing stratiform region of the MCS, where the radar echo was between 25 and 35 dBZ, and the burst of weak radar echo (<30 dBZ) was a key indicator of sprite production. Sprites tended to be produced early in the dissipation stage of the MCS, with an increasing percentage of the +CG flash (POP) rate. During the dissipation stage of the MCS, there were actually two stages that tended to produce sprites with increasing POP rates. During the period of sprite production, BLNET detected a POP rate as high as 54.2%. Meanwhile, 70.24% of the +CG strokes contained continuing currents, with an AM value of 58.17±50.31 ms, making +CG strokes in this MCS favorable for sprite production.