This study quantifies the air volume injected into the stratosphere by overshooting convection detected by GOES-16/17 geostationary infrared imagery and NOAA NEXRAD precipitation echo top during the 2021 and 2022 Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) missions. This analysis seeks to address a key DCOTSS science question, namely “How much tropospheric air and water is irreversibly injected into the stratosphere by convection?” A novel method for defining individual storms or a cluster of adjacent storms as objects and tracking them throughout their lifetime facilitates the analysis. Overshooting convection injected 2,178,154 - 5,360,162 km3 of air into the stratosphere in 2021 and 6,017,486 – 10,642,008 km3 in 2022 over the North American study domain with GOES being higher than GridRad during both years. GOES overshooting detections were more uncertain due to difficulty differentiating updrafts from adjacent broad areas of cold outflow. Overshooting volume from the top 10 storm objects each year contributed 37 to 52% of the total domain wide volume. Total object-lifetime volume from these top 10 events ranged from ~90,000-790,000 km3 for GOES and ~49,000-560,000 km3 for GridRad. It was found that overshooting seldomly exceeded 5% of the total anvil area, demonstrating that very small regions within convection are responsible for impacting stratosphere composition. Despite differences in overshooting characteristics by the two sensors, airmasses initiated from GOES and NEXRAD overshooting and advected forward in time had similar spatial and vertical distributions, indicating that geostationary satellite data could be used to study the long-range transport of overshooting airmasses.

We gridded eleven years of cloud-to-ground (CG) flashes detected by the U.S. National Lightning Detection Network during the warm season in 15 km x 15 km x 15 min grid cells to identify storms with substantial CG flash rates clearly dominated by flashes lowering one polarity of charge to the ground or the other (+CG flashes versus –CG flashes). Previous studies in the central United States had found that the gross charge distribution of storms dominated by +CG flashes included a large upper negative charge over a large middle level positive charge, a reversal of the usual polarities. In each of seven regions spanning the contiguous United States (CONUS), we compared the values of 17 environmental parameters of storms dominated by +CG flashes with those of storms dominated by –CG flashes. These parameters were chosen based on their expected roles in modulating supercooled liquid water content (SLWC) in the updraft because laboratory experiments have shown that SLWC affects the polarity of charge exchanged during rebounding collisions between riming graupel and small ice particles in the mixed phase region. This, in turn, would affect the vertical polarity of a storm’s charge distribution and the dominant polarity of CG flashes. Our results suggest that the combination of parameters conducive to dominant +CG flash activity and, by inference, to anomalous storm charge structure varies widely from region to region, the lack of any favorable parameter value in a given region being offset by favorable values of one or more other parameters.