Toward a climatology of precipitating systems that produce lightning with large impulse charge moment changes

The national Charge Moment Change Network (CMCN) is a new resource for the atmospheric science community. Among other things, it presently provides real-time impulse charge moment change (first ~2 ms; iCMC) information from cloud-to-ground (CG) lightning detected and geolocated by the National Lightning Detection Network (NLDN). This captures the charge moment change from the return stroke and the initial part of any continuing current. The charge moment change is the product of the amount of charge lowered in a CG stroke and the altitude from which the charge was removed.

The iCMC data, though not yielding all potential information regarding charge moment changes, clearly reveal that there is a class of especially energetic lightning discharges which were first suspected as a result of transient luminous event (TLE) observations. The iCMC data are unique in that they show the geographical patterns, in real time, of this class of lightning. Large iCMC values (> 100 C km) are clearly linked to the occurrence of TLEs in warm-season mesoscale convective systems (MCSs). However, further inspection of the iCMC data, over the course of the annual cycle, reveals that large iCMC events are present in other storm types, including overrunning stratiform precipitation in cyclonic storms, west-coast winter storms, and with shallow convection over the Gulf Stream. Large iCMCs even have been detected in several freezing rain situations.

We are developing a climatology for the storm types that produce large (> 100 C km) charge moment changes. The coverage area of the CMCN is essentially that of the contiguous U.S., so a full range of storm types and geographical locations can be studied. The primary data sources will be the CMCN data, with 3-D storm structure documented by the NOAA NEXRAD radar network. Initial results from this climatology will be presented.