Gauthier, Michael R., authorRutledge, Steven A., author2022-03-022022-03-021999https://hdl.handle.net/10217/234485Summer 1999.Also issued as Michael L. Gauthier's thesis (M.S.) -- Colorado State University, 1999.We present a regional, summer season, climatology of cloud-to-ground (CG) lightning immediately east of the central Rocky Mountains from 1996-98 using data from the National Lightning Detection Network (NLDN). We document the spatial and temporal variations of summer season CG lightning activity within the region. Our examination focused on describing how CG lightning characteristics (multiplicity and peak current) for each polarity (positive and negative) changed as the percentage of positive CG lightning changed. Specifically, we found that as the positive CG fraction within a storm increased, the average positive (negative) peak current increased (decreased). Similarly, our findings revealed that increases in positive CG fraction were also associated with small increase in positive CG multiplicity and more significant decreases in negative CG multiplicity values. Additionally, we examined the co-evolving microphysical and electrical characteristics of four "significant" lightning producing storms in northeastern Colorado using the CSU-CHILL multiparameter radar and cloud-to-ground (CG) lightning data. Using the multiparameter variables of Zh, Zc1r, Phv(O), LDR and p, emphasis was placed on determining the three-dimensional distribution of various hydrometeor types in these storms (especially during periods of electrical transition from one CG polarity to another), as well as estimates of rain and hail rates. Our goal in examining these cases was to try and determine the mechanism by which positive ground flashes in mature thunderstorms dominate over negative ground flashes. Specifically, we investigated the following hypothesis: (1) the tilted dipole hypothesis, (2) the enhanced lower positive charge hypothesis, and (3) the precipitation "unshielding" hypothesis. We argue that the majority of our findings tend to support the third hypothesis, precipitation "unshielding", where intense precipitation leads to a large precipitation currents which removes charge from the negative charge center, thereby "unshielding" the upper level positive charge center. Once this "unshielding" occurs, conditions are favorable for positive CG lightning. Typically, peaks in positive CG flash rates were observed within 25 minutes of observed peaks in surface mass fluxes, resulting from the descending ice mass aloft.reportsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Cloud physics -- ColoradoLightning -- ColoradoAtmospheric electricity -- ColoradoText