Thunderstorm Charge Structures in South Dakota, Colorado, and New Mexico

Monday, 15 December 2014
Julia Tilles1, Ronald J Thomas2, William Rison2, Tom Alan Warner3, John Helsdon4 and Paul R Krehbiel2, (1)New Mexico Tech, Physics, Socorro, NM, United States, (2)New Mexico Tech, Langmuir Laboratory, Socorro, NM, United States, (3)ZT Research, Rapid City, SD, United States, (4)South Dakota School of Mines and Technology, Physics, Rapid City, SD, United States
With little exception, New Mexico thunderstorms contain a main negative charge region and a lower (weaker) positive region, whereby the dominate polarity of cloud-to-ground lightning is negative. This Normal Polarity (NP) charge structure is observable via the New Mexico Tech Lightning Mapping Array (LMA), which has been operated by Langmuir Laboratory since the late 1990s. In contrast, an LMA deployed for the 2012 Deep Convective Clouds and Chemistry (DC3) project revealed that thunderstorm charge structures were predominantly anomalous—i.e. not NP—in north-central Colorado. These anomalous charge structures are characterized by positive cloud-to-ground (+CG) lightning, and lower-than-normal CG rates. The difference in charge structure between the two geographic locations could possibly be correlated with the scale of forcing: New Mexico storms are predominantly formed by mesoscale (small-scale) forcing, whereas Colorado can have larger synoptically-forced thunderstorms. To gain further insight into the relationship between the scale of forcing and the resulting charge structures, LMA data from the 2014 Upward Lightning Triggering Study (UPLIGHTS) will be used to determine electrical characteristics of thunderstorms in western South Dakota. The charge structures of similar storm morphologies from each geographic location—central New Mexico, north-central Colorado, and western South Dakota—will be compared.