Using EFM and soundings to examine variations in thunderstorm thermodynamics
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Many different thermodynamic effects can alter thunderstorm charging processes and therefore the overall charge structure. The objective of this research is to understand the thermodynamic processes involved in growth of ice in the mixed-phase region where supersaturated conditions with respect to ice are observed. One goal is to determine whether this leads to changes in the thunderstorm characteristics, most notably, the release of latent heat in the mid to upper levels of the storm and an alteration of the thunderstorm charge structure, including changes in cloud-to-ground lightning and intra-cloud lightning polarity. Data from two different field programs, the Severe Thunderstorm Electrification and Precipitation Study (STEPS) and the Thunderstorm Electrification and Lightning Experiment (TELEX), were used in this study. Three plots were created for analysis. One focused on the electric charge and the relative humidity with respect to liquid water and ice, another focused on the in-storm thermodynamics, and the final focused on the variation in water content and equivalent potential temperature. With these three diagrams it was shown that liquid water is saved for cold cloud processes by some combination of mesoscale environmental factors. The results led to the conclusion that storms which produce mainly positive CGs, and therefore may have regions of inverted thunderstorm charge structure, generally had the characteristics of supersaturation with respect to ice and values near saturation with respect to water in the mixed-phase region. These storms did not follow parcel theory ascent due to large areas of warming which are presumed to be caused by the latent heat of freezing and deposition.