ORCID

https://orcid.org/0000-0001-9278-0099

Date of Award

Fall 2024

Language

English

Embargo Period

12-16-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Atmospheric and Environmental Sciences

Program

Atmospheric Science

First Advisor

Kara Sulia

Committee Members

Kristen Corbosiero, Justin Minder, Fangqun Yu

Keywords

noninductive charging, ice habit, snow aggregation, riming, thunderstorm stimulation

Subject Categories

Atmospheric Sciences

Abstract

Evanescent but powerful, lightning is the vast scale release of storm energy from accumulation of minuscule cloud particle interactions. Although lightning occurrence seems random, thunderstorms “electrify” themselves in methodical ways and show structured patterns. This study explores the role of ice microphysics in thunderstorm charging and discharge through numerical simulation.

A squall line has been simulated ideally and realistically with generally consistent conclusions. Drastically different amount of lightning was produced when using three different microphysical models: Depending on the choice of charging scheme, the National Severe Storm Laboratory (NSSL) two-moment model appropriately captures or overestimate the amount observed by the Lightning Mapping Array (LMA). The Morrison two-moment model (Hail version) and the Adaptive Habit Model (AHM, with shape aware ice and snow parameterization) produce overall underestimated lightning amounts.

Sets of sensitivity tests have been conducted in the AHM focusing on the relative dependence of electrification to 1) ice and snow “habit” or shape, 2) graupel fall speed, 3) graupel growth rate, and 4) choice of charging scheme. It has been found that lightning production is extremely sensitive to all four factors. Controlled boosting of the fall speed increases lightning generation by orders of magnitude. Boosting of graupel growth rate dampens lightning by uptaking vapor and liquid for smaller ice particle growth. Inclusion of ice habit increases ice diameter, boosting charging and subsequently lightning discharge. Shape-aware aggregation of snow shifts the charging and discharge center to the lower sector of the charging zone (0 to -38 °C) slightly above -15°C. Without continuous aggregation of snow, collision with graupel has been found to be ineffective due to the small size of snow. The main reason for the profound lightning production in NSSL is a combination of abundant graupel and supercooled liquid water, and their overlapping with abundant snow.

In summary, lightning production has been found to be sensitive to ice and snow particle size and mixing ratio, their relative fall speed to graupel, and the riming rate in the charging zone, with a “sweet spot” for charging created only when all these ingredients meet.

License

This work is licensed under the University at Albany Standard Author Agreement.

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