Wiebke Deierling, Ph.D. - US grants

Millions of lightning flashes occur per day over the Earth, transferring tremendous power from electrical clouds to Earth's surface in the form of electric current. Lightning discharges also occur between the clouds and the edge of space, producing luminous displays called sprites and elves. These events can occur because cosmic rays from other galaxies and x-rays from the Sun make the edge of space electrically-conducting. It is not well understood how lightning might modify ionospheric conditions that affect communications and navigation (e.g., GPS) systems, or how changes in the space environment might affect electrical processes in polar-region clouds relevant to weather and climate, or how society would be impacted in other ways through electrical connections within the Earth-atmosphere-geospace system. This Broad topic is the subject of the project "Electrical Connections and Consequences Within the Earth System".

It is the purpose of this 5-year multi-institutional basic research investigation to better understand the electrical processes that link together the atmosphere, solid earth and geospace components of the Earth system. The approach is to develop improved understanding of processes controlling the charge and discharge of electrified clouds, the electrical coupling between the atmosphere and ionosphere, and the flow of current throughout the system. The project will culminate in creation of a global model that is capable of replicating much of the experimental data accumulated to date, and that Interfaces with the rest of the atmosphere-ionosphere system within the Whole Atmosphere Community Climate Model (WACCM) at the National Center for Atmospheric Research (NCAR). Other key goals of this project are to educate the public about this field of study, and to motivate and educate a cadre of next-generation scientists on this global view of the Earth-atmosphere-geospace system.

Some of the largest and most electrically active storms on earth occur in west-central Argentina in the lee of the Andes Mountains. These storms initiate at the foothills of the Andes Mountains as well as the Sierras de Córdoba (SDC) and produce extreme lightning amounts, large hail, tornadoes and heavy rainfall. The goal of this project is to advance the understanding of characteristics and causes of lightning in this understudied region of uniquely intense storms and differences in electrification between these storms and other convective storms in different environments that lead to such high impact weather.

Towards these goals, researchers at the University of Colorado (CU) and the University of Alabama in Huntsville (UAH) will study atmospheric conditions and physical processes that control storm electrification and lead to extreme lightning flash rates in conjunction with other high impact weather. Measurements of these severe storms will be taken during the planned RELAMPAGO (Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations) field campaign to be able to address these goals. Such storms have a large economic impact as they pose a hazard to people, property, agriculture and infrastructure. An improved understanding of conditions and processes from the studied storms will lead to better nowcasting and forecasting of severe weather. Furthermore, this project will support educational training of graduate students and a postdoctoral researcher. They will participate in the scientific research through independent studies and participation in the RELAMPAGO field campaign and have the opportunity to collaborate with the US and international researchers from a multitude of disciplines.

Some fundamental relationships between meteorology and electrification are not completely understood, including a lack of knowledge of how microphysical and kinematic processes control the development of charge regions inside deep convective storms. Recent studies in the US suggest that regional differences between microphysical, dynamical and electrical behavior exist. Thus, more research in different regions of the world such as in Argentina is needed to understand the physical connections between storm processes, electrification and lightning characteristics. The team of researchers from CU and UAH will investigate the environmental conditions and physical processes that control storm electrification and lead to extreme lightning flash rates of severe storms in west-central Argentina. The goal of the research is to advance understanding of storms producing extreme flash rates and of differences in electrification among convective storm types and environments that lead to high impact weather. This includes determining what role various storm environmental, kinematic and microphysical processes play in governing charge, charge region development and resultant flash rates and other properties (e.g., type, size, polarity, current, charge neutralized) in these extremely severe storms. Towards this goal, environmental, kinematic and microphysical measurements will be taken during the 9-month Department of Energy (DOE) CACTI (Clouds, Aerosols, and Complex Terrain Interactions) field campaign and the planned NSF/NASA/NOAA RELAMPAGO (Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations) field campaign. As part of RELAMPAGO, CU and UAH will deploy instrumentation to measure lightning characteristics, electric fields, and inferred charge structures of severe storms during the Intensive Observing Period (11/1-12/15/2018). The CU/UAH team will use measurements from radars and atmospheric soundings deployed during RELAMPAGO to obtain thermodynamic, kinematic, and microphysical measurements. These will be used together with lightning measurements from CU/UAH as well as NASA to analyze the environmental conditions favoring extreme lightning production. They will also be used to study the physical cloud processes leading to charge region creation and extreme lightning flash rates.

Thunderstorms that produce deep hail accumulations pose a substantial risk to life and property resulting in motor vehicle accidents, road closures, airport delays, urban and river flooding, and water rescues. Data inhomogeneities and inadequacies in monitoring hail characteristics in thunderstorms leads to low confident in projecting future hail occurrence and evaluation of future climate predictions. The overarching goal of the research is to analyze the microphysical and dynamical conditions necessary for large amounts of in-cloud hail production that lead to deep surface hail accumulations by developing and validating a robust set of characteristic storm properties unique to significant hail accumulation; determining the role of mechanisms enhancing hail production; and determining temporal and spatial variation of hail accumulations in observations and simulations.

Intellectual Merit:
The intellectual merit lies in its contribution to a comprehensive understanding of the dual-polarization and lighting characteristics in severe thunderstorms with significant hail accumulations; how and why they are linked to environmental conditions, storm morphology, terrain, and outflow boundaries; and if state-of-the-art regional climate and weather forecasting models are capable of reproducing hail accumulation characteristics derived from observations. The research will advance our understanding of processes contributing to large hail/graupel production in thunderstorms, improve the forecasting of extreme events that cause natural disasters, and extend current capabilities to directly benefit society.

Broader Impacts:
The broader impacts are that the studies will aid in better forecasting and nowcasting events with significant hail accumulation and provide basis for evaluating forecasting and regional climate simulations. Hailstorms have had large economical impacts through damage to property and agriculture with livestock fatalities and human injuries. This study will provide better insight if hail accumulation also provides useful information to issue reliable warnings to the public and assistance in severe weather management. Undergraduates and graduate students will participate in the scientific research through independent studies, internships, and a Ph.D. thesis. The project will promote the collaborations between the University Corporation for Atmospheric Research's Significant Opportunities in Atmospheric Research and Science program and the University of Colorado's Summer Multicultural Access to Research Training program, which are intended for underrepresented undergraduate students in science, math, and engineering.

The Global Electric Circuit (GEC) refers to the continuous movement of atmospheric electricity between the lower atmosphere, ionosphere and magnetosphere, principally driven by lightning. The work that will be conducted under this award will address several unknown or uncertain aspects of the GEC. The importance of the GEC to society is that electric currents in the atmosphere have impacts on communication and aircraft navigation. The project also includes significant training opportunities for the next generation of scientists at a Minority Serving Institution.<br/><br/>The goal of this project is to reduce uncertainties in two major components of the Global Electric Circuit; the upward current from electrified clouds and the downward fair-weather current. To quantify the upward current the research team will examine electric field observations above clouds that were collected from field campaigns over the past three decades, and derive a relationship between those observations and remote sensing measurements such as from the TRMM and GPM satellite missions. Downward fair-weather current would be quantified through electric field observations in Alaska, Colorado, and Texas, with a focus on refining the definition and uncertainties of fair-weather conditions using cloud and aerosol data. Six specific science questions are posed:<br/><br/>• Q#1: In the spectrum of electrified clouds, is it possible to separate the more important clouds having large contributions to the GEC from those that can be neglected, based on properties seen from radar, microwave radiometers, or other satellite-based measurements? What types of electrified clouds supply significant electric current to the GEC? <br/>• Q#2: What is the role of electrified extratropical synoptic systems in the GEC, especially from those with freezing rain and thundersnow? Can their fractional contribution to the GEC be quantified?<br/>• Q#3: Can the estimated current be refined based on the vertical and horizontal structures of the electrified clouds from measurements of radar, passive microwave radiometers, or other satellite-based measurements? <br/>• Q#4: What are the regional, seasonal, and diurnal distributions of the various thunderstorms and electrified shower clouds (ESCs) and their Wilson current contributions to the GEC?<br/>• Q#5: Can the understanding of local influences to surface electric field be improved by using a collection of observations of cloud and aerosols in northern Alaska, and the differences in the diurnal variations of electric fields obtained at other stations? <br/>• Q#6: How would thunderstorms and ESCs in the Arctic vary under a warming climate? How is the local electric field related to the variations of cloud systems in northern Alaska?<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.