Research Activity
North Slope of Alaska Field Campaign (June 2017-Current) :
This campaign aims to improve our overall understanding of the Global Electric Circuit (GEC) of the atmosphere. We have now been continuously measuring the vertical electric field in Barrow, AK for over 5-years. This high quality measurement of the electric field in the Arctic fills the gap of lack of reliable electric field observations in the northern hemisphere. In recent years, electric field data that has been used to compare to global electrified cloud parameters have come from mainly the southern hemisphere. The North Slope of Alaska is an ideal location for measuring the electric field, because of its stably stratified boundary layer that exists due to the extremely cold temperatures as well as pristine localized environment with little anthropogenic influences. These measurements are critical in interpreting the tie between the fair weather electric field and global thunderstorm and electrified cloud activity. Our research goal is to utilize the relatively cheap and easily calibrated electric field measurements to monitor global thunderstorm activity in the long term.
Long-term Changes in Thunder-Days, and the Relationship to Lightning Flash Density:
My research explores the relationships between long term (1975-current) thunder-day data and the flash density and thunderstorm population measured the the TRMM satellite. A thunder day is defined as auditory thunder observed at a certified ground station by a human observer. We have a 16-year overlap period (1998-2013) between the ground station thunder day data, and the TRMM satellite, which included the Lightning Imaging Sensor (LIS) and the Ku precipitation radar (PR). Data shows that over much of the globe, there is a statistically significant positive correlation between the trend in thunder-days and the trend in flash density during this 16-year period. This allows for the possibility to look at even longer trend in thunder day activity around the globe (in some cases back to 1930) to gain a glimpse into how thunderstorm activity may have changed in the last century.
Relationships among the diurnal fair-weather return current and layered cloud properties during the polar night:
My current research is exploring the relationship between the return current of the GEC and persistent layered clouds that form in the presence of the electric field during the polar night. Preliminary results show that during periods of more global thunderstorm and ESC activity (larger magnitude return current), the cloud bases tend to form higher, the clouds tend to be thicker, and precipitate more numerous particles. Interestingly, since the clouds are forming higher up in the column, they are emitting slightly less downwelling longwave irradiation, and the surface is slightly cooler. This leads to the idea that not only are the global summation of thunderstorms and ESCs influencing polar cloud properties, they are also the driving force of the diurnal cycle of surface temperature during the polar night.
Significantly charged events in the Arctic that do not produce lightning:
My current research aims to establish the first long term record of Electrified Shower Clouds (ESC) in the Arctic. Between the years of June 2017 to December 2022, we observed 92 significantly charged events in Barrow with surface vertical electric fields of at least +2,000 V/m. In every case, these large positive electric fields were associated with a convective cloud, indicating an ESC. With the use of a Ka-band zenith radar at the site, we aim to understand what conditions cause events such as these. With a warming Arctic climate, we hope to monitor the ESC activity, which acts as a precursor to thunderstorms. This could help to understand how convection changes under the warming climate.
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Coupling of the GEC and Lower Ionospheric D and E Regions:
This one-year project aims to improve our understanding of how the AC and DC global atmospheric circuits influence or interact with the lower ionospheric D and E regions of the globe. This study proposes to build upon several previous campaigns conducted by the PI’s, which established electric field meters in both Corpus Christi, TX and Barrow, Alaska. Data from these sites were used to create a fair-weather electric field definition of the vertical electric field, containing only the robust global return signal from the DC global circuit. This study proposes to build and deploy an additional vertical electric field monitoring station at Wallops Island Flight Facility to provide additional valuable information about the spatial and temporal variability of the AC and DC circuits.
The data gathered from this study has the potential to help quantify the potential time lag between the AC and DC global circuits at multiple sites around the United States. The PI’s propose to set up an additional electric field measurement site at Wallops Island, VA. This would allow for simultaneous monitoring of the GEC from the North Slope of Alaska, Southern Texas, and the Northeastern United States. This would provide ideal conditions to measure the time lag of the AC circuit triggered by global lightning activity, and the DC circuit, which encompasses both the contributions from thunderstorms and Electrified Shower Clouds (ESCs).
The data collected in this proposal also has a great potential to be used to determine if the fair-weather return current (DC global circuit) signature is present in the lower D and E regions of the ionosphere. This would provide a quantitative link between lower ionospheric variability and the summation of global electrified cloud occurrence in the future.
Comparing the Vertical Electric Field Above Mid/High Latitude Wintertime Systems to More Traditional Convective Thunderstorm Events:
Questions asked:
• How significantly do large wintertime Mesoscale Convective Systems (MCSs) contribute to the upward vertical electric field, and thus the Global Electric Circuit (GEC) system?
• How do the vertical electric fields (Ez) measured above wintertime systems by the NASA ER-2 aircraft compare to those in the tropics and subtropics? • What is the relationship between the Ez measured onboard the ER-2 aircraft and the nearby NASCOM IR brightness temperature (Tb) during wintertime MCS and tropical convective events?
• Can we determine a potential cause for such dramatically low magnitude electric fields measured above the large wintertime MSC events?
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Findings:
​• The magnitude of the vertical electric field measured during the 2020 IMPACTS flights is significantly lower that that of other vertical electric field measurements measured around the globe also from the ER-2 aircraft.
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• When including properties from mid-high latitude systems, a worse relationship to the Carnegie Curve is present
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Correlation of Tropical Rainfall Measurement Mission (TRMM) Electrified Cloud Parameters to the GEC:
Past research has shown that there is a very strong correlation between the diurnal variation observed in the GEC, and electrified cloud parameters such as global thunderstorm rainfall and flash count. My current research aims to pinpoint the electrified cloud parameters that have the best linear correlation to the GEC at diurnal, seasonal and internal timescales.Understanding these driving forces inside the clouds that act as the "battery" for the GEC, we can possibly predict the future electrical nature of the Earth. Since it has been shown that the GEC responds to the changing climate, it is possible to use this a an additional method for monitoring climate change.
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For my masters thesis research, I used multi-linear modeling as well as an Artificial Neural Network (ANN) to predict the future GEC given the TRMM parameters that I have looked at. Once we can understand the physical process that dives the GEC, and predict the future, we might be able to find very useful and practical applications for the vast electrical energy around us.
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