A 7-Year Record of Significantly Electrified Cloud and Precipitation Events in Barrow, Alaska

In June of 2017, the Multiple Year Electric Field Study-North Slope of Alaska (MYESNSA) field campaign was established at the Department of Energy-Atmospheric Radiation Measurement (DOE-ARM) North Slope of Alaska site in Barrow, AK (71.29 N. 156.79 W). For more than 7-years now, the surface vertical electric field has been recorded at the site. A record of significantly electrified clouds and precipitation events, which are also known as Electrified Shower Clouds (ESCs), has been established using varying thresholds of the magnitude of the surface vertical electric field (i.e. days with >500 V/m, >2,000 V/m, >5,000 V/m, etc.). A total of 332 (120) days observed surface electric field values of at least +500 (+2,000) V/m. Of these, 78% (92%) occur in the relatively warm season between May and October in Barrow, AK. Furthermore, the electric field mills are located approximately 100 m away from a Ka-band Zenith Radar (KAZR) and MicroPulse Lidar (MPL) located on the DOE-ARM site. This allows for the cloud and aerosol properties of each significantly electrified event to be analyzed extensively. Of the 120 significantly electrified days with surface electric fields greater than 2,000 V/m, every case was associated with significant cloud occurrence. This study categorizes the events into weakly electrified, strongly electrified without lightning, and thunderstorm events, and provides statistics of the radar, and lidar properties of each case.

Establishing this dataset could provide useful information regarding risks to aviation in a region which lacks electric field data. These ESCs, which require less intense convection than traditional thunderstorms but still build up significantly large surface electric fields, act as precursors to thunderstorm activity in the Arctic. Barrow, AK typically observes less than one thunderstorm per year on average. However, many more ESCs are observed in this region. This increase in samples can possibly shed light on how convection is changing in the region under a rapidly warming climate.