An Alternative Methodology of Fair-Weather Identification for Ground-Based Measurement of AEF at the Polar Region

We present a novel method to discriminate atmospheric electric field (AEF) variations originating from the global electrical circuit and local meteorological-induced AEF variations. By comparing the AEF values measured at two different heights, the method identifies the AEF data including disturbances caused by charged blowing snow particles, and provides the fair-weather AEF data. The intense positive (fair-weather direction) apparent AEF was measured during strong winds because of the collision of negatively charged blowing snow particles into the sensor electrode of the electric field mill. In general, the volume density of blowing snow particles rapidly decreases with increasing height. Therefore, measured AEF values at the two heights were different. The difference between AEF values measured at the two heights increased at a wind speed of 6 m/s or more. Meanwhile, the statistical analysis showed that the AEF with and without clouds was less than approximately 1 V/m at Syowa Station, which is negligible. In addition, this case study at Syowa Station found no relationship between cloud extension/dissipation and AEF. Accordingly, we propose a practical method to identify the fair-weather conditions by the AEF values at two heights and wind speed observed in the polar region, such as at Syowa Station. When we employ criteria that the difference between the AEF observed at the 1.4 and 10 m heights was within +/- 20 V/m under the wind speed with less than 6.0 m/s to the whole data at Syowa Station, 24% of them were identified as fair-weather data.