Anomalous diurnal variation of atmospheric potential gradient and air‐Earth current density observed at Maitri, Antarctica

Abstract

The scope of this paper is to explore the mechanisms operating over Maitri (70.76°S, 11.74°E, 117 m above mean sea level), a coastal Antarctic station, that produce an anomalous fair‐weather diurnal pattern of the atmospheric electric potential gradient (PG) and air‐Earth current density (AEC). The anomaly in the diurnal variations of AEC and the PG is displaying an ostensible minimum at ~10 UT and a diminished response to the thunderstorm over the African continent in the 14–16 UT time frame. The data sets (2005–2014, except 2012) of the PG, and to some extent, AEC, from Maitri, are used to explore this anomaly. It follows that the fair‐weather electrical phenomena over Maitri can be ascribed to global electrified convection on the one hand and to regional phenomena like convection due to the replacement of warm air by katabatic winds on the other hand. The katabatic winds originate on the polar plateau and blow from ~130° at Maitri which are likely to transport various elements from the mountain slopes, and space charge from the polar plateau is expected to produce various disturbances in the PG and AEC monitored over the coastal Antarctica. This mechanism may be responsible for peaks in the early UT hours and also for the anomalous behavior of atmospheric electrical parameters observed at Maitri. Maitri data are compared with that of Carnegie cruise and Vostok to explain the source of anomaly.

The Global Representativeness of Fair‐Weather Atmospheric Electricity Parameters From the Coastal Station Maitri, Antarctica

“…Identifying suitable PG or AEC density data for the investigation of the global feature is usually done by applying some rejection criterion which is based on the visual observation of the sky condition (i.e., visibility), and the limiting threshold for wind speed, etc., (Deshpande & Kamra, 2001; Minamoto & Kadokura, 2011; Ruhnke, 1962). The global features are well represented/detected in the PG and AEC density variations in Antarctic Plateau (Bering et al., 1991; Burns et al., 1995, 2017; Byrne et al., 1993; Cobb, 1977; Frank‐Kamenetsky et al., 2001; Jeeva et al., 2016). However, these variations also show strong signatures of local electrical disturbances in coastal Antarctica (Burns et al., 1995; Jeeva et al., 2016; Minamoto & Kadokura, 2011).…”

“…As an example, Jeeva et al. (2016) carried out the GEC experiments at Maitri for about 6 years spread during 2006–2020. The lead author found that the strong winds associated with the snow particles, snowfall, and drifting snow caused severe fluctuation in the PG and AEC density variations, during his stay in Antarctica.…”

“…On the contrary, the seasonal variation of the PG at Maitri displays different diurnal characteristics in summer and winter. The most prominent one is that the trend of the PG variation in winter resembles the Carnegie pattern but it is not in the summer season (Jeeva et al., 2016).…”

“…A study from Syowa (69.0°S, 39.5°E), a Japanese research station, situated in another part of the coastal Antarctic region, suggests that the data are usually contaminated by local disturbances, thereby, making it difficult to investigate the relationship between the near‐earth electric field and upper‐atmospheric phenomena (Minamoto & Kadokura, 2011). Another study from Maitri (70.8°S, 11.8°E), an Indian research station situated relatively more interior in the coastal Antarctic region, suggests that there are some anomalous characteristics in the fair‐weather PG (Jeeva et al., 2016). This feature is identified from the comparative studies of the PG data at Maitri with that of Vostok and Carnegie curves.…”

Measuring Global Signals in the Potential Gradient at High Latitude Sites

“…Burns et al (2012) found global signatures in the daily and seasonal variation in PG at Vostok when meteorological disturbances related to temperature and wind speed effects were removed. Furthermore, PG measurements were performed at Maitri station (70.76°S, 11.74°E), reported by Jeeva et al (2016), who found that local katabatic winds could also produce substantial local effects on PG.…”